Improving reproducibility between batches of silver nanoparticles using an experimental design approach

An optimized method for the synthesis of silver nanoparticles (AgNP) using gallic acid as reductant was achieved using design of experiment strategies based on response surface methodologies. Fractional Factorial Design was used in the screening stage, the Box-Behnken method was employed to model the target responses and finally, the optimization step was done using Desirability function. The obtained AgNP presented improved repetitivity and reproducibility of photophysical properties between batches compared to the synthesis method reported in literature. Intra-assays, intermediate precision and reproducibility tests were performed and proved the different AgNP batches presented equal optical responses, average size and size distribution at a 95% confidence level. In addition, a test on shelf life estimated the optimized AgNP preserve their properties at least for 38 days and especially, zeta potential measurements indicated their low tendency to flocculation as long as 120 days. Furthermore, a remarkable improvement in obtaining reproducible Stern-Volmer constants in fluorescence quenching experiments using Carbazole as fluorophore was observed compared to nanoparticles synthesized by a non-optimal method.