Optical Properties Adjustment And Biological Detection Applications Of MoS₂ Quantum Dots

As a typical transition metal sulfide,MoS₂ is well known for its unique physical properties exhibited when the bulk materials are transformed into low dimensional materials.Studies in recent years have shown that,MoS₂ quantum dots have different optical properties from single-layer films,and they also have large specific surface area and excellent biocompatibility.Therefore,it has excellent application prospects in the fields of photonics,catalysis,optoelectronics,biosensors and so on.Focusing on the urgent needs of effective adjustment of the optical properties and the emission mechanism of MoS₂quantum dots,this thesis carried out a series of research.The influencing factors of the luminescence of MoS₂ quantum dots were analyzed.The optical properties are adjusted by modification and doping with rare earth ions.Finally,biodetections based on MoS₂ were successfully achieved.The main results obtained are as follows:?1?MoS₂ quantum dots with a size of about 2.4nm were obtained by ultrasonic stripping method.The effect of solvents on the luminescence of MoS₂ quantum dots was analyzed.It was found that the fluorescence of MoS₂ quantum dots in mixed organic solvents is seriously dependent on the excitation wavelength.After dialysis treatment,multiple emission peaks around 422nm of the MoS₂ quantum dots appeared due to the interaction between the solvent molecules and the crystal surface.However,the emission wavelength does not change along with the excitation wavelength,indicating that the excitation of organic solvent is the reason why the fluorescence of MoS₂ QDs obtained by stripping changes with the excitation wavelength.?2?Water-soluble MoS₂ quantum dots were prepared by hydrothermal method using sulfur-containing ligands as reactants.The optical band gaps of CYS,GSH and MSA modified MoS₂ quantum dots were 2.56eV,2.65eV,and 2.59eV,respectively.The fluorescence spectra show that the ligands can effectively passivate the surface defects of the MoS₂ quantum dots.Therefore,the fluorescence can be enhanced.GSH modified MoS₂quantum dots have the optimal fluorescence,and can be coupled with biomolecules.This provides the possibility of biological detection based on MoS₂ quantum dots.?3?Combining the excellent biocompatibility of MoS₂ quantum dots with the unique fluorescence of rare earth ions,MoS₂:Eu quantum dost,which can be used as bioluminescence labeled in visible light,were prepared.Luminescence of Eu ions were observed under excitation with a 532nm visible laser.The cytotoxicity tests show that,after cultivation in the quantum dot solution with the concentration up to 300?g/ml for 48 hours,the cell survival rate is still above 90%,which indicated that it had good biological safety.Using a sandwich detection scheme,specific detection of 10nM-6.25?M human IgG molecules using MoS₂:Eu quantum dots was finally achieved.