Formation of SiO2@SnO2 core–shell nanofibers and their gas sensing properties

Abstract

SiO₂@SnO₂ core–shell nanofibers (NFs) were successfully prepared by single-spinneret electrospinning and subsequent calcination process. The precursor solutions were prepared from poly(vinylpyrrolidone), SnO₂ precursors, and tetraethylorthosilicate (TEOS) with prehydrolysis. The prehydrolysis of TEOS plays an important role for the formation of core–shell structure. After calcining, the resulting fiber sample had an amorphous SiO₂ core and a shell consisted of SnO₂ particles. The fibers with various morphologies were obtained through adjusting the molar ratio of Sn and Si and the possible formation mechanism of core–shell NFs was proposed. Both Kirkendall effect and grain growth played important roles for the formation of core–shell structure. Furthermore, SiO₂ was used as support material to fix the SnO₂ particles and avoid the collapse of the SnO₂ structure. The amount of SnO₂ precursors directly determined the compactness of the shell, resulting in the different gas sensing properties. The SiO₂@SnO₂ core–shell NF network sensor responds to ethanol, ammonia, benzene, toluene, chloroform, and hexane gases, but it exhibited enhanced gas response to ethanol with a short response time. Those SnO₂ particles formed on the exterior of the fibers provided lots of contact area with the target gas to reduce resistance. In addition, the connectivity between particles also had certain influence on the electrical conductivity of the sample. The results demonstrate that single-spinneret electrospinning can also be used to prepare core–shell fibers with various applications.