Au nanoparticle decorated WO<sub>3</sub> nanorods with enhanced optical limiting activity
Wei Li, Dongdong Huang, Tingting Wang, Chan Zheng, Xueqing Xiao, Shuguang Cai, Wenzhe Chen
Abstract
We report a simple route to assembling gold (Au) nanoparticles (NPs) on the surface of one-dimensional tungsten oxide (WO 3 ) nanorods (NRs) through electrostatic interactions. Transmission electron microscope (TEM) imaging, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet-visible (UV-Vis) and diffuse reflectance UV-vis absorption spectroscopy were used to investigate the morphology, structure, surface characteristics, and linear optical properties of the Au NP/WO 3 NR heterostructures. TEM images, XRD, and UV/Vis spectroscopy results confirmed the successful decoration of Au NPs on the WO 3 NRs. The structure and elemental chemical states of the WO 3 NRs were retained during the self-assembly process. The bandgap of the WO 3 NRs became wider after attachment of the Au NPs owing to the interaction of the dipole moments of the WO 3 NRs and Au NPs under the induction of light. The optical limiting (OL) and nonlinear optical (NLO) properties of the resulting Au NP/WO 3 NR heterostructures were studied using an open-aperture Z-scan technique in the nanosecond regime with a 532-nm laser. The introduction of Au NPs strongly influenced the competition of the saturable absorption and nonlinear scattering (NLS) in the WO 3 NRs. The Au NP/WO 3 NR heterostructure had superior NLO activity to that of un-decorated WO 3 NRs. The main factor contributing to the enhanced NLO effect of the Au NP/WO 3 NR heterostructures was a combination of free carrier absorption, NLS, and efficient charge/energy transfer at the Au NP/WO 3 interface. Our findings show that Au NP/WO 3 NR heterostructures are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.