Decoration of reduced graphene oxide by gold nanoparticles: an enhanced negative photoconductivity.

Photodetection in a visible light region is important in various applications, including computation, environmental monitoring, biological detection and industrial control. Due to this, research studies to develop photoconductive devices have great significance. We report a study on the photoconductivity of reduced graphene oxide (rGO)/gold nanoparticle (AuNP) nanocomposites, emphasizing the enhancement effect induced by AuNPs. rGO/AuNP photoelectric devices were prepared by spincoating rGO onto an AuNP-array-covered silicon substrate. Photoelectric responses under visible light illumination were measured and the results showed that the negative photoelectric responsivity of rGO was improved by 3 orders of magnitude due to AuNPs. The effects of AuNPs on negative photoconductivity (NPC) properties of rGO were investigated, and it was found that AuNPs affected NPC in three aspects: (1) AuNPs form discrete electrodes separated by nanoscale gaps which generated new conduction paths, and hence the conductivity of rGO was enhanced by 3 orders of magnitude; (2) localized surface plasmon resonance (LSPR) of AuNPs effectively enhances total light absorption of rGO; (3) photocurrent between AuNPs and rGO can weaken the NPC property of rGO. The low-cost and mass-producible rGO/AuNP nanocomposites demonstrate high photoelectric responsivity, which hold much promise for NPC devices.