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Ultrasensitive and Highly Selective Gas Sensors Based on Electrospun SnO 2 Nanofibers Modified by Pd Loading
Author(s) -
Yang DaeJin,
Kamienchick Itai,
Youn Doo Young,
Rothschild Avner,
Kim IlDoo
Publication year - 2010
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201001251
Subject(s) - crystallite , nanocrystalline material , materials science , calcination , electrospinning , x ray photoelectron spectroscopy , grain size , chemical engineering , high resolution transmission electron microscopy , microstructure , nanofiber , nanocrystal , grain growth , nanotechnology , composite material , transmission electron microscopy , catalysis , metallurgy , polymer , organic chemistry , chemistry , engineering
This work presents a new route to suppress grain growth and tune the sensitivity and selectivity of nanocrystalline SnO 2 fibers. Unloaded and Pd‐loaded SnO 2 nanofiber mats are synthesized by electrospinning followed by hot‐pressing at 80 °C and calcination at 450 or 600 °C. The chemical composition and microstructure evolution as a function of Pd‐loading and calcination temperature are examined using EDS, XPS, XRD, SEM, and HRTEM. Highly porous fibrillar morphology with nanocrystalline fibers comprising SnO 2 crystallites decorated with tiny PdO crystallites is observed. The grain size of the SnO 2 crystallites in the layers that are calcined at 600 °C decreases with increasing Pd concentration from about 15 nm in the unloaded specimen to about 7 nm in the 40 mol% Pd‐loaded specimen, indicating that Pd‐loading could effectively suppress the SnO 2 grain growth during the calcination step. The Pd‐loaded SnO 2 sensors have 4 orders of magnitude higher resistivity and exhibit significantly enhanced sensitivity to H 2 and lower sensitivity to NO 2 compared to their unloaded counterparts. These observations are attributed to enhanced electron depletion at the surface of the PdO‐decorated SnO 2 crystallites and catalytic effect of PdO in promoting the oxidation of H 2 into H 2 O. These phenomena appear to have a much larger effect on the sensitivity of the Pd‐loaded sensors than the reduction in grain size.