Engineering of facets, band structure, and gas-sensing properties of hierarchical Sn²⁺-Doped SnO₂ nanostructures

Hierarchical SnO₂ nanoflowers, assembled from single-crystalline SnO₂ nanosheets with high-index (113) and (102) facets exposed, are prepared via a hydrothermal method using sodium fluoride as the morphology controlling agent. Formation of the 3D hierarchical architecture comprising of SnO₂ nanosheets takes place via Ostwald ripening mechanism, with the growth orientation regulated by the adsorbate fluorine species. The use of Sn(II) precursor results in simultaneous Sn²⁺ self-doping of SnO ₂ nanoflowers with tunable oxygen vacancy bandgap states. The latter further results in the shifting of semiconductor Fermi levels and extended absorption in the visible spectral range. With increased density of states of Sn²⁺-doped SnO₂ selective facets, this gives rise to enhanced interfacial charge transfer, that is, high sensing response, and selectivity towards oxidizing NO₂ gas. The better gas sensing performance over (102) compared to (113) faceted SnO₂ nanostructures is elucidated by surface energetic calculations and Bader analyses. This work highlights the possibility of simultaneous engineering of surface energetics and electronic properties of SnO₂ based materials. Flower-like hierarchical SnO₂ nanostructures are assembled from single-crystalline SnO₂ nanosheets with high-index (113) and (102) exposed facets. Sn²⁺ self-doping leads to formation of tunable oxygen vacancy bandgap states and extended absorption in the visible spectral range. This work highlights the possibility of simultaneous engineering of surface energetics and electronic properties of SnO₂ based materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.