Trigonal-Pyramidal Coordination-Triggered Conformational Changes in Multiemission Carbon Dots Enable Highly Selective Arsenic Detection

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Developing tools for rapid and accurate arsenic detection is critical to mitigate the risks of consuming groundwater in regions with a high likelihood of (often geogenic) arsenic contamination. Fluorescent sensors are promising platforms; yet, their selectivity is often compromised by interfering water constituents. Inspired by the mechanism of microbial resistance to arsenic, which is enabled by ArsR proteins through exact coordination of three cysteine thiolates with As(III), we synthesized a novel self-calibration sensor (DMSA-M-CDs) with donor-acceptor luminophores by functionalization of multi-emission carbon dots with dimercaptosuccinic acid. This sensor quantitatively detects As(III), the most toxic and most mobile arsenic species, in complex water matrices with a detection limit as low as 1.0 μg/L. DMSA-M-CDs exhibit unprecedentedly high selectivity and robustness against interference by 42 coexisting constituents, and the measured values in real groundwater samples using this sensor are comparable to those by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS). This superior performance is attributed to the formation of a trigonal-pyramidal complex with As(III) via As-S bonds, which triggers conformational changes of donor-acceptor luminophores and, consequently, fluorescence quenching. This bio-inspired strategy for rapid and reliable detection of trace arsenic concentrations in water also offers a novel sensing paradigm to tackle the global threat of heavy metal contamination.