Solvothermal synthesis of in situ nitrogen-doped Ti3C2 MXene fluorescent quantum dots for selective Cu2+ detection

Abstract Two-dimensional MXenes have attracted increasing attention from researchers in the optical, electrical and thermal fields due to their high electric conductivity, thermal conductivity and mechanical properties. MXene quantum dots (QDs) have been highly desired to achieve selective ion detection using highly fluorescent media. In this study, a facile route using amine-assisted solvothermal tailoring was developed to prepare in situ nitrogen-doped Ti3C2 MXene QDs. Pristine MXene was exfoliated to yield MXene with a few layers. Diethylenetriamine, few-layer MXene and N,N-dimethylformamide were blended to perform a solvothermal process, yielding in situ nitrogen-doped MXene QDs with an ∼1 nm thickness and ∼6.2 nm size. The formation of QDs was dynamically monitored. The reduction in the QD size depended on tailoring and in situ nitrogen doping. Fluorescence properties of those QDs were studied. Nitrogen-doped QDs exhibited different fluorescence-quenching responses to various metal cations. Selective Cu2+ detection using the nitrogen-doped QDs mainly depended on a static fluorescence-quenching mechanism. This study might provide opportunities for the large-scale fabrication of in situ element-doped MXene fluorescent QDs.