Salt-templated Growth Of Hollow Nanostructures

With the development of nanotechnology,the preparation of hollow nanostructures has aroused wide interest from researchers.Hollow nanostructures have many unique physicochemical properties,such as large surface area,low density and high loading capacity,which bring promising application prospects in the fields of nanoreactors,catalysis,energy storage,optics and biomedicine.However,due to the low efficiency,high cost and environmentally unfriendly issues of existing synthetic methods,the widespread applications of hollow nanostructure materials are greatly constrained.In order to solve the problems and challenges in the preparation of hollow nanostructures,a green,rubust,efficient,economical and scalable salt-templated method for preparing monodisperse hollow nanostructures is thus developed.The main research contents and results are as follows:In the first part of the work,we studied the mechanism of salt-templated method for the preparation of hollow nanostructures and the monodisperse SiO2 hollow nanomaterials were then successfully synthesized according to this method.At the same time,the size,thickness,porosity and morphology of SiO2 hollow nanomaterials were well controlled:(a)SiO2 hollow spheres with different sizes were prepared by controlling the nucleation and growth process of salt template.(b)Monodisperse SiO2 hollow spheres with different thicknesses were prepared according to the precursor addition of different amounts of shell materials.(c)The hot water etching method was used to control the porosity of SiO2 hollow spheres.(d)Finally,by changing the precipitation conditions of salt templates,the hollow cubic structure of SiO2 was prepared.Moreover,in order to prove the versatility of salt-template method in the synthesis of hollow nanostructures,we also studied the effect of different solvents on the growth of SiO2 hollow nanostructures and synthesized other materials with hollow structures,including hollow-nanostructured polydopamine and nitrogen-doped carbon materials.The salt-template method has much more advantages than other template methods during the preparing process of hollow nanostructures,such as simplification,environmentally friendly,and low cost.In the second part of this work,we extended the salt-template method to the synthesis of composite materials.Two different structural types of Ag@SiO2 composites were prepared according to different reaction temperatures.It was proved that when the reaction temperature was kept at 35?,the growth rate of Ag particles was slower than that of SiO2 shell and thus Ag nanoparticles were remained in the shell of SiO2,forming Agiarge@SiO2 structure.When the reaction temperature was controlled at 15 C,the growth rate of Ag particles was faster than that of SiO2 shells,and the Ag nanoparticles were remained on the SiO2 shell,leading to the Agsmall@SiO2 structure.We also applied two structural catalysts to the reductive degradation of 4-nitrophenol.The Agsmall@SiO2 structural catalyst could convert 4-nitrophenol to 4-nitrophenylamine in 13 min with a conversion of 99%,while the Agiarge@SiO2 structural catalyst required 24 min under the same conversion rate.It was proved that both catalysts presented good stability.Compared with the previously reported noble metal-based catalysts(such as Au,Pd,Ru and so on),Ag@SiO2 exhibits excellent catalytic effect and has a facile and green preparation process,resulting in great price advantage and industrialization prospects.