WO2015028818A1

WO2015028818A1 - Antimicrobial nanocomposites

Info

Publication number: WO2015028818A1
Application number: PCT/GB2014/052630
Authority: WO
Inventors: Tapas Sen
Original assignee: University Of Central Lancashire
Priority date: 2013-08-29
Filing date: 2014-08-29
Publication date: 2015-03-05
Also published as: GB201315407D0

Abstract

The present invention relates to antimicrobial nanocomposites for treating and decontaminating water. The nanocomposites generally have antimicrobial particles (especially with antimicrobial metal species, such as silver species) and magnetic particles (especially superparamagnetic magnetite) immobilized within a porous solid-phase matrix material, such as silica. The combination of components allows the nanocomposites to be used effectively in water treatments (through contact with water), without undesirable leaching of otherwise toxic antimicrobial particles, and permits their facile magnetically-facilitated recovery after such water treatments.

Description

Antimicrobial Nanocomposites

INTRODUCTION

[0001] The present invention relates to an antimicrobial nanocomposite, particular one that is suitable for treating and decontaminating water. The invention also relates to a process of preparing said antimicrobial nanocomposite, an apparatus incorporating said antimicrobial nanocomposite, and various methods of using said antimicrobial nanocomposite.

BACKGROUND

[0002] Clean water, or the lack thereof, has always been an issue of environmental concern throughout the world. The main sources of water pollution are (i) industrial (chemical, organic, and thermal wastes), (ii) municipal (largely sewage consisting of human wastes, other organic wastes, and detergents), and (iii) agricultural (animal wastes, pesticides, and fertilizers). In addition to human activity, geographical location can also have an impact on water purity, e.g. arsenic contamination in ground water has created a major public health issue in Bangladesh and the Eastern region of India whereas nuclear contamination in the ground water is reported to be an issue in nuclear decommissioning area such as Sellafield in UK. The separation of toxic contaminants from industrially-contaminated water using a solid matrix, such as sand, porous alumina-silicates (zeolites), and clays, is well known - their ion exchange properties are generally responsible for their efficacy. Removal of biological contaminants is now the key issue in developing countries due to poor hygiene conditions. In industry, the presence of stagnant water in water pipes assists formation bio-films which can't be readily destroyed by simple chemical treatment. Hence the flow of toxic chemicals and bio-chemicals into rivers and domestic water supplies is a major concern worldwide. Legionella contamination in water at various hospitals has also caused alarm about the microbial contaminants in water related to the health industry. Similarly it is well known that the formation of bio-films in dental water lines can yield microbial contaminants well over the government limit (100 CFU/mL in UK).

[0003] Various water treatments are currently employed in an attempt to address thes water contamination issues. For instance, ozone oxidation is employed, albeit this is very selective in terms of the target substrates. Chemical treatments are often used, but these typically result in toxic by-products. Activated carbon absorption may be used, but the relevant materials typically require regular regeneration. Membrane filtration (UF & MF) is also employed, but this is often inefficient, and is a poor method of removing smaller organic molecules. [0004] Various porous matrices, with pre-determined pore sizes, have been used in commercial filtration kits, both in domestic and laboratory settings, for water treatment purposes. Such matrices are believed to separate out chemical and biological contaminants through both ion exchange and diffusional restriction of bulkier biomolecules through the porous matrix. Such matrices generally need regular recharging and are limited to only a small scale. Moreover, in industrial settings, the presence of stagnant water in water pipes leads to the formation of bio-films which can't be readily destroyed by such simple water treatments. Hence the flow of toxic chemicals and bio-chemicals into rivers and domestic water supplies is still a major problem, despite the availability of such matrices.

[0005] Other known water decontamination methods involve treatments with ozone, AgN0₃, chlorine (and its derivatives), ultraviolet light or other forms of radiation (R. L. Droste, Theory and Practice of Water and Wastewater Treatment, Wiley,New York, 1997). However, these methods generally produce unwanted side-effects to human health. For instance, the formation of toxic volatile organic compounds (VOC) during chemical treatments is a major drawback. Moreover, some of the treatment chemicals (e.g. silver-based chemicals) are themselves highly toxic, and can be difficult or impossible to extract from the water after the relevant water treatments.

[0006] It is therefore an object of the invention to overcome some or all of the problems in inherent in the prior art.

[0007] Another object is to provide a means of decontaminating water. [0008] Another object is to provide a means for antimicrobial decontamination of water, with simple, straightforward, and easy-to-handle materials.

[0009] Another object is to provide a means for simultaneous antimicrobial and chemical decontamination of water, with simple, straightforward, and easy-to-handle materials. [0010] Another object is to provide simple and easy-handling materials for use in the antimicrobial and/or chemical decontamination of water, which are easy to recover after use, and which do not leach any active ingredients into the water undergoing decontamination.

[0011] Another object is to provide versatile materials which can be used in water decontamination treatments in a variety of ways, for instance, within purpose-built filtration devices but also as water-insoluble additives which can be simply added to water to facilitate its decontamination.

[0012] Another object is to provide materials which are compatible with existing filtration or other water-decontamination technology, for instance, materials which can be included in admixture with ion-exchange resins.

BRIEF SUMMARY OF THE DISCLOSURE

[0013] According to a first aspect of the present invention, there is provided an antimicrobial nanocomposite comprising: a porous solid-phase matrix material; antimicrobial particles comprising a metallic antimicrobial agent; and magnetic particles; wherein the antimicrobial particles are non-magnetic.

[0014] According to a second aspect of the present invention, there is provided a process of preparing an antimicrobial nanocomposite, the process comprising forming a porous solid- phase matrix material with antimicrobial particles and magnetic particles dispersed and/or embedded therein; wherein the antimicrobial particles are non-magnetic and comprise a metallic antimicrobial agent.

[0015] According to a third aspect of the present invention, there is provided an antimicrobial nanocomposite obtainable by, obtained by, or directly obtained by the process of the second aspect.

[0016] According to a fourth aspect of the present invention, there is provided an antimicrobial treatment apparatus for disinfecting and/or sterilising a fluid, the apparatus comprising a disinfecting zone configured to receive a fluid in need of disinfection and/or sterilization, wherein the disinfecting zone comprises the antimicrobial nanocomposite of the first or third aspects.

[0017] According to a fifth aspect of the present invention, there is provided a method of disinfecting and/or sterilizing a fluid, the method comprising contacting a fluid in need of disinfection and/or sterilization with the antimicrobial nanocomposite of the first or third aspects (optionally using the antimicrobial treatment apparatus of the fourth aspect).

[0018] According to a sixth aspect of the present invention, there is provided a method of inhibiting growth of or destroying one or more microbes in/on a medium (e.g. a fluid, a solid surface, an atmosphere) comprising or suspected of comprising said one or more microbes, comprising contacting the medium with the antimicrobial nanocomposite of the first or third aspects (optionally using the antimicrobial treatment apparatus of the fourth aspect).

[0019] According to a seventh aspect of the present invention, there is provided a method of decontaminating, reducing contamination of, and/or inhibiting contamination of a medium (e.g. a fluid, a solid surface, atmosphere), comprising contacting the medium with the antimicrobial nanocomposite of the first or third aspects (optionally using the antimicrobial treatment apparatus of the fourth aspect)

[0020] According to an eighth aspect of the present invention, there is provided a disinfected and/or sterilized fluid obtainable by, obtained by, or directly obtained by the method of disinfecting and/or sterilizing of the fifth aspect.

[0021] According to a ninth aspect of the present invention, there is provided a treated medium obtainable by, obtained by, or directly obtained by the method of inhibiting growth of one or more microbes in/on a medium of the sixth aspect or the method of decontaminating, reducing contamination of, and/or inhibiting contamination of a medium of the seventh aspect. [0022] According to a tenth aspect of the present invention, there is provided a method of recovering an antimicrobial nanocomposite from a fluid and/or medium treated in accordance with any of the methods of the fifth, sixth, or seventh aspects, comprising filtering off and/or applying a magnetic field to the used antimicrobial nanocomposite. [0023] According to an eleventh aspect of the present invention, there is provided an antimicrobial nanocomposite obtainable by, obtained by, or directly obtained by recovering the antimicrobial nanocomposite in accordance with the method of the tenth aspect.

[0024] Features, including optional, suitable, and preferred features of any aspect of the present invention may, where appropriate, be also features, including optional, suitable, and preferred features of any other aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a better understanding of the present invention, and to show how embodiments of the same are put into effect, reference is now made, by way of example, to the following figures, in which:

[0026] Figure 1 shows TEM images of an antimicrobial nanocomposite.

[0027] Figure 2 shows TEM images of an antimicrobial nanocomposite.

[0028] Figure 3 shows an EDX spectrum of a membrane of an antimicrobial nanocomposite, with silver nanoparticles.

[0029] Figure 4 shows a bar chart showing quantitative composition data for the antimicrobial nanocomposite which was the subject of Figure 3.

[0030] Figure 5 shows an EDX spectrum of a membrane of an antimicrobial nanocomposite, with magnetite nanoparticles. [0031] Figure 6 shows a bar chart showing quantitative composition data for the antimicrobial nanocomposite which was the subject of Figure 5.

[0032] Figure 7 shows electron microscope images of MHAg03: (a) SEM image; and (b) TEM image.

[0033] Figures 8a-c shows (a) nitrogen gas adsorption data; (b) mercury intrusion data; and (c) macropore size distribution; in relation to MgAg03.

[0034] Figures 9a/b show XRF spectra of (a) pure silver nanoparticles; and (b) MHAg03 nanocomposite. [0035] Figure 10 shows cultures of E-coli: (a) in the absence of any materials as controlled; (b) in the presence of pure silver nanoparticles; (c) in the presence of MHAgOl nanocomposite; (d) in the presence of MHAg02 nanocomposite; and (e) in the presence of MHAg03

nanocomposite. [0036] Figures 1 1 a-c show cultures of E-coli: (a) in the absence of any materials (control); (b) in the presence of pure silver nanoparticles; (c) in the presence of MHAgOl nanocomposite; (d) in the presence of MHAg02 nanocomposite; and (e) in the presence of MHAg03

nanocomposite.

[0037] Figures 12a-c show SEM micrograph images of (a) core Fe₃0₄ nanoparticles; and (b)/(c) core-shell silica coated magnetite particles.

[0038] Figures^'! 3a-c show TEM micrographs of (a/b) mesoporous silica coated core-shell superparamagnetic iron oxide nanoparticles with a magnetic core and mesoporous silica shell; and (c) a low angle X-ray diffraction pattern of said particles.

[0039] Figurel 4 shows TEM images of pure mesoporous silica nanoparticles. [0040] Figure 15 shows TEM images of products of Example 3, namely the product of step (iii)/(Ag/Fe₃0₄@Si0₂) (left); the product of step (iv)/(Ag/Fe₃04@Si0₂)@Si02 (middle), and the product of step (v)/(Ag/ Fe₃0₄@Si0₂)@Si0₂)mSi0₂ (right).

[0041] Figure 16 shows the degradation profile of Acid Orange 7 using a (AgCI/Ag)/Fe₃0₄@nSi0₂ nanocomposite synthesized from 50 mg Fe₃0₄@nSi0₂, 25 mg AgN0₃ and excessive FeCI₃ solution.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0042] Herein, the term "microbe" is well known in the art and suitably refers to a microorganism. This may include viruses, though in some embodiments this definition excludes viruses for being non-living entities.

[0043] Herein, the term "antimicrobial" is well known in the art, and refers to an ability to inhibit growth of or destroy microbes. [0044] Herein, the term "particle size" or "pore size" refers respectively to the length of the longest dimension of a given particle or pore. Both sizes may be measured using a laser particle size analyser and/or electron microscopes (e.g. tunneling electron microscope, TEM, or scanning electron microscope, SEM). [0045] "Nanocomposites" are well known in the art and, herein, the term "nanocomposite" suitably refers to a multiphase solid material where at least one of the phases has one, two or three dimensions less than or equal to 350 nanometers (nm), optionally less than or equal to 250 nm, optionally less than or equal to 100 nm, or else structures having nano-scale repeat distances or pores between the different phases that make up the material. In the context of the present invention, a "nanocomposite" suitably comprises pores with one, two or three dimensions less than or equal to 100 nanometers (nm). Nanocomposites are discernible by X- ray diffraction, though other techniques known in the art may also be used to confirm the presence, nature, and/or size of nanoparticles and/or pores. For instance, the structural properties of nanocomposites can be analysed and verified using a laser particle size analyser and/or electron microscopes (e.g. tunneling electron microscope, TEM, or scanning electron microscope, SEM).

[0046] Herein, the term "nanoparticles", "nanocrystals" and "nanocrystalline" is intended to refer to particles having at least one dimension measuring less than or equal to 350nm, optionally less than or equal to 250nm, optionally less than or equal to 100nm, suitably at least two dimensions, and potentially all three dimensions. Nanoparticles are discernible by X-ray diffraction, though other techniques known in the art may also be used to confirm the presence, nature, and/or size of nanoparticles - e.g. a laser particle size analyser and/or electron microscopes (e.g. tunneling electron microscope, TEM, or scanning electron microscope, SEM).

[0047] The term "mesoporous" is well known in the art, and herein generally refers to materials containing pores with diameters between 2 and 50 nm.

[0048] Herein, a "porous solid-phase matrix material" is a porous substance, suitably with water-permeable pores.

[0049] Herein, "antimicrobial particles" are particles which exhibit antimicrobial activity, and which comprise, consist essentially of, or consist of a metallic antimicrobial agent. [0050] Herein, "magnetic particles" are particles which exhibit magnetic properties, and suitably exhibit a magnetic field, preferably spontaneously, though in some embodiments the magnetic field may be induced following the application of an external magnetic field.

[0051] Herein, the "porous solid-phase matrix material", "magnetic particles" and "antimicrobial particles" are different species.

[0052] Herein, a "metallic antimicrobial agent" is an agent containing an antimicrobially-active metal species. The metallic antimicrobial agent may be an antimicrobial metal compound (e.g. metal salt), an antimicrobial metal complex, or even an antimicrobial elemental metal (i.e. metal(O)). As such, the "active metal species" may be: one or more metal ions, the combination of one or more metal ions with one or more counterions or ligands, and/or one or more elemental metals.

[0053] Unqualified references herein to "antimicrobial activity" may either refer to antimicrobial activity in general or more specifically (e.g. against particular micro-organisms defined herein, whether in the Example section or elsewhere). [0054] Herein, references to an "active species" within any given component suitably refers to a species responsible for the relevant functional activity. For instance, the active metal species within the antimicrobial particles is primarily responsible for the antimicrobial activity, whereas the active magnetic species in the magnetic particles is primarily responsible for the magnetism of the magnetic particles. Suitably the active species may constitute at least 30 wt% % of the component or active agent in question, suitably at least 50 wt%, suitably at least 70 wt%, more suitably at least 80 wt%, more suitably at least 90 wt%, and most suitably at least 99 wt%. It is important to recognise that metal alloys may exhibit antimicrobial activity even though the active metal species may not even be the predominant species.

[0055] Herein, the term "consist essentially of", when used to describe the proportion of a given ingredient within a material, suitably means the material comprises at least 70 wt% of the given ingredient, more suitably at least 80 wt%, more suitably at least 90 wt%, more suitably at least 95 wt%, and most suitably at least 99 wt%.

[0056] Unless stated otherwise, any reference herein to an "average" value is intended to relate to the mean value.

[0057] Herein, particles (e.g. antimicrobial and/or magnetic particles) are considered "immobilized" within the porous solid-phase matrix material of the nanocomposites of the invention when said particles do not leach out of the porous solid-phase matrix material upon elution (e.g. with water). In the event of doubt, immobilisation may be determined by a comparison of eluate compositions following identical elutions (e.g. with water, or 0.1 M aqueous HCI) of each of an antimicrobial nanocomposite of the invention and a control composite in which the relevant particles (e.g. antimicrobial and/or magnetic particles) have been merely mixed (i.e. via solid-phase mixing), substantially homogenously, with the pre-formed porous solid-phase matrix material. If fewer particles (or soluble/insoluble derivatives thereof) have leached into the eluate of the antimicrobial nanocomposite than the eluate of the control composite, then immobilization may be considered to have occurred in the case of the antimicrobial nanocomposite. Preferably the immobilization condition is deemed to be met where the concentration of particles (or soluble/insoluble derivatives thereof) in the eluate of the antimicrobial nanocomposite is less than or equal to 90% of the concentration of particles (or soluble/insoluble derivatives thereof) in the eluate of the control composite, suitably less than or equal to 50%, more suitably less than or equal to 20%, most suitably less than or equal to 10%.

General Methodology and Advantages of the Invention [0058] The present invention provides novel antimicrobial nanocomposites, which are particularly ideal for use in water treatments, for instance, to decontaminate water, be it water for a mains water supply, or waste water for safe disposal/discharge. The antimicrobial nanocomposites of the invention are multifunctional in that they can be suitably used to simultaneously purify water of microbes as well as chemical contaminants, without risk of contaminating the water with the active ingredients of the antimicrobial nanocomposites (e.g. via leaching) and are readily recoverable after water treatments so that they may be regenerated and/or reused.

[0059] The antimicrobial nanocomposites of the invention work on the principle that antimicrobial particles and magnetic particles can be immobilized within a porous solid-phase matrix material whilst remaining accessible for contact with water via the pores of the matrix material. This allows water to make contact with and thereby be affected by the active species within the antimicrobial particles and/or magnetic particles, without the risk of undesirable leaching of said active species. Moreover, the antimicrobial nanocomposites of the invention allow for the provision of antimicrobial particles which are essentially magnetized by proxy (i.e, through close association with the magnetic particles) thereby allowing for their magnetic recovery, which may be otherwise impossible for non-magnetic antimicrobial particles.

[0060] The antimicrobial nanocomposites of the invention may be advantageously incorporated into pipework, and such like, so as to reduce or eliminate undesirable bio-film formation, for instance, such as that which occurs in stagnant industrial or dental water lines. Alternatively, the antimicrobial nanocomposites may be incorporated into a water reservoir, or at an outlet of a water dispenser. The antimicrobial nanocomposites can be easily incorporated into a filtration device, which can be easily fitted to water treatment, water flow, or water dispensing devices, to facilitate purification of any water therein. [0061] The antimicrobial nanocomposites of the invention are durable, and do not require the frequent recharging and regeneration required of other water-purifying materials. Moreover, they may be produced on a scale of sufficient magnitude to be applicable in the purification of large quantities of water.

[0062] The invention allows highly toxic antimicrobial agents to be used against unwanted microbes without the risk of leaching, and without problematic recovery inherent with prior art uses of highly toxic antimicrobial agents. Moreover, the methods of formation of the antimicronial nanocomposites ensures that the nanocomposites are reliable in terms of any leaching risk.

[0063] The antimicrobial nanocomposites of the invention are extremely easy to handle, whether during manufacture, upon storage, upon manufacture of an antimicrobial treatment apparatus incorporating said nanocomposites, or during their subsequent use and/or recovery. They are also extremely compatible with existing technologies, and may be retrofitted into existing systems to bolster the antimicrobial efficacy of existing decontamination systems.

[0064] Finally, the antimicrobial nanocomposites of the invention have a high absorption capacity whilst still allowing rapid flow therethrough (which can be a problem with membranes), and as such a large proportion of contacted water is effectively exposed to antimicrobial treatment.

Antimicrobial Nanocomposite

[0065] The present invention provides an antimicrobial nanocomposite as defined herein. According to an aspect of the invention, there is provided an antimicrobial nanocomposite comprising: a porous solid-phase matrix material; antimicrobial particles comprising a metallic antimicrobial agent; and magnetic particles.

[0066] Suitably the antimicrobial particles are (substantially) immobilized or otherwise retained within the antimicrobial nanocomposite, suitably so that they cannot be eluted out of the antimicrobial nanocomposite (e.g. through elution with water). Suitably the magnetic particles are (substantially) immobilized or otherwise retained within the antimicrobial nanocomposite, suitably so that they cannot be eluted out of the antimicrobial nanocomposite (e.g. through elution with water). Suitably, the antimicrobial particles and/or magnetic particles have a solubility in water at 25°C of less than 0.1 g/L, suitably of less than 0.05g/L, suitably of less than 0.03g/L. Suitably, the antimicrobial particles and/or magnetic particles are insoluble in water at 25°C.

[0067] The "porous solid-phase matrix material", "magnetic particles" and "antimicrobial particles" are different components, and the antimicrobial particles and magnetic particles suitably comprise a different active species (i.e. the species primarily responsible for

antimicrobial activity in the antimicrobial particles are different to the species primarily responsible for the magnetism exhibited by the magnetic particles). Suitably, the antimicrobial particles are non-magnetic.

[0068] The antimicrobial nanocomposite itself suitably comprises nanocomposite particles (e.g. matrix particles), which may be suitably defined as per the antimicrobial nanocomposite itself (e.g. in terms of ingredients and properties, etc.). The antimicrobial nanocomposite itself suitably comprises a hierarchically ordered porous silica matrix with interconnecting pores sized between 10 and 350 nm, which may be suitably defined as per the antimicrobial nanocomposite itself (e.g. in terms of ingredients and properties, etc.). Suitably, the antimicrobial

nanocomposite comprises antimicrobial nanoparticles sized between 5 and 100 nm, suitably between 10 and 50 nm.

[0069] The antimicrobial nanocomposite may have a specific surface area of at least 200m²/g, suitably at least 260m²/g, suitably at least 300m²/g, suitably at least 500m²/g. m²/g. Suitably, the antimicrobial nanocomposite (or the nanocomposite particles thereof) have pores sized between 10 and 300 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm Suitably, the average pore size of the antimicrobial nanocomposite (or nanocomposite particles thereof) is between 1 and 600 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm.

[0070] The antimicrobial particles and/or the magnetic particles may be (substantially) uniformally distributed within the porous solid-phase matrix material. Alternatively, the antimicrobial particles and/or magnetic particles may be distributed within the porous solid- phase matrix material so as to be locally concentrated in certain zones.

[0071] The antimicrobial particles and/or the magnetic particles are suitably dispersed within the porous solid-phase matrix material (e.g. within pores) or otherwise embedded within the porous solid-phase matrix material (e.g. with a core-shell arrangement). As would be understood by those skilled in the art, particles described as "dispersed within or otherwise embedded within" a given material are suitably present within the bulk of said material, i.e. not only at the surface of said material. However, due to the porous nature of the antimicrobial nanocomposites of the invention, particles that are "dispersed within or otherwise embedded within" the material may still be contactable with a substance to be treated (e.g. water in need of sterilization).

[0072] Where the antimicrobial particles and/or the magnetic particles are dispersed within the porous solid-phase matrix material, suitably the porous solid-phase matrix material is hierarchically ordered. [0073] Where the antimicrobial particles and/or the magnetic particles are embedded within the porous solid-phase matrix material (e.g. with a core-shell arrangement), suitably the porous solid-phase matrix material is mesoporous.

[0074] The antimicrobial nanocomposites of the invention may optionally be incorporated into a further carrier material, for instance, a synthetic carrier such as synthetic fibres, plastics materials, films, etc.

[0075] In an embodiment, the antimicrobial nanocomposite (100 wt%) comprises::

- 30-90 wt% a porous solid-phase matrix material;

- 5-30 wt% antimicrobial particles; and

- 2-40 wt% magnetic particles.

[0076] In an embodiment, the antimicrobial nanocomposite (100 wt%) comprises:

- 70-85 wt% a porous solid-phase matrix material; 15-20 wt% antimicrobial particles; and

10-30 wt% magnetic particles.

[0077] Suitably the antimicrobial nanocomposite comprises the porous solid-phase matrix material, antimicrobial particles, and magnetic particles, and optionally any other components, in relative amounts which avoid any of the components leaching into water when washed therewith.

Dispersed Particle Structure

[0078] In an embodiment, the antimicrobial particles and/or the magnetic particles are dispersed within the porous solid-phase matrix material, suitably within the pores of the porous solid-phase matrix material.

[0079] Suitably, the antimicrobial particles and/or the magnetic particles reside upon inner walls of the pores of the porous solid-phase matrix material.

[0080] Suitably, the porous solid-phase matrix material (and hence the nanocomposite itself) has a hierarchically-ordered three-dimensional structure. Suitably, such the hierarchically- ordered structure results from template-based formation of the porous solid-phase matrix material.

[0081] Suitably, such template-based formation employs a template, such as a latex or colloidal template (which may optionally be used in the form of a monolith, e.g. a packed solid material). In a particular embodiment, a polystyrene latex template is used, suitably in the form of a packed monolith of polystyrene particles. Suitably, a mobile precursor (e.g. liquid or gel, e.g. a sol gel) carrying the porous solid-phase matrix material (or precursor thereof, e.g. TEOS for silica) (and optionally one or more of the other components or precursors thereof) is suitably passed through the template, before being dried and/or calcined (e.g. at elevated temperature). Suitably, the template itself (e.g. polystyrene template), and optionally other organic

components (e.g. surfactants, film-formers, etc.), is removed by calcination.

[0082] The template-based formation of the hierarchically-ordered porous solid-phase matrix material may be performed in the presence of a suitable surfactant, for instance a non-ionic surfactant, such as a mono-, di-, or tri-block co-polymer comprising polyoxyethylene and/or polyoxypropylene blocks (e.g. Pluronic F₁₂₇). Suitably, any such surfactant(s) are present within the mobile precursor (e.g. liquid or gel) carrying the porous solid-phase matrix material (or precursor thereof, e.g. TEOS for silica). As such, the ultimate hierarchically-ordered structure may comprise such surfactant(s) or traces thereof (where attempts have been made to wash out said surfactant(s) or remove them via calcination).

[0083] The template-based formation of the hierarchically-ordered porous solid-phase matrix material may be performed in the presence of one or more further polymeric materials, such as polyvinylpyrrolidone (PVP) and/or polyvinylacetate (PVA). Suitably, any such film-forming material(s) are present within the mobile precursor (e.g. liquid or gel) carrying the porous solid- phase matrix material (or precursor thereof, e.g. TEOS for silica). As such, the ultimate hierarchically-ordered structure may comprise such film-forming material(s) or traces thereof (where attempts have been made to wash out said film-forming materials or remove them via calcination).

[0084] The template-based formation of the hierarchically-ordered porous solid-phase matrix material is suitably performed in the presence of the antimicrobial particles or a precursor thereto. Where the template-based formation is performed in the presence of a precursor to the antimicrobial particles, suitably such a template-based formation is also performed in the presence of a reagent or under conditions which transform the precursor to the antimicrobial particles (suitably in situ). Suitably, any such antimicrobial particles or precursor(s) thereof are present within the mobile precursor (e.g. liquid or gel) carrying the porous solid-phase matrix material material (or precursor thereof, e.g. TEOS for silica). As such, the ultimate

hierarchically-ordered structure suitably comprises such antimicrobial particles and optionally precursor(s) and/or calcinated derivatives thereof. [0085] Suitably, the hierarchically-ordered structures may be formed with any or all ingredients (or precursors thereto) of the final antimicrobial nanocomposite being present within the mobile precursor of the porous solid-phase matrix material during the production process. This includes any "additional components". In this manner, the ingredients may be more effectively immobilized within the final antimicrobial nanocomposite. [0086] Suitably, the hierarchically-ordered structures have pores sizes between 1 and 600 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm. Suitably, the average pore size of the hierarchically-ordered structures is between 10 and 300 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm.

[0087] Suitably, the hierarchically-ordered structures are a nanocomposite monolithic matrix. [0088] Suitably, the incorporation of the antimicrobial metal compounds can be verified by X- ray fluorescence (XRF).

[0089] In an embodiment, the hierarchically-ordered antimicrobial nanocomposite (100 wt%) has a composition defined by:

- 30-90 wt% a porous solid-phase matrix material; - 5-30 wt% antimicrobial particles; and

- 2-40 wt% magnetic particles.

[0090] In an embodiment, the hierarchically-ordered antimicrobial nanocomposite (100 wt%) has a composition defined by: - 70-85 wt% a porous solid-phase matrix material; 15-20 wt% antimicrobial particles; and 10-30 wt% magnetic particles.

Embedded Particle Structure

[0091] In an embodiment, the antimicrobial particles and/or the magnetic particles are embedded within the porous solid-phase matrix material.

[0092] In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units each having a core (suitably comprising antimicrobial particles and/or magnetic particles) encapsulated within a (optionally mesoporous) shell of porous solid-phase matrix material. The core-shell units are suitably particles, and may suitably be microspheres. The (optionally mesoporous) shell forming a shell layer adjacent to the core may constitute an inner shell layer, whilst the core-shell units may comprise one or more further outer shell layers (e.g. one inner shell and two outer shells). Such outer shell layers suitably comprise a porous solid-phase matrix material, which suitably comprises the same porous solid-phase matrix material as any inner shell layer. Moreover, such outer shell layers are suitably mesoporous (especially where the inner shell layers are mesoporous). An outer shell layer suitably overlies a shell layer decorated or otherwise embedded with antimicrobial particles and/or magnetic particles. Such an arrangement suitably helps to retain said antimicrobial particles and/or magnetic particles within the nanocomposite, through preventing leaching.

[0093] Antimicrobial particles and/or the magnetic particles (most suitably antimicrobial particles) may suitably reside within and/or, most suitably, between adjacent shell layers (e.g. antimicrobial particles may be disposed between the inner shell layer and an adjacent outer shell layer). Suitably, porous solid-phase matrix material is (substantially) absent from the core(s). Antimicrobial particles and/or magnetic particles may be present inside or outside the core(s), though suitably one is present inside (at the exclusion of the other) and the other is outside the core (at the exclusion of the other).

[0094] One or other or both of the antimicrobial particles and magnetic particles may suitably be embedded within (i.e. inside) (optionally mesoporous) shell(s) of the porous solid-phase matrix material. In such embodiments, the embedded antimicrobial particles and/or magnetic particles may suitably form a core within the (optionally mesoporous) shell(s). In a particular embodiment, magnetic particles are embedded within (optionally mesoporous) shell(s) of the porous solid-phase matrix material, suitably thereby providing a core comprising or consisting of magnetic particles. In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units each having a core, comprising or consisting of magnetic particles, which core is encapsulated within a (optionally mesoporous) shell of porous solid-phase matrix material.

[0095] One or other or both of the antimicrobial particles and magnetic particles may suitably be deposited (or decorated) upon (optionally mesoporous) shell(s), and/or otherwise dispersed within pores of the (optionally mesoporous) shell(s) (whether within an inner or outer shell layers, though preferably within an inner shell layer). In a particular embodiment, antimicrobial particles are deposited (or decorated) upon the (optionally mesoporous) shell(s), and/or otherwise dispersed within pores of the (optionally mesoporous) shell(s). In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units each having a core, comprising antimicrobial particles and/or magnetic particles, which is encapsulated within a (optionally mesoporous) shell of porous solid-phase matrix material, wherein the (optionally mesoporous) shell is either decorated with antimicrobial particles and/or magnetic particles and/or otherwise comprises antimicrobial particles and/or magnetic particles within pores of the (optionally mesoporous) shell.

[0096] In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units each having a core, comprising magnetic particles, which is encapsulated within a (optionally mesoporous) shell of porous solid-phase matrix material, wherein the (optionally mesoporous) shell is either decorated with antimicrobial particles and/or otherwise comprises antimicrobial particles within pores of the (optionally mesoporous) shell. In such embodiments, antimicrobial particles may be absent from the core(s), and magnetic particles may be absent outside said core(s). Suitably one or more outer shells surround the shell decorated with antimicrobial particles and/or otherwise comprising said antimicrobial particles within its pores.

[0097] In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units each having a core, comprising magnetic particles, encapsulated within a (optionally mesoporous) inner shell layer of porous solid-phase matrix material, wherein the inner shell layer is decorated with antimicrobial particles, and the decorated inner shell layer is further encapsulated by one or more outer shell layers, most suitably two outer shell layers. In such embodiments, antimicrobial particles may be absent from the core(s), and magnetic particles may be absent outside said core(s).

[0098] The antimicrobial nanocomposite may suitably comprise a surfactant, suitably a cationic surfactant (e.g. CTAB) embedded within or decorated upon one or more (optionally mesoporous) shell layers. Most suitably any such surfactant is embedded within or decorated upon the outermost of any (optionally mesoporous) shell layers of a core-shell unit. Such a surfactant may behavior as a template allowing the formation of micelles to produce mesopores.

[0099] In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units (suitably microspheres) comprising a core and multiple shell layers, the core-shell units suitably including: - a core comprising magnetic particles;

- an inner shell layer comprising or consisting of porous solid-phase matrix material;

- antimicrobial particles decorated upon the outer surface of, and/or within, the inner shell layer;

- a first outer shell layer comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant);

- and optionally a second outer shell layer (suitably the outermost shell layer) comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

[00100] In a particular embodiment, the antimicrobial nanocomposite comprises core-shell units (suitably microspheres) comprising a core and multiple shell layers, the core-shell units suitably including:

- a core comprising antimicrobial particles and also magnetic particles; - an inner shell layer comprising or consisting of porous solid-phase matrix material;

- optionally antimicrobial particles decorated upon the outer surface of, and/or within, the inner shell layer;

- and optionally a second outer shell layer (suitably the outermost shell layer) comprising or consisting of porous solid-phase matrix material embedded with or decorated with a surfactant.

[00101 ] The core-shell units are suitably microspheres, and are suitably particles having a particle size between 0.2 and 2μηι, suitably between 0.3 and 1 μηι, suitably about 400μηι. Suitably, the average particle size of the core-shell units is between 0.2 and 2μηι, suitably between 0.3 and 1 μηι, suitably about 400μηι.

[00102] Suitably, the core-shell unit have pores sizes between 1 and 600 nm, suitably between 2 and 150 nm, suitably 2 to 8 nm. Suitably, the average pore size of the core-shell units is between 1 and 600 nm, suitably between 2 and 150 nm, suitably 2 to 8 nm.

[00103] Suitably, the incorporation of the antimicrobial metal compounds can be verified by X- ray fluorescence (XRF).

[00104] In an embodiment, the hierarchically-ordered antimicrobial nanocomposite (100 wt%) has a composition defined by: - 30-90 wt% a porous solid-phase matrix material;

- 5-30 wt% antimicrobial particles; and

- 2-40 wt% magnetic particles.

[00105] In an embodiment, the hierarchically-ordered antimicrobial nanocomposite (100 wt%) has a composition defined by: - 70-85 wt% a porous solid-phase matrix material;

15-20 wt% antimicrobial particles; and 10-30 wt% magnetic particles.

[00106] The antimicrobial nanocomposite may comprise silica-coated magnetic particles.

[00107] In accordance with a further aspect of the invention, there is provided a nanocomposite that is antimicrobial and/or capable of chemically degradomg toxic pollutants. The

nanocomposite is optionally non-antimicrobial but otherwise comprises all of the features of the herein-described antimicrobial nanocomposites with an embedded particle structure (i.e. core- shell structures).

Porous solid-phase matrix material [00108] The porous solid-phase matrix material is suitably a material with a porous structure through which any relevant "fluid in need of disinfection and/or sterilization" (e.g. water) can permeate. Suitably the porous solid-phase matrix material comprises pores, suitably interconnected pores. Suitably such a porous structure is also permeable to any relevant microbes, for instance, that may be suspended within a relevant "fluid in need of disinfection and/or sterilization" (e.g. water).

[00109] The porous solid-phase matrix material may be microporous, mesoporous, and/or hierarchically-ordered as described herein.

[00110] The porous solid-phase matrix material may have a specific surface area at least 200m²/g, suitably at least 260m²/g, suitably at least 300m²/g, suitably at least 500m²/g. m²/g. Suitably, the porous solid-phase matrix material (or the particles thereof) have pores sized between 1 to 600nm 10 and 300 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm. Suitably, the average pore size of the antimicrobial nanocomposite (or nanocomposite particles thereof) is between 10 and 300 nm, suitably between 20 and 200nm, suitably between 50 and 150 nm. [00111 ] The porous solid-phase matrix material may suitably comprise silica (Si0₂), silicates, zeolites, aluminates, aluminosilicates, or clays.

[00112] In a particular embodiment, the porous solid-phase matrix material is or comprises silica (whether doped or not). In an embodiment, the silica has a hierarchically-ordered structure, optionally as defined anywhere herein. Hierarchically-ordered porous silica, and its process of preparation, is described in the Example section and also in the literature (T. Sen^*, J. L. Casci, G. J. T. Tiddy and M. W. Anderson, "Synthesis and Characterisation of Novel Hierarchically Ordered Porous Silica Materials" Chemistry of Materials 16, 2044 (2004)). In another embodiment, the silica is in the form of a layered shell structure, for instance, with a porous silica shell layer around a core of antimicrobial particles and/or magnetic particles (most suitably around magnetic particles). A porous silica layered shell structure, and its process of preparation, is described in the Example section and also in the literature (T. Sen^*, A. Sebastanali, I. J. Bruce "Novel Mesoporous Silica-magnetite: Fabrication and Applications in Magnetic Bio-separations" Journal of the American Chemical Society 128, 7130 (2006)).

[00113] The porous solid-phase matrix material suitably constitute between 30 and 90 wt% of the total antimicrobial nanocomposite, suitably between 70 and 85 wt% thereof.

[00114] The porous solid-phase matrix material is preferably non-antimicrobial, suitably at least less antimicrobial than the antimicrobial particles. [00115] The porous solid-phase matrix material is preferably non-magnetic, suitably at least less magnetic than the antimicrobial particles.

Antimicrobial particles

[00116] The antimicrobial particles are particles which exhibit antimicrobial activity, and which comprise, consist essentially of, or consist of a metallic antimicrobial agent. The metallic antimicrobial agent is itself antimicrobial, and comprises an antimicrobially-active metal species. The metallic antimicrobial agent may be an antimicrobial metal compound (e.g. metal salt), an antimicrobial metal complex, or even an antimicrobial elemental metal (i.e. metal(O)). As such, the "active metal species" may be metal ions, the combination metal ions with counterions or ligands, or elemental metal species.

[00117] Antimicrobial activity may be assessed by standard methods well known in the art, by methods defined in the Examples herein, or by reference to the surface antimicrobial activity exhibited by the metal in question (i.e. the "active metal species" within the antimicrobial particles).

[00118] The antimicrobial particles may suitably consist essentially of, or consist of the metallic antimicrobial agent. Alternatively, the antimicrobial particles may be a composite in their own right, and may comprise one or more metallic antimicrobial agents, and may additionally comprise an additional component. In some embodiments, the antimicrobial particles may be.g. an alloy, and thus the metallic antimicrobial agent may be a component part thereof.

[00119] Suitably the antimicrobial particles (and/or a surface of the metallic antimicrobial agent or active species thereof) exhibit greater antimicrobial activity than a particular comparative surface (e.g. silica, iron, Cobalt etc.) - i.e. where antimicrobial activity is defined as a relative property.

[00120] Though the metallic antimicrobial agent in question may suitably exhibit general antimicrobial activity against a range of microbial organisms (e.g. water-born micro-organisms such as E.Coli, Legionella, Cholera), in some embodiments the metallic antimicrobial agent is antimicrobially active against one or more specific microbes of interest. For instance, the antimicrobial particles (and/or a surface of the metallic antimicrobial agent or active species thereof) may suitably exhibit antimicrobial activity towards one or more particular types of microbe present, or suspected of being present, in a medium (e.g. a fluid, a solid surface, an atmosphere) to be treated. For instance, a medium to be treated may be known to be or suspected of being contaminated with one or more particular microbes (e.g. E. coll, methicillin- resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi), and therefore the antimicrobial particles (and/or a surface of the metallic antimicrobial agent or active species thereof) suitably exhibit antimicrobial activity against said microbe(s). In a particular embodiment, the antimicrobial particles (and/or a surface of the metallic antimicrobial agent or active species thereof) are sufficiently antimicrobial to destroy (suitably when in contact therewith) one or more of E. coli, methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus, Clostridium difficile, influenza A virus, adenovirus, and fungi.

[00121 ] The antimicrobial particles (and/or a surface of the metallic antimicrobial agent or active species thereof) suitably exhibit greater antimicrobial activity than the magnetic particles, suitably whether or not in the presence of a magnetic field.

[00122] Suitably the antimicrobial particles are non-magnetic. Suitably the antimicrobial particles are non-magnetic in a spontaneous sense.

[00123] The metallic antimicrobial agent comprises an antimicrobial metal species (whether ionic or neutral), which is suitably the antimicrobially-active metal species. Suitably the metallic antimicrobial agent comprises an antimicrobial transition metal species, suitably an antimicrobial d-block metal species. Most suitably, the metallic antimicrobial agent comprises an

antimicrobial Group 1 1 metal species (i.e. as defined by the International Union of Pure and Applied Chemistry (lUPAC) system), suitably a copper, silver, or gold species. In a particular embodiment, the metallic antimicrobial agent comprises a copper or silver species. In a particular embodiment, the metallic antimicrobial agent comprises a copper species. In a particular embodiment, the metallic antimicrobial agent comprises a silver species.

[00124] In a particular embodiment, the metallic antimicrobial agent is or comprises an antimicrobial metal compound, for instance, a metal oxide (e.g. a silver oxide or copper oxide, most suitably silver oxide - e.g. Ag₂0). In an embodiment, the metallic antimicrobial agent is or comprises an antimicrobial elemental metal (i.e. metal(O)), for instance, silver (0) or copper (0), most suitably silver (0). In an embodiment, the metallic antimicrobial agent may include a combination of metal compounds and/or elemental metals, wherein at least one is antimicrobial, and suitably all are antimicrobial. For example, the antimicrobial particles may comprise silver(O) and Ag₂0.

[00125] In a particular embodiment, the metallic antimicrobial agent is silver(O), a silver compound (e.g. silver oxide, e.g. Ag₂0), or a mixture thereof. In a particular embodiment, the metallic antimicrobial agent is silver(O). In a particular embodiment, the metallic antimicrobial agent is a silver compound, suitably a silver oxide, suitably Ag₂0. [00126] In a particular embodiment, the active metal species of the antimicrobial particles are copper or silver species, suitably copper (0) or silver (0).

[00127] In a particular embodiment, the active metal species of the antimicrobial particles is copper (0). As such, the antimicrobial particles may be copper or an alloy thereof (e.g. brass, bronze, cupronickel, copper-nickel-zinc).

[00128] In a preferred embodiment, the active metal species of the antimicrobial particles is silver (0). As such, the antimicrobial particles may be, consist essentially of, or even consist of, silver (0). [00129] The antimicrobial particles suitably comprise particles with a particle size between 1 and 200nm, suitably between 2 and 100 nm, most suitably between 5 and 50 nm. The antimicrobial particles suitably have an average particle size between 1 and 200nm, suitably between 2 and 100 nm, most suitably between 5 and 50 nm. The antimicrobial particles are suitably nanoparticles. [00130] In preferred embodiments, the antimicrobial particles are antimicrobial nanoparticles comprising or consisting of a silver-containing and/or copper-containing antimicrobial agent (e.g. see above). In a preferred embodiment, the antimicrobial particles are nanoparticles of silver (0) and/or a silver compound (e.g. Ag₂0).

[00131 ] The antimicrobial particles suitably constitute between 5-30 wt% of the total antimicrobial nanocomposite, suitably between 15 and 20 wt% thereof.

Magnetic particles

[00132] The magnetic particles comprise a magnetic substance. The magnetic substance may be any suitable magnetic substance. Suitably the magnetic particles are paramagnetic, ferromagnetic, ferrimagnetic, or superparamagnetic. Most suitably the magnetic substance is superparamagnetic or in a superparamagnetic form. Such magnetic properties can be readily ascertained by techniques well known to those skilled in the art.

[00133] The magnetic substance may be or comprise a magnetic metal compound or a magnetic element metal. Thus, the magnetically-active species may be ionic or neutral, depending on the circumstances.

[00134] The magnetic particles suitably comprise, consist essentially of, or consist of a magnetic d-block metal compound. The magnetic particles suitably comprise, consist essentially of, or consist of a magnetic d-block metal oxide(s). The magnetic particles suitably comprise, consist essentially of, or consist of an iron compound, suitably an iron oxide or composition of iron oxides. In a particular embodiment the magnetic particles comprise, consist essentially of, or consist of Fe₃0₄ (e.g. magnetite). In a particular embodiment, the magnetic particles consist essentially of Fe₃0₄ (e.g. magnetite). As such, in a preferred embodiment, the magnetic particles are Fe₃0₄ (e.g. magnetite) particles.

[00135] The magnetic particles suitably comprise particles with a particle size between 1 and 350 nm, suitably between 5 and 250 nm, most suitably between 10 and 200nm. The magnetic particles suitably have an average particle size between 1 and 350 nm, suitably between 5 and 250 nm, most suitably between 10 and 200nm. In a preferred embodiment, the magnetic particles are nanoparticles, suitably superparamagnetic nanoparticles.

[00136] In a preferred embodiment, the magnetic particles are Fe₃0₄ (e.g. magnetite) nanoparticles.

[00137] The magnetic particles suitably constitute between 2-40 wt% of the total antimicrobial nanocomposite, suitably between 10-30 wt% thereof.

Optional Additional Components

[00138] The antimicrobial nanocomposite may suitably comprise one or more additional components. Such additional components may impart their own functional effect, or may be residues (suitably inert residues) from the antimicrobial nanocomposite formation process. [00139] The antimicrobial nanocomposite may further comprise a photocatalyst. Such a photocatalyst may enhance and/or trigger antimicrobial activity of the antimicrobial

nanocomposite, for instance, when the antimicrobial composite is exposed to electromagnetic radiation of the appropriate wavelength (e.g. visible light is preferred if plausible). Such a photocatalyst may enhance and/or trigger chemical degradation of toxic pollutants, for instance, when the antimicrobial composite is exposed to electromagnetic radiation of the appropriate wavelength (e.g. visible light is preferred if plausible). In some embodiments, the antimicrobial particles and/or magnetic particles may themselves be photocatalytic.

[00140] The antimicrobial nanocomposite may further comprise a surfactant. One or more of the one or more surfactants may suitably assist in the fruitful contact of any chemical or microbial species with the antimicrobial nanocomposite. The antimicrobial nanocomposite may suitably comprise one or more surfactants. Suitably surfactants may include cationic

surfactants (e.g. cetyltrimethylammonium bromide, CTAB) or non-ionic surfactants (e.g.

comprising polyoxyethylene and/or polyoxypropylene polymeric blocks - e.g. Pluronic F127). Such a surfactant may be present as a result of the process of forming the antimicrobial nanocomposite - e.g. non-ionic surfactants (e.g. Pluronic F127) may be employed during a template-based formation of hierarchically-ordered structures. Alternatively, a surfactant may be introduced deliberately to achieve a desired functional effect (e.g. as if CTAB is used).

Specific Embodiments and Nanocomposite Structures

[00141 ] In a particular embodiment: the porous solid-phase matrix material is a hierarchically-ordered porous silica-based material (suitably Si0₂) ; the antimicrobial particles are silver-containing nanoparticles (i.e. of silver (0) and/or a silver compound - e.g. Ag₂0); and the magnetic particles are superparamagnetic Fe₃0₄ nanoparticles.

[00142] Suitably, the silver-containing nanoparticles and the superparamagnetic Fe₃0₄ nanoparticles are dispersed within the hierarchically-ordered porous silica-based material, with both the silver-containing nanoparticles and the superparamagnetic Fe₃0₄ nanoparticles residing in the walls of the pores of the porous silica-based material. The antimicrobial nanocomposite may further comprise one or more of a reducing agent or derivative thereof (used to reduce a precursor of the silver-containing nanoparticles), a surfactant (e.g. mono-, di-, or tri-block co-polymer comprising polyoxyethylene and/or polyoxypropylene blocks (e.g. Pluronic F₁₂₇)), a further polymeric material and/or dispersing agent (e.g. PVP and/or PVA), and a latex or colloidal template material (e.g. polystyrene latex), most suitably only in trace quantities (e.g. collectively suitably less than or equal to 5 wt% of the overall antimicrobial nanocomposite, suitably less than or equal to 2 wt%, suitably less than or equal to 1 wt%). [00143] In another particular embodiment, the antimicrobial nanocomposite comprises core- shell unit particles, each having a core, an inner shell layer, and one or more outer shell layers, wherein: the core comprises superparamagnetic Fe₃0₄ nanoparticles, as the magnetic particles; and the inner shell layer comprises a porous silica-based material; and the one or more outer shell layers comprise a porous silica-based material, wherein one of the outer shell layers optionally comprises a surfactant; the antimicrobial particles are silver-containing nanoparticles (i.e. of silver (0) and/or a silver compound - e.g. Ag₂0), which are located either within the core, deposited (or decorated) upon the inner and/or outer shell(s), and/or otherwise dispersed within pores of the porous silica-based material of the inner and/or outer shell(s).

[00144] Suitably, the porous silica-based material of the inner and outer shells is mesoporous. Suitably, the silver-containing nanoparticles are deposited (or decorated) between the inner shell layer and an outer shell layer directly adjacent to the inner shell layer. Suitably, the outermost of the one or more outer shell layers comprises a surfactant dispersed within the porous silica-based material thereof, most suitably a cationic surfactant (e.g. CTAB).

[00145] In an embodiment, the antimicrobial nanocomposite may comprise a mixture of nanocomposites exhibiting a dispersed particle structure as defined herein and nanocomposites exhibiting the embedded particle structure as defined herein (i.e. core-shell units). In other embodiments, the antimicrobial nanocomposites are either one form or the other.

[00146] It is straightforward to determine the structure of the antimicrobial nanocomposites of the invention by analytical techniques well known in the art, and described further in the examples.

Process of Preparing Antimicrobial Nanocomposites

[00147] The present invention provides a process of preparing an antimicrobial nanocomposite, the process comprising forming a porous solid-phase matrix material with antimicrobial particles and magnetic particles dispersed and/or embedded therein. The antimicronial nanocomposite, porous solid-phase matrix material, antimicrobial particles, magnetic particles, and any other relevant components may be as defined anywhere herein. [00148] Suitably, the antimicrobial particles are formed in situ in the presence of the porous solid-phase matrix material and/or its precursor.

[00149] Suitably, the antimicrobial particles are formed in situ during the formation of the antimicrobial nanocomposite (i.e. whilst in contact with other components, e.g. porous solid- phase matrix material, or precursors thereof). For instance, the antimicrobial particles may be formed from a precursor dispersed within or deposited upon the porous solid-phase matrix material.

[00150] In an embodiment, preparing the antimicrobial nanocomposite comprises forming a porous solid-phase matrix material with antimicrobial particles and magnetic particles dispersed therein (i.e. a dispersed particle structure as defined herein). As such, the process may comprise dispersing the antimicrobial particles and magnetic particles (and/or precursors thereof) within the porous solid-phase matrix material (and/or precursors thereof) and suitably forming a hierarchically-ordered porous solid-phase matrix material around the antimicrobial particles and magnetic particles. Suitably formation of the hierarchically-ordered porous solid- phase matrix material takes place simultaneously with the formation of either or both of the antimicrobial particles and magnetic particles (which may themselves suitably be formed from precursor materials).

[00151 ] In an embodiment, preparing the antimicrobial nanocomposite comprises forming a porous solid-phase matrix material with antimicrobial particles and magnetic particles embedded therein (i.e. an embedded particle structure, as per the core-shell units defined herein). As such, the process may comprise coating the antimicrobial particles and/or magnetic particles with the porous solid-phase matrix material, suitably as a series of core-shell layers.

[00152] In an embodiment, preparing the antimicrobial nanocomposite may comprise mixing nanocomposites formed in accordance with the dispersed particle structure with nanocomposites form in accordance with the embedded particle structure. Formation of Dispersed Particle Structure - Hierarchically Ordered Methodology

[00153] The process for preparing the antimicrobial nanocomposite suitably comprises template-based formation of the porous solid-phase matrix material around the antimicrobial particles and magnetic particles. Suitably the antimicrobial particles and magnetic particles form in situ either as the porous solid-phase matrix material is formed around them or within the porous solid-phase matrix material after it is formed around the precursors of the antimicrobial particles and magnetic particles.

[00154] Suitably, such template-based formation employs a template, such as a latex or colloidal template (which may optionally be used in the form of a monolith, e.g. a packed solid material). Such a packed monolith suitably has small channels and/or pores within which a hierarchically ordered porous matrix material may be formed. In a particular embodiment, a polystyrene latex template is used, suitably in the form of a packed monolith of polystyrene particles. Suitably the porous solid-phase matrix material, antimicrobial particles, magnetic particles, and/or precursors thereof, are contacted with or otherwise introduced to the template (i.e. into crevices and/or channels therein) and a hierarchically-ordered structure is formed in situ before the template is then removed.

[00155] The process of preparing the antimicrobial nanocomposite may suitably comprise: i) providing: a) a mobile precursor (e.g. liquid, slurry, or gel) comprising the porous solid- phase matrix material or precursor thereof (e.g. TEOS for silica); b) a mobile precursor comprising the antimicrobial particles or a precursor thereof; and c) a mobile precursor comprising the magnetic particles or a precursor thereof; wherein any combination of a), b), and/or c) are optionally provided together as a single combined mobile precursor; ii) providing a solid template include crevices and/or channels; iii) introducing the mobile precursor(s) into the crevices and/or channels of the template to provide a filled template; iv) facilitating or allowing solidification of the mobile precursor(s) within the crevices and/or channels of the filled template; v) removing the template to leave a hierarchically ordered antimicrobial nanocomposite.

[00156] Suitably any, some or all, of the mobile precursors comprise water as a mobilizing solvent.

[00157] The mobile precursor comprising the porous solid-phase matrix material or precursor thereof suitably comprises or is otherwise formed from the precursor thereof (i.e. a precursor capable of being transformed into a porous solid phase matrix material), and optionally comprises a surfactant, for instance, a non-ionic surfactant, such as a mono-, di-, or tri-block copolymer comprising polyoxyethylene and/or polyoxypropylene blocks (e.g. Pluronic F₁₂₇). The mobile precursor comprising the precursor of the porous solid-phase matrix material is suitably a sol-gel, suitably a sol-gel capable of forming a porous silica matrix material. Suitably such a sol-gel comprises tetraethyl orthosilicate (TEOS) or another precursor material capable of being hydrolysed (especially acid-hydrolysed) to form silica. Suitably the sol-gel additionally comprises an acid, for instance, hydrochloric acid.

[00158] The mobile precursor comprising the antimicrobial particles or a precursor thereof, suitably comprises or is otherwise formed from the precursor thereof. The precursor thereof is suitably a water-soluble antimicrobial metal compound, preferably a silver compound, for instance, silver nitrate (AgN0₃). The mobile precursor comprising the precursor of the antimicrobial particles suitably comprises a reducing agent, suitably a water-soluble reducing agent (e.g. sodium borahydride), capable of reducing precursor of the antimicrobial particles (e.g. silver compound) into a reduced form thereof (e.g. silver(O)). The mobile precursor comprising the precursor of the antimicrobial particles suitably comprises a film-forming compound (e.g. polyvinyl alcohol, PVA, and/or polyvinylpyrrolidone, PVP). The mobile precursor comprising the antimicrobial particles or a precursor thereof, may be provided so as to comprise the antimicrobial particles, for instance, following formation of such particles upon contact of the precursor with a reducing agent. This may, for instance, be the case where silver nitrate is contacted with sodium borohydride under appropriate conditions. However, the mobile precursor may be provided with the antimicrobial particles as yet (substantially) unformed.

[00159] The mobile precursor comprising the magnetic particles or a precursor thereof suitably comprises or is otherwise formed from the precursor thereof. The precursor thereof is suitably a water-soluble magnetic metal compound, preferably an iron compound, for instance, an iron chloride (FeCI₂ and/or FeCI₃).

[00160] Suitably, the mobile precursor comprising the antimicrobial particles or a precursor thereof, and mobile precursor comprising the magnetic particles or a precursor thereof, are provided in combination as a single combined mobile precursor of both. Moreover, all mobile precursors a) to c) are suitably provided in combination as a single combined mobile precursor, though optionally mobile precursor a) is initially prepared separately.

[00161 ] The solid template suitably comprises pre-fabricated template particles of an organic polymeric material, suitably particles of a plastics material, suitably particles of polystyrene. Suitably the solid template comprises a packed monolith of said pre-fabricated template particles, suitably packed under pressure, suitably to provide crevices and/or channels therebetween. The particles are suitably sized between 50 and 1000 nm. In a particular embodiment the solid template is a packed monolith of pre-fabricated polystyrene particles. The monolith may be suitably packed via centriguation and optionally drying thereafter. [00162] Introducing the mobile precursor(s) into the crevices and/or channels of the template suitably involves passing the mobile precursor(s) through a packed monolith as described above, optionally repeatedly, to provide a filled template. Such passage of the mobile precursor(s) through the packed monolith may be facilitated through vacuum suction or pressure. The mobile precursor(s) may be passed through the monolith either sequentially, simultaneously, in any combination, or as a combined single mobile precursor. Suitably passing the mobile precursor(s) through the packed monolith proceeds until the crevices and/or channels therein are considered to be substantially saturated with mobile precursor(s) (i.e.

hence the term, filled template).

[00163] The filled template may then be optionally separated from any excess mobile precursor(s).

[00164] Solidification of the mobile precursor(s) within the crevices and/or channels of the filled template is then allowed to ensue, or otherwise facilitated/accelerated (e.g. through heating, drying, and/or calcination). Preferably, the filled template is at least dried (e.g. oven dried at 50°C for 24 hrs, or an equivalent drying cycle). The filled template may be subjected to calcination (e.g. heating at a temperature of over 400°C, suitably over 450°C, suitably over 500°C, suitably over 550°C). Such calcination may facilitate solidification, or it may be otherwise performed after solidification or partial solidification to remove the template.

[00165] After solidification, the template is suitably removed. This may suitably be effected via calcination of the filled template (post-, pre-, or during solidification). Calcination suitably involves heating the filled template at a temperature of at least 400°C, suitably at least 450°C, suitably at least 500°C, suitably at least 550°C, suitably for a time sufficient to remove the template (suitably at least 90% thereof, more suitably at least 95% thereof), suitably at least 1 hour, suitably for at least 5 hours. Calcination may ensue following a gradated increase in temperature over time. Such calcinations suitably remove the template, and suitably removes all organic components. Traces of template and/.or other organic components (e.g. surfactants, film-formers, etc.) may be left behind. Calcination suitably yields a hierarchically ordered antimicrobial nanocomposite.

Formation of Embedded Particle Structure - Core-Shell Unit Methodology

[00166] The process for preparing the antimicrobial nanocomposite suitably comprises forming core-shell units, each having a core (suitably comprising antimicrobial particles and/or magnetic particles) encapsulated within at least one (optionally mesoporous) shell of porous solid-phase matrix material. The (optionally mesoporous) shell forming a shell layer adjacent to the core may constitute an inner shell layer, whilst the core-shell units may comprise one or more further outer shell layers (e.g. one inner shell and two outer shells). Such outer shell layers suitably comprise a porous solid-phase matrix material, which suitably comprises the same porous solid- phase matrix material as any inner shell layer. Moreover, such outer shell layers are suitably mesoporous (especially where the inner shell layers are mesoporous). The core and successive shell layer(s) are suitably formed sequentially, layer by layer. Antimicrobial particles and/or magnetic particles may also be deposited/decorated within or upon any of the shell layer(s).

[00167] Suitably, the process for preparing the antimicrobial nanocomposite comprises: i) Forming a core comprising either or both magnetic particles and/or antimicrobial particles; ii) Coating the core with an inner shell layer comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant); iii) Optionally decorating the inner shell layer with, or depositing therein, either or both antimicrobial particles and/or magnetic particles; iv) Optionally coating the inner shell layer (whether or not deposited/decorated with magnetic and/or antimicrobial particles) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

[00168] In step i), formation of the core may involve providing either or both magnetic particles and/or antimicrobial particles, optionally as a mixture thereof. Such particles may be formed through precipitation of the relevant particles from solution, and subsequent extraction of the solid particles (e.g. via filtration, centrifugation, or evaporation of solvents). In a particular embodiment, step i) involves providing a core or magnetic particles (i.e. without antimicrobial particles). Suitably the magnetic particles are as defined herein, most suitably magnetite nanoparticles.

[00169] In step ii), coating of the core suitably involves contacting the particles obtained from step i), most suitably magnetic particles only, with a porous solid phase matrix material or precursor thereof (e.g. as defined above in relation to the hierarchically ordered process - e.g. a sol-gel, suitably comprising TEOS where the porous shell layers are intended to be porous silica) and causing an inner shell layer of porous solid phase matrix material to form around the particles obtained from step i). Suitably this may involve dispersing the particles (suitably magnetite nanoparticles) from step i) in a suitable solvent (e.g. ethanol or water), and treating the dispersion with a mobile precursor (e.g. liquid, slurry, or gel) comprising the porous solid- phase matrix material or precursor thereof (e.g. TEOS for silica). Such a mobile precursor suitably comprises water as a solvent and optionally a base. The mobile precursor may also optionally comprise a surfactant, such as a cationic surfactant (e.g. CTAB), such that the surfactant remains embedded within the inner shell layer around the core.

[00170] Where the process comprises step iii) (e.g. where the core comprises only one of either magnetic particles or antimicrobial particles), the core-shell units from step ii) are suitably contacted with antimicrobial particles, magnetic particles, or precursors thereof to either decorate the outer surface of the inner shell layer with the relevant particles or otherwise impregnate the inner shell layer with said particles. Suitably, whichever particles are not present within the core are deposited/decorated upon/within the inner shell layer. As such, step iii) may suitably comprise decorating the outer surface of the inner shell layer with antimicrobial particles. Such decoration may be performed by contacting the core-shell units obtained from step ii) with a mobile precursor comprising the antimicrobial particles or a precursor thereof. Such a mobile precursor may be as defined above in relation to the hierarchically ordered structures. The mobile precursor comprising the antimicrobial particles or a precursor thereof may suitably comprise or be formed from the precursor thereof. . The precursor thereof is suitably a water-soluble antimicrobial metal compound, preferably a silver compound, for instance, silver nitrate (AgN0₃). The mobile precursor comprising the precursor of the antimicrobial particles suitably comprises a reducing agent, suitably a water-soluble reducing agent (e.g. sodium borahydride), capable of reducing precursor of the antimicrobial particles (e.g. silver compound) into a reduced form thereof (e.g. silver(O)). The resulting decorated particles are suitably collected (e.g. with a magnet), and optionally further washed. [00171 ] Where the process comprises step iv) (e.g. where decorated particles are produced using step iii)), such decorated particles are suitably coated with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant). Additional outer shell layers may be suitably applied to the decorated particles in the same manner as the inner shell layer was applied to the core - i.e. by contacting the particles obtained from step ii) or step iii), most suitably decorated particles from step iii), with a porous solid phase matrix material or precursor thereof (e.g. as defined above in relation to the hierarchically ordered process - e.g. a sol-gel, suitably comprising TEOS where the porous shell layers are intended to be porous silica) and causing an outer shell layer of porous solid phase matrix material to form around the particles obtained from step ii) or iii). Suitably this may involve dispersing the particles from step ii) or iii) in a suitable solvent (e.g. ethanol or water), and treating the dispersion with a mobile precursor (e.g. liquid, slurry, or gel) comprising the porous solid-phase matrix material or precursor thereof (e.g. TEOS for silica). Such a mobile precursor suitably comprises water as a solvent and optionally a base. The mobile precursor may also optionally comprise a surfactant, such as a cationic surfactant (e.g. CTAB), such that the surfactant remains embedded within the inner shell layer around the core. Further additional outer shell layers may be added in the same manner.

[00172] In a particular embodiment, the process for preparing the antimicrobial nanocomposite comprises: i) Forming a core comprising magnetic particles (e.g. magnetite nanoparticles); ii) Coating the core of magnetic particles with an inner shell layer of porous silica (optionally embedded with or decorated with a surfactant) to form a core-shell unit, suitably by contacting the magnetic particles with a sol-gel; iii) Decorating the inner shell layer with antimicrobial particles (e.g. nanoparticles of silver (0) and/or a silver compound, e.g. Ag₂0) to produce decorated core-shell units, suitably by contacting the core-shell unit of step ii) with a precursor of the antimicrobial particles (e.g. silver nitrate); and iv) Coating the decorated core-shell units of step iii) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant), suitably by contacting the decorated core-shell units of step iii) with a sol-gel.

[00173] In another embodiment, the process for preparing the antimicrobial nanocomposite comprises: i) Forming a core comprising both antimicrobial particles and magnetic particles

(e.g. nanoparticles of silver(0)/silver compound and magnetite nanoparticles);

Coating the core with an inner shell layer of porous silica (optionally embedded with or decorated with a surfactant) to form a core-shell unit, suitably by contacting the core particles with iii) Optionally coating the core-shell units of step ii) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant), suitably by contacting the core- shell units of step iii) with a sol-gel.

Uses of Antimicrobial Nanocomposites

[00174] The antimicrobial nanocomposites of the invention may be readily used in the treatment, purification, disinfection, sterilization, and/or decontamination of a fluid in need thereof (e.g. water). The antimicrobial nanocomposites may be used in water treatments and/or water processing, be it mains/municipal water, local water supplies, bottled water, water supplies in dentists or hospitals (e.g. for post-dental mouth washings), or waste water effluent. Moreover, such water treatments and processing may be applicable in water reservoirs, desalination plants, power plants, industrial facilities, residential water supplies, commercial water supplies, catalytic treatments, chemical processing, food and beverage production, hydrometallurgy, and pharmaceutical production. In all cases, the antimicrobial

nanocomposites of the invention can improve the quality of the water, whether it be for consumption or disposal. In a particular embodiment, the methods and composites defined herein may be applied to treating water in dental water lines.

[00175] As such, the present invention provides an antimicrobial treatment apparatus for disinfecting and/or sterilising a fluid, the apparatus comprising a disinfecting zone configured to receive a fluid in need of disinfection and/or sterilization, wherein the disinfecting zone comprises the antimicrobial nanocomposite as defined herein. The disinfecting zone may comprise other materials in addition to the antimicrobial nanocomposite, including optionally existing materials used in water treatments (e.g. ion-exchange resins).

[00176] The apparatus may be a filtration device or kit (where any or all of the parts may be provided separately and/or any number of parts may be partially assembled). The filtration device may be a stand-alone device through which fluids (e.g. water) may be selectively passed or pumped (e.g. via pressure or vacuum), or alternatively it may be a device suitable for fitting in-line with pre-established fluid flow lines (e.g. pipe lines or taps) - as such the filtration device may comprise an attachment portion for fitting to a fluid flow line, wherein said attachment portion is suitably allows fluid to flow from said fluid flow line into any input ports of the filtration device. [00177] Alternatively, the apparatus may be or comprise a tube or pipe containing the antimicrobial nanocomposite. The antimicrobial nanocomposite may suitably be (substantially) fixed in position within the tube or pipe, for instance, the antimicrobial nanocomposite may be fixed to (or embedded within) the inner wall(s) of the tube or pipe. As such, bio-films may be prevented from forming within the tube or pipe. The tube or pipe may be a tube or pipe, or part of a tube or pipe, within a water-dispensing device. The water-dispensing device may be a dental water-dispensing device, and the tube or pipe may be part of dental water lines. The tube or pipe may be purpose-built to be attachable (e.g. by virtue of attachment portions at one or both ends of said tube or pipe) to separate tubes or pipes, thereby enabling its facile installation within existing fluid-flow systems. [00178] The assembled apparatus may suitably comprise a fluid input port and a fluid output port linked together via a fluid channel, wherein the fluid channel comprises along its path a disinfecting zone comprising a bed of the antimicrobial nanocomposite. Fluid may be passed or pumped through the apparatus, initially via the input port, through the fluid channel, over the bed of antimicrobial nanocomposite (where disinfection/sterilization occurs), and out of the output port for use, disposal, or recirculation within the apparatus. The fluid may be passed through the apparatus several times for increased disinfection/sterilization. The disinfecting zone may comprise cartridges of antimicrobial nanocomposite to allow for their easy

replacement.

[00179] The present invention also provides a method of disinfecting and/or sterilizing a fluid, the method comprising contacting a fluid in need of disinfection and/or sterilization with the antimicrobial nanocomposite as defined herein. Such a method may be conducted using the abovementioned apparatus or any other suitably apparatus. Alternatively, such a method, and those which follow, may be performed by mixing the antimicrobial nanocomposite with the relevant fluid, and optionally thereafter removing (e.g. via filtration and/or magnetic separation) the antimicrobial nanocomposite from contact with the fluid. For instance, rather than passing the fluid over a bed of the antimicrobial nanocomposite, the antimicrobial nanocomposite may be mixed with the fluid and the mixture thereafter optionally agitated before then optionally removing the nanocomposite therefrom. The method may therefore involve immersing the antimicrobial nanocomposite within water (e.g. a reservoir) rather than passing water over the antimicrobial nanocomposite.

[00180] In some embodiments, the antimicrobial nanocomposite may be exposed to a magnetic field during fluid/water treatments/processing in order to bolster the efficacy of the treatments. In particular, such magnetic fields may facilitate chemical decontamination. Moreover, such magnetic fields may facilitate the treatment of chemicals yielded from the antimicrobial action of the antimicrobial nanocomposites. In many embodiments, the antimicrobial nanocomposites of the invention perform simultaneous chemical and microbial decontamination, whether in the presence of or absence of a magnetic field.

[00181 ] In some embodiment, especially where the antimicrobial nanocomposite comprises a photocatalyst, the antimicrobial nanocomposite may be exposed to electromagnetic radiation (suitably visible light or ultraviolet light, most suitably visible) during fluid/water

treatments/processing in order to boost the efficacy of the treatments. Such photocatalytic treatments may, in particular, facilitate chemical decontamination, but also potential microbial decontamination. [00182] The present invention provides a method of inhibiting growth of or destroying one or more microbes in/on a medium (e.g. a fluid, a solid surface, an atmosphere) comprising or suspected of comprising said one or more microbes, comprising contacting the medium with the antimicrobial nanocomposite as defined herein. As such, the nanocomposites may be incorporated into a surface that is required to be clean of microbes. Thus, the present invention further provides a substrate or surface comprising or incorporating the antimicrobial nanocomposite as defined herein.

[00183] The present invention also provides a method of decontaminating, reducing contamination of, and/or inhibiting contamination of a medium (e.g. a fluid, a solid surface, atmosphere), comprising contacting the medium with the antimicrobial nanocomposite as defined herein.

[00184] The present invention further provides a disinfected and/or sterilized fluid obtainable by, obtained by, or directly obtained by the method of disinfecting and/or sterilizing defined herein. [00185] The present invention provides a treated medium obtainable by, obtained by, or directly obtained by the method of inhibiting growth of one or more microbes in/on a medium as defined herein or the method of decontaminating, reducing contamination of, and/or inhibiting

contamination of a medium as defined herein.

Recovering Used Antimicrobial Nanocomposites

[00186] The present invention further provides a method of recovering an antimicrobial nanocomposite from a fluid and/or medium treated in accordance with any of the methods defined herein, comprising filtering off and/or applying a magnetic field to the used antimicrobial nanocomposite. A unique feature of the antimicrobial nanocomposites is that the antimicrobial agent is essentially magnetized by proxy so as to be magnetically recoverable.

EXAMPLES

[00187] The invention will now be further described by way of the following further, non-limiting, examples.

Materials and Equipment

[00188] All chemicals used in this study were of analytical grade where percentage purity varied from 97 to 99.5. Single stranded DNA primers of specific sequences obtained from MOLBIOL, Germany.

[00189] Characterisation of product nanoparticles was conducted either as a dried solid or in suspension by: SEM (Hitachi S4800, Japan and FEI Quanta 200, USA instruments), TEM (JEOL JEM2100F instrument), XRD (Bruker D8 Advanced instrument), N₂ adsorption (Micromeritics ASAP2010), mercury porosimetry (Micromeritics, Autopore IV) and XRF instruments.

Example 1 -Hierarchically-Ordered Silica-Based Antimicrobial Nanocomposites (magnetic)

[00190] Two multi-step methods (Methods A and B) of synthesizing a superparamagnetic, antimicrobial hierarchically-ordered porous silica support are now described.

Method- A: Sol-gel, antimicrobial, and magnetic agents pre-mixed before nanocomposite formation

Step-1 :

[00191 ] The chemicals used in Step 1 were as follows:

1 . Deionised water 10mL

2. N-butanol 4.2ml_

3. 0.5M HCI (hydrochloric acid) 5ml_

4. Pluronic F127 0.5483g

5. Tetraethyl orthosilicate (TEOS) 20m L

[00192] The method used in Step 1 was as follows:

• TEOS added to a conical flask and stirred

· Water and 0.5M HCI were added and stirred into the TEOS

• Pluronic F127 and n-butanol were added in to the above mixture and left to stir for 20 minutes

Step-2

[00193] The chemicals used in Step 2 were as follows:

1 . 0.002M sodium borohydride (NaBH₄) 30ml_ 2. 0.3% polyvinylpyrrolidone (PVP) 2drops (~0.5ml_)

3. Polyvinyl alcohol (PVA): 1 .2832g

4. 0.1 M silver nitrate (AgN0₃): 2ml_

5. 1 M FeCI₂ 1 ml_

6. 2M FeCI₃ 1 ml_

7. Ammonium hydroxide (NH₄OH)

[00194] The method used in Step 2 was as follows:

• Sodium borohydride was added to a conical flask and stirred in ice bath

• Silver nitrate was then added to the solution and stirred. No colure change observed · 0.3% PVP was then added to the above solution and stirred

• The pH of the solution was then adjusted to 12.02 using ammonium hydroxide before the addition of the FeCI₂ and FeCI₃.

• The FeCI₂ and FeCI₃ solutions were then added to the above solution. The resultant solution became black in colour

· The conical flask was then removed from the ice-bath and the PVA was added and stirred with a gentle heat (approximately 50°C) until the PVA had dissolved

Step 3

[00195] The method used in Step 3 was as follows: · Final mixture from step 2 was added to the solution from step 1 . The resultant mixture stirred further for 20 minutes

Step 4

[00196] Step 4 used prefabricated polystyrene particles of various batches with monodispersed sizes (300nm, 400nm, 600nm and 800nm).

[00197] The method used in Step 4 was as follows:

[00198] Polystyrene particles were packed by centrifugation at 5000rpm for 1 hrs. A white solid was settled at the bottom of the centrifuge tube. Water was removed and then the white solid was dried overnight at 60°C [00199] The dried solid was placed onto a Buchner funnel set up with vacuum line. The gel solution from step 3 was then vacuum filtered by passing repeatedly through the solid polystyrene particles. The white polystyrene latex particles turned into black in colour. The filtered solid deposited on the Buchner funnel were collected and dried at 50°C for 24 hrs. The product was then collected and calcined at 560°C for 10 hrs with a heating rate of 5°C per minutes in the presence of air to remove the organics present in the composites.

Method-B: Without pre-mixing of sol-gel, antimicrobial, and magnetic agents

[00200] Method-B was the same as Method-A in that Steps 1 to 2 were identical, but different in that Step 3 of Method-A was removed. As such, Step 4 of Method-B involved:

Step 4:

[00201 ] Polystyrene particles were packed by centrifugation at 5000rpm for 1 hrs. A white solid was settled at the bottom of the centrifuge tube. Water was removed and then the white solid was dried overnight at 60°C

[00202] The dried solid was placed onto a Buchner funnel set up with vacuum line. The gel solution from step 1 was then vacuum filtered by passing repeatedly through the solid polystyrene particles. The polystyrene particles were shinny in light without any change in colour. Solution from step 2 then dripped gently over the solid under vacuum filtration. The resultant solid turned to dark brown in colour. The filtered solid deposited on the Buchner funnel were collected and dried at 50°C for 24 hrs. The product was then collected and calcined at 560°C for 10 hrs with a heating rate of 5°C per minutes in the presence of air to remove the organics present in the composites.

Characterisation of Hierarchically-Ordered Antimicrobial Silica-based Nanocomposites of Methods-A and B

[00203] Materials from both methods exhibited strong magnetic response. The materials were characterised further using TEM, SEM, FT-IR and EDAX. [00204] FIGs. l and 2 show typical TEM images antimicrobial nanocomposites made in accordance with Methods A and B. The right-hand image in FIG. 1 shows silver nanoparticles at the bottom-right of the image, whilst the right-hand image in FIG.2 shows magnetite nanoparticles at the bottom-right thereof.

[00205] The presence of siliver nanoparticles and their chemical composition in the

nanocomposites was determined using Energy dispersive X-ray (EDX). [00206] The energy dispersive X-ray (EDX) analysis was performed to investigate the existence and distribution of elements in different nanocomposites. Measurements were carried out by moving the electron beam to different positions and examine different particles.

[00207] FIG. 3 shows the EDX spectrum of a membrane with silver nanoparticles, FIG. 4 illustrates quantitative composition data, and Table 1 (below) further indicates the amount of each element present in the nanocomposites. The data confirms the presence silver

nanoparticles in silica matrix.

Table 1. EDX data for membrane with silver nanoparticles

ESeraefii Peak Area. N» We¾ht% We £i†% Ak¾ :% Compd% Fom ata iiiiTiiasr

Area Sigma factor uxm.. ^■Ssqma of ions 171S ^* 30 1.000 1.000 38:71 2.S5 31.63 82.80 3,30

Ag L. 412. Ί22 1 70 A 1.G0G 16.01 4,18 3.41 Ag2D

O 45.28 5.11 64.96 8:.€S

Toiate ^■100.00

[00208] FIG. 5 shows a typical EDX spectrum of magnetite-containing silica matrices, whereas FIG. 6 illustrates quantitative composition data, and Table 2 (below) indicates the amount of each element present in the nanocomposites. The data confirms the presence magnetite in a silica matrix.

Table 2. EDX data for magnetite containing silica

Elemen Peak Area k Abs e¾h ¾ W«¾ht%^' Atomic% Compd% ormula umber

Ar s Sigma fesstor Corns. Sigma o ions

Si 310 42 1.000 1 ,000 34.22 20 27. M 73.20 Si02 3.4?

Fs 2§5 34 1.170 1 ,000 23,03 2,7 S.4? 26 O F«0 1.06

O 44.95 4,28 §3,84 8.00

Totals 100,00

[00209] The final composition of the nanocomposites resulting from Method-A above are:

Si0₂ - 70 to 85% of Si0₂

Ag₂0 - 15 to 20% of Ag₂0

FeO - 10 to 30%

Example 2 -Hierarchically-Ordered Silica-Based Antimicrobial Nanocomposites (nonmagnetic) [00210] Non-magnetic analogues of the antimicrobial nanocomposites of Example 1 were prepared in order to demonstrate the antimicrobial and structural properties thereof. Though the nanocomposites themselves fall outside the scope of the claimed invention, they are illustrative of some of the advantages thereof.

Production of hierarchically-ordered porous silica dispersed with silver nanoparticles

[00211 ] The hierarchically-ordered porous silica non-magnetic antimicrobial nanocomposite was prepared as follows: a) Polystyrene latex template: Polystyrene particles were packed by centrifugation at 5000rpm for 1 hrs. A white solid was settled at the bottom of the centrifuge tube. Water was removed and then the white solid was dried overnight at 60°C. b) Preparation of silica gel containing silver sol: 20ml_ of Tetraethyl orthosilicate was added to a solution containing 0.542g of Pluronic F₁₂₇, 10ml_ of deionised H₂0, 4.2ml_ of n- butanol, 5ml_ of 0.5M HCI (5ml, 0.1 M). Then 30ml_ sodium borohydride (0.002M), 2ml_ silver nitrate solution of variable concentrations (0.001 M to 0.05M) and 0.3% PVP of 2drops, 1 .263 g of PVA were added to the 1 ^st solution. c) The gel from step b was passed through polystyrene monolith (4.1 1 g) synthesised from step a. Then dried overnight at 60°C. d) The dried material was then calcined in air at 500°C at a heating rate of 1 °C min^"1 and labelled as MHAg01 to MHAg03/calcined. e) The presence of silver in the nanocomposites was determined by X-ray fluorescence (XRF).

Characterisation of Structural Properties of the Antimicrobial Nanocomposite of Example 2

[00212] Table 3 presents the hierarchically-ordered porous silica with various silver concentration and their characteristic properties (surface area and pore sizes). Table 3 Characteristic of silver nanoparticles and silver nanoparticles embedded hierarchically ordered porous silica

[00213] Materials exhibited high surface area with large macropore volume of up to 94%. FIG. 7 presents the electron microscope images of silver nanoparticles embedded hierarchically ordered porous silica. The SEM image (FIG. 7a) clearly exhibit the macropore structure with interconnecting windows whereas TEM image exhibit dark spots perhaps due to the presence of silver nanoparticles.

[00214] Figure 7 shows electron microscope images of MHAg03: (a) SEM image; and (b) TEM image.

[00215] Surface area, macropore volume and macropore size distribution have been presented in FIGs. 8a-c. The presence of hysteresis in the nitrogen adsorption isotherm (FIG.8a) is an indication of the presence of mesoporosity. The high value of cumulative intrusion value of mercury adsorption (FIG.8b) is an indication of large pore volume (-90%) with average pore diameter of 100nm due to interconnecting macroporous windows (FIG.8c).

[00216] FIGs. 8a-c shows (a) nitrogen gas adsorption data; (b) mercury intrusion data; and (c) macropore size distribution; in relation to MgAg03.

[00217] The presence of silver in the nanocomposites has also been verified by X-ray fluorescence spectroscopy (XRF) (see FIG. 9). The characteristic peak at 22keV is due to the AgK_a band. [00218] FIGs. 9a/b shows XRF spectra of (a) pure silver nanoparticles; and (b) MHAg03 nanocomposite.

Antimicrobial activity of antimicrobial nanocomposites of Example 2 [00219] Escherichia co// was grown overnight in nutrient broth at 37°C. The broth culture was serially diluted to10 ⁵ in ¼ strength Ringers solution. Aliquots of the test samples were placed in Eppendorf tubes. In the case of the silver nanoparticle suspension, 0.1 mL was used and for nanocomposites 0.1 g materials were used. To the tubes containing the test samples, 1 .OmL of the bacterial suspension was introduced. The control was the bacterial suspension alone in Ringers solution.

[00220] After incubation at 37°C for 24hrs, 0.1 mL of each of the test samples was spread onto plates of nutrient agar which were, in turn, incubated at 37°C for a further 24hrs. A zone inhibition study was then conducted.

[00221 ] A culture of Escherichia coli strain W31 10 was grown overnight in nutrient broth (LabM) at 37°C. The broth was serially diluted to 10^~4 in ¼ Ringers solution (LabM). 0.1 mL of this cell suspension was used to prepare two spread plates of the test organism by incubating them at 37°C for 24 hrs. The tips of 5 plastic, sterile inoculation loops were aseptically removed with flamed scissors and placed onto the surface of the spread plate for zone inhibition.

[00222] All of the test samples produced a complete reduction of the bacterial population after incubation (see FIG. 7).

[00223] FIG.10 shows cultures of E-coli: (a) in the absence of any materials as controlled; (b) in the presence of pure silver nanoparticles; (c) in the presence of MHAgOl nanocomposite; (d) in the presence of MHAg02 nanocomposite; and (e) in the presence of MHAg03 nanocomposite.

[00224] One of each of the test samples was placed within the loops (see figure 1 1 a) in sufficient quantity to fill them. The plates were then incubated for 24hrs at 37°C. C. The control was ¼ strength sterile Ringers solution. On one plate, a detectable zone of inhibition was produced around the loop, by sample containing pure silver nanoparticles (see loop 1 in FIG. 1 1 b) whereas a reduction of colony size was observed in the area within the loop when compared with colonies outside the loop (see FIG. 1 1 c) for nanocomposites (see loops 2 to 5 in FIG. 1 1 b). These observations indicate that the silver nanoparticles are bound irreversibly to the hierarchically ordered porous silica matrix in the nanocomposites (MHAgOI to 03).

[00225] FIGs. 1 1 a-c show cultures of E-coli: (a) in the absence of any materials (control); (b) in the presence of pure silver nanoparticles; (c) in the presence of MHAgOI nanocomposite; (d) in the presence of MHAg02 nanocomposite; and (e) in the presence of MHAg03 nanocomposite.

Example 3 - Mesoporous silica-coated superparamagnetic core-shell nanocomposites

[00226] The following methods describe the synthesis of mesoporous silica-coated

superparamagnetic core-shell nanocomposites, which are antimicrobial and/or capable of chemically degradomg toxic pollutants.

(i) Production of superparamagnetic iron oxide (Fe^O materials of uniform sizes and shapes

[00227] FeCl3 6H2O (3.25g), trisodium citrate (1 .3 g), and sodium acetate (NaAc, 6.0 g) were dissolved in ethylene glycol (100 mL) under magnetic stirring. The obtained yellow solution was then transferred and sealed into a Teflon-lined stainless-steel autoclave (200 mL in capacity). The autoclave was heated at 200 °C for 10 h, and then allowed to cool down to room

temperature. The black products were washed with deionized water and ethanol for 3 times, respectively.

(ii-A) Production of silica coated superparamagnetic core-shell nanocomposites of uniform sizes and shapes (Fe304(3⁾Si02)

[00228] Core-shell Fe304@Si02 microspheres were prepared through a versatile Stober sol-gel method as follows. An ethanol dispersion of the Fe304 magnetite particles (3.0 mL, 0.05 g/mL), synthesized in step (i), was added to a three-neck round-bottom flask charged with absolute ethanol (280 mL), deionized water (70 mL) and concentrated ammonia solution (5.0 mL, 28 wt%) under ultrasound for 15 min. Afterward, 4.0 mL of TEOS was added dropwise in 10 min, and the reaction was allowed to proceed for 10 h at room temperature under continuous mechanical stirring. The resultant core-shell Fe304@Si02 microsphere products were separated and collected with a magnet, followed by washing with deionized water and ethanol for 3 times, respectively.

fii-B) Production of mesoporous silica coated superparamagnetic core-shell nanocomposites of uniform sizes and shapes (Fe304@Si02/CTAB)

[00229] Core-shell Fe304@Si02 microspheres were prepared using the same silica coating method as per step (ii-A) above, but instead in the presence of a cationic surfactant cetyl trimethyl ammonium bromide (CTAB).

[00230] 0.026 g AgN0₃ was dissolved in ethanol (150 mL) under ultrasound for 1 hr. Afterward, 1 ml of n-butylamine ethanol solution (0.01 g/mL) and 50 mL of ethanol solution containing certain amount of Fe₃0₄@Si0₂ (0.015-0.033 g) from step (ii-A) were successively added. The whole solution was allowed to react at 50°C under continuous mechanical stirring for 1 hr. The resultant product was separated and collected with a magnet, followed by washing with deionized water and ethanol for 3 times respectively.

(iv) Synthesis of (Ag/Fe^04@SiO_z)@Si0^nanocomposite

[00231 ] The (Ag/Fe₃0₄@Si0₂) product of step (iii) was dispersed into a three-neck round- bottom flask charged with absolute ethanol (280 mL), deionized water (70 mL) and

concentrated ammonia solution (5.0 mL, 28 wt%) under ultrasound for 15 min. Afterward, 4.0 mL of TEOS was added dropwise in 10 min, and the reaction was allowed to proceed for 10 h at room temperature under continuous mechanical stirring. The resultant product was separated and collected with a magnet, followed by washing with deionized water and ethanol for 3 times, respectively. (v) Synthesis of (Ag/ Fe 04@SiO?)@SiO?)mSi0^nanocomposite

[00232] The (Ag/Fe₃0₄@Si0₂)@Si0₂ product of step (iv) was dispersed into three-neck round- bottom flask charged with absolute ethanol (20 mL), deionized water (40 mL), 6 mL of CTAB solution (0.1 M, 4 mL of water and 2 mL of ethanol) and concentrated ammonia solution (1 .0-1 .5 mL, 28 wt%) under ultrasound for 15 min. Afterward, 0.4 mL of TEOS was added dropwise in 10 min, the reaction was allowed to proceed for 16 h at room temperature under continuous mechanical stirring. The resultant product was separated and collected with a magnet, followed by washing with deionized water and ethanol for 3 times, respectively.

Characterisation of Structural Properties of the Nanocomposite of Example 3

[00233] FIG.12 shows SEM micrograph images of (a) core Fe₃0₄ nanoparticles; and (b)/(c) core-shell silica coated magnetite particles. The core iron oxide nanoparticles exhibit particles of uniform sizes (~200nm) and a spherical morphology. Upon silica coating, the core-shell silica magnetite nanoparticles are uniform in size (~320nm) and spherical in morphology (FIG.1 b and c).

[00234] FIGs.13a-c show TEM micrographs of (a/b) mesoporous silica coated core-shell superparamagnetic iron oxide nanoparticles with a magnetic core and mesoporous silica shell; and (c) a low angle X-ray diffraction pattern of said particles. The characteristic low angle diffraction peaks correspond to mesoporosity of the materials. The similar materials without magnetite core has also been prepared which exhibited mesoporous structure (Fig.3) with surface area of 375m²/g.

[00235] FIG.14 shows TEM images of pure mesoporous silica nanoparticles.

[00236] Silver embedded materials are shown in FIG. 15. FIG.15 shows TEM images of products of Example 3, namely the product of step (iii)/(Ag/Fe₃0₄@Si0₂) (left); the product of step (iv)/(Ag/Fe₃0₄@Si0₂)@Si02 (middle), and the product of step (v)/(Ag/

Fe₃0₄@Si0₂)@Si0₂)mSi0₂ (right). Silver nanoparticles are nicely distributed either on the surface of the nanoparticles or embedded inside the shell structure. Chemical Degradation of toxic pollutants using the nanocomposites of Example 3

[00237] Decomposition of toxic organic pollutants (specifically Acid Orange 7 - see FIG. 16) was demonstrated using an (AgCI/Ag)/Fe₃0₄@nSi0₂ nanocomposite. The particular nanocomposite was synthesized from 50 mg Fe₃0₄@nSi0₂ and 25 mg AgN0₃, and excess FeCI₃ solution. The resulting Ag and FeCI₃ then generated a redox couple with AgCI and FeCI₂.

[00238] The (AgCI/Ag)/Fe₃0₄@nSi0₂ nanocomposite was then contacted with 40 mL of 20 mg/L A07 (acid-orange 7) solution and exposed to visible light irradiation. FIG. 16 shows the degradation profile of Acid Orange 7 using a (AgCI/Ag)/Fe₃0₄@nSi0₂ nanocomposite synthesized from 50 mg Fe₃0₄@nSi0₂, 25 mg AgN0₃ and excessive FeCI₃ solution.

Degradation of A07 was almost complete within 2 hr, even with such a small amount of the AgCI/Ag photocatalyst (see FIG. 16).

Claims

1 . An antimicrobial nanocomposite comprising: a porous solid-phase matrix material; antimicrobial particles comprising a metallic antimicrobial agent; and magnetic particles; wherein the antimicrobial particles are non-magnetic and are dispersed within the porous solid- phase matrix material or otherwise embedded within the porous solid-phase matrix material.

2. The antimicrobial nanocomposite of claim 1 , wherein the antimicrobial particles and the magnetic particles are immobilized within the antimicrobial nanocomposite.

3. The antimicrobial nanocomposite of any preceding claim, wherein the porous solid- phase matrix material has a hierarchically-ordered three-dimensional structure.

4. The antimicrobial nanocomposite of any preceding claim, wherein the antimicrobial particles and the magnetic particles are dispersed within the pores of the porous solid-phase matrix material.

5. The antimicrobial nanocomposite of any preceding claim, wherein the antimicrobial nanocomposite comprises core-shell units each having a core, comprising antimicrobial particles and/or magnetic particles, which core is encapsulated within a shell of porous solid- phase matrix material.

6. The antimicrobial nanocomposite of claim 5, wherein the shell forming a shell layer adjacent to the core is an inner shell layer, and the core-shell units comprise one or more further outer shell layers.

7. The antimicrobial nanocomposite of claim 6, wherein the core comprises magnetic particles, and antimicrobial particles are deposited upon shell(s) and/or otherwise dispersed within pores of said shell(s), and one or more outer shell layers surround any shell(s) decorated with antimicrobial particles and/or otherwise comprising said antimicrobial particles within its pores.

8. The antimicrobial nanocomposite of any of claims 5 to 7, wherein the antimicrobial nanocomposite comprises a surfactant embedded within or decorated upon one or more shell layers.

9. The antimicrobial nanocomposite of any of claims 5 to 8, wherein the core-shell units include:

- a core comprising magnetic particles;

- and optionally a second outer shell layer comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

10. The antimicrobial nanocomposite of any of claims 5 to 8, wherein the core-shell units include:

- a core comprising antimicrobial particles and also magnetic particles;

- and optionally a second outer shell layer comprising or consisting of porous solid-phase matrix material embedded with or decorated with a surfactant.

1 1 . The antimicrobial nanocomposite of any preceding claim, wherein the porous solid- phase matrix material is or comprises silica.

12. The antimicrobial nanocomposite of any preceding claim, wherein the metallic antimicrobial agent comprises an antimicrobial transition metal species.

13. The antimicrobial nanocomposite of claim 12, wherein the metallic antimicrobial agent comprises a copper, silver, or gold species

14. The antimicrobial nanocomposite of claim 13, wherein the metallic antimicrobial agent comprises a silver species.

15. The antimicrobial nanocomposite of claim 14, wherein the metallic antimicrobial agent is silver(O), a silver compound, or a mixture thereof.

16. The antimicrobial nanocomposite of claim 15, wherein the metallic antimicrobial agent is or comprises silver (0).

17. The antimicrobial nanocomposite of any preceding claim, wherein the magnetic particles comprise a magnetic substance that is superparamagnetic or in a superparamagnetic form.

18. The antimicrobial nanocomposite of claim 17, wherein the magnetic particles comprise Fe₃0₄.

19. The antimicrobial nanocomposite of claim 18, wherein the magnetic particles are magnetite nanoparticles.

20. The antimicrobial nanocomposite of any preceding claim, wherein: the porous solid-phase matrix material is a hierarchically-ordered porous silica-based material (suitably Si0₂); the antimicrobial particles are silver-containing nanoparticles; and the magnetic particles are superparamagnetic Fe₃0₄ nanoparticles.

21 . The antimicrobial nanocomposite of any preceding claim, wherein: the antimicrobial nanocomposite comprises core-shell unit particles, each having a core, an inner shell layer, and one or more outer shell layers, wherein: the core comprises superparamagnetic Fe₃0₄ nanoparticles, as the magnetic particles; and the inner shell layer comprises a porous silica-based material; and the one or more outer shell layers comprise a porous silica-based material, wherein one of the outer shell layers optionally comprises a surfactant; the antimicrobial particles are silver-containing nanoparticles, which are located either within the core, deposited (or decorated) upon the inner and/or outer shell(s), and/or otherwise dispersed within pores of the porous silica-based material of the inner and/or outer shell(s).

22. The antimicrobial nanocomposite of any preceding claim, wherein the antimicrobial nanocomposite comprises:

- 70-85 wt% a porous solid-phase matrix material;

15-20 wt% antimicrobial particles; and

10-30 wt% magnetic particles.

23. A process of preparing an antimicrobial nanocomposite, the process comprising forming a porous solid-phase matrix material with antimicrobial particles and magnetic particles dispersed and/or embedded therein; wherein the antimicrobial particles are non-magnetic and comprise a metallic antimicrobial agent.

24. The process of claim 23, wherein the process comprises template-based formation of the porous solid-phase matrix material around the antimicrobial particles and magnetic particles.

25. The process of claim 24, wherein the porous solid-phase matrix material, antimicrobial particles, magnetic particles, and/or precursors thereof, are contacted with or otherwise introduced to the template (i.e. into crevices and/or channels therein) and a hierarchically- ordered structure is formed in situ before the template is then removed.

26. The process of any of claims 23 to 25, wherein the process comprises: i) providing: a) a mobile precursor (e.g. liquid, slurry, or gel) comprising the porous solid- phase matrix material or precursor thereof; mobile precursor comprising the antimicrobial particles or a precursor thereof; and c) a mobile precursor comprising the magnetic particles or a precursor thereof; wherein any combination of a), b), and/or c) are optionally provided together as a single combined mobile precursor; ii) providing a solid template include crevices and/or channels; iii) introducing the mobile precursor(s) into the crevices and/or channels of the template to provide a filled template; iv) facilitating or allowing solidification of the mobile precursor(s) within the crevices and/or channels of the filled template; v) removing the template to leave a hierarchically ordered antimicrobial nanocomposite.

27. The process of claim 25 or 26, wherein the template is removed by calcination of the filled template.

28. The process of claim 23, wherein the process comprises forming core-shell units, each having a core of antimicrobial particles and/or magnetic particles encapsulated within at least one shell of porous solid-phase matrix material.

29. The process of claim 28, wherein the process comprises: i) Forming a core comprising either or both magnetic particles and/or antimicrobial particles; ii) Coating the core with an inner shell layer comprising or consisting of porous

solid-phase matrix material (optionally embedded with or decorated with a surfactant); iii) Optionally decorating the inner shell layer with, or depositing therein, either or both antimicrobial particles and/or magnetic particles; iv) Optionally coating the inner shell layer (whether or not deposited/decorated with magnetic and/or antimicrobial particles) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

30. The process of claim 29, wherein the process comprises: i) Forming a core comprising magnetic particles; ii) Coating the core of magnetic particles with an inner shell layer of porous silica (optionally embedded with or decorated with a surfactant) to form a core-shell unit; iii) Decorating the inner shell layer with antimicrobial particles to produce decorated core-shell units, suitably by contacting the core-shell unit of step ii) with a precursor of the antimicrobial particles; and iv) Coating the decorated core-shell units of step iii) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

31 . The process of claim 29, wherein the process comprises: i) Forming a core comprising both antimicrobial particles and magnetic particles; ii) Coating the core with an inner shell layer of porous silica (optionally embedded with or decorated with a surfactant) to form a core-shell unit; iii) Optionally coating the core-shell units of step ii) with one or more outer shell layers comprising or consisting of porous solid-phase matrix material (optionally embedded with or decorated with a surfactant).

32. An antimicrobial treatment apparatus for disinfecting and/or sterilising a fluid, the apparatus comprising a disinfecting zone configured to receive a fluid in need of disinfection and/or sterilization, wherein the disinfecting zone comprises the antimicrobial nanocomposite of any of claims 1 to 22 or the antimicrobial nanocomposite obtained by the process of any of claims 23 to 31 .

33. The antimicrobial treatment apparatus of claim 32, comprising a fluid input port and a fluid output port linked together via a fluid channel, wherein the fluid channel comprises along its path the disinfecting zone, wherein the disinfecting zone comprises a bed of the antimicrobial nanocomposite.

34. The antimicrobial treatment apparatus of claim 32 or 33, wherein the apparatus is a filtration device.

35. The antimicrobial treatment apparatus of claim 32 or 33, wherein the apparatus is or comprises a tube or pipe containing the antimicrobial nanocomposite.

36. A method of disinfecting and/or sterilizing a fluid, the method comprising contacting a fluid in need of disinfection and/or sterilization with the antimicrobial nanocomposite of any of claims 1 to 22 or the antimicrobial nanocomposite obtained by the process of any of claims 23 to 31 .

37. The method of claim 36, wherein the fluid is water, and the method is a water treatment method.

38. A method of recovering an antimicrobial nanocomposite from a fluid and/or medium treated in accordance with the method of any of claims 36 to 37, comprising filtering off and/or applying a magnetic field to the used antimicrobial nanocomposite.

39. An antimicrobial nanocomposite, a process for preparing an antimicrobial

nanocomposite, an antimicrobial treatment apparatus, a method of disinfecting and/or sterilizing a fluid, or a method of recovering an antimicrobial nanocomposite, as substantially hereinbefore described with reference to Examples 1 and 3 and the accompanying Figures.