Surface Plasmon Resonance Based Optimization of Irradiation Doses and Alginate Content on Radiosynthesis of Silver Nanoparticles

The coherent oscillations of conduction electrons near surface of silver nanoparticles (AgNPs) forms a strong surface plasmon resonances (SPR) in the visible spectrum which strongly correlates with its properties in suspension. The present study explores the use of central composite design (CCD) of response surface methodology (RSM) to optimize the two process parameters (irradiation dose and alginate content) on the radiosynthesis of AgNPs without addition of isopropanol as hydroxyl radical scavenger. The CCD-RSM matrix involved 13 run experiments in which the nondestructive UV-Vis spectroscopy method was applied in determination of optimization responses, i.e. the peak absorbance, peak wavelength (λmax) and full width at half maximum (FWHM) of the SPR band. The results showed that the AgNPs successfully synthesized after gamma ray irradiation without addition of isopropanol. The regression models fitted the quadratic models. All responses were significantly influenced by irradiation dose factor through the synergistic linear relationship and the antagonistic quadratic relationship. While, the insignificant effect of alginate content in this study indicates that alginate only plays as a stabilizing agent. The optimum conditions were obtained desirability value of 0.954 where the irradiation dose and alginate content were at 12.7 kGy and 1.00 % (w/v), respectively. The multiresponse optimization model were correspond well with experimental validation results at 95 % confidence interval. Under the optimum condition, the AgNPs suspension was at concentration of 92.7 ppm from yield ratio of 89.65 %, which had spherical shape with average size of 9.96 ± 6.87 nm, hydrodynamic diameter of 11.36 nm, and polydispersity of 0.13.