green synthesis of carbon dots from pumpkin seeds for fluorometric determination of l-cysteine

Abstract: l-cysteine (l-cys) is an important sulfur-containing compound which is extensively used in the food industry, environmental research, drugs formulation and cosmetics. an abnormal level of l-cys can cause heart diseases, liver problems, l-cystinuria, and acquired immune deficiency syndrome. accordingly, detection of low concentrations of l-cys using a sensitive, rapid, selective and cost effective analytical method in the environmental, industrial and biological matrixes is of great interest. various techniques including spectrophotometry, chromatography, capillary electrophoresis, flow injection analysis, electrochemistry and spectrofluorometry were used for determination of l-cys. in recent years, fluorescence carbon dots (cds) have been widely applied as fluorescent probes to monitor analytes due to their excellent optical properties. thus, in this work, a sensitive and selective biosensors based on carbon dots prepared from pumpkin seeds coupled to fluorometric technique was design and successfully used for determination of trace amount of l-cys. after addition of l-cys to the carbon dots solution, the fluorescence intensity was decreased. experimental factors affecting the fluorescence intensity such as ph, amount of carbon dots, reaction time and salt concentration were investigated and optimized. under the optimum conditions, the calibration curve was obtained over the range of 5 – 500 nm and limit of detection was 1.5 nm.