Influence of pH on the preparation of dispersed Ag-TiO2 nanocomposite

In this paper, data concerning the effect of pH on the morphology of Ag-TiO2 nanocomposite during photodeposition of Ag on TiO2 nanoparticles is reported. TiO2 nanoparticles prepared by sol-gel method were coated with Ag by photodeposition from an aqueous solution of AgNO3 at various pH levels ranging from 1 to 10 in a titania sol, under UV light. The as-prepared nanocomposite particles were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and N-2 adsorption/desorption method at liquid nitrogen temperature (-196 A degrees C) from Brunauer-Emmett-Teller (BET) measurements. It is shown that at a Ag loading of 1.25 wt.% on TiO2, a high-surface area nanocomposite morphology corresponding to an average of one Ag nanoparticle per titania nanoparticle was achieved. The diameter of the titania crystallites/particles were in the range of 10-20 nm while the size of Ag particles attached to the larger titania particles were 3 A +/- 1 nm as deduced from crystallite size by XRD and particle size by TEM. Ag recovery by photo harvesting from the solution was nearly 100%. TEM micrographs revealed that Ag-coated TiO2 nanoparticles showed a sharp increase in the degree of agglomeration for nanocomposites prepared at basic pH values, with a corresponding sharp decrease in BET surface area especially at pH > 9. The BET surface area of the Ag-TiO2 nanoparticles was nearly constant at around a value of 140 m(2) g(-1) at all pH from 1-8 with an anomalous maximum of 164 m(2) g(-1) when prepared from a sol at pH of 4, and a sharp decrease to 78 m(2) g(-1) at pH of 10.