Chitosan embedded with Ag/Au nanoparticles: investigation of their structural, optical and sensing properties

Quantitative detection of hydrogen peroxide (H2O2) is reported by utilizing an optical sensor based on the Surface Plasmon Resonances (SPR) of Ag and Au nanoparticles embedded in chitosan, a biopolymer. Ag and Au nanoparticles, fabricated by chemical reduction approach, were incorporated individually in chitosan matrix by solution casting method. Subsequently, their presence in the host matrix was confirmed using UV-visible spectroscopy, X-Ray diffractometer (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Field Emission Scanning Electron Microscopy (FESEM) along with Energy Dispersive Analysis of X-Ray (EDAX) spectroscopy. Structural changes induced in chitosan with addition of varying concentration of Ag or Au nanoparticles were studied using Fourier transform infrared (FTIR) spectroscopy. Optical energy gap of chitosan decreased from 3.82 +/- 0.28 eV to 1.84 +/- 0.19 eV for Ag-chitosan nanocomposite (Nc) film containing 0.50 wt% Ag nanoparticle while to a value of 2.14 +/- 0.08 eV for Au-chitosan Nc film containing 0.5 wt% of Au nanoparticle. A significant difference in position and intensity of SPR absorption band was observed as a function of variable concentration of H2O2. The detection limit of these optical sensors is upto 0.3 mu M concentration of H2O2.