WO2012071605A1 - Procédé pour préparer des nanoparticules d'or - Google Patents

Procédé pour préparer des nanoparticules d'or Download PDF

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WO2012071605A1
WO2012071605A1 PCT/AU2011/001541 AU2011001541W WO2012071605A1 WO 2012071605 A1 WO2012071605 A1 WO 2012071605A1 AU 2011001541 W AU2011001541 W AU 2011001541W WO 2012071605 A1 WO2012071605 A1 WO 2012071605A1
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pim
iii
membrane
solution
gold nanoparticles
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PCT/AU2011/001541
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English (en)
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Spas Dimitrov Kolev
Robert Walter Cattrall
Ya Ya Nutchapurida Bonggotgetsakul
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The University Of Melbourne
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Priority claimed from AU2010905260A external-priority patent/AU2010905260A0/en
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Publication of WO2012071605A1 publication Critical patent/WO2012071605A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures

Definitions

  • the present invention generally relates to the field of nanoparticle formation and in particular to processes which generate gold nanopaiticles on the surface of a polymer substrate.
  • the invention particularly relates to processes for preparing monolayers of gold nanopaiticles on the surface of polymer inclusion membranes (PIMs), and PIMs with gold nanopaiticles deposited on the surface thereof.
  • PIMs polymer inclusion membranes
  • Au nps Gold nanopaiticles
  • Au nps have become a popular topic for research due to their unique photonic, electronic, magnetic and catalytic properties.
  • Different sizes and structures for Au nps can be prepared using a wide variety of methods which result in changes in their appearance and properties. This has led to many important applications (e.g. novel biomedical imaging techniques and therapies; sensor development for detecting biological molecules and heavy metals ions; catalytic surfaces for various reactions).
  • there are two main processes for Au nps synthesis namely, linear-template methods and template-free self-assembly methods.
  • Linear-template methods involve the use of templates to grow Au nps in the presence of a suitable reducing reagent.
  • the templates used range from linear polymers, biomoJecules (e.g. DNA and proteins), inorganic nanowires and nanotubes,. and step edges on solid substrates (e.g. electrodepositing of nps on solid substrates).
  • the preparation of Au nps on linear polymers such as Nafion, po!y(vinyl chloride) (PVC) and cellulose triacetate (CTA) has been studied.
  • membrane-based processes for selective separation of heavy metals have attracted considerable attention, They have many advantages over other processes as they use lower amounts of solvents than solvent extraction and the membrane systems are usually compact and robust, enabling them to be easily implemented in existing industrial processes.
  • Polymer inclusion membranes are a relatively new type of liquid membranes formed by casting a solution containing an extractant, . a plasticizer and/or modifier and a base polymer dissolved in a volatile solvent and allowing the solvent to evaporate.
  • the resulting membrane is transparent and visually homogeneous and has a number of advantages over the other liquid membrane types (e.g. supported liquid membranes, bulk liquid membranes and emulsio liquid membranes), particularly in terms of stability.
  • the extractant often referred to as the carrier, is usually a complexing agent or an ion-exchanger and is an essential component for metal extraction.
  • a plasticizer e.g. 2-nitrophenyloctyl ether (2- NPOE)
  • modifier e.g. 1-dodecanol
  • the present invention utilizes similar PIM based methodology with the distinct advantage of being able to prepare monolayers of gold nanoparticles predominantly on the surface of the membrane.
  • the present invention provides a process for preparing monolayers of gold nanoparticles on a PIM surface in an efficient and high yielding manner.
  • the present invention provides a method of preparing gold nanoparticles on the surface of a polymer inclusion membrane (PIM) including the steps of:
  • step (ii) contacting the PIM with an acid solution comprising a Au(III) species and extracting at least a portion of the AuQII) species from the acid solution into the PIM to form a PIM loaded with said ⁇ ( ⁇ ) species; and iii. treating the loaded PIM from step (ii) with a Au(III) reducing agent characterised in mat the agent cannot readily reduce the Au(IIl) species within the PIM, leading to the formation of gold nanoparticles on the surface of the PIM,
  • FIG. 2 (a)-(d). Photographs of PVC/Aliquat 336/DD PIMs loaded with Au(M) after 24 h exposure to solutions of 1.00 mol L "1 of (a) L-ascorbic acid, (b) NaBHj, (c) tri-sodium citrate, and (d) di-sodium ethylenediaminetetraacetate NazEDTA.
  • FIG. 6 (a)-(d). Photographs of PVC/AIiquat 3367DD PIMs loaded with Au(lll) after 24 h exposure to solutions of 1.00 M EDTA at pH (a) 4.0, (b) 4.5, (c) 6.0, and (d) 8.0.
  • Figure 8 Size distribution histogram for Au nps on the surface of a PIM conditioned with 0.10 mol L "1 EDTA at pH 6.
  • FIG. 12 (a)-(e). Photographs of PVC/Aliquat 336/DD PIMs with different Au(III) extraction time and exposed to 0.100 M EDTA solutions at pH 6 for 24 h
  • Figure 14 (a)-(g). Photographs of PVC/Aliquat 336 DD PIMs loaded with Au(III) after different exposure periods to 0,100 M EDTA solutions at pH 6 (a) 1 h, (b) 2 h, (c) 3 h, (d) 4 h, (e) 5 h i (f) 10 h, and (g) 24 h.
  • Figure 19 Graphs depicting the relationship between the amount of Hg accumulated onto the Au-PI based on (a) the concentration of Hg in the ambient air for different adsorption periods (2-7 days) or (b) the duration of adsorption for different concentrations of Hg in the ambient air.
  • the present invention is predicated on the discovery that a monolayer of gold nanoparticles can be prepared on the surface of a PIM through the reduction of Au(III) species by a reducing agent which cannot readily reduce the Au(HI) species in the bulk environment of the PIM and as such the reduction occurs almost exclusively at the PIM surface.
  • Polymer inclusion membranes are generally known in the art, and may also be referred to as "polymer liquids", “gelled liquids”, “polymeric plasticized”, “fixed-site carriers” or “solvent polymeric membranes”.
  • SLMs supported liquid membranes
  • PIMs are generally not characterised as having low interfacial surface areas and mass transport rates. PIMs also do not suffer the problem of emulsion breakage which tends to plague emulsion liquid membranes (ELMs).
  • PIMs according to the present invention are generally formed by mixing (casting) a solution which contains a Au(III) species extractant (ie the quaternary ammonium salt), a plasticizer/modifier and a base polymer.
  • a solution which contains a Au(III) species extractant (ie the quaternary ammonium salt), a plasticizer/modifier and a base polymer.
  • the casting process is typically facilitated with the use of organic solvents (such as ethers (eg THF, dicthylether) and chlorinated solvents (eg dichloromethane)), which are typically removed during membrane formation (eg by air drying or in vacuo).
  • organic solvents such as ethers (eg THF, dicthylether) and chlorinated solvents (eg dichloromethane)
  • the extraction process referred to herein involves the controlled transport of Au(III) species into the membrane. Such a process is facilitated by a carrier (referred to herein as the "extractant") that is essentially a Au(IH) complexing agent or an ion-exchanger.
  • the extractant is the immobilised quaternary ammonium salt.
  • quaternary ammonium salt is represented by formula (1):
  • R'-R 4 are independent alkyl chains and X ⁇ is an anion.
  • R 1 is a C1-C4 alkyl chain
  • R 2 -R 4 are independently C8-C30 alkyl chains.
  • R 1 is a CI-CJ alkyl chain
  • R ? -R 4 are independently Ce-Cio alkyl chain, and more preferably Cg-Cio alkyl chain.
  • X ⁇ is an anion such as chloride, nitrate or bromide!
  • the immobilised quaternary ammonium salt is Aliquat 336 ® (Cognis Corp.).
  • Aliquat 336 is a mixture of compounds of formula (1) where Ri is methyl, R2-R4 are mixtures of C» (octyl) and CH> (capryl) chains (predominantly Cg), and X ⁇ is chloride.
  • the quaternary ammonium salt constitutes from 5 - 40% m/m of the PIM, preferably from about 10% - 30% m/m and more preferably from about 15 - 25% m/m of the P1M.
  • the PIM according to the present invention may be formed from any suitable base polymer which provides mechanical strength to the membrane.
  • the polymer is selected from polyvinyl chloride) (PVC), cellulose triacetate (CTA), and cellulose tributyrate (CTB), or suitable derivatives thereof.
  • PVC polyvinyl chloride
  • CTA cellulose triacetate
  • CTB cellulose tributyrate
  • the polymer is PVC, CTA or a derivative thereof.
  • the polymer is PVC. - Gr ⁇
  • the polymer constitutes from about 40-80% m/m of the PIM, preferably from about 50-75% m m, more preferably from about 55-75% m m, and even more preferably about 70% m m.
  • the PIM preferably also comprises a plasticizer or modifier component.
  • T e role of the plasticizer is to penetrate between polymer molecules and to "neutralize" the polar groups of the polymer with its own polar groups or to merely increase the distance between the polymer molecules and hence reduce the strength of the intermolecular forces.
  • the plasticizer may be any suitable organic compound which is able to function as described above. Suitable organic compounds include those containing a hydrophobic alkyl backbone with one or several highly solvating polar groups.
  • the role of the modifier is to increase the solubility of the extracted chemical species in the membrane liquid phase.
  • the plasticizer/modifier is selected from the group consisting of 2- nitrophenyl octyl ether (2-NPOE), dibutyl butyl phosphorate (DBBP), 1-hexanol, 1- heptanol, 1-octanol, 1-nonanol, 1-decanol, l-dodecanol, 1-tctradecanol, o- ratrophenylpentyl ether (oNPPE), tributylphosphate (TBP), dioctylphthalate (DOP), bis(2- ethylhexy terephthalate (DDTP), dioctylsebacate (DOS) and t -(2- emylliexyl)phosphate(T2EHP).
  • the plasticizer is selected from TBP, 2-NPOE, 1-tetradecanol and 1- dodccanol.
  • the plasticizer is l-dodecanol.
  • the plasticizer/modifier constitutes from about S-40% m/m of the PIM, preferably about 5 - 30% m/m and more preferably from about 5-15% m/m.
  • the ratio (based on % m/m) of polymer : quaternary ammonium salt : pIastici2fir/modifier is 5:2:3 - 7:1:2.
  • the ratio range (based on % m/m) of polymer : quaternary ammonium salt : plasticizer/modifier is about 7:2:1 to 16:3:1.
  • the ratio is about 7:2:1, for instance, a preferred composition is 70% m m PVC, 20% m/m Aliquat 336 and 10% m/m 1-dodecanol. d) Optional other components
  • the PIMs of the present invention may also include additional components to aid in the extraction process.
  • the PIMs may include other quaternary ammonium salts, plasticizcrs/modifiers and base polymers, antimicrobial agents (for instance, to inhibit membrane fouling), antioxidants (for increased stability), porosity agents (porogens), ferromagnetic particles, and residual amounts of casting solvents. Extraction of Au(III) species
  • the extraction process comprises the step of contacting an aqueous acid solution (containing a negatively charged Au(III) complex) with the PIM (as characterised above).
  • contacting includes any means by which the acid solution comes into physical contact with the PIM such that the AuflH) species from the solution can be extracted by the PIM.
  • the extraction process involves ion- exchange chemistry between the anion of the extractant (i.e., the chloride anion of a quaternary ammonium chloride) and the negatively charged Au(III) complex.
  • Th quaternary ammonium AuQII) ion-pair thus formed on the surface f the membrane will diffuse into the bulk membrane.
  • the Au(III) can be thought of as essentially being accumulated in the bulk of the membrane and at least partially on its surface.
  • Contacting in the above manner includes adding or physically immersing the PIM with or into the acid solution (for instance, in a batcbwise extraction process) or allowing a flow of the Au(III) solution to come into contact with a surface of the PIM (such as in a continuous extraction process).
  • Possible configurations for batchwise and continuous extraction/stripping (regenerating) processes would be known by those of ordinary skill in the art and are discussed in more detail below.
  • the Au(III)species may be any species which is able to perform ion-exchange chemistry with the extractant of the PIM under the conditions set out herein.
  • the Au(III) species must be negatively charged (e.g. AuCl- to be able to exchange with the chloride anion of Aliquat 336 or it can be a neutral species capable of forming a complex with the chloride ion of Aliquat 336 (e.g. AuC3 ⁇ 4).
  • the usual way of extracting Au(M) int the membrane mentioned above is from acid solutions, for instance, HC1 solutions, where suitable negatively charged or neutral Au(III) complexes are formed.
  • the Au(III) species is present in an acid solution with a concentration of 1 -5M, such as 2-4M, for instance, about 2.5, 3, 3.5 or 4 M.
  • the Au(Hl) species can be supplied commercially as HAuCl* (from Aldrich Chemical Company) dissolved in about 2.5M HC1.
  • the acid solution of Au(III) is preferably contacted with PIM so as to provide the maximum surface area of PIM to absorb (and hence extract) the Au(III).
  • the treatment process involves immersing the PIM in the aqueous solution.
  • Immersion of the PIM may be achieved by any convenient means and will depend on the form of the PIM (i.e., beads, hollow fibres, sheets, plates, etc).
  • the PIM beads may be immersed in the solution and dispersed by mechanical agitation such as stirrers and the like or with the use of mixing pumps immersed in the aqueous solution, or by the use of gas (eg air) bubbled through the aqueous solution. Sufficient shear forces will need to be imparted on the solution to optimise dispersion of PIM beads.
  • the PIM is said to be loaded with Au(III) (i.e., loaded PIM).
  • the process of the present invention may typically involve an additional step of physically separating the loaded PIM from the aqueous acid solution prior to the reduction step.
  • Physical separation may be achieved by allowing the loaded PIM to settle or by simply filtering through a mesh of appropriate porosity.
  • Other means for separation and collection of the loaded PIM include (for instance, on an industrial scale) the use of vacuum collectors, magnetic transport (for instance where the PIM comprises magnetic particles), belts, pipes, disks, drums, auger screws, etc. Whatever the means it is preferred that the separation and collection process does not (to any great extent) cause mechanical wear which may lead to attrition of the PIM.
  • An important feature of the present invention is the treatment of the loaded PIM with a reducing agent.
  • the reducing agent is said to be characterised in that it is not capable of readily reducing the Au(III) species within the bulk of the PIM thus leading to the formation of a gold nanoparticles on the surface of the PIM.
  • One notable reducing agent for the present process is EDTA (ethylenediaminetetraacetic acid).
  • EDTA ethylenediaminetetraacetic acid
  • the reduction process is said to be completed once >90% of the PIM surface is covered with Au nps. In an embodiment this coverage can be achieved by exposing the PIM to an EDTA solution for about 24 h. Exposure as used herein refers to contacting the EDTA solution with the spent OT loaded PI , for instance, by immersion, mixing or shaking.
  • the reducing agent is selected from a compound of formula (II):
  • n is an integer from 1 to 6 (preferably 2);
  • n to q are independently selected from an integer from 1 to 4 (preferably n, o, p, and q are all 1),
  • the reducing agent is a citric acid salt, for instance, trisodium citrate.
  • the average size of the Au nanoparticles on the PIM surface is from about 10-30 nm.
  • the average size of the Au nanoparticles is from about 15-25 nm.
  • the average size of the Au nanoparticles is about 20 nm.
  • the reduction step is conducted at a pH of 5,0-6.8, and more preferably in a range of 5.5-6.5, and preferably at about 6.
  • the reducing agent of present invention such as, EDTA (and polyamino carboxylic acid reducing agents like EDTA) requires water to reduce Au(IIi) to metallic gold and that water is not available within the membrane (i.e., hydrophobic membrane bulk).
  • Reducing agents used in prior art methods such as NaBRi do not need water to facilitate the reduction process and as such these agents can operate inside the membrane bulk. Accordingly, it is postulated that for this reason (at least in part), the reduction process occurs almost exclusively at the membrane surface.
  • the invention provides a PIM comprising gold in the form of Au(III) and metallic gold nanoparticles wherein at least 80 % of the gold is in the form of metallic gold nanoparticles which are present on the surface of said PIM.
  • the remaining 20% of the gold either as metallic gold or Au(lII) will reside in the bulk of the PIM.
  • more than 90% of the gold nanoparticles are present on the surface of satd PIM.
  • the PIM is preferably a PVC polymer based PIM.
  • the PIM is preferably a PVC polymer based PIM
  • the gold nanoparticles are spherical with an average size of about 1 -30 run.
  • the gold nanoparticles at the surface of the membrane as produced by the present invention may be used to react directly with suitable reactive species (e.g., molecules and ions, and metals such as mercury vapour) in a variety of applications due to their photonic, electronic, magnetic, and catalytic properties.
  • SE analysis of the surface of the PIMs of the present invention revealed that the Au nps are formed predominantly (and in embodiments, almost exclusively) as a monolayer which will enhance the functioning of the Au nps through increased surface area.
  • the PIMs of the present invention are thus of interest in optical sensing, passive sampling and catalytic applications.
  • PIMs of the present invention which are characterized with a surface of Au nps (or Au-PIM) may be employed in the passive sampling of mercury in air.
  • Passive sampling which is the sampling over a long period of time (e.g., from days to many months), is a simple and low cost technology that allows the sampling of a huge array of chemicals at numerous locations. It also allows the determination of the average concentration of bio-available analytes over time, which is not possible with spot sampling due to their ever-fluctuating concentrations in nature and/or episodic contamination. This approach also allows the study of the uptake and accumulation of chemicals, e.g. metals, and organic pollutants, in organisms.
  • the invention provides for the incorporation of the Au- PIMs of the present invention into a passive sampling device.
  • the present inventors have also found that the Au-PIMs of the present invention have a strong adsorption ability and high capacity for metallic mercury (Hg°) accumulated from the air by forming an amalgam.
  • the passive sampling device incorporating the Au-PIMs of the present invention is used for the monitoring of mercury vapour in air.
  • the invention also provides a method of monitoring mercury in an air sample, said method comprising the step of contacting an air sample with a passive sampling device whioh comprises a Au-PIM of the present invention • wherein the air sample is exposed to the Au-PIM.
  • the monitoring process described above also typically involves a detection step.
  • This detection step may involve any one which is currently employed to detect the production of the Au-Hg amalgam. For instance, such a reaction may lead to a colour change in the Au nps which can be detected using standard colorimetric techniques, for instance, a localized surface plasmon resonance (LSPR) - based colorimetric detection method.
  • LSPR localized surface plasmon resonance
  • mercury in the amalgam on the surface of the Au nps can be dissolved by . immersing the PIM into a suitable acidic solution where it can be determined by a suitable analytical method (eg atomic fluorescence spectrometry).
  • a suitable analytical method eg atomic fluorescence spectrometry
  • Aliquat 336 (AQ), (Aldrich, a mixture of quaternary ammonium chlorides), high molecular weight powdered PVC (Fluka), cellulose triacetate (CTA) (Aldrich), 1-dodecanol (DD) (Aldrich), dichloromethane (Lab-scan, Australia) and tetrahydrofuran (Chem-supply, Australia) were used as received.
  • Au(III) calibration standards were made from a 1000 mg L Au(III) standard solution (BDH Spectrosol).
  • Au(III) solutions for membrane extraction were prepared from HAuCl 4 (Aldrich) dissolved in 2,5 M HC1.
  • Aqueous solutions (0.10 M) of L-ascorbic acid (Sigma), tri-sodium citrate (Cbera-supply, Australia) and sodium borohydride (Ajax Finechem, Australia) were used for the reduction of Au(III).
  • BDTA solutions were prepared from the disodium salt (Fison) and the pH was adjusted with 0.10 M hydrochloric acid or sodium hydroxide solutions.
  • the solution concentration of Au(III) was determined by atomic absorption spectrometry (AAS, Hitachi Z-2000 Series Polarized Zeeman atomic absorption spectrophotometer, Japan).
  • the temperature controlled extraction experiments were conducted in conical flasks positioned on a thermostated orbital mixer incubator (Model OM11, Ratek) for temperatures of 20°C and above and on a platform orbital mixer (Model OM6, Ratek) located in a commercial refrigerator (CLEOO, temperature controller E5CN, OMRON) for temperatures below 20°C.
  • Optical microscopy and membrane thickness measurements were conducted with a Motic SMZ-140 stereo microscope (Motic, China) with 60x magnification in combination with a MoticCam 1000 microscope camera (Motic, China).
  • concentration of EDTA was determined by visible spectrophotometry (Libra S12, Biochrom).
  • the surface analysis of gold coated PIMs was conducted by a quadrupole laser ablation inductively coupled plasma mass spectrometer (ICP-MS) (Model 810, Varian).
  • Membranes were immersed in 100 mL of 100 mg L 1 Au(IlT) solutions containing 2.5 M HC1 in conical flasks which were shaken under controlled temperature on a platform orbital mixer at 150 rpm. Samples of the Au(III) solution (0.4 mL) were removed at predetermined time intervals throughout the course of the experiment. The samples were diluted to 8 mL with deionized water and the Au(III) concentration was determined by AAS.
  • IR spectra of the membranes (250*3 mg) studied were recorded prior to being immersed in conical flasks, each containing.100 mL of 1.0 10° M EDTA solution.
  • the flasks were shaken on a platform orbital mixer incubator for a predetermined period of time at 20°C. if not stated otherwise.
  • Samples of the EDTA solutions (0.1 mL) were removed at different time intervals throughout the course of the experiment.
  • the samples were mixed with 0.1 mL of 2.0 10 "3 M ZnfPARfc solution, diluted to 10 mL with deionized water, and the solution absorbance was measured at 491 nm.
  • the membranes were then rinsed with deionized water to remove trace amounts of EDTA from the surface of the PIMs.
  • the membranes were then allowed to dry in air for 12 h prior to recording their. IR spectra.
  • IR spectrum of EDTA in nujol was also recorded on Br discs coated with a thick layer of Na 2 EDTA in nujol and then compared with the IR spectra of PIMs recorded prior and after EDTA extraction.
  • Au(II0 loaded PVC membranes were immersed in 0.10 mol L '1 solutions of the following reducing agents: L-ascorbic acid, NaBttt, tri-sodium citrate and Na ⁇ EDTA (pH 4.5). The solutions were shaken for a period of 24 h. After rinsing with deionized water and drying in air, the membranes were examined visually (Fig. 2). It can be seen that the membranes immersed in L-ascorbic acid and NaBH 4 solutions appear black while membranes immersed in tri-sodium citrate and EDTA have a highly metallic surface appearance and are dark brown and light reddish-brown, respectively.
  • FIG. 3 SEM images of the membranes and their cross sections were captured and are shown in Fig. 3.
  • the images of membranes exposed to L-ascorbic acid, NaBH* and tri-sodium citrate show the formation of Au nanocrystallites with different and irregular shapes, and even sponge like structures in the case of tri-sodium citrate (Figs. 3a, 3b and 3c).
  • the nanocrystalUtes vary in size from 100 nm for L-ascorbic acid to 5 nm for NaBH*.
  • the sponge like network for tri-sodium citrate appears to have a pore size of approximately 20 nm.
  • citric acid has a slightly larger molar mass (192.1 Da) than the practically monoprotic L-ascorbic aid (176.1) with pK» values of 4.10 and 11.60.
  • the borohydride anion is much smaller than the anions of both acids mentioned above. Therefore it can be expected that the citrate ion-pairs with the Aliquat 336 cations are bulkier than the borohydride and L- ascorbate ion-pairs. This explains the more pronounced formation of Au nps on the membrane surface in the case of reduction with citrate compared to exposing the membrane to the other two reducing agents (Fig.
  • the main reasons for this phenomenon could be: (1) the larger size (molar mass of 292.4 Da) and multiple negative charges (pK* values 2.00, 2.69, 6.13, and 10.37) of the EDTA anions which prevented their extraction into the PIM and slowed down the mass transfer of the corresponding ion-pairs within the membrane; and/or (2) the lack of water within the membrane required to facilitate the oxidation of EDTA.
  • An oxidation mechanism of EDTA by Au(III) has been proposed which involves the participation of water, while the oxidation of the other reducing agents studied (i.e. NaBK . L-ascorbic acid, tri-sodium citrate) did not require the presence of water.
  • EDTA can exist in several ionized species with charges from - I (acidic conditions) to -4 (alkaline conditions). The charge of the EDTA ion will determine its ability to form an ion-pair with the Aliquat 336 cation and to be transported within the membrane. Also, the actual Au(III) reduction mechanism involving EDTA could be iniluenced by solution pH. Therefore it was of interest to investigate the effect of solution pH on the formation of Au nps. In the associated experiments Au(III) loaded PIMs were immersed in 0.10 mol L ⁇ ' EDTA at pH 4.0, 4.5, 6.0, or S.O. The photographic images of the membranes, presented in Fig. 6, show that the colour of the membranes change from yellow at pH 4 to light metallic reddish-brown at pH 4.S and darker metallic brown at pH 6.0 and pH 8.0.
  • the optimal pH for the formation of a surface layer of Au nps was selected as 6.0.
  • the size distribution of the Au nps at pH 6.0 was obtained from the SEM image of the membrane and the corresponding histogram is shown in Fig. 8. It can be seen that the size range is quite narrow, with the average size being 20 nm.
  • the small amount and size of the Au nps was probably due to the decreased mass transfer rate of the Au(III) ion-pair from the bulk of the , membrane towards its surface.
  • a substantially larger amount of surface Au nps were formed at 20 and 30°C with an average particle size of 20 and 30 run, respectively (Figs. 16b and 16c).
  • the membranes became unstable that Au nps formed were not uniform both in terms of size and distribution.
  • the effect of the shaking rate on the formation of Au nps was studied by immersing ⁇ ( ⁇ ) loaded PIMs in 0.10 M EDTA solutions at pH 6 and varying the shaking rate from 0 to 150 rpm (0, 50, 75, 100, and 150 rpm). Irrespectively of the shaking rate all membranes appeared to be of metallic reddish brown colour and the SEM images of their cross-scctions showed insignificant Au nps formation within the bulk of the membranes.
  • the shaking rate affected strongly the size and distribution of the Au nps on the membrane surface.
  • the Au nps clumped together to form non-uniformly distributed Au nanocrystallites at shaking rates of 75 rpm or lower (Fig. 17a). However, at shaking rates of 100 rpm and ISO rpm, the Au nps became more evenly distributed and of more uniform size, i.e. average size of 24 and 20 nm, respectively (Figs. 17b and 17c).
  • Au nps Gold nanoparticles
  • Au-PIM polymer inclusion membrane
  • the Au-PIM has Strong adsorption ability and high capacity for metallic mercury (Hg°) accumulation from the air by forming an amalgam.
  • Hg° was generated on-line by reducing Hg** with NaBK,.
  • the resultant Hg vapour was purged with air and swept through an adsorption bottle (HDPE) f 1 liter in capacity in which the passive sampler was deployed.
  • a small electric fan was used inside the bottle to generate disturbance and improve the diffusion of Hg vapour.
  • the Hg vapour concentration in the bottle was reasonably constant through the experimental period.
  • Hg accumulated on the passive sampler was stripped with HNO3 and determined with atomic fluorescence spectrometry (AFS) and the amount of Hg accumulated was correlated with the concentration of this metal in the gaseous phase (air) in contact with the Au-PIM.

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Abstract

La présente invention porte de façon générale sur le domaine de la formation de nanoparticules, et, en particulier, sur des procédés qui génèrent des nanoparticules d'or sur la surface d'un substrat polymère. L'invention porte en particulier sur des procédés pour préparer des monocouches de nanoparticules d'or sur la surface de membranes polymères à inclusion (PIM), et sur des membranes polymères à inclusion avec des nanoparticules d'or déposées sur la surface de celles-ci.
PCT/AU2011/001541 2010-11-29 2011-11-29 Procédé pour préparer des nanoparticules d'or WO2012071605A1 (fr)

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AU2010905260A AU2010905260A0 (en) 2010-11-29 "Process for Preparing Gold Nanoparticles"
AU2010905260 2010-11-29

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WO2016171769A1 (fr) * 2015-04-21 2016-10-27 Battelle Memorial Institute Collecte, libération et détection d'analytes à l'aide de matériaux de prélèvement polymères composites
CN109550405A (zh) * 2018-11-26 2019-04-02 江南大学 一种离子选择性聚合物包含膜的制备方法及其应用
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2502069A1 (es) * 2013-03-27 2014-10-02 Universidad Politécnica De Cartagena Membranas poliméricas de inclusión basadas en líquidos iónicos
WO2016171769A1 (fr) * 2015-04-21 2016-10-27 Battelle Memorial Institute Collecte, libération et détection d'analytes à l'aide de matériaux de prélèvement polymères composites
US10254248B2 (en) 2015-04-21 2019-04-09 Battelle Memorial Institute Collection, release, and detection of analytes with polymer composite sampling materials
US10453664B2 (en) 2015-04-21 2019-10-22 Battelle Memorial Institute Collection, release, and detection of analytes with polymer composite sampling materials
US10533968B2 (en) 2015-04-21 2020-01-14 Battelle Memorial Institute Collection, release, and detection of analytes with polymer composite sampling materials
US11581176B2 (en) 2015-04-21 2023-02-14 Battelle Memorial Institute Collection, release, and detection of analytes with polymer composite sampling materials
CN109550405A (zh) * 2018-11-26 2019-04-02 江南大学 一种离子选择性聚合物包含膜的制备方法及其应用

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