Sonda baseada em nanopartículas fluorescentes para detecção seletiva de íons dicromato em amostra de solo

Abstract

Hexavalent chromium [Cr(VI)] is widely recognized for its high toxicity, environmental persistence, and carcinogenic potential. In this context, fluorescent nanomaterials such as Carbon Quantum Dots (CQDs) stand out as promising platforms for the development of sensitive, selective, and economically viable sensors aimed at monitoring this contaminant. Accordingly, this study aims to develop a sensing strategy based on CQDs with high quantum yield, capable of detecting Cr(VI), in the form of dichromate ions, in soil samples. The CQDs were synthesized using a hydrothermal method, subsequently purified, and characterized by spectroscopic, structural, and microscopic techniques. The nanoparticles exhibited an average size of approximately 1.5 nm, and their surfaces were found to contain functional groups such as carbonyl, carboxyl, and amine, which facilitated interaction with the target analyte. Additionally, the fluorescence quantum yield achieved was 40.6%. After optimizing the experimental conditions, a chemical sensor for the detection and quantification of Cr(VI) was developed, employing a turn-off sensing mechanism predominantly based on Inner Filter Effect (IFE) and dynamic quenching phenomena. The developed probe demonstrated high selectivity for the dichromate oxyanion, even in the presence of potential interfering species. Finally, the sensor’s sensitivity was validated through detection and quantification limits, estimated at 2.8 and 8.6 mg kg-1, respectively. Recovery experiments conducted with real soil samples corroborated the potential of the proposed methodology, underscoring the efficacy of the probe for environmental monitoring of dichromate ions, a naturally occurring species of Cr(VI).