Dual sensing of tetracycline and L-Lysine using green synthesized carbon dots from Nigella sativa seeds

Abstract

In this study, carbon dots (CDs) that exhibit bright-blue fluorescence were hydrothermally synthesized from Nigella sativa seeds and employed for selective and quantitative detection of tetracycline (TC) and L-lysine (L-Lys). Specifically, TC addition led to quenching of CDs’ fluorescence intensity, while the enhanced fluorescence was spotted in the presence of L-Lys. CD quenching was attributed to both dynamic and static mechanisms, which is different from earlier-reported studies. In contrast, the introduction of L-Lys supported the emergence of hydrogen bonds between CDs and L-Lys, and consequently resulted in an increase in photoluminescence (PL) intensity. PL quenching was linearly correlated with TC concentration ranged from 0.01 to 40 μM with 14 nM detection limit. A linear correlation was observed for L-Lys in the concentration range of 0–500 μM and displayed a limit of detection of 453 nM. CDs showed TC detection in the range of 95.2–102.5% in tap water, river water, urine, and powdered milk. Likewise, CDs have been successfully utilized for detecting L-Lys in serum samples with a recovery range of 98.9–100.3%. The study describes the use of a dual sensing strategy for TC and L-Lys using green synthesized CDs. This study will provide an in-depth insight into the mechanism of TC and L-Lys detection by CDs, which will help to understand the role of different nanoparticles in sensing applications. © 2020 Elsevier Ltd