tSilver nanoparticles were successfully assembled in self-organized polyhedral TiO2; synthesized byhybrid template consisting of pluronic-85, hexadecyltrimethylammoinm bromide and triethanol amine(TPHtAg2), as well as in platelets TiO2; synthesized only via hexadecyltrimethylammonium bromide(THAg2). X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, diffusereflectance UV–vis spectroscopy as well as N2sorptiometry were used for the characterization of phasecomposition, surface morphology, valent states of Ag/TiO2, optical and surface texturing properties. Thesenanomaterials were tested as catalysts for 4-nitrophenol (4-NP) reduction in presence of aqueous NaBH4under visible-light irradiation. The results showed that the THAg2catalyst exhibited the best photocat-alytic performance in the reduction of 4-NP into 4-aminophenol (4-AP) and revealed 98% conversionfollowing 2 min irradiation with rate constant equal 0.025 s−1. On the other hand, the TPHtAgS2catalyst,derived from using Ag2SO4as a precursor instead of AgNO3, indicates a conversion comprised of 80% atsimilar reaction conditions. The superiority of the photocatalytic reduction of THAg2was due to exposingAg+ions together with Ag0nanoparticles (5 nm) and to the photo-induced role of carbon atoms; formedas a result of the non-complete decomposition of the template, and its synergistic effect with the anatasephase. On the contrary, TPHtAg2showed strong chemical interaction of Ag+ions within the hybrid tem-plates and as a result inhibits the reduction of Ag+ion as well as the adsorption of 4-NP and eventuallyindicates no activity. The decreased activity and stability of TPHtAgS2compared with THAg2was due toincreasing the particles size of Ag0(10 nm), diminishing the accessibility and reactivity of Ag+ions; whichcould have been worked as trapping sites with Ago, and the limited effect of residual S2-ions, depictedfrom XPS measurements. |
