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. (C) 2012 Elsevier Ltd. All rights reserved.