The role of graphene oxide and its reduced form in the in situ photocatalytic growth of silver nanoparticles on graphene-TiO2 nanocomposites

Graphene oxide or reduced graphene oxide-TiO2 (TGO or TRGO) nanocomposites were decorated with Ag nanoparticles (AgNPs) using the photoreduction method. The photocatalytic growth of AgNPs on TGO and TRGO nanocomposites was compared, while keeping the other parameters (i.e., thickness, chemical composition, crystalline structure and the percentage of an area of TiO2 covered by GO or RGO flakes) unchanged. The morphology, structure and chemical composition of TGO-Ag or TRGO-Ag nanocomposites were investigated with the use of SEM-EDS, XPS and Raman spectroscopy. AgNPs were found to be distributed on the surface of TiO2 and on GO or RGO flakes. In-depth research undertaken to explain the effect of GO or RGO used in nanocomposites with TiO2 on the growth of AgNPs showed that there were considerable differences in size and distribution of AgNPs grown on TiO2 and on GO/RGO areas covering TiO2. In addition, the number (n) and size (d) of AgNPs on TGO (n = 37AgNPs/mu m(2) ; d = 29 +/- 3 nm) or TRGO (n = 34AgNPs/mu m(2); d = 32 +/- 3 nm) do not differ significantly. The theoretical calculations of the weight of silver deposited on the same sample showed that the mass of silver was, on average, twice as high on both types of graphene (9.1(TGO) and 11.2(TRGO) pg/mu m(2)) as on TiO2 (4.8(TGO) and 5.7(TRGO) pg/mu m(2)).