Fabrication and characterization of conductive silk fibroin–gold nanocomposite films

This research proposes a one-step fabrication of novel conducting silk fibroin (SF) nanocomposites (NCs) in which in situ generation of nanoparticles from their precursor are achieved. Here, the gold salt (HAu^IIICl₄·H₂O) is reduced to gold nanoparticles (AuNPs) using SF, a renewable natural biopolymer, and SF–AuNPs NCs are developed via solution casting method. The optical absorption spectra recorded using the UV–Visible spectroscopy (UV–Vis) witnesses the generation of anisotropic particles by showing two absorption bands. Also, the calculated optical band gap energy (E_g) value decreases from 4.2 to 2.4 eV with the increasing concentration of AuNPs. The X-ray diffraction (XRD) profile of the NCs confirms the presence of AuNPs. The scanning electron microscopy (SEM) micrographs clearly admit the successful formation of AuNPs in the host polymer matrix with homogeneous dispersion. The size and evolution of the different shaped AuNPs are confirmed by the transmission electron microscopy (TEM) study. An increase in DC conductivity from 1.48 × 10⁻⁹ to 7.12 × 10⁻⁹ S/cm and decrease in frequency-dependent dielectric constant are observed with the increase in AuNPs. The obtained result suggests that the insulating behaviour of the SF can be effectively changed into a conducting nature with the in situ creation of AuNPs in the SF matrix.