Porous SnO₂ Nanofibers Embedded with Hollow Hetero-Metal Oxide Nanospheres for Enhanced Gas Sensing

Developing high-performance sensing materials is essential for fabricating gas sensors with superior sensitivity and selectivity. In this paper, we present a generalizable electrospinning-thermal oxidation method combined with a sacrificial template approach to synthesize porous SnO₂ nanofibers embedded with hollow heterometal oxide nanospheres (M_<i>x</i>O_<i>y</i>, where M = Fe, Co, Ni, Cu, or Zn), referred to as M_<i>x</i>O_<i>y</i>@SnO₂. Carbonaceous spheres (CSs) act as templates, absorbing metal ions (M^<i>n</i>+) to form CSs@M^<i>n</i>+ composites. These are incorporated into precursor nanofibers via electrospinning, yielding bead-chain-like one-dimensional structures. Upon calcination in air, the structures transform into M_<i>x</i>O_<i>y</i>@SnO₂ porous nanofibers, while retaining their morphology. Compared to pristine SnO₂ nanofibers, the M_<i>x</i>O_<i>y</i>@SnO₂ counterparts exhibit significantly enhanced sensing performance toward volatile organic compounds. Each heterometal oxide imparts selectivity to a specific analyte: Fe₂O₃ for <i>n</i>-propanol, Co₃O₄ for acetone, NiO for triethylamine, CuO for ethanethiol, and ZnO for <i>n</i>-butanol. The enhanced sensing response arises from the synergistic effects of porous, hollow architectures and one-dimensional heterojunctions. This work offers a strategy for constructing multifunctional gas sensing materials by embedding hollow nanospheres into porous nanofibers using combinatorial chemistry.