Chitosan Curcumin Film as a Sensor for Detection of O-Nitrophenol and Fluoride Ion Using Fluoresce Quenching Technique

Abstract

Curcumin was immobilized in chitosan films fabricated by solvent casting method. The amount of curcumin immobilization was more when methanol was used as a solvent to dissolve curcumin than the butanol solvent. The maximum amount of curcumin immobilized per gram of chitosan film was 0.023 g. Immobilized curcumin was not released back in water even after prolong contact of the films with water. Fluorescence intensity of the films got quenched when these films were in contact with an aqueous solution of o-nitrophenol (ONP) and sodium fluoride (NaF). The extent of quenching depended on the concentration of these attributes. Fluorescence intensity was highly pronounced even when the concentration of ONP and fluoride (FL) was as low as 2.0 x 10–6 M and 2.5 x 10–5 M, respectively. UV-vis spectroscopy could not detect 2.5 x 10–6 M ONP; similarly, ion chromatography was not sensitive towards 2.5 x 10–5 M FL. Since the extent of quenching varies linearly with the concentration of ONP and FL in aqueous solution, the Stern-Volmer equation can be used for quantification of these.