Synthesis of TiO₂ Nanoparticles Utilizing Hydrated Reverse Micelles in CO₂

Abstract

Titanium dioxide nanoparticles were produced by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of reverse micelles formed in CO2 with the surfactants ammonium carboxylate perfluoropolyether (PFPECOO-+NH4) (Mw = 587) and poly(dimethyl amino ethyl methacrylate-block-1H,1H,2H,2H-perfluorooctyl methacrylate) (PDMAEMA-b-PFOMA). Based on dynamic light scattering measurements, the amorphous TiO2 particles formed by injection of TTIP are larger than the reverse micelles, indicating surfactant reorganization. The size of the particles and the stability of dispersions in CO2 were affected by the molar ratio of water to surfactant headgroup (w(o)), precursor concentration, and injection rate. The amorphous particle size did not change upon depressurization and redispersion in CO2. PDMAEMA-b-PFOMA provided greater stability against particle aggregation at higher reactant concentration compared with PFPECOO-+NH4. The crystallite size after calcination, which was examined by X-ray diffraction and transmission electron microscopy, increased with w(o).

Dissolution of Trihexyltetradecylphosphonium Chloride in Supercritical CO2

“…A broadened spectrum could also result from increased solution heterogeneity, which is conceivable if C153 is partitioning into distinctly different solvent environments. Dissolution of amphiphilic molecules into a bulk supercritical fluid phase, including scCO 2 , has demonstrated the formation of a micellar environment in supercritical fluids [67][68][69][70][71][72]. While we are not suggesting micellization of [P 6,6,6,14 ] + Cl − , these reports show that molecules similar to this IL have been solubilized in supercritical fluids.…”

Green Intelligent Nanomaterials by Design (Using Nanoparticulate/2D-Materials Building Blocks) Current Developments and Future Trends

“…These microemulsions are formulated in a pressure cell to which the second reactant is added using a high-pressure syringe pump. Hence, the NP reactions that take place are similar to those occurring in normal liquid w/o microemulsions as noted in microemulsions-based synthesis of Ag NPs where NP recovery by CO 2 venting and rapid expansion method is possible [220,227,229,230,232].…”

Highly dispersed behavior of thermal plasma-synthesized TiO2 nanoparticles in water

“…5(b)]. Some inhomogeneous parts in the coating surface of the Plasma A powder Journal of the Ceramic Society of Japan 119 [4] 303-306 2011 suspension might be due to the relatively broad size distribution of the powder particles, and may be reduced when a sharp distribution of primary particle size is attained.…”