Increase of metallic silver nanoparticles in Chitosan:AgNt based polymer electrolytes incorporated with alumina filler

In the present work, the possibility of increasing the amount of metallic silver particles in chitosan (CS)-based polymer nano-composites was discussed. To prepare the electrolyte, a fixed amount of silver nitrate (AgNO3) inorganic salt was added to the natural CS biopolymer. Various techniques, such as UV–vis, SEM, EDX and impedance spectroscopy, were used to characterise the samples. Remarkable enhanced surface plasmonic resonance (SPR) peaks were observed at 420 nm in the UV–vis spectra of the samples incorporated with various amounts of alumina (Al2O3) nano-particles. The intensity of SPR peaks increased with increasing alumina concentration. The SEM image of pure CS showed a smooth surface and little white specks were observed in the SEM image of CS: AgNO3 system. The number of white specks were increased on the surface of the samples incorporated with 1 and 3 wt% of alumina. The sharp intense peaks due to metallic silver particles appeared in the EDX spectra at 3–3.6 keV. The second loop did not manifest for the CS: AgNO3 system because the amount of Ago nanoparticles were low. The distinguishable second loops were observed in impedance plots of CS: AgNO3 systems containing 1 and 3 wt% of alumina filler. The second loop in impedance plots was ascribed to metallic silver particles and its diameter increased with increasing alumina concentrations. The experimental data was fitted with electrical equivalent circuits (EEC). The EEC model reveals that the samples filled with Al2O3 filler needs two circuits for exhibiting best fitting. The dielectric constant increased at 1 wt% of alumina and then it decreased as alumina was increased to 3 wt%. The AC conductivity spectra were presented for all of the samples. The maximum DC conductivity of about 2.3 × 10−6 S/cm was obtained for the CS: AgNO3 system doped with 1 wt% alumina. The DC conductivity decreased at 3 wt% alumina due to the reduction of more silver ions to metallic silver particles.