The Effect of Alkanes on the Formation of Ultrafine Silver Bromide Particles in Ionic W/O Microemulsions

Abstract

Ultrafine Ag8r particles formed in wlo microemulsions with different chain iength of aikanes were studied by UV-VIS spectrophotometry, stopped-fiow spectrophotometry and transmission electron microscopy.The ultraflne particies of Ag8r (5-7 nm in diameter) were obtained by mixing two separately prepared microemuision systems both containing AOT, n-hexane and an aqueous soiution of either AgN0 3 or Na8r. The size distribution of the near-Ly sphericai Ag8r particles broadened from S to about 10 nm as chain length of alkane was increased from n-hexane to n-octane. When n-dodecane or a higher alkane was used, the microemulsion system became increasingly unstable causing precipitation of Ag8r .

Preparation of nanoparticles of silver halides, superconductors and magnetic materials using water-in-oil microemulsions as nano-reactors

“…On the other hand, a substantially fluid interface in the microemulsion enhances the rate of precipitation. Thus, by controlling the structure of the interface, one can change the reaction kinetics in microemulsions by an order of magnitude [57]. It has been further shown that the structure of oil, alcohol and ionic strength of the aqueous phase can significantly influence the rigidity of the interface and the reaction kinetics [28,57].…”

“…We have shown that the interfacial rigidity of droplets in microemulsions can be controlled by the structure of the oil, surfactant or cosurfactant [28,57]. A high interfacial rigidity leads to a low inter-droplet attraction and low rate of precipitation, while a fluid interface leads to a higher rate of precipitation.…”

“…It can also be seen that these dispersions are very stable with little or no aggregation of AgC1 particles even after a week. This has been explained on the basis of a low attractive interaction between the microemulsions droplets containing the AgC1 nanoparticles [57,88].…”

“…These include in situ synthesis of nanoparticles of AgC1 [881 and AgBr [57]; and microemulsion mediated synthesis of highly dense and microhomogeneous Y-Ba-Cu-O (123) and B-Pb-Sr-Ca-Cu-O (2223) high temperature ceramic superconductors [89][90][91], high coercivity barium ferrite for high-density perpendicular recording [92,93], superparamagnetic y-Fe203 nanoparticles [941 and zinc oxide based varistors [95]. The synthesis of these materials and their structure and properties are described in the following sections.…”

New Trends on the Synthesis of Inorganic Nanoparticles Using Microemulsions as Confined Reaction Media

“…Bandyopadhyaya et al (Bandyopadhyaya et al, 1997) (Chew et al, 1990) have studied the effect of alkanes in the formation of AgBr particles in ionic W/O microemulsions (using AOT as surfactant), where the transmittance of the reactions were followed with time with UV-Vis and Stopped-Flow Spectrophotometry. They have found an increase on reaction rate with the chain lenght of the alkane.…”