Rapid, in-field speciation of Cr(vi) in aqueous samples using photoluminescent MoS2 quantum dots and portable fluorimetry with digital image analysis

• Published in: Analytical methods Vol. 16; no. 38; pp. 6546 - 6552
• Main Authors: Khoshmaram, Leila, Emami, Mina, Jalili, Roghayyeh, Imani-Nabiyyi, Amin
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 03.10.2024
• Subjects: Chromium; Correlation coefficient; Correlation coefficients; Developed countries; Digital imaging; Environmental monitoring; Fluorescence; Fluorescent indicators; Fluorimetry; Fluorometers; Image analysis; Image processing; Molybdenum disulfide; Photoluminescence; Portability; Quantum dots; Rivers; Sampling instruments; Signal analysis; Speciation; Water analysis; Water sampling
• DOI: 10.1039/d4ay00688g
• ISSN: 1759-9660; 1759-9679

This study explores a novel approach for in-field speciation of Cr(vi) in various aqueous samples employing nontoxic, MoS2 quantum dots (QDs) as a fluorescent probe. The proposed fluorimetric method, compatible with commercial instruments, utilizes a portable custom-built fluorimeter equipped with a multi-wavelength LED array. The method seamlessly incorporates digital image analysis, with fluorescence signals recorded by a smartphone for detection and signal analysis. Digital image analysis decomposes fluorescence intensity into RGB components, enabling rapid analysis and instantaneous sharing of results. The optimized method yielded a linear calibration graph ranging from 50 to 5000 μg L−1, with a correlation coefficient of 0.98. The relative standard deviation for determination of 500 μg L−1 Cr(vi) was 0.52% for five replicate measurements. Successfully applied to wastewater and river water samples, this method combines efficiency, portability, and versatility for in-field Cr(vi) speciation and provides an accessible environmental monitoring tool for less developed countries facing budget and skilled workforce limitations.