Gold nanoparticles microemulsions

Hernandez J, Solla-Gullon J, Herrero E. 2004. Gold nanoparticles synthesized in a water-in-oil microemulsion Electrochemical characterization and effect of the surface structure on the oxygen reduction reaction. J Electroanal Chem 574 185-196. 

Gold Nanoparticle Synthesis Using Nonionic Surfactant-Based Microemulsion Systems... 

Gold nanoparticles from 2.5 to 5 nm sizes have also been prepared by using a biphasic Winsor II [126] (a water-in-oil microemulsion that is in equilibrium with the excess water phase) type microemulsion of diethyl ether/AOT/water. The surfactant, AOT, performs the dual role of forming a microemulsion and the transferring of charged metal ions from the aqueous to organic phase. This provides gold nanoparticles, which are readily dispersed in the nonpolar phase. 

Many reports are available where the cationic surfactant CTAB has been used to prepare gold nanoparticles [127-129]. Giustini et al. [130] have characterized the quaternary w/o micro emulsion of CTAB/n-pentanol/ n-hexane/water. Some salient features of CTAB/co-surfactant/alkane/water system are (1) formation of nearly spherical droplets in the L2 region (a liquid isotropic phase formed by disconnected aqueous domains dispersed in a continuous organic bulk) stabilized by a surfactant/co-surfactant interfacial film. (2) With an increase in water content, L2 is followed up to the water solubilization failure, without any transition to bicontinuous structure, and (3) at low Wo, the droplet radius is smaller than R° (spontaneous radius of curvature of the interfacial film) but when the droplet radius tends to become larger than R° (i.e., increasing Wo), the microemulsion phase separates into a Winsor II system. 

Manna A, Imae T, Yogo T, Aoi K, Okazaki M (2002) Synthesis of gold nanoparticles in a Winsor II type microemulsion and their characterization. J Colloid Interface Sci 256 297-303... 

Considering that the conventional gathering of nanoparticles from microemulsions is difficult, tedious and not remunerative due to limited quantity, Bonini etal. [230] developed a flame spraying technique for microemulsions with gold nanoparticles. The process is reminiscent of the emulsion combustion technique of Tani et al. [172, 173], but has been used for deposition of nanostructured coatings on substrates. 

A two-microemulsion method was used by Arcoleo and Turco Liveri [398], where n-heptane and NaAOT were used as the oil phase and surfactant respectively. In addition, the two separate microemulsions contained HAUCI4 solution in one and N2H4.H2SO4 solution in another, which when mixed, yielded gold nanoparticles. 

Chiang [232] published a detailed study of gold nanoparticle synthesis from W/O microemulsions. Two microemulsions, containing (i) NaAOT/Span 80/ isooctane/aqueous solution of HAUCI4 and (ii) NaAOT /Span 80/isooctane/aqueous solution of N2H5OH were mixed together to obtain gold particles ... 

Gold Nanoparticles Han and coworkers [49] proved that the CO -continuous microemulsions with IL domains could solubilize HAuCl and prepared gold particles by a process of rapid expansion of a supercritical solution into a liquid solvent. Au nanoparticles were formed in the reverse micelles, when the weight ratio of HAuCl to 1,1,3,3-tetramethylguanidinium trifluoroacetate (TMGT) was 0.01. However, Au networks were obtained at a higher concentration of HAuCl. ... 

Bimetallic Palladium/Gold Nanoparticles Zhang and coworkers [57] synthesized bimetallic palladium/gold nanoparticles in the IL-based microemulsion. The palladium and gold precursors were dissolved in dispersive and continuous phase of microemulsion (H2O/TX-100/[bmim][PFJ), respectively. [PdCy ions were reduced in situ by TX-lOO in dispersive water phase to prepare Pd nanoparticles and then [AuClJ crossed through the interface film and reacted with the as-prepared Pd nanoparticles to form Pd Au nanoparticles. 

Some miscellaneous examples of QD synthesis using surfactant systems are described below. A layer-by-layer [206] structure of dithiol self-assembled monolayers (SAM) and CdS mono- and multilayer nanoparticles were fabricated on a gold substrate covered with alkanedithiol. SAMs were formed by an alternate immersion of the substrate into ethanolic solutions of dithiol, and dispersion of CdS nanoparticles (ca. 3nm in diameter), the latter of which was prepared in A0T/H20/heptane w/o microemulsions. 

Guo and co-workers have synthesized trioctyl phosphine oxide (TOPO) stabilized iron nanoparticles by the microemulsion method with an average diameter of 3 nm [192]. The amorphous particles are known to effectively catalyze reactions such as the decomposition of H2O2. A specific advantage of this method is that the presence of O2 does not hamper the electrocatalytic currents obtained for H2O2. Gold colloids capped with a mixed monolayer of alkylthiol and amidoferrocenyl-... 

Using the microemulsion technique, metallic cobalt cobalt/platinum alloys , and gold-coated cobalt/platinum nanoparticles have been synthesized. MFep (M Mn, Co, Ni, Cu, Mg, or Cd, etc.) are among the most important magnetic materials and have been widely used for electronic applications . 

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