Negative differential resistance and improved optoelectronic properties in Ag nanoparticles-decorated graphene oxide–riboflavin hybrids

Silver nanoparticles (Ag NPs) are decorated on graphene oxide (GO)–riboflavin (R) hybrids produced with three different compositions. The SEM micrographs of the GO–R–Ag materials show a helical fibrillar morphology different from the bar and wrinkled sheet morphology of R and GO, respectively. FT-IR spectra indicate that GO produces a supra molecular complex with R and Ag NPs are stabilized by both R and GO. The UV–vis spectra show a large shift of surface plasmon band from 390 to 570 nm and the circular dichroism spectra indicate a drastic change in the GO–R–Ag system over the GO–R system for a weight ratio of GO to R of 13, suggesting that Ag NPs are wrapped by both the GO–R hybrid and R moieties. The PL-intensity of R increases in the GO–R hybrids but it decreases in the GO–R–Ag ones. The dc-conductivity of the GO–R hybrids increases by 2–3 orders of magnitude on addition of Ag NPs. The I–V characteristic curves of the GO–R–Ag (GO/R = 1/3) material shows a negative differential resistance. Possible reasons from the charge trapping on the Ag NPs followed by stabilization by R are discussed and a model using the density of states approach is proposed.