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Murali Sastry - One of the best experts on this subject based on the ideXlab platform.
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La0.7Sr0.3MnO3 nanoparticles coated with Fatty Amine
Applied Physics Letters, 2006Co-Authors: Rajashree Rajagopal, Renu Pasricha, Murali Sastry, J. Mona, Sangeeta Kale, Tanushree Bala, P. Poddar, B. L. V. Prasad, Darshan C. Kundaliya, S. B. OgaleAbstract:We report on the synthesis of La0.7Sr0.3MnO3 (LSMO) nanoparticles having perovskite structure and particle size of the order of 30nm. The process involves citrate-gel synthesis, size filtering, and surface coating with a shell of octadecyl Amine (ODA) using electrostatic interaction-assisted novel chemical route. Magnetic measurements show the Curie temperature of ∼360K establishing the desired stoichiometry and phase. Fourier transform infrared studies bring out that the Amine group of ODA interacts with the LSMO surface. Refluidization yields uniform redispersion of the coated and dried powder.
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Phase transfer of platinum nanoparticles from aqueous to organic solutions using Fatty Amine molecules
Journal of Chemical Sciences, 2004Co-Authors: Ashavani Kumar, Hrushikesh M. Joshi, Rajendra Srivastava, Suguna Adyanthaya, Renu Pasricha, Anandrao B. Mandale, Murali SastryAbstract:In this report we demonstrate a simple process based on Amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylAmine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and non-polar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR)
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phase transfer of silver nanoparticles from aqueous to organic solutions using Fatty Amine molecules
Journal of Colloid and Interface Science, 2003Co-Authors: Ashok Kumar, Hrushikesh M. Joshi, Renu Pasricha, A.b. Mandale, Murali SastryAbstract:We demonstrate the phase transfer of silver nanoparticles synthesized in an aqueous medium into hexane containing the cationic surfactant octadecylAmine (ODA). During vigorous shaking of the biphasic mixture, rapid phase transfer of the silver nanoparticles into the organic phase was observed. The phase transfer of the silver nanoparticles arises due to coupling of the silver nanoparticles with the ODA molecules present in organic phase via either coordination bond formation or weak covalent interaction. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder and are readily redispersible in different organic solvents. The nature of binding of the ODA molecules to the silver nanoparticle surface was characterized using UV-vis spectroscopy, thermogravimetry, transmission electron microscopy, nuclear magnetic resonance spectroscopy, X-ray photoemission spectroscopy, and Fourier transform infrared spectroscopy.
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Growth of TiO2 nanoparticles in thermally evaporated Fatty Amine thin films by a method of ion entrapment
Journal of Materials Chemistry, 2003Co-Authors: Shiv Shankar, Renu Pasricha, Anandrao B. Mandale, Debabrata Rautaray, N. R. Pavaskar, Murali SastryAbstract:The synthesis of titania nanoparticles within thermally evaporated octadecylAmine (ODA) thin films is described. Synthesis of the nanoparticles was achieved by electrostatically entrapping TiF62− ions in thin films of the Fatty Amine by a simple immersion technique followed by in-situ hydrolysis of the metal ions. Without any further heat treatment, it was observed that titania nanoparticles of the brookite polymorph were formed within the film. By this simple procedure, uniformly distributed fairly monodisperse titania nanoparticles of ca. 4 nm diameter were synthesized within the lipid matrix and investigated using a host of techniques.
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Sequential entrapment of PNA and DNA in lipid bilayers stacks
Chemical Communications, 2001Co-Authors: Vidya Ramakrishnan, Maya Sable, Moneesha D'costa, Krishna N. Ganesh, Murali SastryAbstract:Sequential immobilization of single stranded DNA and complementary PNA molecules in thermally evaporated Fatty Amine films is demonstrated and evidence for their in-situ hybridization is presented.
Vijaya Patil - One of the best experts on this subject based on the ideXlab platform.
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Lamellar Langmuir–Blodgett films of hydrophobized colloidal gold nanoparticles by organization at the air–water interface
Thin Solid Films, 2001Co-Authors: Murali Sastry, Anand Gole, Vijaya PatilAbstract:The organization of hydrophobically modified colloidal gold nanoparticles at the air–water interface and the formation thereafter of lamellar, multilayer films of the nanoparticles by the Langmuir–Blodgett (LB) technique is described in this paper. The hydrophobization of the gold colloidal particles was accomplished by the electrostatic extraction of carboxylic acid derivatized gold particles (synthesized in an aqueous medium, 35 A in size) from solution into thermally evaporated Fatty Amine films by a simple immersion procedure. The acid–base complex formed by the association of the carboxylic acid groups bound to the colloidal particle surface and the Amine groups in the lipid matrix leads to the formation of a strongly-bound hydrophobic sheath of Fatty Amine molecules around the particles. The colloidal gold particles can thereafter be dissolved in different organic solvents, dried and redispersed repeatedly without significant aggregation of the gold particles. The hydrophobic gold particles were dissolved in a spreading solvent and organized on the surface of water. The organization of the particles and the formation of multilayer films by the Langmuir–Blodgett technique was followed by surface pressure–area isotherm measurements of the colloidal particle Langmuir monolayer, quartz crystal microgravimetry, ultraviolet-vis spectroscopy and Fourier transform infrared spectroscopy. It was observed that a close-packed monolayer of the colloidal particles was formed on the surface of water and that excellent multilayer films of the colloidal nanoparticles can be grown on different supports by sequential transfer by the LB technique.
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Formation of close-packed silver nanoparticle multilayers from electrostatically grown octadecylAmine/colloid nanocomposite precursors
Langmuir, 2000Co-Authors: Vijaya Patil, Murali SastryAbstract:The formation of close-packed silver nanoparticle thin films via a two-stage self-assembly approach is described. In the first step, surface-modified silver colloidal particles are extracted from aqueous solution via electrostatic interactions into thermally evaporated Fatty Amine films. Thereafter, the excess Fatty Amine molecules in the organic matrix are removed by dissolution in a range of organic solvents of varying dielectric properties. Thermogravimetric and quartz crystal microgravimetric studies indicate that, irrespective of whether the dissolution medium is polar or nonpolar, except for a monolayer of Amine molecules in direct contact with the colloidal particle surface, almost complete Fatty Amine dissolution occurs leading to a considerable increase in the packing density of the silver colloidal particles. While UV−vis spectroscopy measurements of the films after Amine removal suggest subtle differences in the final structure of the films prepared from the different solvents, atomic force mic...
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Role of Particle Size in Individual and Competitive Diffusion of Carboxylic Acid Derivatized Colloidal Gold Particles in Thermally Evaporated Fatty Amine Films
Langmuir, 1999Co-Authors: Vijaya Patil, R. B. Malvankar, Murali SastryAbstract:We have recently shown that nanocomposites of colloidal particles in a Fatty lipid matrix can be grown via a diffusion process controlled by selective electrostatic interactions. In this paper, a detailed investigation of the diffusion of carboxylic acid derivatized gold colloidal particles of different sizes into thermally evaporated octadecylAmine films using quartz crystal microgravimetry (QCM), transmission electron microscopy, and UV−vis absorption and Fourier transform infrared (FTIR) spectroscopies is described. The QCM kinetics of gold cluster incorporation has been analyzed in terms of a one-dimensional Fickian-type diffusion model, and it is found that the cluster diffusivity increases with decreasing cluster size. The pH at which maximum cluster incorporation in the Amine occurs was found to be dependent on the cluster size as well. FTIR spectroscopy of the Fatty Amine-gold particle composites indicated weak coupling of the clusters to the protonated Amine groups as well as interesting cluster ...
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surface derivatization of colloidal silver particles using interdigitated bilayers a novel strategy for electrostatic immobilization of colloidal particles in thermally evaporated Fatty acid Fatty Amine films
Langmuir, 1998Co-Authors: Vijaya Patil, Murali SastryAbstract:We have recently demonstrated that interdigitated bilayers of Fatty acid molecules self-assemble on nanoscale curved surfaces, thereby highlighting an important difference between self-assembly on planar surfaces where such structures have not been reported to form. On a more practical level, this approach leads to a new strategy for derivatization of colloidal particle surfaces without the use of terminally functionalized molecules. In this paper, we use this new strategy to derivatize colloidal silver particle surfaces with carboxylic acid and Amine functional groups and, thereafter, to incorporate the colloidal particles in thermally evaporated conjugate Fatty lipid films via electrostatically controlled diffusion from the sol. The diffusion of the colloidal particles in the thermally evaporated organic films has been followed using quartz crystal microgravimetry and modeled on the basis of a 1-D diffusion process and the cluster diffusivities determined. It is observed that both the charge on the clus...
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Electrostatically controlled diffusion of carboxylic acid derivatized silver colloidal particles in thermally evaporated Fatty Amine films
The Journal of Physical Chemistry B, 1998Co-Authors: Murali Sastry, Vijaya Patil, Sudhakar R. SainkarAbstract:We have recently demonstrated that carboxylic acid derivatized silver colloidal particles can be incorporated in thermally evaporated Fatty Amine films by immersion of the films in the silver sol and that the process is controlled through electrostatic interactions [Sastry, M.; Patil, V.; Mayya, K. S. Langmuir 1997, 13, 4490]. In this paper, we analyze the influence of colloidal particle concentration, solution pH, and film thickness on the kinetics of cluster incorporation in thermally evaporated Fatty Amine films obtained from quartz-crystal microgravimetry (QCM) measurements in terms of a one-dimensional (1-D) Fickian-type diffusion model. Although it is found that 1-D diffusion adequately represents the cluster mass uptake kinetics observed using QCM, an interesting film-thickness dependence on the diffusivity was observed. The nature of the cluster-diffusion curves were quite different for Amine films annealed prior to immersion in the colloidal solution. In these cases, the 1-D-diffusion model with ...
Francesca Ravera - One of the best experts on this subject based on the ideXlab platform.
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Properties of Fatty Amine–Silica Nanoparticle Interfacial Layers at the Hexane–Water Interface
The Journal of Physical Chemistry C, 2012Co-Authors: Catherine P. Whitby, Daniel Fornasiero, John Ralston, Libero Liggieri, Francesca RaveraAbstract:The formation and properties of composite layers of silica nanoparticles and an oil-soluble (Fatty) Amine surfactant at the oil–water interface have been studied using interfacial tensiometry, rheology, and contact angle measurements to characterize the synergy between the particles and surfactant. The initially hydrophilic particles interact with the surfactant only at the water–hexane interface. Synergistic interactions are required for interface stabilization. A key result is that nanoparticle attachment is driven by surfactant adsorption at the liquid interface. Particles are efficiently bound to the interface once the adsorbed surfactant layer is close to saturation. Surfactant adsorption onto the particle surfaces optimizes the particle wettability and promotes particle aggregation into networks that enhance the viscoelasticity of the interface. The implications of these results for controlling the formation and kinetic stability of emulsions containing particles and surfactant are discussed.
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properties of Fatty Amine silica nanoparticle interfacial layers at the hexane water interface
Journal of Physical Chemistry C, 2012Co-Authors: Catherine P. Whitby, Daniel Fornasiero, John Ralston, Libero Liggieri, Francesca RaveraAbstract:The formation and properties of composite layers of silica nanoparticles and an oil-soluble (Fatty) Amine surfactant at the oil–water interface have been studied using interfacial tensiometry, rheology, and contact angle measurements to characterize the synergy between the particles and surfactant. The initially hydrophilic particles interact with the surfactant only at the water–hexane interface. Synergistic interactions are required for interface stabilization. A key result is that nanoparticle attachment is driven by surfactant adsorption at the liquid interface. Particles are efficiently bound to the interface once the adsorbed surfactant layer is close to saturation. Surfactant adsorption onto the particle surfaces optimizes the particle wettability and promotes particle aggregation into networks that enhance the viscoelasticity of the interface. The implications of these results for controlling the formation and kinetic stability of emulsions containing particles and surfactant are discussed.
Anand Gole - One of the best experts on this subject based on the ideXlab platform.
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Enhanced Temperature and pH Stability of Fatty Amine−Endoglucanase Composites: Fabrication, Substrate Protection, and Biological Activity
Langmuir, 2001Co-Authors: Anand Gole, Santosh Vyas, Anil Lachke, S R Sainkar, Murali SastryAbstract:Endoglucanase, one part of the multicomponent enzyme cellulase, is an extremely important enzyme in the textile industry (biopolishing), the pulp and paper industry (de-inking operations and recycling of used paper), and the detergent industry. One major problem in such applications is the inactivation of the enzyme at elevated temperatures and pH conditions. We present herein details of the encapsulation of this enzyme in thermally evaporated Fatty Amine films and studies of the enzymatic activity of the biocomposite film under different pH and temperature conditions. Substrate protection of the enzyme by carboxymethyl cellulose was essential to stabilize the enzyme against inactivation in the lipid matrix. The optimum operation temperature shifted to higher values relative to that of the free enzyme in solution. The enhanced stability at high temperatures coupled with significant catalytic activity of the enzyme−lipid biocomposite films at elevated pH conditions indicate immediate application of the bio...
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enhanced temperature and ph stability of Fatty Amine endoglucanase composites fabrication substrate protection and biological activity
Langmuir, 2001Co-Authors: Anand Gole, Santosh Vyas, S R Sainkar, Anil Lachke, Murali SastryAbstract:Endoglucanase, one part of the multicomponent enzyme cellulase, is an extremely important enzyme in the textile industry (biopolishing), the pulp and paper industry (de-inking operations and recycling of used paper), and the detergent industry. One major problem in such applications is the inactivation of the enzyme at elevated temperatures and pH conditions. We present herein details of the encapsulation of this enzyme in thermally evaporated Fatty Amine films and studies of the enzymatic activity of the biocomposite film under different pH and temperature conditions. Substrate protection of the enzyme by carboxymethyl cellulose was essential to stabilize the enzyme against inactivation in the lipid matrix. The optimum operation temperature shifted to higher values relative to that of the free enzyme in solution. The enhanced stability at high temperatures coupled with significant catalytic activity of the enzyme−lipid biocomposite films at elevated pH conditions indicate immediate application of the bio...
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Lamellar Langmuir–Blodgett films of hydrophobized colloidal gold nanoparticles by organization at the air–water interface
Thin Solid Films, 2001Co-Authors: Murali Sastry, Anand Gole, Vijaya PatilAbstract:The organization of hydrophobically modified colloidal gold nanoparticles at the air–water interface and the formation thereafter of lamellar, multilayer films of the nanoparticles by the Langmuir–Blodgett (LB) technique is described in this paper. The hydrophobization of the gold colloidal particles was accomplished by the electrostatic extraction of carboxylic acid derivatized gold particles (synthesized in an aqueous medium, 35 A in size) from solution into thermally evaporated Fatty Amine films by a simple immersion procedure. The acid–base complex formed by the association of the carboxylic acid groups bound to the colloidal particle surface and the Amine groups in the lipid matrix leads to the formation of a strongly-bound hydrophobic sheath of Fatty Amine molecules around the particles. The colloidal gold particles can thereafter be dissolved in different organic solvents, dried and redispersed repeatedly without significant aggregation of the gold particles. The hydrophobic gold particles were dissolved in a spreading solvent and organized on the surface of water. The organization of the particles and the formation of multilayer films by the Langmuir–Blodgett technique was followed by surface pressure–area isotherm measurements of the colloidal particle Langmuir monolayer, quartz crystal microgravimetry, ultraviolet-vis spectroscopy and Fourier transform infrared spectroscopy. It was observed that a close-packed monolayer of the colloidal particles was formed on the surface of water and that excellent multilayer films of the colloidal nanoparticles can be grown on different supports by sequential transfer by the LB technique.
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Glucose induced in-situ reduction of chloroaurate ions entrapped in a Fatty Amine film: formation of gold nanoparticle–lipid composites
PhysChemComm, 2001Co-Authors: Anand Gole, Anandrao B. Mandale, Ashok Kumar, Sumant Phadtare, Murali SastryAbstract:The formation of gold nanoparticle–lipid composite films by glucose-induced reduction of chloroaurate ions entrapped in thermally evaporated Fatty Amine films is described. Simple immersion of films of the salt of octadecylAmine and chloroaurate ions (formed by immersion of thermally evaporated Fatty Amine films in chloroauric acid solution) in glucose solution leads to the facile in-situ reduction of the metal ions to form gold nanoparticles in the Fatty Amine matrix. The formation of gold nanoparticles is readily detected by the appearance of a violet color in the film and thus forms the basis of a possible new, gold nanoparticle-based colorimetric sensor for glucose. The formation of the Fatty Amine salt of chloroauric acid and the subsequent reduction of the metal ions by glucose has been followed by quartz crystal microgravimetry, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy and transmission electron microscopy measurements.
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Encapsulation and biocatalytic activity of the enzyme pepsin in Fatty lipid films by selective electrostatic interactions
Chemical Communications, 2000Co-Authors: Anand Gole, Chandravanu Dash, Mala Rao, Murali SastryAbstract:The encapsulation of pepsin by electrostatically controlled diffusion from solution into thermally evaporated Fatty Amine films is described and the catalytic activity of the immobilized enzyme on hemoglobin is investigated.
Ashok Kumar - One of the best experts on this subject based on the ideXlab platform.
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phase transfer of silver nanoparticles from aqueous to organic solutions using Fatty Amine molecules
Journal of Colloid and Interface Science, 2003Co-Authors: Ashok Kumar, Hrushikesh M. Joshi, Renu Pasricha, A.b. Mandale, Murali SastryAbstract:We demonstrate the phase transfer of silver nanoparticles synthesized in an aqueous medium into hexane containing the cationic surfactant octadecylAmine (ODA). During vigorous shaking of the biphasic mixture, rapid phase transfer of the silver nanoparticles into the organic phase was observed. The phase transfer of the silver nanoparticles arises due to coupling of the silver nanoparticles with the ODA molecules present in organic phase via either coordination bond formation or weak covalent interaction. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder and are readily redispersible in different organic solvents. The nature of binding of the ODA molecules to the silver nanoparticle surface was characterized using UV-vis spectroscopy, thermogravimetry, transmission electron microscopy, nuclear magnetic resonance spectroscopy, X-ray photoemission spectroscopy, and Fourier transform infrared spectroscopy.
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phase transfer of aqueous colloidal gold particles into organic solutions containing Fatty Amine molecules
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001Co-Authors: Murali Sastry, Ashok Kumar, Priyabrata MukherjeeAbstract:We demonstrate the phase transfer of colloidal gold particles synthesized in an aqueous medium into toluene containing the cationic surfactant, octadecylAmine (ODA). During vigorous shaking of the biphasic mixture, rapid transfer of the gold particles into the organic phase was observed. The phase transfer of the colloidal gold particles arises due to coupling of the gold particles with the organic phase ODA molecules via either coordination bond formation or weak covalent interaction. This process renders the particles sufficiently hydrophobic and soluble in the organic phase. The ODA-stabilized colloidal gold particles could be separated out in the form of a powder and readily dissolved in different organic solvents. The nature of binding of the ODA molecules to the gold particle surface was characterized using thermogravimetry/differential thermal analysis, as well as Fourier transform infrared spectroscopy. To the best of our knowledge, this is the first demonstration of the phase transfer of colloidal gold particles by direct co-ordination to primary Amines. The protocol described herein does not require the use of acid, a feature common to similar phase transfer protocols involving alkanethiols as the co-ordinating and hydrophobizing agent.
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Glucose induced in-situ reduction of chloroaurate ions entrapped in a Fatty Amine film: formation of gold nanoparticle–lipid composites
PhysChemComm, 2001Co-Authors: Anand Gole, Anandrao B. Mandale, Ashok Kumar, Sumant Phadtare, Murali SastryAbstract:The formation of gold nanoparticle–lipid composite films by glucose-induced reduction of chloroaurate ions entrapped in thermally evaporated Fatty Amine films is described. Simple immersion of films of the salt of octadecylAmine and chloroaurate ions (formed by immersion of thermally evaporated Fatty Amine films in chloroauric acid solution) in glucose solution leads to the facile in-situ reduction of the metal ions to form gold nanoparticles in the Fatty Amine matrix. The formation of gold nanoparticles is readily detected by the appearance of a violet color in the film and thus forms the basis of a possible new, gold nanoparticle-based colorimetric sensor for glucose. The formation of the Fatty Amine salt of chloroauric acid and the subsequent reduction of the metal ions by glucose has been followed by quartz crystal microgravimetry, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy and transmission electron microscopy measurements.
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Amphoterization of colloidal gold particles by capping with valine molecules and their phase transfer from water to toluene by electrostatic coordination with Fatty Amine molecules
Langmuir, 2000Co-Authors: Ashok Kumar, Priyabrata Mukherjee, Ayon Guha, S. D. Adyantaya, A.b. Mandale, Rajiv Kumar, Murali SastryAbstract:The surface modification of colloidal gold particles with the amino acid valine is demonstrated. Self-assembly of valine on the gold particles is accomplished in the aqueous phase, linkage with the gold particles possibly occurring through covalent interaction of the Amine group with the surface gold atoms. Derivatization with the amino acid in this manner imparts amphotericity to the gold particles, the particles being negatively charged at pH values greater than 6 (the isoelectric point of valine) and positively charged below this pH. The charge reversal on the gold particles is demonstrated by electrostatic self-assembly of the colloidal gold particles on glass (which is negatively charged at pH > 3) by immersion of the substrate alternately into the valine-capped gold solutions maintained at pH = 3.5 and 8.5. The phase transfer of the aqueous valine-capped gold colloidal particles by electrostatic linkage with Fatty Amine molecules present in toluene is also described. The two-phase method described h...
