A simple and inexpensive route to synthesize porous silica microflowers by supercritical CO2

In this work, a simple and inexpensive route to synthesize porous silica microflowers has been developed. By adding supercritical CO2 into the sodium silicate aqueous solutions, the porous silica microflowers were obtained. The results of scanning electron microscopy, transmission electron microscopy and nitrogen adsorption isotherms show that through the easy control of CO2 pressure, the morphologies and porosity properties of the obtained silica can be tuned. During this process, supercritical CO2 works not only as a reactant but also as a modifier to the morphology and porosity of silica. Moreover, the growth of silica microflowers was investigated by changing the reaction time. The silica microflowers show optical properties in the wavelength range of 340-480 nm.