In this regard, on combining the results of our study, we can imagine Selleckchem PRN1371 the water phase in the quiescent medium to be composed of two regions: an ‘interfacial region’ existing just below the silica source-water interface and a ‘bulk region’ comprising the remaining water bulk phase located below the interfacial region. The growth behavior in each region is unique as a result of variations in reactant availability and local concentration. A schematic representing the proposed growth process in each region is given in Figure 11. Surfactant molecules originally present in the water phase assemble into rod and wormlike micelles during the
premixing of the acidic water medium (Figure 11a). Silica species start to diffuse slowly through the interface and undergo hydrolysis with water forming an amorphous film at the micelle-free interface. Due to the absence of mixing, slow diffusion makes the hydrophobic silica precursor initially present in the interfacial region. However, some experimental factors were noticed to shift silica condensation to the bulk region GSK126 manufacturer by facilitating the diffusion of the silica species into that region. These factors are the acid type, hydrophilicity of silica source, and surfactant involved. In the interfacial region, the diffusing species assemble with surfactant
micelles forming silica-surfactant seeds that can grow by the addition of more silica and surfactant species. selleckchem Figure 11 A schematic representation of the quiescent interfacial-bulk growth mechanism. (a) Initial two-phase configuration and the suggested interfacial and bulk regions, (b) interfacial region where slow linear supply of silica source in packed micelles yields linear growth of ordered silica fibers, and (c) Fluorometholone Acetate bulk region where facilitated silica diffusion to loosely packed micelles yields 3D growth of low-ordered spheres
and gyroids. In the TBOS studies with HCl (sample MSF), growth was restricted to the interfacial region where the seeds begin to grow by the addition of more silica and micelles at the interface. Silica species were consumed instantly by the seeds at the interface. The slow supply and instant consumption of TBOS was seen as a linear diffusion, and the seeds grow likewise into linear fibrous shapes  as shown in Figure 11b. The fibers have a highly ordered hexagonal structure. One aspect of this order is evaporation at the interface. Due to solvent evaporation, both surfactant micelles and uncondensed silica-surfactant seeds are closely packed (higher local concentrations) which enhances condensation and promotes restructuring of the pores. It is also known that pores can restructure as long as the condensation is not complete. The longer the growth time, the better is the order of end product grown in the interfacial region .