Mechanism of fluorescent quenching in ship fuel nitrogen content detection using Nb-doped SnO2 quantum dots as the fluorescent probe

Abstract

The mechanism of fluorescence variation in quantum dots (QDs) is crucial for the performance of fluorescence probes. However, the complex mechanisms involved in QDs make the accurate detection of ship fuel nitrogen content (FNC) to mitigate combustion emission pollution a challenging task. Herein, we demonstrate that Nb doping-induced band structure modulation can alter the electronic and optical properties of SnO₂ QDs, and use the fluorescence quenching effect to explain the mechanism for detecting FNC. In this study, we established a low-cost, simple-to-operate, high-accuracy, and low-detection-limit method for detecting FNC, based on the fluorescence quenching phenomenon of Nb-SnO₂ QDs. The method has a linear range of 0.51 % m/m to 0.66 % m/m, a detection limit of 0.011 % m/m, R² = 0.99512, and a recovery rate ranging from 95.79 % to 102.2 %. Density functional theory (DFT) calculations were used to analyze the adsorption structures of four typical functional groups –NH₂, −SH, –COOH, and –OH on the Nb-SnO₂ (110) surface, revealing the adsorption energy and charge transfer during the detection process. It was found that Nb doping enhances the adsorption capability of SnO₂ QDs for –NH₂. Finally, the fluorescence quenching mechanism was determined to be the photoinduced electron transfer (PET). This mechanism provides important insights for the subsequent doping modulation of QDs’ band structure and optical properties, as well as for the development of other fluorescence probes.