A novel approach to Hg²⁺ determination in water samples using carbon dots based on paper and fluorescence digital image analysis

BACKGROUND: This work proposes the use of a simple, inexpensive method for the hydrothermal synthesis of fluorescent carbon dot nanoparticles (CDs) from rice starch aimed at the determination of Hg2+ in water. The proposed method involved using a paper -based analytical device coupled to a 3D plate, with a UV -LED chamber and a smartphone for the acquisition and analysis of the fluorescence digital images of the CDs. RESULTS: The size of the carbon dots ranged from 0.5 to 3 nm, with an average particle size of similar to 1 nm. The functionalization of carbon dots with methimazole allowed a high selective for Hg2+ determination. The results obtained showed a linear response R2 of 0.997 and Hg(2+ )concentration in the range of 0.5-45.0 similar to mol L-1 with a limit of detection and limit of quantitation of 0.23 and 0.62 similar to mol L-1, respectively. The results of the study show that there were no significant differences, at 95% confidence level, between the data obtained from the application of the proposed method and the reference method. CONCLUSION: The proposed method is in line with the principles of green chemistry, as it involves the use of renewable sources for starch extraction and a hydrothermal synthesis process that does not employ toxic reagents. In addition, the method employs only 15 similar to L reagent/sample. (c) 2024 Society of Chemical Industry (SCI).