Synthesis and optical characterization of high-quantum-yield UV-emitting MXene quantum dots

Nitride MXene-based quantum dots (MQDs) display photoluminescence with deep ultra-violet (UV) excitation, which suggests a superior performance for light-emitting applications in the UV region. We synthesized titanium nitride (Ti2N) MQDs by solvothermal synthesis using ethanol as the solvent and our Ti2N MQDs exhibited UV emission centered at ~370 nm wavelength with a maximum 17% of the quantum yield (QY). Band structure calculations and X-ray photoelectron spectroscopy measurements indicate that Ti2N MQDs synthesized by using the solvothermal process are free of fluorine which is normally prevalent on the surfaces of MQDs prepared by an ordinary hydrothermal process. We were able to control the center wavelength of emission and further improved QY up to 26% with the choice of various solvothermal solvents. The results shed light on the mechanism of UV emission and QY enhancement of MQDs helping their practical applications, especially for photonic devices in the UV range.