Estratégia de sensoriamento de íons permanganato a partir de um nanocompósito de Pontos Quânticos de Carbono

Abstract

Potassium permanganate (KMnO4) is a chemical compound widely used in fish farming and aquaculture activities due to its antibacterial potential. Because it lacks specific regulations, its indiscriminate use can cause harmful effects on the present species. The objective of this study was to develop a sensing platform based on Carbon Quantum Dots for the monitoring and detection of permanganate ions in aquatic matrices aimed at fish farming activities. For the synthesis of these nanoparticles, the solvothermal method was used, with citric acid and ethylenediamine as precursors and ethanol as solvent. Furthermore, the CQDs were also characterized by spectroscopic and structural techniques to identify the functional groups present on their surface, and by microscopic techniques, in which sizes of 1.5 nm were identified. The CQDs exhibited a quantum yield of 19.3% and absorption bands at 240 and 350 nm, moreover, the maximum fluorescence emission behavior at 450 nm was shown to be independent of different excitation wavelengths. Subsequently, experimental condition studies, such as the effect of concentration, pH, and interferents, were carried out to improve and establish the optimal parameters for sensing. Calibration curves with MnO4 ⁻ allowed the determination of the Limit of Detection (LOD) and Limit of Quantification (LOQ) for the sensor, which were 1.0 mg L⁻¹ and 3.05 mg L⁻¹, respectively. In addition, assays with a real sample from a water reservoir located in the city of General Sampaio, Ceará, were performed with additions of KMnO4 standard, obtaining recovery results within the 95–105% error range. Finally, a polymeric support for the sensor was prepared based on CQDs and polyvinyl alcohol, and monitoring tests for the MnO4 ⁻ ion proved efficient based on fluorescence quenching effects, indicating the feasibility of using the sensor in the field in aquatic matrices such as tilapia and other fish species breeding ponds.