Utilizing a Deformation/Aggregation-Based Approach for Determination of Selenium Using Plasmonic Silver Nanoparticles

In the present study, a simple and low-cost spectrophotometric method was reported for the quantification of selenium. The method was based on the surface manipulation of citrate-capped silver nanoparticles by selenium in ammonia-ammonium nitrate buffer solution (pH = 9). Citric acid on the surface of nanoparticles could reduce selenium ions to Se⁰ atoms which can react with the silver atoms to form Ag₂Se surrounding silver particles. This process resulted in the deformation and aggregation of nanoparticles which can be detected by a decrease in response intensity. The effect of important experimental parameters such as pH, buffer type and concentration, volume of silver nanoparticle solution, and incubation time on analytical response were investigated and optimized. Under the optimal conditions, the calibration graph was linear in a concentration range of 0.05 to 0.8 µmol L⁻¹ with a detection limit of 0.024 µmol L ⁻¹. The method was successfully used for the selenium analysis in Selen plus ACE capsule, selenium sulfide shampoo, and walnuts with satisfactory results.