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J Nanopart Res (2010) 12:18891896 DOI 10.1007/s11051-009-9751-6
RESEARCH PAPER
Gas sensing properties of MoO3 nanoparticles synthesized by solvothermal method
Won-Sik Kim Hong-Chan Kim Seong-Hyeon Hong
Received: 14 February 2009 / Accepted: 29 August 2009 / Published online: 17 September 2009 Springer Science+Business Media B.V. 2009
Abstract MoO3 nanoparticles were prepared by thermally oxidizing the MoO2 nano-crystallites synthesized by solvothermal reaction, and their gas sensing properties were investigated. Ethanol and water mixed solvents were used in the solvothermal synthesis, and it was observed that the phase, size, and morphology of the products were strongly dependent on the composition of solvents. Well-crystallized and spherical MoO2 nano-crystallites (*20 nm) were obtained in the mixed solvent (water:ethanol = 40:10 in vol), and subsequent heat treatment at 450 C produced the well-separated, slightly elongated MoO3 nano-particles of *100 nm.
The nano-particle MoO3 gas sensor responded to both oxidizing and reducing gases, but it exhibited the extremely high gas response toward H2S with a short response time (\10 s). In particular, the magnitude of gas response of nano-particle MoO3 gas sensor was about 10 times higher than that of micron-sized commercial MoO3 powder sensor at 20 ppm H2S.
Keywords Solvothermal Nanoparticle
MoO3 Gas sensor H2S
Introduction
Molybdenum trioxide (MoO3) is a wide band gap(3.2 eV) n-type semiconductor (Rabalais et al. 1974) and a well-known electrochromic (Yang et al. 1998), photochromic (Yao et al. 1992), and display material (Zhou et al. 2003). MoO3 was used as a catalyst for oxidation of hydrocarbon, alcohol, propane, methane (Dominguez-Esquivel et al. 1986; Zhang and Oyama 1996; Yoon et al. 1995; Liu et al. 1984), and reduction of NOx (Larrubia et al. 2000). Recently,
MoO3 has been attracted as a new gas sensing material and found to be responded to both oxidizing (NOx) and reducing gases (H2, NH3, and CO; Ferroni et al. 1998; Mutschall et al. 1996; Barazzouk et al.
2006; Sunu et al. 2003; Imawan et al. 2001).
The high surface-to-volume ratio associated with nanostructures makes their electrical responses extremely sensitive to the species adsorbed on the surface (Xu et al. 1991). Various MoO3 nanostructures including nanorods, nanowires, nanobers, nanoribbons, and nanobelts were fabricated using hydrothermal, solvothermal, electrodeposition, and physical vapor deposition methods (Xia et al. 2006; Song et al. 2005; Li et al....