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Nanocomposites based on TiO2 loaded with Ag nanoparticles obtained via sol-gel method were investigated by means of Raman spectroscopy and sorption measurements. Furthermore, the detection capability of trace amounts of congo red and crystal violet molecules from aqueous solutions was also tested by employing Surface Enhanced Raman Spectroscopy (SERS). It was found that upon thermal treatment the crystallinity degree of the samples increases, the surface area and pore volumes decrease which explains the lower detection limits of the annealed samples. More exactly, in the case of untreated sample a concentration of 10-7 M for crystal violet and 10-5 M for congo red was detected, while after thermal treatment the less porous samples led to the detection of 10-5 M for crystal violet and 10-4 M for congo red. [ABSTRACT FROM AUTHOR]

The influence of Au nanoparticles dimension on the photocatalytic performances of the TiO2 aerogels-Au composites was evaluated. Structural and morphological peculiarities of the TiO2 aerogel, unloaded and loaded with 5 and 22 nm Au nanoparticles, were studied by transmission electron microscopy technique, X-ray diffraction and N2-sorption measurements. UV-Vis diffuse reflectance measurements were performed to determine the band gap energies. The photocatalytic activity was evaluated by monitoring the salicylic acid photodegradation. It was found that the Au nanoparticles promote the anatase phase crystallization and produce the decrease of the specific surface area and band gap energy values. The porous composite with the smallest Au nanoparticles dimension exhibits the best photocatalytic performances. [ABSTRACT FROM AUTHOR]