WO2022124973A1 - A colloidal composite particle dispersion for use in an antimicrobial and virucidal surface coating - Google Patents

Abstract

The disclosure relates to a colloidal composite particle dispersion for use in an antimicrobial and virucidal surface coating, comprising a composite of: (a) a poly(ionic liquid) particle comprising a n-alkyl substituent in the repeating unit; and (b) metal nanoparticles that are deposited on the poly(ionic liquid) particles; wherein the composite particle is in a polar protic solvent, such as water-based solution. The disclosure further relates to a coating composition for antimicrobial and virucidal surface coating, a method for applying the coating composition, and a method for preparation of a colloidal composite particle dispersion.

Description

A COLLOIDAL COMPOSITE PARTICLE DISPERSION FOR USE IN AN ANTIMICROBIAL AND

VIRUCIDAL SURFACE COATING

Technical field

The present disclosure relates to a colloidal composite particle dispersion for use in an antimicrobial and virucidal surface coating, a coating composition for antimicrobial and virucidal surface coating, a method for applying the coating composition, uses of the colloidal composite particle dispersion and/or the coating composition, and a method for preparation of a colloidal composite particle dispersion as defined in the independent claims.

Background art

World Health Organization (WHO) declared in March 2020 a pandemic and a global crisis caused by a new coronavirus, SARS-CoV-2 (COVID-19) that was discovered to be the cause of a rapidly spreading outbreak of respiratory disease. By November 2020, more than 50 million infection cases and 1 million deaths have been confirmed.

Coronaviruses are so named because of their characteristic solar corona (crown-like) appearance when observed under an electron microscope. The SARS-CoV-2 virion is spherical with an average size of 78 nm. SARS-CoV-2 is a delicate but highly contagious virus capable of spreading primarily from person to person around the world. It can also spread when an infected person coughs or sneezes and a droplet lands on a surface or object, which is touched by a person and then the person's nose, mouth or eyes. On a personal level, hygiene measures are recommended to prevent the spread of disease, especially in areas where individuals might be in contact with patients or contaminated fomites. Washing hands with soap and water or with alcohol-based hand rubs are effective for interrupting virus transmission.

Though coronaviruses are relatively easy to destroy by using disinfectants like ethanol (62- 71%), or hydrogen peroxide (0.5%) by breaking their delicate envelope that surrounds the tiny microbe, recent studies show SARS-CoV-2 can remain viable or infectious on various surfaces for several hours to days if without any disinfectants. Ethanol-based disinfectants are so far the most widely used due to the easy access to ethanol, but the drawback is the quick evaporation of ethanol so a surface stays clean only upon repeated treatment of ethanol-based disinfectants.

Scientists and industry companies have realized that Cu- or Ag-coated surface can sanitize by itself by neutralizing the contaminated coronavirus quickly, thus eliminating the possibilities of its transfer to the human body and its subsequent spreads

EP-A-3462526 discloses a biomedically active material, comprising atomically dispersed metal species on the surface of a carbon material. The metal species are dispersed in an ionic liquid. The carbon atoms have a sp² hybridization. The intended use is for example as a coating in an electrode for oxidation.

US2020239709A1 discloses a composite resin comprising silver nanoparticles and a polymer. The silver nanoparticles are formed by reduction of silver ions. The resin can be used e.g. as an antimicrobial surface coating.

KR101465866B1 discloses polymer-silver nanoparticles including 2-(2-acetoxy) ethyl methacrylate and silver. The nanoparticles can be used for antibiosis activity, as a coating material.

Charan et al. (European Polymer Journal, Vol 60, Nov 2014, p 114-122 (ISSN 0014-3057)) discloses poly(ionic liquids) as "smart" stabilizers for metal nanoparticles. Surface coating by use of Cu or Ag nanoparticles assisted by a polymer matrix are used to prevent the spread of coronavirus. However, most studies and commercial products aim to target surfaces exposed to air. Either the production of such composite film is conducted in non-aqueous solution or their surface coating films are unstable in aqueous condition (the polymer matrix is soluble in water).

Thus, antimicrobial surface coatings comprising metal ions (such as silver) bound by a polymer are known. However, such coatings have limited utility, e.g. under wet conditions. Further, the production process of such coatings typically require the use of multiple chemicals/solvents that are hazardous and/or environmentally challenging. There is thus a need for improved surface coatings for these purposes. Summary

It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problems. More specifically, it is an object of the invention to provide a waterborne material providing an antimicrobial and virucidal activity, and that can be used for a broader range of surface coatings, e.g. both outdoor and indoor, thereby requiring wetstable properties.

According to a first aspect there is provided a colloidal composite particle dispersion for use in an antimicrobial and virucidal surface coating, comprising a composite of: (a) a colloidal poly(ionic liquid) particle that is molecularly insoluble in water and comprises a n-alkyl substituent; and (b) metal nanoparticles that are deposited on the poly(ionic liquid) particles; wherein the composite particle is in a polar protic solvent, such as a water-based solution.

Thus, by using poly(ionic liquid) particles with an alkyl chain substituent (typically a long alkyl chain) in each repeating unit, as carrier of metal species to produce the colloidal poly(ionic liq uid)/meta I composite particles in polar protic media, such as water-based solution, such colloidal dispersion can be sprayed onto various surfaces to kill occurring microbes and viruses, such as COVID 19. As the used poly( ion ic liquid) polymers are not soluble in water (though their particles are waterborne and can be dispersed in water), the formed composite films are stable in both dry and wet condition, e.g. for outdoor surface coating.

According to some embodiments, the cation of the polymer particle is chosen from imidazolium, triazolium, tetraalkylammonium and tetraalkylphosphonium.

These cations have proven to be especially suitable for the purposes of the invention, because these cationic polymer particles can be easily prepared by free radical polymerization in an aqueous environment.

According to some embodiments, the n-alkyl substituent is chosen from the interval of octyl to octadecyl substituent, because these long alkyl chains make the polymer insoluble in water-based solution. In some embodiments, the n-alkyl substituent is chosen from the interval of dodecyl (C12) to tetradecyl (C14) substituent. According to some embodiments, the metal nanoparticle is chosen from Cu or Ag. In some embodiments the metal nanoparticle is chosen from Cu. These metals have proven to be especially effective for antimicrobial and/or virucidal applications. According to some embodiments, the polar protic solvent is an aqueous media, where the water content is above 50%. Hereby, the spray-coating for protective surfaces against microbes or viruses, such as COVID-19, is fully water-based, and can easily be used to protect surfaces also in both dry and wet condition, as well as it is environmentally friendly.

According to a second aspect there is provided a coating composition for antimicrobial and virucidal surface coating, comprising the colloidal particle dispersion according to any of the embodiments of the first aspect, and optionally additional ingredients such as dye and/or odorant molecule(s), odor control chemical(s), to change color and/or smell, stabilizer(s), surfactant(s) and/or pH modifier(s),, wherein the coating composition exhibits water stability.

According to some embodiments, hydrophobic fluorescent molecules are included in the composition to improve visibility of the coating surface.

According to a third aspect there is provided a method for applying the coating composition.

According to some embodiments, the coating composition is for use in spray applications. Hereby, the coating composition is easily applied to suitable surfaces, for which it is desirable to achieve an antimicrobial and/or virucidal activity, thereby limiting or eliminating the risk of e.g. virus spreading and/or contamination.

According to some embodiments, the coating composition is applied as a film having a thickness in the interval of 10-500 pm, for indoor and/or outdoor applications. Such film can e.g. be used to cover various devices, machines and products in order to limit and/or inactivate the spreading of microbes and/or viruses.

According to a fourth aspect, use of the colloidal composite particle dispersion and/or the coating composition in virucidal applications, such as for deactivation or elimination of COVID 19 at a suitable indoor and/or outdoor surface, is provided.

According to a fifth aspect there is a method provided for preparation of a colloidal nanoparticle dispersion, comprising the steps of: (a) providing a -ionic liquid monomer with a n-alkyl substituent, wherein n is in the interval from 8 to 18;

(b) polymerizing the n ionic liquid monomer with a n-alkyl substituent in a polar protic solvent, such as a water-based solution, in the presence of a radical initiator to produce a colloidal poly(n-alkyl-ionic liquid) particle dispersion;

(c) adding a metal salt to the dispersion of step (b), and

(d) reducing the metal salt by adding a reducing agent to the dispersion of step (c) thereby obtaining a colloidal poly(ionic liquid)/metal composite particle dispersion.

Hereby, a method for preparing a dispersion for use in antimicrobial and/or virucidal coatings is provided.

In some embodiments, the n-alkyl chain-ionic liquid monomer provided in step (a) is in a concentration of about 0.5-20% (weight).

In some embodiments, the reducing agent of step (d) is added in a 2 molar equivalent ratio to the metal salt to ensure full reduction of metal salts to metal nanoparticles.

Thus, the solution according to the invention is to use poly( ion ic liquid) particles with long alkyl substituent in the repeating unit as carrier of metal (preferably Ag or Cu) species to produce the colloidal poly(ionic liquid)/metal composite particles in polar protic solvent media (preferably aqueous media). Such colloidal dispersion can be sprayed onto various surface to kill microbes and/or viruses, such as SARS-CoV-2. As the used poly(ionic liquid) polymers are not soluble in water (though their particles can be dispersed in water), the formed composite films are stable in both dry and wet condition, e.g. for outdoor surface coating. Also, the invention provides such material in an environmentally friendly way. Such spray liquids can be produced in water as a green solvent and after spray-coating the poly(ionic liquid)/metal colloidal composite particles can resist wet conditions, so that they can be used both indoor and outdoor.

Effects and features of the second, third, fourth and fifth aspects are to a large extent analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the other aspects. The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure.

Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular features of the dispersion or the coating composition described or steps of the methods described since such products and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like.

Furthermore, the words "comprising", "including", "containing" and similar wordings do not exclude other elements or steps.

Brief descriptions of the drawings

The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and nonlimiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings and Examples.

Figure 1 shows a cryogenic transmission electron microscopy (cryo-TEM) image of the poly(l-n-dodecyl-3-vinylimidazolium bromide) particles. The size is around 20-50 nm.

Figure 2 shows a cryo-TEM image of the poly(ionic liquid)/Cu colloidal composite particles. Cu nanoparticles are located onto the poly(ionic liquid) particles. The Cu nanoparticles are around 1-4 nm (highlighted by white arrows; the PIL particles are 20- 50 nm in size).

Figure 3 shows the virucidal activity of surfaces coated with pristine PIL, and a PIL/Cu particle composite.

Figure 4 schematically illustrates the process of deactivation of SARS-CoV-2 virions by the formed surface coating by PIL/copper composite nanoparticles. Figure 5 discloses a ¹H-NMR spectra of poly(3-dodecyl-l-vinylimdiazolium bromide) in CDCh. Figure 6 discloses a TGA plot of PIL nanoparticles under air from room temperature to 900 °C

Figure 7 discloses a schematic representation of the surface spray coating of a glass substrate by an aqueous colloidal dispersion of PIL/Cu composite particles.

Figure 8 (A, B) discloses cryo-TEM images of the pristine PIL nanoparticles dispersed in aqueous solution.

Figure 9: A) SEM image of the PIL/Cu composite nanoparticles on a glass substrate, B) Cryo- TEM image of PIL/Cu nanoparticles dispersed in aqueous media. C) XRD patterns of PIL and the PIL/Cu composite nanoparticles, D) TGA curve of the PIL/Cu composite nanoparticles under air from room temperature to 900 °C. Figure 10 (A, B) discloses water contact angle measurements of glass substrates coated with PIL nanoparticles, and the PIL/Cu composite nanoparticles, respectively. C) Characterization of antiviral activity of glass slides coated with PIL nanoparticles and the composite of the PIL/Cu nanoparticles against SARS-CoV-2 virions at various times.

Definitions

The term "a colloidal dispersion" is to be interpreted as a mixture that has particles ranging between 15 nm and 1 mm in diameter, and are essentially evenly distributed throughout the solution. The term "a colloidal composite particle dispersion" is to be interpreted as a mixture that has particles with combination of two or more materials with different physical and chemical properties ranging between 1 nm and 1 mm in diameter, and are essentially evenly distributed throughout the solution.

The term "composite" is to be interpreted as a combination of two or more materials with different physical and chemical properties.

The term "antimicrobial" is to be interpreted as an agent that kills microorganisms or stops their growth. The term "virucidal" is to be interpreted as an agent having the capacity to or tending to destroy or inactivate viruses

The term "poly(ionic) liquid" is to be interpreted as a group of charged polymers that are produced by the polymerization of ionic liquids or by covalent attachment of ionic liquids into the repeating unit of polymers.

The term "nanoparticle" is to be interpreted as particles with their size in the range of 1 to 100 nm.

The meaning of the term "polar protic solvent" is in the context of this invention referred to the following reference:

The term "water-based solution" is to be interpreted as either pure water or a mixture in which water is more than 50% in volume.

The term "water stability" is to be interpreted as the microstructures of the composite film do not change in contact with water.

The term "solubility in water" is to be interpreted as the ability of a solute to molecularly dissolve in water as a solvent.

The term "suitable surface" is to be interpreted as a surface of indoor and/or outdoor type and/or conditions, to which the coating composition and/or the colloidal composite particle disperson can be applied, thereby providing the desired antimicrobial and virucidal effects.

Detailed description

The present disclosure will now be described with reference to the following detailed disclosure of aspects and embodiments, as well as according to the accompanying examples and drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person. The first aspect of this disclosure shows a colloidal particle dispersion of 0.01 to 50 % in concentration (weight), preferably of 0.1-10 % (weight) for use in an antimicrobial and virucidal surface coating, comprising a composite of: (a) a poly(ionic liquid) particle comprising a n-alkyl substituent in each repeating unit; and (b) metal nanoparticles that are deposited on the poly(ionic liquid) particles; wherein the composite particle is in a polar protic solvent, such as a water-based solution.

The poly(ionic liquid) ("PIL") particles typically have a size in the interval of 15 nm to 1mm, preferably 15 nm to 100 pm, more preferably 15 nm to 10 pm, and most preferably 20 nm to 1 pm. The polymer particles of the invention are typically not molecularly soluble in water. Instead they are dispersible in water.

The solid content of the colloidal particle dispersion is typically in the interval from 0.01 - 50 % (weight), preferably 1-10 % (weight). Poly(ionic liquid) is therefore present in an interval from 0.01 - 50 % (weight), preferably in the interval from 0.1 to 10 % (weight), and more preferably from 1 to 5% (weight). Metal nanoparticles are deposited on the poly(ionic liquid) particles at a content in the interval from 0.01-50 wt%, preferably in the interval from 0.1- 20 wt%, and most preferably in the interval from 1-15 wt%,.

Typical conditions for the surface coating to be efficient are e.g. a temperature in the interval of 0-100 °C, preferably 10-60 °C, more preferably 15-35 °C, and most preferably around room temperature, such as about 20-25 °C. The air moisture can e.g. be up to about 95% relative humidity.

The main mechanism for the coating to be efficient for viruses and microbials works by the release of either Cu²⁺ ions or Ag⁺ ions to kill virus or microbes. The surface coating of the present invention is active against many different microbes Campylobacter, Clostridium perfringens, E. coli, listeria, salmonella, bacillus cereus, botulism, and shigella and viruses such as SARS-CoV-2, norovirus, and hepatitis A virus..

In some embodiments the cation of the poly(ionic liquid) particle is chosen from imidazolium, triazolium, tetraalkylammonium and tetraalkylphosphonium, wherein the most preferred cation is imidazolium because it is the most widely reported one in literature and the most widely used in our society. In some embodiments the n-alkyl substituent is chosen from the interval of octyl C8 to octadecyl C18 substituent. Most preferred are the C12 and C14 substituents, because the monomers with C12 and C14 alkyl substituents can produce stable poly(ionic liquid) particles at high concentrations above 10 wt%.

In some embodiments the metal nanoparticle is chosen from Cu or Ag, especially Cu.

The polar protic solvent is typically an aqueous media, but for some applications the polar protic solvent may also be chosen from e.g. ethanol, isopropanol, ethyl glycol and triethyl glycol.

The second aspect of this disclosure shows a coating composition for antimicrobial and/or virucidal surface coating, comprising the colloidal particle dispersion according to the first aspect, and optionally additional ingredients such as dye and/or odorant molecule(s), odor control chemical(s), in order to change color and/or smell, stabilizer(s), surfactant(s) and/or pH modifier(s), wherein the coating composition exhibits water stability. Hydrophobic fluorescent molecules, e.g. carotene and Nile red, can be added to or included in the composition to improve the visibility of the coating surface. These dye molecules are stored in the poly(ionic liquid) particles due to their hydrophobic interaction in the aqueous dispersion. For coating compositions, the dispersion typically has a concentration in the interval of 0.1-50 % (weight), depending on the application and the desired properties of the coating. The dispersion in a low concentration (below 15%) is preferred for coating of a surface with thickness less than 100 micron meters, while the dispersion in a high concentration (above 15%) is favoured for coating of a surface with thickness more than 100 micron meters. Typically, no other ingredients than the dispersion of the present invention are necessary for obtaining the coating composition. In such cases, the dispersion of the first aspect of the invention can be used as the coating composition, and hence the embodiments and features related to the coating composition will be fully applicable to the dispersion of the invention as such.

Typically, the coating composition of the present invention can be stored under the following conditions: temperature: 2-100 °C under normal pressure, i.e. so that the water phase is prevented from freezing as well as boiling. The composition can be stored for a long time, such as months, or even up to about 2 years or more. The coating composition can be used in several types of applications and/or methods (also referred to as a third aspect), as long as the overall objective is met, i.e. to provide an antimicrobial and/or virucidal coating on a relevant type of surface (i.e. a target surface). For example, the dispersion of the invention may be used in spray applications. Such spray contains the polymer/metal composite colloidal particles typically in the concentration of 0.5 to 5 % (weight). Preferably, the metal is Ag or Cu, especially Cu. The dispersion can easily be sprayed onto the target surface to be protected. In order to obtain full effect, the surfaces should be fully covered by the coating, i.e. spray should be applied so that the entire target surface is covered and protected, thereby limiting or eliminating the occurrence of microbial and/or viral particles adhering to and being able to survive, grow and/or spread, e.g. so that viruses are prevented from contaminating a surface and spreading to humans and/or animals.

Other specific features of the coating composition of the invention and its application and use:

• Typical thickness: 5-500 micrometers, even though any thickness outside this interval may also be formed in accordance with the invention.

• Size of surface to be covered by the coating/film: The coating can be applied to any surface size, as long as it is practically possible, i.e. that the spray coating machine used or any other device used for applying the material, is adapted to apply the surface size. Hence, using a spray coating machine as disclosed in Example 5, a surface size of 10 cm x 10 cm can be applied. For larger surfaces to be coated, such as tables or the like, having sizes like several squaremetres, or smaller surfaces, a spray coating machine or device having properties adapted for such surface sizes can be used. The skilled persons would be able to understand and adapt the device(s) used for the specific application, e.g. by using and/or adapting spray application devices typically used for other purposes, such as typical spray bottles for personal use and/or spray machines used in automotive industry or in paint applications.

• The coating may be applied to most surfaces. In some cases where the surface energy is very low, such as the surface of fluorinated or perfluoronated plastics, e.g. Teflon, a primer may preferably be applied before applying the coating, to increase the binding strength of the coating to the surface. In a further aspect, the coating composition and/or the colloidal composite particle dispersion is used in virucidal applications, such as for deactivation or elimination of SARS- CoV-2 from a surface.

Further, in some embodiments, the composite material of the invention, e.g. in the form of a film, can be used in applications such as air circulation machines to deactivate any SARS- CoV-2 in the indoor air. Such rooms can e.g. be living houses, working areas, trains, and planes or other transport means.

The film comprising the composite material of the invention, can for example be formed as disclosed in detail in Example 5 using a spray coating machine. Typically, such film has thickness of 5 to 500 micron meters, depending on the solid content of the dispersion. Thus, dispersion having a high solid content will typically be used for formation of a film having a relatively higher thickness, and a dispersion having a low solid content will typically be used for formation of a film having a relatively lower thickness.

The fifth aspect of this disclosure shows a method for preparation of a colloidal particle dispersion according to the first aspect, comprising: (a) providing an ionic liquid monomer with a n-alkyl substituent, wherein n is in the interval from 8 to 18; (b) polymerizing the n- alkyl chain ionic liquid monomer in a polar protic solvent such as water-based solution by adding a radical initiator, initiating the polymerization to produce a colloidal poly(n-a I kyl- ionic liquid) particle dispersion; (c) adding a metal salt to the dispersion of step (b), and (d) reducing the metal salt by adding a reducing agent to the dispersion of step (c) to obtain a colloidal poly(ionic liquid)/metal composite particle dispersion.

The n-alkyl chain-ionic liquid monomer is typically provided in step (a) in a concentration of about 0.5 -20 % (weight). The ionic liquid monomer is typically synthesized (see Example 2).

In step (b), the water-soluble radical initiator (e.g. V-501, V-50, VA-044, and VA-086) is typically added at a concentration of about 0.5-3 % (weight) of the n-alkyl chain-ionic liquid monomer. The water-soluble initiator can easily be purchased. The skilled person would know how to obtain the initiator. The metal salt, typically a Cu or Ag salt chosen from the list of CuCb, CuBr?, CufOAc /AgOAc, CnfNOsh/AgNC , copper/silver acetylacetonate, and copper/silver phosphate, is typically added in step (c) at 0.1 to 50 % (weight) of the polymer nanoparticles, preferably about 1 to 10 % (weight) of the nanoparticles. The reduction of step (d) can be performed in several different ways, as long as the necessary reduction is obtained. For example, the metal salt can be reduced by adding a reducing agent to the dispersion of step (b) to obtain the final desired composite dispersion. In a preferred embodiment the reducing agent is added in a 2 molar equivalent ratio to the metal salts to ensure the full reduction of metal salts to metal nanoparticles. The reducing agent can for example be chosen from sodium borhydride (preferably used at room temperature), vitamin C, citric acid, polyols or hydrazine (N2H4) (preferably used at 80 °C or above). When using a silver salt, sodium borhydride is typically used as reducing agent. Depending on the choice of reducing agent, water-soluble by-products may occur after step (d). An additional method step comprising dip-washing the product of step (d) may be introduced to remove such by-products.

Typically, suitable conditions for the preparation of the composite dispersion of the invention are the following:

• Temperature: the polymerization (step (b)) is typically performed in the interval from 50-90 °C, preferably about 70 °C. The reduction (step (d)) is typically performed at a temperature suitable for the chosen reducing agent (reductant), and may vary from about room temperature (15-25 °C) to about 80-100 °C, whatever is suitable for the reducing agent, and as long as the water-based dispersion does not freeze or boil.

• Duration: the polymerization reaction (step (b)) should typically last for about 12 hours, or as long that is necessary for completion. By using TEM and cryo-TEM, completion of the desired reactions and the obtained structures can be shown.

The invention will now be further explained by the following examples, showing exemplary embodiments of the invention, but should not be construed as limiting the scope of the invention.

EXAMPLES

Example 1

In accordance with the present invention, the inventors produced poly(ionic liquid) nanoparticles from a long alkyl chain-ionic liquid monomer, 3-n-alkyl-l-vinylimidazolium bromide in water. This polymerization forms a stable poly(ionic liquid) nanoparticle dispersion in water, although the poly(ionic liquid) itself is molecularly insoluble thus aggregates into nanoparticles that are dispersed in water.

Without purification, Cu salts, such as copper acetate, copper chloride or cooper acetylacetonate, was added into this solution, followed by addition of a reductant e.g. hydrazine (N2H4) at 80 °C to reduce the Cu salts into Cu nanoparticles, and these Cu nanoparticles are located on the surface of poly(ionic liquid) nanoparticles (Cu nanoparticles are typically 1-4 nm in size, and polymer nanoparticles are typically 15-50 nm in size).

This step forms a stable poly(ionic liquid)/Cu colloidal composite particle dispersion. By spray-coating this dispersion onto a glass plate followed by a dip-washing (30 s) in water, the inventor then tested its virucidal activity towards COVID 19 in Karolinska Institute. Within 3 hours, 99.5% SARS-CoV-2 was deactivated in this test condition.

An example of using poly(3-n-dodecyl-3-vinylimidayolium bromide)/Cu colloidal composite nanoparticles for spray-coating to form an anti- SARS-CoV-2 surface is shown here.

Example 2 - Synthesis of the ionic liquid monomer with C-12 alkyl substituent

9.4 g of 1-vinylimidazole and 25g of bromododecane (1:1 molar ratio) and 20ml of ethanol were mixed together inside 100ml round bottom flask at 40 °C for 16 hrs. A needle was used to reduce the pressure inside the flask. In the next day, the reaction mixture was added drop by drop to IL diethyl ether and the precipitate was filtered off gently, and dried at 40 °C using vacuum oven.

Example 3 - Polymerization of C12 PIL-NP

5g of monomer and 150 mg of a water-soluble thermal initiator VA-086 were added to 100 ml of water inside a 250ml round bottom Schlenk flask. The flask was treated with three freeze-pump-thaw cycles. The reaction was stirred at 70°C for 16 hrs. Next day, the polymer solution was filtered off using a filter paper and a funnel to remove impurities and big aggregation of nanoparticles. Figure 1 shows a cryogenic transmission electron microscopy (cryo-TEM) image of the synthesized poly(ionic liquid) nanoparticles.

Example 4 - Preparation of C12-Cu NP solution

2ml of C12 PIL-NP solution was diluted with 9ml of water. Then 1ml water containing 10 mg of copper acetate salt was added to the solution. After 30 min, either 5 mg of sodium borhydride in 5 ml of water, or 50 mg of vitamin C, or 0.2 ml of aqueous hydrazine solution (80 wt%) was added to the solution. Very gentle change of color happened during this step. The solution was sonicated for ca. 20 min. Then, in case vitamin C or hydrazine was used as reductants, the solution was placed in an oil bath under stirring at 80°C for overnight. The next day, the color of the solution changed to pink . Next, the solution was sonicated again for ca. 20 min. In the following, by using a 5 pm filter and a syringe the solution was filtered off to remove any big aggregations of Cu-NPs. Figure 2 is a cryo-TEM image of the poly(ionic liquid)/Cu colloidal composite nanoparticles.

Example 5 - Coating procedure

A glass slip with size of 24x24 mm and thickness of 0.5mm was treated with an oxygen Plasma instrument to make the substrate surface hydrophilic and clean for 3 min. At the final stage, with help of a spray coating machine (a spray machine with pore size of 100 micron meters, a flow rate of 2 ml per min, and a point size of 6.5 cm x 6.5 cm at a distance of 8.5 cm), the hydrophilic surface of glass slip was coated with C12-Cu Np dispersion for ca. 30 seconds with a film thickness of 5 to 500 micron meters, depending on the solid content of the dispersion and the spray time.

Example 6 - Antiviral activity tests of hybrid coating

Cover glasses were placed into a 6-well plate and 10 pL containing a known number of infectious units of SARS-CoV-2 was applied in the center of the glass. The droplet was immediately covered by uncoated cover glass to spread the virus on the whole area. After incubation at specified time, usually 5, 30, and 180 min, 490 pL IX PBS was added to the coverslips, the top coverslip was lifted and the virus-exposed sides of both coverslips were washed with PBS by pipetting 3 times to collect the virus species. The inventors collected the whole washing and used for titer determination. The outcome in Figure 3 shows that within 30 min, 90% of SARS-CoV-2 is deactivated, and 180 min for 99.5% deactivation.

Example 7 - Colloidal dispersion of poly(ionic liquid)/Cu composite particles for protective surface coating against SAR-CoV-2 Herein, the inventors report a waterproof anti-SARS-CoV-2 protective film prepared by spray-coating of an aqueous colloidal dispersion of poly(ionic liquid) /copper (PIL/Cu) composite nanoparticles onto a substrate. The PIL dispersion was prepared by suspension polymerization of 3-dodecyl-l-vinylimdiazolium bromide in water at 70 °C. The copper acetate salt was added into the PIL nanoparticle dispersion and in-situ reduced into copper nanoparticles anchoring onto the PIL nanoparticles. Despite being waterborne, the PIL in bulk is intrinsically insoluble in water and the formed coating is stable in water. The formed surface coating by PIL/copper composite nanoparticles was able to deactivate SARS-CoV-2 virions by 90.0% in 30 min and thus may effectively prevent the spread of SARS-CoV-2 through surface contact (see figure 4). This method may provide waterborne dispersions for a broad range of antivirus protective surface coatings for both outdoor and indoor applications.

The emergence of a current pandemic, caused by a novel coronavirus, severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has brought a rapid viral infection over 200+ countries and more than three million deaths globally by the time of this report. The transmission from infected to healthy persons can be transferred through cough, respiratory droplets, biofluids or close contacts. These respiratory pathogens can remain infectious on insentient surfaces for hours to two-three days

Consequently, the determination of antiviral coating materials with high antiviral activity and broad applicability on various surfaces may eliminate the possible infection transfers and reduce the speed of virus spread ^[3-5] Metal nanoparticles historically have been proven to show a wide range of virucidal and bactericidal activities due to their effectiveness at a low dosage, small size, high surface area, and acting as ion reservoirs to control the release of bioactive ions. Metal nanoparticles demonstrate the capability to generate reactive oxygen species to destroy the virus and attach to DNA or RNA, and accordingly they can prevent the replication of microorganisms. Since past decades, various types of metal nanoparticles, such as silver (Ag), copper (Cu), iron, iron oxide, gold, and titanium oxide, with antibacterial and virucidal activity have been described vastly in literatures. Among those, Ag nanoparticles are the most widely explored in the literature because of their high effectivity versus infections and high demands in industrial applications. Regardless of multitude benefits of Ag nanoparticles, Cu nanoparticles with high antimicrobial (especially antifungal), low cost and wide availability and abundance can be alternatively utilized ^[6-12]. If not surface-protected, a rapid aggregation of a dispersion of native metal nanoparticles can cause a large decrease in their reactivity. A common method to overcome this problem is to stabilize metal nanoparticles with organic compounds, such as low molecular weight ligands and chelating polymers by selective functionalization of their surface I^13-17].

Poly(ionic liquidjs (PILs) as a subclass of polyelectrolytes are polymer materials with adjustable physiochemical characteristics due to covalently incorporated ionic liquid-like ion pairs in the polymer chains, and usually possess mechanical stability, durability, ion conductivity and multifunctionality I¹⁸-¹⁹]. This unique combination broadens the application scope of PILs in comparison to conventional polyelectrolytes in versatile research areas such as biosensors I²⁰-²¹!, biomaterials I^22-26], energy materials I^27-30], just to name a few. Besides, the self-assembly of PILs has provided new aspects in the direction of functional nanomaterials I^31-34]. Thus, it is the inventor's opinion that well-defined self-assembled PIL nanoparticles can be promising candidates to support and stabilize metal nanoparticles to maintain metal's antiviral and antibacterial activity I³⁵-³⁶!. Previously the inventor group investigated straightforward self-assembly of imidazolium and triazolium-based PIL nanoparticles with different alkyl chain lengths and tunable structures. These PILs due to the presence of long alkyl chain can self-assemble into multi and unilamellar vesicles, or wasp- like dispersible nanoparticles when they are produced in water ^[37-39] although these PILs in bulk are water-insoluble. In this contribution, the inventors investigated the potential anti-SARS-CoV-2 activity of a composite film consisting of spray-coated PIL/Cu nanoparticles from their aqueous colloidal dispersion. Detailed materials characterization certified the establishment of smaller Cu nanoparticles onto the PIL nanoparticles. The inventor's virucidal activity tests show high virucidal activities of such films against SARS-CoV-2 virions, pointing out potential applications of such spray-coatings for indoor and outdoor surfaces to decline the infection and transmission of SARS-CoV-2 virions via contaminated surfaces.

1. Experimental

1.1 Chemicals 1-Vinylimidazole (99%) and copper (II) acetate monohydrate were purchased from Alfa Aesar. 1-Bromododecane was purchased from Acros Organic. 2,2'-Azobis[2-methyl-N-(2- hydroxyethyl)propionamide] (VA-086) was purchased from FUJIFILM Wako Chemicals. L- ascorbic acid and hydrazine hydrate 35 % solution in water were purchased from Sigma- Aldrich. All chemicals were used without any further purification. Solvents were of analytical grade.

1.2 Instruments

Nuclear magnetic resonance (NMR): ¹H-NMR spectra were recorded at room temperature using a Bruker DPX-400 spectrometer operating at 400 MHz. CDChwas used as a solvent for the measurement. Scanning electron microscopy (SEM): The morphology of the samples was recorded on a JEOL 7000 operated at 3 kV. Samples were coated with a thin gold layer for 40 seconds before examination.

Transmission electron microscopy (TEM): The morphology of the nanoparticles was measured using a JEOL JEM-2100 transmission electron microscope (JEOL GmbH, Eching, Germany) operated at an acceleration voltage of 200 kV. Nanoparticles suspended in water were dried on continuous carbon-coated copper TEM grids (200 mesh, Science Services).

Cryogenic transmission electron microscopy (cryo-TEM): Cryo-EM specimens were prepared by applying a 4 pL drop of a dispersion sample to Lacey carbon-coated copper TEM grids (200 mesh, Science Services) and plunge-frozen into liquid ethane with an FEI vitrobot Mark IV set at 4 °C and 95% humidity. Vitrified grids were either transferred directly to the microscope cryogenic transfer holder (Gatan 914, Gatan, Munich, Germany) or stored in liquid nitrogen. Imaging was carried out at temperatures around 90 K. The TEM was operated at an acceleration voltage of 200 kV, and a defocus of the objective lens of about 2.5-3 pm was used to increase the contrast. Cryo-EM micrographs were recorded at a number of magnifications with a bottom-mounted 4 x 4 k CMOS camera (TemCam-F416, TVIPS, Gauting, Germany). The total electron dose in each micrograph was kept below 20 e-A^-2. X-ray diffraction (XRD): XRD measurements were carried out using a Bruker D8 diffractometer in the locked coupled mode (20 ranging from 10° to 80°) with Cu Kai radiation. The PIL/Cu composite sample was measured with an air-tight XRD holder from Bruker.

Thermal gravimetric analysis (TGA): TGA measurements were performed using a PerkinElmer (TGA 8000) from 25 to 900 °C under a constant argon flow (30 mL min^-1) with a heating rate of 10 K min^-1.

Contact angle measurement: The contact angle was measured using the image of a sessile drop with DI water at the points of intersection (three-phase contact points) between the drop contour and the projection of the surface (baseline) (KRUSS instruments, DSA25E, CA).

1.3 Synthesis of the ionic liquid monomer (3-dodecyl-l-vinylimdiazolium bromide)

9.4 g of 1-vinylimidazole and 25g of 1-bromododecane (1:1 molar ratio) and 20 ml of ethanol were mixed together inside a 100 ml round bottom flask at 40 °C for 16 h. A needle was used to reduce the pressure inside the flask. In the next day, the reaction mixture was added drop by drop to IL diethyl ether and the precipitate was filtered off gently, and dried at 40 °C using vacuum oven.

1.4 Synthesis of poly(l-n-dodecyl-3-vinylimidazolium bromide) nanoparticle dispersion 5g of monomer and 150 mg of a water-soluble thermal initiator VA-086 were added to 100 ml of water inside a 250ml round bottom Schlenk flask. The flask was treated with three freeze-pump-thaw cycles. The reaction was stirred at 70°C for 16 h. Next day, the polymer dispersion was filtered off using a filter paper and a funnel to remove impurities and big aggregation of nanoparticles. The proton nuclear magnetic resonance (¹H-NMR) spectra is shown in Figure SI, where the chemical shifts of all signals are well-assigned to individual protons in polymer.

1.5 Preparation of the PIL/Cu colloidal nanoparticle dispersion 2 ml of the PIL nanoparticle dispersion was diluted with 9 ml of water. Then 1 ml of water containing 40 mg of copper acetate salt was added to the solution. After stirring for 2 h, aqueous hydrazine solution (35 wt.%) was dropwise added to the solution. Very gentle change of color happened during this step. The solution was sonicated for ca. 20 min. Then, the solution was placed in an oil bath under stirring at 80°C for overnight. The next day, the color of the solution changed to pink. Next, the solution was sonicated again for ca. 20 min. In the following, by using a 5 pm filter and a syringe the solution was filtered off to remove any big aggregates.

1.6 Coating procedure A glass slip with size of 24 x 24 mm and thickness of 0.5 mm was treated with an oxygen Plasma instrument for 3 min to make the substrate surface hydrophilic and clean. At the final stage, with help of a spray coating machine (a spray machine with pore size of 100- micron meters, a flow rate of 2 ml per min, and a point size of 6.5 cm x 6.5 cm at a distance of 8.5 cm), the hydrophilic surface of glass slip was coated with the PIL/Cu nanoparticles dispersion for ca. 30 seconds with a film thickness of ca. 100-micron meters. The rinsed film was dried under vacuum (5 x 10^-2 mbar) at 80 °C overnight.

1.7 Antiviral activity tests of hybrid coating Cover glasses were placed into a 6 cm dish and 50 pL containing a known number of infectious units of SARS-CoV-2 was applied in the centre of the glass. The droplet was immediately covered by uncoated cover glass to spread the virus on the whole area. After incubation at specified time, usually 5, 15, 30, 60 and 180 min, 1950 pL IX PBS was added to the coverslips, the top coverslip was lifted and the virus-exposed sides of both coverslips were washed with PBS by pipetting 3 times to collect the virus species. All washes were collected and used for titre determination by plaque assay. Briefly, Vero E6 cells (ATCC-CRL- 1586), maintained in Dulbecco's modified Eagle medium (Gibco) supplemented with 10% fetal calf serum and 1% penicillin-streptomycin and cultured at 37 °C in a humidified incubator with 5% CO2, were washed with PBS, and two-fold serial virus dilutions of SARS- CoV-2 was added in 200 pL minimal essential medium (Invitrogen) supplemented with 0.2% bovine serum albumin, 2 mM L-glutamine, and 20 mM HEPES with periodic shaking for 1 h 37°C. Virus solutions were then removed and cells washed with PBS before addition of 1 mL of prewarmed overlay (2% Methylcellulose: propagation media containing 2% FBS= 2:3). At 48-72 h post infection, cells were fixed with 4% formaldehyde and stained with crystal violet solution after removal of the overlay and plaques were manually quantified. The determination of all virus titres was performed in triplicate.

2. Supplementary Data 2.1 ¹H-NMR spectrum of PIL

See Figure 5.

2.2 TGA analysis of PIL nanoparticles

See Figure 6.

Results and discussion

The stepwise fabrication of the spray-coating film onto a glass slide with a colloidal dispersion of PIL/Cu composite nanoparticles is provided in Figure 7. The colloidal nanoparticle dispersion comprises a composite of PIL nanoparticles containing Cu nanoparticles that are located on PIL nanoparticles. The synthesis and characterization details of the PIL used in this study, named poly(l-n-dodecyl-3-vinylimidazolium bromide) are provided in Supporting Information.

The convenient method to obtain Cu nanoparticles in the solution phase is the chemical reduction of a copper salt by a proper reducing agent. Several reducing agents can be utilized at different reaction temperature, e.g. sodium borohydride at room temperature, hydrazine (N2H4, at 80 °C), and ascorbic acid (vitamin C, at 100 °C) I^40-42]. Depending on the choice of the reducing agent, water-soluble by-products may be generated after the reduction of copper salt. An additional step of dip-washing of the film product in clean water for 30 s is added to remove any by-product.

In a typical surface coating procedure, copper acetate was added into the aqueous dispersion of PIL nanoparticles. In following, a reductant hydrazine (N2H4) was added at 80 °C to reduce the Cu ions into Cu nanoparticles, which are stabilized in situ by the surface of PIL nanoparticles. To ensure the full reduction of metal salts to metal nanoparticles, the reducing agent was added in a 2 molar equivalent ratio to the metal salt. Next, via a spray setup, the dispersion solution was sprayed onto the surface of a glass slide, which due to the water-insolubility of the PIL forms a waterproof film that remains intact when dipped washed in water. The film on the glass slide was then placed under vacuum (5 x 10^-2 mbar) and fully dried in an oven at 80 °C at least for 2 hours. More detailed information about the coating preparation method is provided in Supporting Information.

In Figure 8 A,B, cryogenic transmission electron microscopy (cryo-TEM) images of the PIL nanoparticles with a long dodecyl substituent on the vinylimidazolium repeating unit in aqueous solution are provided. The dark dots represent the PIL nanoparticles in a spherical shape. The native inner morphology is clearly distinguishable, where a quasi-spherical onionlike vesicular nanostructure is identified with its size variation in the range of 20-50 nm. The dark ring within the nanoparticles represents the ionic mainchain domain, and the higher contrast originates from the Br anion that serves also as a contract agent here. The grey ring zones come from the packed alkyl substituents that are of a lower contract in the TEM. The number of bilayers of co. 3.42 nm in thickness is countable in the typical range of 4-8 and is dependent on the size of nanoparticles. Previously, the analysis of small-angle X-ray scattering (SAXS) measurements showed a d spacing of 3.40 nm for PIL nanoparticles with a dodecyl substituent ^[39], which is in agreement with the value determined here by the cryo-

TEM tests.

The scanning electron microscopy (SEM) shown in Figure 9A visualizes a composite of PIL/Cu colloidal nanoparticles in a spherical shape with a similar size as the pristine PIL nanoparticles. The sample morphology on the glass substrate does not change after the glass plate was immersed in water for 10 minutes, a phenomenon that arises from the insoluble nature of the PIL nanoparticle in water and its strong surface-binding function. But the presence of Cu nanoparticles cannot be demonstrated by SEM due to their rather small size. Therefore, cryo-TEM for the PIL/Cu colloidal composite was employed (Figure 9B). Clearly, Cu nanoparticles of 1-4 nm in size are observed to locate on PIL nanoparticles, highlighted by white arrows. It is worthwhile to mention that particles smaller than 1 nm may exist but are not observable due to the weak contrast between the PIL matrix and the Cu nanoparticles in the cryo-TEM image. In order to confirm the existence of Cu nanoparticles in the composite dispersion, X-ray diffraction (XRD) patterns of the dried PIL nanoparticles and PIL/Cu composite were recorded and are compared in Figure 9C. The comparison between these two patterns reveals that the PIL nanoparticles are obviously in an amorphous state, and the presence of all three sharp peaks in the XRD pattern of the PIL- Cu composite sample is in accordance with the standard pattern of pure face-center cubic metallic Cu (JCPDS, File No 04-0836); the three peaks at 43°, 55°, and 74° correspond to the (111), (200), and (220) reflections I⁴³-⁴⁴!. In Figure 9D, the thermogravimetric analysis (TGA) of the PIL/Cu colloidal composite in air shows a 5 wt.% mass loss at 250 °C, and then a rapid decomposition up to 600 °C, followed by a constant mass loss till a final residue of 13.7% at 900 °C. By contrast, the TGA plot of the pristine PIL nanoparticles shows a complete decomposition already at 600 °C (Figure S2). The difference in mass residue between two samples determines a metallic Cu content of 9.6 wt.% in the PIL/Cu composite particles. This is in good agreement with our combustion-based elemental analysis result of 10.1 wt% of Cu in the composite.

To explore the property of the coated surface with the as-prepared dispersion of PIL/Cu colloidal nanoparticles, water contact angle measurements were performed (Figure 10 A,B). The presence of Cu nanoparticles in the composite of PIL/Cu nanoparticles decreases the contact angle from 83.6° for pristine PIL nanoparticles to 65.4° for the composite, very possibly due to the increased surface hydrophilicity arising from the Cu nanoparticles I⁴⁵-⁴⁶!.

The virucidal activity of glass substrates coated with pristine PIL, and the composite of PIL/Cu nanoparticles is shown in Figure 10C. Substrates were incubated with SARS-CoV-2-containing solution for indicated times and residual infectivity was analysed by plaque assay. The pristine PIL nanoparticles coated on the glass substrate have little-to-no virucidal effect on SARS-CoV-2 virions in the first 60 min compared to uncoated glass. By contrast, the plot of virucidal activity of the composite of PIL/Cu nanoparticles indicates that within 30 min, 90% of SARS-CoV-2 virions is deactivated, and 180 min is enough for 99.5% deactivation. Thus, the introduced Cu nanoparticles play a decisive role in the antivirus function here. Copper nanoparticles have been a favorable choice as protective coating due to their known virucidal function. Note that the film coating sticks to the surface, unlike the majority of ethanol-based liquid disinfectants that need to be repeatedly used to eliminate virus from surfaces. In this context, the colloidal dispersion of PIL/Cu composite nanoparticles is more effective in long-term protection of surfaces against SARS-CoV-2 virions and helping reduce their spread through surface contact.

Conclusions

In conclusion, the inventors have practiced the preparation of a composite film containing imidazolium-based PIL nanoparticles with a dodecyl substituent and the Cu nanoparticles located on them. The unique quasi-sphere multilamellar structure of PIL nanoparticles enables the water-insoluble PIL to be well-dispersed in water in the form of nanoparticles. In combination of the cationic charge on the PIL, the PIL nanoparticles can effectively stabilize Cu nanoparticles on their surface. The waterborne composite nanoparticles can spray onto and coat the substrate surface. The virucidal activity test proves such surface coatings have potential application to deactivate SARS-CoV-2 virions from surfaces.

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The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, including the examples, and the appended claims.

Claims

1. A colloidal composite particle dispersion for use in an antimicrobial and virucidal surface coating, comprising a composite of: (a) a colloidal poly(ionic liquid) particle that is molecularly insoluble in water and comprises a n-alkyl substituent; and (b) metal nanoparticles that are deposited on the poly(ionic liquid) particles; wherein the composite particle is in a polar protic solvent, such as a water-based solution.

2. The colloidal composite particle dispersion according to claim 1, wherein the cation of the colloidal poly(ionic liquid) particle is chosen from imidazolium, pyridinium, triazolium, tetraalkylammonium and tetraalkylphosphonium.

3. The colloidal composite particle dispersion according to claim 1 or 2, wherein the n-alkyl substituent of the colloidal poly(ionic liquid) particles is chosen from the interval of octyl (C8) to octadecyl (C18) substituent.

4. The colloidal composite particle dispersion according to claim 3, wherein the n-alkyl substituent of the colloidal poly(ionic liquid) particles is chosen from the interval of dodecyl (C12) to tetradecyl (C14) substituent.

5. The colloidal composite particle dispersion according to any of claims 1-4, wherein the metal nanoparticle is chosen from Cu or Ag.

6. The colloidal composite particle dispersion according to claim 5, wherein the metal nanoparticle is Cu.

7. The colloidal composite particle dispersion according to any of claims 1-6, wherein the polar protic solvent is an aqueous media, having a water content above 50%.

8. A coating composition for antimicrobial and/or virucidal surface coating, comprising the

28 colloidal composite particle dispersion according to any of claims 1-7, and optionally other ingredients such as dye and/or odorant molecules, wherein the coating composition exhibits water stability.

9. The coating composition according to claim 8, wherein hydrophobic fluorescent molecules are included in the composition.

10. Method for applying the coating composition of claims 8-9, wherein the coating composition is applied to a suitable indoor and/or outdoor surface as a film having a thickness in the interval of 10-500 pm.

11. Method for applying the coating composition of claim 10, wherein the coating compostion is applied as a spray.

12. Use of the colloidal composite particle dispersion of any of claims 1-7 and/or the coating composition of any of claims 8-9, in virucidal applications including deactivation or elimination of viruses, such as SARS-CoV-2, at a suitable indoor and/or outdoor surface.

13. A method for preparation of a colloidal composite particle dispersion according to claims 1-7, comprising the steps of:

(a) providing a ionic liquid monomer comprising a n-alkyl substituent, wherein n is in the interval from 8 to 18;

(b) polymerizing the ionic liquid monomer comprising the n-alkyl substituent in a polar protic solvent, such as a water-based solution, in the presence of a radical initiator, to produce a colloidal poly(n-alkyl-ionic liquid) particle dispersion;

(c) adding a metal salt to the dispersion of step (b), and

(d) reducing the metal salt by adding a reducing agent to the dispersion of step (c); thereby obtaining a colloidal poly(ionic liquid)/metal composite particle dispersion.

14. The method according to claim 13, wherein the n-alkyl chain-ionic liquid monomer is provided in step (a) in a concentration of about 0.5-20% (weight).

15. The method according to any of claims 13 or 14, wherein the reducing agent of step (d) is added in a 2 molar equivalent ratio to the metal salts to ensure full reduction of metal salts to metal nanoparticles.