Transfers of Colloidal Silica from Water into Organic Solvents of Intermediate Polarities

Surfactant-Mediated Transfer of Colloidal Silica Particles from Water into an Immiscible Weakly Polar Solvent

“…Recurrently observed even though weakly rationalized (13), this convergence upheld our attempt to correlate the mobility of the transferred particles to that of the associated solid in pure DH. Mobility results appear in Table 2 together with the corresponding size estimates.…”

“…Whereas the steric protection imparted by polymers is brought into common practice, the osmotic attractive force in mixed colloids (3) and the recurrently highlighted interfacial organization of the solvent in silica suspensions (4 -11) are less conspicuous phenomena. The latter structural effect was also evidenced in n-octane as a repulsive barrier at very short gaps between mica sheets (12), being again invoked in our current investigation of silica organosols (13). Colloidal stability in organic solvents is weakly documented and mostly restricted in the case of native silica surfaces to Stöber particles (10,14,15) unexposed to bulk water.…”

“…The number average diameter (obtained by transmission electron microscopy), density, and specific surface area of these silica particles were previously determined to be 81.8 nm, 2.21 g/cm 3 , and 33.6 Ϯ 0.8 m 2 /g, respectively, substantiating their nonporous character. By DLS at 50, 70, 90, and 120°, the average hydrodynamic diameter and polydispersity index were found to be 87.2 Ϯ 0.4 nm and 8%, respectively (13). DBDAB obtained from Fluka was further purified by successive recristallizations from ethyl acetate and from water.…”

Formation of Surfactant-Stabilized Silica Organosols

“…Previously, groups have successfully vectored silica nanoparticles from aqueous sols into specific low dielectric solvents: Kasseh and Keh used sequential azeotropic distillation to form stable dispersions of silica particles in n -propanol and subsequently 1,2-dichloroethane . It should be noted that during the process, significant surface silanisation with the propanol chains occurred, explaining the stability in both solvents, although these layers were not dense enough to afford stability in an apolar solvent (octane).…”

Application of Zetametry To Determine Concentrations of Acidic and Basic Impurities in Analytical Reagents

“…Although the idea or disregarding the presence of ions in “pure” organic solvents and the effects of these ions on the ζ potentials was criticized, many other researchers made use of this concept . In addition, many values of ζ potentials of minerals in allegedly pure nonaqueous media were recently reported without attempts to explain the mechanism of surface charging. The decisive role of impurities is obvious when Wright et al reported ζ = +207 mV for silica in acetonitrile and Kaseh and Keh reported ζ = −100 mV for silica in the same solvent!…”