Facet-Controlled Synthesis of CeO 2 Nanoparticles for High-Performance CeO 2 Nanoparticle/SnO 2 Nanosheet Hybrid Gas Sensors.

CeO 2 nanocubes with metastable {100} facets and CeO 2 nanooctahedrons with the most stable {111} facets are herein fabricated by controlling the morphology and facets of CeO 2 nanoparticles. SnO 2 nanosheet-based assembled films coated with these CeO 2 nanocubes or CeO 2 nanooctahedrons yield {100} CeO 2 nanocubes/SnO 2 nanosheets and {111} CeO 2 nanooctahedron/SnO 2 nanosheet hybrid gas sensors, respectively. The hybrid sensors with CeO 2 nanoparticles exhibited enhanced sensing responses to numerous chemical species relative to a pristine SnO 2 nanosheet gas sensor, including acetone, hydrogen, ethanol, ammonia, acetaldehyde, and allyl mercaptan. In particular, the responses of {100} CeO 2 nanocubes/SnO 2 nanosheets and {111} CeO 2 nanooctahedron/SnO 2 nanosheet gas sensors to acetone or allyl mercaptan were 6.8 and 10.3 times higher, respectively, than that of the pristine SnO 2 nanosheet gas sensor. Furthermore, the sensor response to ammonia was 2.5 times higher than that of a commercial volatile organic compound (VOC) gas sensor (TGS2602, Figaro Engineering Inc.). The CeO 2 nanocube-based sensor with exposed metastable {100} facets promotes the adsorption and oxidation of VOCs owing to the higher surface energy of the metastable {100} facets and therefore exhibits a higher sensing performance than the CeO 2 nanooctahedron-based sensor with an exposed {111} facet. The developed sensors show excellent potential for the detection of gas markers in human breath and perspiration for disease diagnosis.