Easy preparation of gold nanostructures supported on a thiolated silica-gel for catalysis and latent fingerprint detection

Herein, we report an extremely simple, fast and controllable method for preparing gold nanoclusters (GNC) and gold nanospheres (GNS) in situ onto a thiol-organofunctionalized silica gel (MPS) for catalysis and detection of latent fingerprints (LFPs). The silica gel surface was suitably modified with thiol groups by a silylation reaction method using 3-(mercaptopropyl)trimethoxysilane (MPTS). Spectroscopic data (UV-visible-NIR and PL) have shown that the as-prepared thiol-modified silica is able to reduce Au3+ ions in situ, producing orange-red light emitting GNCs. For preparing GNS, on the other hand, it was necessary an adsorption step followed by a reduction with NaBH4. Various experimental conditions for the preparation of GNS were studied, such as the gold precursor and reducing agent concentrations and the reaction time. TEM, XRD and UV-visible-NIR analyses showed, respectively, the presence of approximately spherical particles with a face-centered cubic structure and a plasmon resonance band, which is controllable by changing those synthesis parameters. The as-prepared samples have shown high catalytic activity for the reduction of an AZO dye in aqueous solution, being able to decolorize 92% of the dye content within only 40 min. GNS/MPS and bare MPS have also shown enhanced activity for detecting LFPs deposited over porous and non-porous surfaces, including glass, polymer, paper, metal, leather, ceramic and wood. Our method has shown to be a suitable alternative for conventional techniques, it is easier to apply, fast-responsive, reusable, durable and thermally stable.