Flower-like SnO2 nanopowders prepared by a hydrothermal method were surface modified with palladium via impregnation.The crystal structure,morphology,and surface chemistry states of the samples were characterized by means of X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and X-ray photoelectron spectroscopy（XPS）,respectively.The gas sensing performances were also investigated.For a hydrothermal temperature of 220℃,flower-like SnO2 nanoparticles consist of nanorods with diameters of 40 nm and lengths of 100 nm.The XPS and XRD results reveal that palladium exists in the Pd~0 chemical state but the crystal is too small to be detected.The 0.3 wt%Pd modified SnO2 sensor shows better sensitivity,up to 21,for 70μL/L ethanol gas at an optimal working temperature of 250℃.The quick response time（3 s） and fast recovery time（~20 s） are the main characteristics of this sensor.
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