Unexpected gas sensing properties of SiO2/SnO2 core-shell nanofibers under dry and humid conditions

SiO2/SnO2 core-shell nanofibers were synthesized using TEMPO-oxidized cellulose nanofibers as templates. The gas sensing properties of the synthesized SiO2/SnO2 core-shell nanofibers were evaluated under dry and humid conditions and compared to practical SnO2 nanoparticles produced by a hydrothermal method. The sensor responses were analyzed by monitoring the electric resistance changes upon the introduction of H-2 or CO analytes. Surprisingly, the SiO2/SnO2 nanofibers showed a prominent sensor response at a higher temperature at which the adsorbed oxygen on the SnO2 nanoparticles desorbs under dry conditions. Unexpectedly, the SiO2/SnO2 nanofibers are available in humid atmosphere since they are less influenced by H2O poisoning compared to the SnO2 nanoparticles. Such an intriguing phenomenon could be interpreted in terms of the lower susceptibility of the major adsorbed oxygen species toward water vapor.