Quantum Dot-Enhanced Localized Plasmonic Detection of Chloride Ions in Lipid-Based Medium

This study presents the development of an innovative optical sensor leveraging localized surface plasmon resonance (LSPR) for the sensitive and selective detection of chloride ions, which is crucial as chloride ions play a key role in the formation of 3-monochloropropane-1,2-diol (3-MCPD) esters during the refining process. By accurately detecting chloride ions, this sensor could help mitigate the formation of harmful 3-MCPD esters, improving the safety and quality of lipid-based mediums by utilizing a novel composite of nitrogen-doped carbon quantum dots (NCQDs) and triangular silver nanoparticles (AgNTs). The incorporation of amino groups on the NCQD significantly enhances chloride ion detection through electrostatic interactions between the NCQD and the negatively charged chloride ions. The AgNT-NCQD composite was meticulously self-assembled onto a silanized glass substrate, resulting in a robust LSPR sensor film. Our experimental findings demonstrate positive performance of the AgNT-NCQD film-based LSPR sensor over conventional AgNT films, evidenced by a high correlation coefficient ( ${R}^{{2}} =0.9625$ ). The sensor exhibited remarkable sensitivity, achieving 0.92 $nmppm^{-{1}}$ , with a detection limit of 2.16 ppm across a concentration range of 0–6 ppm. Notably, the sensor displayed a specific positive shift toward chloride ions, with negligible interference from $Cd^{{2}+}$ and $Fe^{{2}+}$ , while $Zn^{{2}+}$ and $Cu^{{2}+}$ induced a negative shift in the LSPR signal, likely due to their influence on the sensing layer thickness. This research underscores the effectiveness of the AgNT-NCQD composite sensor in detecting chloride ions within lipid-based mediums, highlighting its potential application in food safety and quality control. The sensor’s high sensitivity, selectivity, and minimal cross-interference position it as a promising tool for advanced analytical applications in the food industry.