Synthesis of novel RuO2/NaBi(MoO4)2 nanosheets composite and its gas sensing performances towards ethanol

A novel NaBi(MoO4)(2) nanosheets were synthesized by a two step method which included a solvent thermal and a hydrothermal treatments. The RuO2/NaBi(MoO4)(2) composite was prepared by mixed NaBi(MoO4)(2) nanosheets with RuCl3 ethanol solution and sequent heat treatment. Characterizations by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller analysis indicated that the NaBi(MoO4)(2) nanosheets were tetragonal scheelite phase with the thickness of 10-15 nm, their agglomerates were porous material with specific surface area of 14.2 m(2)/g. The sensors based on as-prepared NaBi(MoO4)(2) and RuO2/NaBi(MoO4)(2) nanosheets showed a high gas response, fast response (less than 10 s), trace detection capacity (1 ppm), and selectivity to ethanol with no cross-sensitivity towards moisture and acetone etc. A new gas-sensing mechanism for NaBi(MoO4)(2) is proposed, which is different to the adsorbed oxygen sensing mechanism for SnO2 and ZnO. Here, the ethanol molecules are catalytically oxidized by MoO42- tetrahedron, and the electrons transfer to Bi-31 which reduced into Bi-0 metal. The results of X-ray photoelectron spectroscopy prove bismuth metal existence. The conductivity change comes from Bi quantum dots and free electrons resulting from oxygen vacancies formation in gas-sensing process. The gas sensing response of RuO2/NaBi(MoO4)(2) increases two times higher than that of as-prepared NaBi(MoO4)(2) nanosheets. Therefore, the RuO2/NaBi(MoO4)(2) sensor is a promising candidate for fast, sensitive and selective detection of ethanol. (C) 2016 Elsevier B.V. All rights reserved.