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

Abstract

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 ~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 Hg²⁺ concentration in the range of 0.5–45.0 μmol L⁻¹ with a limit of detection and limit of quantitation of 0.23 and 0.62 μmol 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 μL reagent/sample. © 2024 Society of Chemical Industry (SCI).