composite nanofibers were synthesized recently by Khorami and co-workers, who reported highly sensitive toward ethanol [19]. It also has been reported that the response of SnO2-In2O3-CdO compounds toward 300ppm formaldehyde can reach 559 [20]. However, among them, there have been few researches devoting themselves to fabricate methanol gas sensors. Li’s research group synthesized ZnO/SnO2 complex nanostructures using a simple glucose-assisted hydrothermal method. The as-fabricated sensor toward 100 ppm of methanol was 9.6 [11]. Wang et al. reported the synthesis of SnO2 inverse opal with sol-gel method and the response of the SnO2 inverse opal sensor was as high as 95 for 500ppm methanol gas detection [21]. It should be mentioned that Han et al. also successfully prepared Ce-doped In2O3 porous nanospheres and showed excellent sensing performance toward methanol [22]. Although methanol gas sensors have been investi- gated by few groups, the gas responses of these gas sensors are too poor to meet the standard required. Furthermore, the sensors with high gas response to methanol have aroused tremendous interest on account of their highlighted roles in the areas of public safety and environmental monitoring.
As a typical n-type semiconducting metal oxide, tin oxide (SnO2 ) is the most potential metal oxide used as gas-sensing material because of its low cost and good chemical stability. Indium oxide (In2O3) has also been proven to be a highly sensing material for the detection of various gases [23]. Moreover, the adding of palla- dium and platinum has been proved to be a simple and efficient route to enhance the sensing properties because of the catalyst nanoparticles catalytically activating the dissociation of molecular oxygen, inducing a deeper layer. At the same time, they can exert an active effect as catalysts on dehydrogenation and ring-opening of hydrocarbons [11]. However, to the best of our knowledge, there are no reports on the preparation of SnO2-Pd-Pt-In2O3 compos- ite and no reports have shown that SnO2-Pd-Pt-In2O3 composite has an excellent response for methanol. In this contribution, we newly designed, the pure tin oxide (SnO2) was synthesized by a facile hydrothermal method. Then the palladium-platinum-In2 O3 composited nanocrystalline SnO2 (SnO2 -Pd-Pt-In2 O3 composite) was prepared via a solid-phase reaction method. Subsequently, the phase and microstructures of the composite were thoroughly characterized. The sensor based on SnO2-Pd-Pt-In2O3 composite exhibited good methanol sensing properties, especially for the gas response which is ultra-high. Furthermore, a possible sens- ing mechanism of the composite is discussed. It is believed that the composite could further provide potential for application as a highly effective methanol gas sensor.