Optical ascorbic acid sensor based on the fluorescence quenching of silver nanoparticles.

A sensitive and selective fluorimetric sensor for the assay of ascorbic acid (AA) using silver nanoparticles as emission reagent was investigated. In this study, silver nanoparticles were prepared based on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. The nanoparticles were water-soluble, stable and had a narrow emission band. They were used as a fluorescence probe for the assay of ascorbic acid on its quenching effect on the emission of silver nanoparticles. The principal reason for quenching is likely to be a complexation between ascorbic acid and silver nanoparticles. The quenching mechanism was established by Stern-Volmer law. Under the optimum conditions, the quenched fluorescence intensity was linear with the concentration of ascorbic acid in the range of 4.1 x 10(-6) to 1.0 x 10(-4) m (r = 0.9985) with a detection limit of 1.0 x 10(-7) m. The RSD for repeatability of the sensor for the assay of ascorbic acid concentration of 3.0 x 10(-5) and 4.0 x 10(-6) m was found to be 1.5 and 1.3%, respectively. The proposed method was applied to the determination of ascorbic acid in vegetables and vitamin C tablets.