Characterization and optical properties of reduced graphene oxide doped nano-crystalline vanadium pentoxide

Abstract

In this paper, the structural and optical properties of reduced graphene oxide (rGO) doped vanadium pentoxide nanocrystalline films were studied. rGO was synthesized using modified Hummer method and confirmed by EDX, XRD and HRTEM. XRD measurements showed good fit with known card JCPDS 40-1296 of vanadium pentoxide with nanocrystals structure oriented toward the c-axis. The line of (002) in XRD graphs is getting weaker by the addition of rGO till nearly missing at the higher concentrations indicating intercalation of rGO within the vanadium layers. The average particle size measured decreased with increasing rGO content from 4.86 to 3.17 nm. Optical properties were studied by measuring the absorption, reflectance and transmittance of the prepared samples using double-beam UV–Vis spectrophotometers. The optical constants like refractive index n, extinction coefficient k, real and imaginary dielectric constants, absorption coefficient α, and optical band gap Eop of the nanocrystalline films have been evaluated. The absorption coefficient decreases with increasing rGO content, which may be attributed to decrease in lattice distortion owing to rGO content due to the decrease of particle size as indicated in the XRD and HRTEM. Optical measurements revealed that there are two different optical gaps present. The optical gap Eop1 was found to decrease with increase in rGO content, while the optical gap Eop2 was found to increase with increase in rGO content. The carrier’s concentrations as well as the effective mass were calculated assuming hydrogen-like model. The good absorption in the UV region of rGOxV2O5·nH2O films are promising candidate for solar cell photostabilizer applications.