Designed synthesis of chlorine and nitrogen co-doped Ti3C2 MXene quantum dots and their outstanding hydroxyl radical scavenging properties

As a novel zero-dimensional (0D) material, metal carbides and/or carbonitrides (MXenes) quantum dots (MQDs) show unique photoluminescence properties and excellent biocompatibility. However, due to the limited synthesis methods and research to date, many new features have yet to be uncovered. Here, to explore their new properties and expand biological applications, chlorine and nitrogen co-doped Ti3C2 MXene quantum dots (Cl, N-Ti3C2 MQDs) were designed and synthesized, and their hydroxyl radical scavenging properties were investigated for the first time, revealing outstanding performance. Cl, N-Ti3C2 MQDs was directly stripped from bulk Ti3AlC2 by electrochemical etching, while N and Cl are successfully introduced to carbon skeleton and Ti boundaries in the etching process by electrochemical reactions between selected electrolytes and Ti3C2 skeleton, respectively. The obtained Cl, N-Ti3C2 MQDs exhibit large surface-to-volume ratio due to small particle size (ca.3.45 nm) and excellent higher scavenging activity (93.3 %) and lower usage (12.5 μg/mL) towards hydroxyl radicals than the previous reported graphene-based nanoparticles. The underlying mechanism of scavenging activity was also studied based on the reduction experiment with potassium permanganate (KMnO4). The reducing ability of the intrinsic Ti3C2 structure and electron donation of double dopants are the main contributors to the outstanding scavenging activity.