Silica Hollow Spheres with Nano-Macroholes Like Diatomaceous Earth

Abstract

Artificial synthesis of hollow cell walls of diatoms is an ultimate target of nanomaterial science. The addition of some water-soluble polymers such as sodium polymethacrylate to a solution of water/oil/water emulsion system, which is an essential step of the simple synthetic procedure of silica hollow spheres (microcapsules), led to the formation of silica hollow spheres with nano-macroholes (>100 nm) in their shell walls, the morphologies of which are analogous to those of diatom earth.

Facile preparation of hierarchically porous carbon using diatomite as both template and catalyst and methylene blue adsorption of carbon products

“…It is the most abundant form of silica on earth and is easily obtained at very low cost [9]. Composed of biogenetic amorphous silica and classified as noncrystalline opal-A in mineralogy, diatom shell is characteristic of highly developed porosity and particularly macroporous structure [12][13][14] and thus has been used as the template for the preparation of macroporous materials [15,16]. The sizes of the macropores of diatomite range from nanometric to micrometric domains.…”

Hollow particles as controlled small space to functionalize materials

“…Some hollow particles with a nanometer to micrometer diameter have been successfully fabricated using the double emulsion process usually composed of water-in-oil-in-water (W 1 /O/W 2 ). 40) Generally, the (W 1 /O/W 2 ) double-emulsion system consists of individual oil globules that contain smaller droplets of the Fig. 2.…”

“…Based on Fujiwara et al 40),46), 47) for the hollow silicate microspheres, the reaction of sodium silicate with a precipitant is utilized. The W 1 /O emulsion is made of W 1 (consists of water and sodium silicate) and O (oil phase) with a surfactant for stabilizing the emulsion.…”

“…8),24),57),75),76) As already mentioned, nano/micro-sized hollow particles are good for storage and charge carriers. 40),77)82) Silicate particles are accepted materials for drug delivery due to their non-toxicity. Therefore, hollow silicate particles have been extensively studied for biomedical applications because of its biocompatibility and well-established in terms of bioconjugation methods using silane chemistry.…”

Hierarchical fabrication of silica cocoon with hexagonally ordered channel constructed wall via an emulsion-assisted process

“…In the swelling agent-assisted synthesis of porous materials, the addition of organic swelling agents enable the formation of oilin-water (O/W) emulsions [10], in which oil droplets are dispersed in a continuous aqueous phase. The formation of O/W emulsions can greatly affect both mesostructure assembly and macroscale morphology growth.…”