Au Nanoparticle Decorated WO3 Nanorods with Enhanced Optical Limiting Activity

We report a simple route to assembling gold (Au) nanoparticles (NPs) on the surface of one-dimensional tungsten oxide (WO3) 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/WO3 NR heterostructures. TEM images, XRD, and UV/Vis spectroscopy results confirmed the successful decoration of Au NPs on the WO3 NRs. The structure and elemental chemical states of the WO3 NRs were retained during the self-assembly process. The bandgap of the WO3 NRs became wider after attachment of the Au NPs owing to the interaction of the dipole moments of the WO3 NRs and Au NPs under the induction of light. The optical limiting (OL) and nonlinear optical (NLO) properties of the resulting Au NP/WO3 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 WO3 NRs. The Au NP/WO3 NR heterostructure had superior NLO activity to that of un-decorated WO3 NRs. The main factor contributing to the enhanced NLO effect of the Au NP/WO3 NR heterostructures was a combination of free carrier absorption, NLS, and efficient charge/energy transfer at the Au NP/WO3 interface. Our findings show that Au NP/WO3 NR heterostructures are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.