Preparation And Performance Of MXene Quantum Dots

MXene-based low-dimensional materials are named for their layered structure similar to graphene.Since their discovery by Yury Gogotsi’s research team in 2011,these materials have shown great potential in applications such as batteries,supercapacitors,electromagnetic interference shielding,sensors,optoelectronic devices,and solar cells.With the development of MXene materials,the first MXene quantum dots were successfully synthesized in 2017,opening up new research directions for theoretical and experimental studies of quantum dots.MXene quantum dots have advantages such as high hydrophilicity,low biotoxicity,good photoluminescence（PL）performance,good biocompatibility,and high selectivity for target analytes,thus they have been widely applied in fields such as optoelectronics,biology,catalysis,and energy.However,there are currently issues with the synthesis methods of MXene quantum dots,such as long experimental cycles and high danger coefficients.In this regard,we have explored a safe and efficient method for synthesizing MXene quantum dots,and applied it to the preparation of Ti₃C₂Tx MXene quantum dots,Ti₂CTx MXene quantum dots,Nb₂CTx MXene quantum dots,and Nb₄C₃Tx MXene quantum dots.The main research findings are as follows:（1）Synthesis of Ti₃C₂Tx MXene:A method using HCl+Li F&Na OH etching of MAX phase was proposed for the synthesis of Ti₃C₂Tx MXene,and it was compared with HF etching and Na OH etching.The results show that this method has higher safety and larger interlayer spacing.The increase in interlayer spacing will introduce more defects,which will provide more active sites and ion diffusion channels for the material.（2）Synthesis of Ti₃C₂QDs:Through in-depth analysis and comparison of the MXenes obtained by the three different etching methods mentioned above,Ti₃C₂QDs synthesized by HCl+Li F&Na OH etching followed by solvent thermal ultrasound treatment were found to have excellent excitation-dependent performance,making them a popular material in the field of multicolor imaging in biology.At the same time,the fluorescence quantum yield of Ti₃C₂QDs can reach 12.53%,which is higher than the average level of quantum dot fluorescence quantum yield of MXene currently.（3）Applications of Ti₃C₂QDs:Ti₃C₂QDs exhibit fluorescence quenching effects towards Fe³⁺,Cr₂O₇^2-,and Cu²⁺,making them useful as detection probes and highly selective fluorescence sensors.Among them,the lowest detection limit concentration of Ti3C2 QDs towards Fe³⁺can reach 10^-6mol/L,which is the lowest Fe³⁺concentration that all MXene quantum dots can currently detect（4）Synthesis of Ti₂C QDs,Nb₂C QDs and Nb₄C₃QDs:To verify the applicability of the method of HCl+Li F&Na OH etching and solvent thermal-ultrasonic co-preparation of MXene quantum dots,we applied this method to Ti₂Al C,Nb₂Al C,and Nb₄Al C₃,and confirmed by XRD,XPS,FT-IR and other characterization methods that this method can be used to synthesize Ti₂C QDs,Nb₂C QDs and Nb₄C₃QDs,with fluorescence quantum yields of 6.03%,8.53%,and 9.69%,respectively.This method provides a new idea for the synthesis of subsequent MXene quantum dots.（5）Application of Ti₂C QDs:Ti₂C QDs can be used for targeted detection of Cu²⁺.Within the range of 6.25×10^-5～0.01 mol/L,the concentration of Cu²⁺is linearly related to the change in fluorescence intensity of Ti₂C QDs.In practical applications,the corresponding point on this linear relationship can be found based on the fluorescence quenching proportion,and the concentration of Cu²⁺in the test substance can be calculated.