Recent advances in nanoparticle synthesis with reversed micelles.

Microemulsion method: A novel route to synthesize organic and inorganic nanomaterials

We report the effects of intermicellar exchange rate on absorption spectra and particle size of silver nanoparticles synthesized in reverse micelles of AOT The silver nanoparticles are prepared by the method of mixing of two microemulsions, one containing the silver nitrate and the other containing sodium borohydride The intermicellar exchange rate is varied by changing the organic solvent, surfactant (SDS, NP-5, and DTAB), and organic (benzyl alcohol and toluene) additives The higher intermicellar exchange rate is found to give smaller particle size and blue shift in the absorption spectra An interesting and potentially useful effect has been observed in that addition of a small amount of a nonionic surfactant significantly reduces the particle size

Effects of Intermicellar Exchange Rate on the Formation of Silver Nanoparticles in Reverse Microemulsions of AOT

Reverse micelles as nanosized aqueous droplets existing at certain compositions of water-in-oil microemulsions are widely used today in the synthesis of many types of nanoparticles. However, without a rich conceptual network that would correlate the properties and compositions of reverse micellar microemulsions to the properties of to-be-obtained particles, the design procedures in these cases usually rely on a trial-and-error approach. As like every other science, what is presently known is merely the tip of the iceberg compared to the uninvestigated vastness still lying below. The aim of this article is to present readers with most of the major achievements from the field of materials synthesis within reverse micelles since the first such synthesis was performed in 1982 until today, to possibly open up new perspectives of viewing the typical problems that nowadays dominate the field, and to hopefully initiate the observation and generation of their actual solutions. We intend to show that by refining th...

Synthesis of materials within reverse micelles

Low-water content reverse micelles have been formed in cyclohexane employing Triton X-100 or AOT (bis(2-ethylhexyl) sulfosuccinate sodium (salt) as the surfactant. Steady-state and time-resolved luminescence quenching studies, using Ru(bpy)32+ as the luminophore and Fe(CN)63- or MV2+ as the quencher, have shown that at low-water content, reverse micelles can not properly solubilize polar species but the surfactant molecules tend to reorganize themselves around the polar molecules forming structures that depend on the nature of the surfactant and the charge. When titanium isopropoxide is solubilized in such reverse micelles, it is slowly hydrolyzed and it polymerizes to give an −O−Ti−O−Ti− network. Gelling is faster in the case of AOT than in the case of Triton X-100-based solutions. Gelling, i.e., polymerization, is a complex process that mainly depends on the surfactant, which tends to organize itself around the polar TiO2 particles. Gels can be deposited by dip coating on glass slides as thin films of t...

Formation of TiO2 Nanoparticles in Reverse Micelles and Their Deposition as Thin Films on Glass Substrates

A modeling approach is developed to account for the important effects of intermicellar exchange on the ultrafine particle formation in reverse micelles. A set of fusion−fission schemes is specifically proposed and used for modeling intermicellar metal exchange. The dynamic effects largely differing in their time scales are decoupled using a two-staged approach. Growth of metal particles is simulated to occur through intramicellar attachment of free metal atoms from an instantaneous reduction reaction and as well as by transfer and attachment through intermicellar exchange. Simulation results predict increase in particle size with aqueous core size and total aqueous phase volume, increase in particle number density with surfactant concentration at fixed aqueous phase to surfactant molar ratio, a minimum in average particle size as a function of salt concentration, and increase in particle size polydispersity with salt concentration and aqueous core size. Low values of the order of 10-1 are found for the nu...

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Papers

Ultrafine Metal Particle Formation in Reverse Micellar Systems: Effects of Intermicellar Exchange on the Formation of Particles