Facile Preparation of Gold Nanoparticles Silica Composite Film Embedded in Anodized Aluminium Oxide-Glass Substrate

Thin film based on gold nanoparticles or AuNPs is typically used as catalyst in the industrial processes due to their high stability and good reusability. In this work, a thin AuNPs-silica composite film was fabricated firstly from sol-gel method by mixing gold(I) pyrazolate complex to medium comprised of ethanol, deionized water, and hydrochloric acid, followed by addition of tetrabutyl orthosilicate as silica source. Next, 70 μL of the sol-gel solution were spin-coated on several type of substrates such as glass, anodized aluminium oxide or AAO, and combination of both to yield gold complex/silica composite thin film. It was found that gold complex/silica composite film fabricated on combination of both AAO-glass substrate gave the best quality based on its surface thickness, layer uniformity and film brittleness. Later, the thin film was selected and subjected to thermal hydrogen reduction at 210 °C for 2 hours to facilitate the formation of gold nanoparticles to give AuNPs/silica_AAO-glass film. Before the heat treatment, the light-brownish colour of the original gold complex/silica_AAO-glass film in daylight will appear as a pinkish red film under UV light, suggesting the interaction between gold atoms as supported by its luminescence spectrum at 692 nm. Upon heat treatment, the resulting AuNPs/silica_AAO-glass film gave a deep-red colour indicating the successful formation of AuNPs. The presence of AuNPs in the film was further confirmed based on its absorption peak at 545 nm, X-ray diffraction pattern at 2θ= 38.20º for d111plane in wide-angle region, transmission electron microscopy images showing a small and sphere shape particles as well as its elemental composition in energy dispersive X-ray analysis. Moreover, scanning electron microscope images of AuNPs/silica_AAO-glass film also suggested that the AAO pores is fully filled with the composite and is in accordance with its surface roughness study via atomic force microscopy analysis.