Synthesis and substantially enhanced gas sensing sensitivity of homogeneously nanoscale Pd- and Au-particle decorated ZnO nanostructures

We successfully prepared Pd- and Au-nanoparticle-decorated ZnO nanostructures (Pd-ZnO and Au-ZnO) by combining sputtered Pd and Au ultrathin films on ZnO surfaces and by postannealing in vacuum. The Pd and Au nanoparticles were homogeneously distributed on ZnO surfaces without substantial aggregation. The ranges of the Pd- and Au-nanoparticle diameters were 4-11 nm and 5-8 nm, respectively. The photoluminescence spectra of the Pd-ZnO and Au-ZnO exhibited a quenched UV emission-band intensity and an increased visible-light emission band intensity compared with those of pure ZnO nanostructures. The results of X-ray photoelectron spectroscopy analysis in this work showed that the Pd-ZnO obtained a higher amount of chemisorbed oxygen and enhanced selectivity to acetone compared with the Au-ZnO. The gas responses of the ZnO nanostructured sensors were substantially improved with noble-metal nanoparticle decoration. The enhanced adsorbed oxygen and molecule-ion conversion rate in using nanoscale noble-metal particle decoration might account for the observed results.