Tailoring of electrical and optical properties of regenerated silk fibroin films with metal oxides

Abstract

In this study, silk fibroin was used as a matrix to incorporate the metal oxide nanoparticles i.e. zinc oxide (ZnO) and copper oxide (CuO) to form transparent nanocomposite films by solvent casting method. The effect of metal oxide nanoparticles and their concentrations on the conductivity of silk fibroin film were detected by a four-point probe instrument. As the thickness of the films was reduced, the conductivity increased. Hall Effect experiment was carried out to determine the carrier (electron or holes) concentration and identification of the semiconducting behaviour of nanocomposite films. Pure silk fibroin (SF) film showed p-type semiconducting behaviour. Incorporation of zinc oxide and copper oxide nanoparticles in the silk fibroin matrix makes it n-type and p-type semiconductor, respectively. Uniform dispersion of metal oxide nanoparticles in the silk fibroin matrix was observed through field emission scanning electron microscopy. The UV–Vis spectra of nanocomposite films showed 82–84% transmittance and reduction in refractive index. Addition of metal oxide nanoparticles reduced the β sheet content and percentage crystallinity of silk fibroin as observed by FTIR and XRD, respectively. The structural alterations at the molecular level reveal their relationship with electrical and optical properties.