Rapid and high yield synthesis of hollow silica nanoparticles using an NH4F catalyst

摘要

The rapid synthesis of hollow silica nanoparticles based on the CaC〇_3 template method is proposed. Typically, it contains two steps for the silica coating on a CaCO_3 template by a sol-gel reaction and template removal by a dilute acid solution. To promote the conversion of tetraethoxysilane (TEOS) to a silica shell on the CaCO_3 template, the effects of fluoride catalysts on the TEOS consumption rate during the silica coating were investigated using energy dispersive spectroscopy (EDS). The TEOS consumption rate of the NH4F-catalyzed system reached 100% within 15 min while the conventional NH_4OH system took 120 min to consume the TEOS. The obtained samples using the NH4F system for 15 min showed a uniform hollow structure with a thin silica shell. For the KF system as the other fluoride catalyst, the TEOS consumption rate did not reach 100% even after 120 min. When the polystyrene (PS) template was used with the NH4F system, dense silica particles were formed as well as hollow structures. Based on these results, a rapid and high yield of hollow silica nanoparticles can be achieved by not only F~-, but also NH_4~+ using the CaCO_3 template method.