CdTe-paper-based visual sensor for detecting methyl viologen

This study developed a method on detecting methyl viologen (paraquat) using a CdTe-paper-based visual sensor. The CdTe Qdots were immobilized on the paper using glycerin. The volume percentages of CdTe in glycerin were optimized to be 50%. The sensing principle is that the methyl viologen quenches the fluorescence intensity of CdTe Qdots in a concentration dependent manner. The sensor is linearly response to the logarithm concentration of the methyl viologen in the range from 0.39 μmol/L to 3.89 mmol/L with a detection limit of 0.16 μmol/L and the correlation coefficient R² of 0.99. Three parallel experiments at the methyl viologen concentration of 38.89 μmol/L give a relative error of 2.45%, which indicates a good reproducibility. The sensor is not disturbed by other pestisides including omethoate, anilofos, machete and glyphosate isopropylamine salt. The advantages of this sensor are disposable, stable, convenient, and easy to operate.