Graphene nanoribbon doped PVA nanocomposites for improved UVC blocking and luminescence down-shifting applications

Graphene nanoribbon (GNR) is quasi-one dimensional carbon based nanomaterial, distinct from graphene and less explored nanofiller in optical and optoelectronic applications. Herein flexible poly vinyl alcohol (PVA) nanocomposites of 0, 0.25, 0.5 and 0.75 wt % compositions of GNR were prepared by using solution intercalation technique and characterized by spectroscopic methods to assess their structural and optical characteristics. The characterization of PVA@GNR nanocomposites revealed Vander Waals binding of GNR to PVA chains and also considerable crystallographic changes in PVA matrix upon the incorporation of GNR. The optical investigations showed UV-visible absorption in the wavelength range of 200-280 and 350-520 nm which enhanced on increase in GNR dopant concentration. The decrease in the optical band gap and Urbach energy was also observed for the nanocomposites with increase in dopant concentrations thereby suggesting the formation of localized states in the forbidden band region. The refractive index, absorption coefficient, extinction coefficient and optical conductivity of PVA nanocomposites showed excellent agreement with the band gap revelations and indicated UVC light blocking properties in the wavelength of 200-280 nm. Further, the GNR incorporated PVA nanocomposites exhibited improved thermal stability, wettability transitions (hydrophilic to near hydrophilic) and excellent luminescent down-conversion properties with a high Stokes's shift (100 nm) compared to pristine PVA nanocomposites. The study concludes that the proposed PVA@GNR nanocomposites can ideally fit optical and photovoltaic device applications owing to their transparency coupled with UV blocking and luminescence down-shifting attributes.