Synthesis of TiO_2NWS@Au_NPS Composite Catalyst for Methylene Blue Removal

In this article, HBP-NH₂-modified titania nanowire (TiO_2NWS)-decorated Au nanoparticles (TiO_2NWS@Au_NPS) were synthesized by one-step method. The role of HBP-NH₂ concentration in the formation of TiO_2NWS was investigated. The fineness and uniformity of pure TiO_2NWS were enhanced by absorbed amino groups from amino-terminated hyperbranched polymer (HBP-NH₂). The morphology and crystal structure of TiO_2NWS and TiO_2NWS@Au_NPS were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fournier transform infrared (FTIR) spectroscopy. The chemical states of gold, titanium and oxygen were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that at the concentration of HBP-NH₂ 100 g/L, the mean diameter of TiO_2NWS was nearly 72 nm and Au nanoparticles were uniformly distributed on the surface of TiO_2NWS. The presence of Au_NPS improved the photocatalytic properties of TiO_2NWS under UV light irradiation. The Au load was believed to improve the utilization rate of the photoelectron and activated the adsorbed oxygen. The obtained TiO_2NWS@Au_NPS decomposed 99.6% methylene blue (MB) after 300 min when subjected to UV light irradiation. After five cycles of the catalyzing process, the TiO_2NWS@Au_NPS still retained over 90% of its catalytic ability for MB. The Au deposition was found responsible for the high catalytic activity of TiO_2NWS@Au_NPS.