Probing of ascorbic acid by CdS/Dendrimer nanocomposites: A spectroscopic investigation

Abstract

Gamma irradiation method has provided a route for synthesis of highly water-soluble, good quality luminescent CdS/Dendrimer nanocomposites with amino- or carboxyl-terminated PAMAM dendrimer. An attempt has been made to probe ascorbic acid with the as-synthesized CdS/Dendrimer nanocomposites (DNC). Ascorbic acid (AA) is an important biological antioxidant and also marker for different diseases in clinical chemistry as well as in quality control in food industry. Micromolar concentrations of AA significantly quenched the photoluminescence (PL) of both amino (NH2) and carboxylic (COOH) functionalized semiconductor nanocomposites. The quenching followed a linear Stern–Volmer equation and time-resolved photoluminescence (PL) spectroscopy confirmed its static nature. A strong size dependence of quenching pattern was observed. The binding constants, and the corresponding thermodynamic parameters ΔGθ, ΔHθ, ΔSθ at different temperatures were calculated. CdS DNC showed selectivity towards ascorbic acid even in the presence of possible interfering molecules, such as uric acid, tartaric acid and citric acid. Nanocomposites based assay technique could override the complications involved in multitudes of assay procedures, providing a, simple and fast new strategy for the quantification of AA in the range of 16.6–100μM (R=0.998, n=9). The proposed method was applied for the detection of ascorbic acid in vitamin C tablet with satisfactory results.