Dependence of mechanical and electrical properties of silver nanocubes impregnated bacterial cellulose-silk fibroin-polyvinyl alcohol films on light exposure

Flexible and transparent substrate materials were fabricated by using bacterial cellulose (BC), silk fibroin protein (SF) and/or polyvinyl alcohol (PVA). The BC-SF and BC-SF-PVA films obtained were further modified by impregnation with silver nanocubes (AgNC). The influences of the silver nanocubes and white light illumination on the electric and viscoelastic properties of the films were investigated. Complex conductivity measurements showed that the films with PVA component are more sensitive to light exposure and there is an increase in conductance when the sample is illuminated. The films that contained silver nanocubes showed higher values of specific susceptance than their unmodified counterparts. DMA analyses revealed that the storage shear moduli of the films increase with addition of silver nanocubes. It was also found that the relaxation transition observed at elevated temperatures in the BC-SF-PVA-AgNC films is highly sensitive to the light exposure. Above the glass transition of PVA, both storage- and loss-shear moduli change dramatically if the sample is illuminated during the measurements with respect to the case when it was kept in the dark.