Gamma rays induced synthesis of graphene oxide/gold nanoparticle composites: structural and photothermal study

Gamma irradiation provides an alternative pathway to conventional gold nanoparticle synthesis because it is simple, fast, and economical. Here, we employed gamma irradiation at low doses (1-20 kGy) to obtain gold nanoparticles (Au NPs) anchored onto graphene oxide (GO) sheets. GO was selected as a suitable platform for the nucleation and growth of Au NPs because of its large surface area and good dispersibility in water due to the presence of polar oxygen-containing functional groups in its structure. Gamma irradiation at all the applied doses led to the reduction of chloroauric acid and the formation of evenly distributed Au NPs at the GO surface, simultaneously causing the reduction of GO and partial restoration of the graphene structure. As-prepared Au NPs have predominately spheric shapes and the smallest nanoparticles were reported for the dose of 1 kGy. The increase in the irradiation dose caused either the growth of larger particles (5 and 10 kGy) or the broad dis-tribution of particles' sizes (20 kGy). All samples showed a temperature increase upon exposure to 800 nm laser and photothermal efficiency was the highest for the sample prepared at 20 kGy.