| As an important low-dimensional semiconductor material at present,the three dimensions of quantum dots are less than two times of their exciton Bohr radius,so that they have a good quantum confined effect,and the fluorescence emission has a strong dimensional correlation.It had been widely used in the field of photoelectric materials and life science,showing a good prospect.Quantum dots have common ?-? group elements or ?-? group element configuration,the present study focuses on ?-? quantum dots and the study of Cd-containing and Zn-containing quantum dots is common.Compared to the certain biotoxicity of Cd,the biotoxicity of Zn-containing quantum dots is relatively low and compatibility between the surface ligand and biomolecule are good.Therefore,Zn-containing quantum dots was more widely used in the biological field.Research on the correlation properties of Zn-containing quantum dots is of great significance to promote the application of quantum dots in the biological field.In this paper,Zn Se quantum dots were synthesized by the water phase method,using the biomolecule glutathione as the surface stable ligand.It was characterized by X-ray diffraction(XRD),electron microscopy(TEM)and other characterization methods,and it was confirmed that Zn Se quantum dots with a diameter of 3 nm and coated by glutathione surface ligands having good biocompatibility were synthesized.The stokes shift of the quantum dots was 15 nm,the fluorescence emission peak was 375 nm and the intensity was strong.These date proved that the Zn Se quantum dots with good quality were synthesized.Based on the Zn Se quantum dots prepared,starting from the application of quantum dots in biological field,the response of fluorescence dynamics to different p H values were studied by ultraviolet visible absorption spectrum(UV-VIS),fluorescence spectrum(FL),time resolved fluorescence spectrum and the possible applications in biological system were discussed.It was found that the fluorescence decay of Zn Se quantum dots had two lifetimes,about 4 ns and 24 ns,which were respectively derived from non-local carrier recombination in the nucleus and local carrier recombination in surface states.Moreover,the fluorescence lifetime of Zn Se quantum dots was responsive to different p H values,and had the maximum response sensitivity in the p H range of 6?8.The experiment further found that the ratio of two lifetimes had a good linear correlation in different p H values,and the maximum linear slope was within the range of p H value of 6?8.The study proved that the Zn Se quantum dots were feasible to be applied as p H probes in biological systems,and we innovatively used the response of its time-resolved fluorescence spectrum to p H as a method for detecting p H,avoiding the influence of concentration,excitation power and other factors by using the traditional steady-state method fluorescence spectrometry,which has a certain stability.In addition,the interaction between ligands on the surface of Zn Se quantum dots and quantum dots was further studied by two-dimensional infrared spectroscopy,and the related properties of quantum dots were explained from the perspective of ligands.By comparing the ligands and the free form glutathione molecules with spectral peak position,peak shape,vibrational relaxation,anisotropic dynamics,we studied the Zn Se quantum dots on the surface of ligand molecular dynamics,and found that the influence of the quantum dots on the surface of ligand molecules mainly existed in the dynamics of the anisotropic dynamics and the ligand molecular structure itself,the evolution of the dynamic process and related properties changed little.This study showed that quantum dots did not have a strong influence on the relevant properties of surface coupled molecules,and when they are used as biomolecular markers in biological systems,they may have a small influence on the biological activity of the labeled molecules,making them suitable for the application of biomolecular markers. |
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