Bhattacharya Angana, Samanta Dipanjan, Shaw Manisha, Shaik Md Abdus Salam, Basu Rajarshi, Mondal Imran, Pathak Amita
Department of Chemistry, Indian Institute of Technology, Kharagpur, West Bengal 721302, India.
ACS Appl Bio Mater. 2025 Jan 20;8(1):503-518. doi: 10.1021/acsabm.4c01416. Epub 2024 Dec 12.
Blue-emissive nitrogen-doped chiral carbon dots (d-NCD230 and l-NCD230) exhibiting antipodal chiroptical activity, synthesized from the thermal pyrolysis of citric acid and d/l-aspartic acid in 1:2 molar ratios, have been explored as chirality-based fluorescent turn-off/on probes for the detection of Hg and l-cysteine (l-Cys). Circular dichroism (CD) spectroscopy revealed that the chiroptical activity originates from a synergy among intrinsic chirality, chiral precursors on the NCD surface, and hybridization of lower energy levels within the embedded chiral chromophore. Quantitative analysis of optical asymmetry using the Kuhn asymmetry factor () at the CD signal of 312 nm showed a higher value for d-NCD230 (1.03 × 10) compared to l-NCD230 (1.13 × 10). Moreover, we have demonstrated chirality transfer and chiral inversion phenomena in d/l-NCDs by preparing carbon dots with different precursor ratios at different temperatures and probing them through CD spectroscopy. The NCDs exhibited selective fluorescence quenching in the presence of Hg, demonstrating linearity in the Stern-Volmer plot. Limits of detection (LODs) for Hg were calculated to be 129 and 192 nM for d-NCD230 and l-NCD230, respectively, in the 0-150 μM concentration range. The quenching mechanism involves nonradiative electron transfer due to Hg binding to oxygen-rich functional groups on the d/l-NCD230 surface. The slight variation in LOD values between d-NCD230 and l-NCD230 indicates the negligible effect of the chirality on Hg sensing. Notably, the fluorescence intensity of d/l-NCD230 could be restored upon adding l-cysteine, with d-NCD230 showing a more pronounced enhancement than l-NCD230. This differential response is attributed to a preferential stereoselective interaction arising from the homochirality of d-NCD230/Hg and l-cysteine. These findings demonstrate the potential of chiral nitrogen-doped carbon dots as sensitive and selective probes for Hg and l-cysteine, with implications for environmental monitoring and biological sensing applications.
通过柠檬酸和d/l-天冬氨酸以1:2摩尔比进行热解合成的具有反对手性光活性的蓝色发射氮掺杂手性碳点（d-NCD230和l-NCD230），已被探索用作基于手性的荧光关闭/开启探针，用于检测汞和l-半胱氨酸（l-Cys）。圆二色性（CD）光谱表明，手性光活性源于固有手性、NCD表面的手性前体以及嵌入的手性发色团内较低能级的杂化之间的协同作用。在312 nm的CD信号处使用库恩不对称因子（）对光学不对称性进行定量分析，结果显示d-NCD230（1.03×10）的值高于l-NCD230（1.13×10）。此外，我们通过在不同温度下制备具有不同前体比例的碳点并通过CD光谱对其进行探测，证明了d/l-NCDs中的手性转移和手性反转现象。NCDs在汞存在下表现出选择性荧光猝灭，在Stern-Volmer图中呈线性关系。在0-150μM浓度范围内，d-NCD230和l-NCD230对汞的检测限（LOD）分别计算为129和192 nM。猝灭机制涉及由于汞与d/l-NCD230表面富含氧的官能团结合而导致的非辐射电子转移。d-NCD230和l-NCD230之间LOD值的微小变化表明手性对汞传感的影响可忽略不计。值得注意的是，加入l-半胱氨酸后，d/l-NCD230的荧光强度可以恢复，d-NCD230的增强比l-NCD230更明显。这种差异响应归因于d-NCD230/汞和l-半胱氨酸的同手性产生的优先立体选择性相互作用。这些发现证明了手性氮掺杂碳点作为汞和l-半胱氨酸的灵敏且选择性探针的潜力，对环境监测和生物传感应用具有重要意义。
