Synthesis Of Hollow Mesoporous Silica Spheres With Controlled Porous Structures And Its Gold Nanoparticles Uploading

Hollow mesoporous SiO2 microspheres can be used as carriers for guest molecules such as chemical substances,drugs,and genes,due to their low costs,good biocompatibility,easily modified surfaces and large specific surface areas,but different guest molecules have different requirements on the shell pore structure of them.In recent years,preparation and application of hollow mesoporous SiO2 microspheres with controlled pore size have gained extensive attention.Template method is one of the most common methods for the preparation of hollow mesoporous SiO2 microspheres,there are many types of templates and their sizes are easy to control.Therefore,it is easy to control the size and morphology of the SiO2 microspheres through the template,and the purpose of regulating pore structure of hollow mesoporous SiO2 microspheres can be achieved by removing them through calcination and etching.In this paper,methacryloxyethyltrimethylammonium chloride(DMC)modified polystyrene colloidal particles p(St-co-DMC)served as templates for inducing silica deposition on its surface in a relatively mild system,then core/shell p(St-co-DMC)@SiO2 hybrid nanospheres were prepared.The polymer cores were removed by high-temperature calcination to obtain hollow mesoporous SiO2 microspheres,which had a shell thickness of about 5 nm and the hollow cavity sizes were about 100 nm.By changing the type of silicon source precursor(TEOS,TMOS+C18TMS,TEOS+C18TMS),the hydrolysis of silicon source precursors can be slowed down,because the addition of C18TMS can introduce trisiloxane bond groups to the system and its organic long chain can form a more loose SiO2 skeleton.The relative velocity of the condensation reaction and the pore size of the hollow mesoporous SiO2 microspheres can be adjusted within the range of 10 nm-16 nm.The use of N-3-(trimethoxysilyl)propylethylenediamine(TSD)in combination with TEOS introduced an alkamino group on the inner surface of the hollow mesoporous SiO2 sphere,so that ultrafine Au nanoparticles with a diameter of about 10 nm can be formed inside the SiO2 cavity with the reduction of chloroauric acid(HAuCl4).Since the Au nanoparticles are confined inside the SiO2 shell,side reactions such as agglomeration and poisoning are reduced,and the recycling efficiency is high.Nano gold particles with different sizes and numbers can be obtained in different concentration of HAuCl4 solution(1.0 mM,2.0 mM,and 3.0 mM).Then the catalytic reduction of 4-nitroaniline was used as a model to compare the catalytic performance of Au@Void@SiO2 nanospheres prepared by three different silicon sources.The experimental results show that the catalytic efficiencies of three type of Au@Void@SiO2 nanospheres(group SE,group SM+18 and group SE+18)are all higher than that of Au nanoparticles with the same size and the same equivalent,the corresponding reaction rate constant k are 5.06×10-3 S-1,4.45×10-3S-1 and 5.35×10-3S-1.And the increase in SiO2 shell pore size(group SM+18<group SE<group SE+18)helps to improve the catalytic efficiency of Au@Void@SiO2 nanospheres.The yolk-shell Au@Void@SiO2 nanospheres used as catalysts showed good catalytic performance,not only they had a high conversion(>90%),but also retained similar catalytic performance after 5 cycles.