Experimental and theoretical study on the excellent amine-sensing performance of Au decorated WO3 needle-like nanocomposites

This study reports a facile strategy to assemble excellent amine-sensing nanocomposites consisting of WO3 nanoneedles and Au nanoparticles through surface modification. Consequently, the Au decorated WO3 nano-composites were synthesized using a hydrothermal method coupled with the in-situ reduction reaction. The resulting WO3 nanoneedles were measured to be similar to 10 mu m in length with unequal diameters along the growth direction. Specifically, the tip diameters were of 100 +/- 15 nm, and the widest diameters were of 200 +/- 15 nm. Furthermore, Au nanoparticles with sizes of similar to 5 nm were evenly distributed on the surface of WO3 nanoneedles. The gas-sensing performance of the WO3 nanoneedles and the Au modified WO3 nanocomposites were evaluated by testing the change of resistance in the resulting materials toward various concentrations of 1-butylamine. It was found that the net WO3 nanoneedles alone are capable of offering an excellent response (15.1-100 ppm of 1-butylamine at the optimized working temperature of 340 degrees C). The surface modification of WO3 nanoneedles with Au nanoparticles has been proved to further enhance sensing performances by magnitudes of two folds along with superior selectivity compared to the net WO3 nanoneedles. Moreover, according to a further unexpected fact, the optimum working temperature was found to drop from 340 degrees to 240 degrees C with Au surface modification. Additionally, Density Functional Theory (DFT) simulations were applied to understand the adsorption behavior of 1-butylamine on the WO3 (001) surface. The calculation indicated that 1-butylamine enables active interaction with the WO3 (001) surface, confirmed by the formation of a new bond between N atom (1-butylamine) and W atom (WO3). Among the target gases (e.g., ammonia, 1-butanol, acetone, ethanol, and 1-butylamine), 1-butylamine exhibits the highest adsorption energy (-1.490 eV) on the WO3 (001) surface. This helps explain the excellent selectivity toward 1-butylamine. The enhanced sensing property can be attributed to the electronic and chemical sensitization of the Au loaded nanoparticles. These findings may endorse the potential applicability of WO3 and Au-WO3 nanoparticles in amine sensing.