Optical Characterization And Detection Applications Of Carbon-based MXenes Quantum Dots

As a new two-dimensional graphene-like material,MXenes has shown great potential applications in catalysis,energy storage,adsorption and sensing.MXenes quantum dots（MQDs）materials have many advantages,such as low biological toxicity,excellent optical properties,easy surface modification and good water solubility.At present,there are few kinds of MQDs,and the knowledge of their chemical composition and structure,surface defects and bonding characteristics is very limited.In this paper,four kinds of MQDs with different atomic layers are studied,and the effects of precursor types and synthesis conditions on their structures and optical properties are investigated.At the same time,the reaction mechanism and fluorescence emission mechanism in the synthesis process were analyzed and discussed.Finally,we have made some efforts and explorations on the application of MQDs materials in ion and molecular detection.The main contents of this thesis are as follows:（1）Four MXenes with different atomic layers,V₂CT_x,Nb₂CT_x,Ti₃C₂T_x,and Nb₄C₃T_x,were used as precursors to prepare MQDs by hydrothermal method.Through the characterization and analysis of the size,morphology,composition and structure of the products,it is realized that the fewer atomic layers of the precursor,the more defects may be contained in the products.Combined with the crystal structure and optical characterization,the intrinsic relationship between the structure and optical properties is revealed,and it is realized that the surface and internal defects of the crystal will introduce defect energy levels between the band gaps and affect the optical properties.（2）V₂C-QDs and Ti₃C₂-QDs were used to detect the concentrations of metal ions and organic small molecules in water system.V₂C-QDs was applied to the detection of iron ion concentration.The linear detection range of the probe was 5.00-500.00ΜM,and the detection limit was 76.00 n M.Ti₃C₂-QDs was applied to the determination of tartrazine in the range of 0.25-60.00μm with a detection limit of71.30 n M.The analysis of the measured data and the verification of Parker equation show that the mechanism of the probe is mainly internal filtering effect.