High dielectric thin films based on UV-reduced graphene oxide and TEMPO-oxidized cellulose nanofibres

The dielectric response of thin, flexible films, prepared from graphene oxide (GO) and 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) oxidized cellulose nanofibres (TCNF) is studied using the solution casting method, and further subjected to the UV irradiation treatment under nitrogen atmosphere for GO reduction. The reduction of GO and its interactions with TCNF has been proven by ATR-FTIR, FESEM, UV–Vis, Raman, and XRD spectroscopy measurements. The film’s improved storage modules and deformability by temperature are demonstrated by dynamic mechanical analysis. The dielectric constant of the TCGO-3 (contains 3 wt.% GO) composite film reaches up to 74.05, whereas its 5 h UV treated counterpart even up to 119.2 at a high frequency of 1 MHz. The ac conductivity of the latter film sample reaches ~ 0.0053 Sm^{− 1}. These outstanding dielectric responses of such films indicate their potential to be utilized in energy storage devices, as well as demonstrating their preparation in an environmentally friendly way.