Au nanoparticle-decorated porous SnO2 hollow spheres: a new model for a chemical sensorElectronic supplementary information (ESI) available: A photograph of the sensor and the working principle of the gas sensing test. See DOI: 10.1039/c0jm00457j

Au nanoparticle-decorated porous SnO 2 hollow spheres, which are different from the conventional noble metal-doped thick or thin semiconductor films, are prepared and systematically investigated as a new model for chemical gas sensors. The synthesized Au-decorated porous SnO 2 hollow spheres are characterized by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-optical emission spectroscopy. The Au content in the SnO 2 support was determined as 5.63 wt% by XPS and 5.90 wt% by ICP, respectively, indicating the homogeneous dispersion of Au nanoparticles on SnO 2 hollow spheres. Experimental results show that, by using ethanol as a probe molecule, this new model exhibits excellent sensing performances in terms of high response, fast response-recovery, superior selectivity and good stability. The enhanced sensing features are attributed to the improved gas diffusion and mass transport induced by the unique porous structure, the formation of conjugated electron depletion layers on both the outer and inner surfaces of the SnO 2 hollow spheres and the catalytic effect of the Au nanoparticles. It is believed that the strategy of combining the porous nanostructure and catalytic activity of noble metals can further provide potential for other applications. Au-decorated SnO 2 hollow sphere sensors exhibit excellent sensing performances to ethanol in terms of high response, fast response-recovery, good selectivity and stability.