Thermal and light-induced electrical properties in nanocomposites of reduced graphene oxide and silver nanoparticles

We present synthesis of nanocomposites of silver nanoparticles with reduced graphene oxide (Ag-rGO) using one-step, one-pot method where polyvinylpyrrolidone and ethylene glycol are, respectively, utilized as capping and reducing agents. The average particle size of Ag NP reduces by 16-folds when the composite is formed with rGO. We have examined the anharmonicity, thermal expansion, and thermal conductivities in rGO and Ag-rGO, while evaluating their crystallite sizes and defect densities using temperature-dependent Raman spectroscopy. The thermal conductivity of rGO and Ag-rGO at similar to 300 K have been found to be 2.86 +/- 0.09 Wm (-1) K-1 and 1.69 +/- 0.06 Wm (-1) K-1 , respectively. Owing to increase in defects in Ag-rGO, their thermal conductivity has been found to be smaller than that of rGO. In addition, I-V hysteresis loops are obtained for rGO and Ag-rGO and are used to explain variation in space charges and electrical resistances in the presence and absence of plasmonic excitation. In rGO, the electrical resistance remains nearly constant irrespective of the illumination, whereas in Ag-rGO a significant drop in the resistance upon illumination at 532 nm is observed. The increase in current is ascribed to plasmon-mediated charge transfer from nanoparticles to rGO surface.