Deposition of gold nanoparticles on β-FeOOH nanorods for detecting melamine in aqueous solution

This study demonstrates a facile but efficient approach to deposit metallic (gold) nanoparticles on β-FeOOH nanorods to obtain Au/β-FeOOH nanocomposites without the assistance of any polymers or surfactants at ambient conditions. In this method, a strong reducing agent (NaBH ₄) can be used to extensively produce Au nanoparticles, converting β-FeOOH into Fe ₃O ₄ and depositing gold particles onto magnetic Fe ₃O ₄ simultaneously. The microstructure, composition, and chemical properties of the obtained nanocomposites are characterized by various advanced techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectroscopy. Moreover, the Au/β-FeOOH nanocomposite can be used to detect trace melamine using UV spectrum in the ultraviolet wavelength range (190-260nm), in which the nanocomposites show a higher sensitivity toward melamine due to the promotion of symmetry-forbidden bands (n→π ^*) of melamine molecules and also avoid the disturbance of commercial products containing solid colloids or food colorings that distort visual spectrum during the detection of chemical sensing. The deposition mechanisms and their sensing detection toward melamine are discussed.