Research On Fluorescence Properties Of Single Quantum Dots In ITO Semiconductor Nanomaterials

CdSe/ZnS quantum dots(QDs)are semiconductor devices that tightly confine electrons and holes in all three spatial dimensions.They have broad absorption spectrum,narrow emission spectrum as well as high fluorescence quantum yield.Therefore,they could be widely used in optoelectronic devices,fluorescence imaging and quantum information and so on.However,QDs have strong fluorescence blinking and fluorescence non-polarization,which limit their application.For example,single-photon sources based on QDs are used for quantum cryptography.Fluorescence blinking of QDs would cause error information.When measuring tracking process of biological life,the fluorescence blinking makes it difficult to obtain dynamical evolution of the research object at real time.In addition,QDs have no polarization characteristics,which limits its application on liquid crystal display quantum information processing and so on.As single quantum system,QDs' fluorescence properties is extremely sensitive to its nano environment.In this paper,we realized that single QDs interact with indium tin oxide(ITO)to the benefit of interfacial electron transfer between them and then filled capture states in the shell of QDs,effectively to suppresse their fluorescence blinking.Meanwhile ITO can change the band-edge exciton fine structure of QDs and its dielectric environment then cause higher linearly polarized radiation of QDs.The main contents of this paper include:1.We introduced the experimental setup of confocal microscopy imaging system and wide-field imaging system respectively,detailed description of preparation of QDs sample,collection and analysis methods of datas.Optical physical properties and research status of QDs were given.2.We studied the effects of semiconductor nanomaterials(ITO)on the fluorescence properties of single QDs.We measured the fluorescence properties of single QDs by laser scanning confocal microscopy imaging system.Compared with the emission of QDs on SiO2 glass,it is found that ITO could suppress the fluorescence blinking of QDs.It is found that the on-and off-state probability densities of QDs on different substrates both can be fit by a truncated power law.The on-state probability density of single QDs in ITO is approximately two orders of magnitude higher than QDs on SiO2 cover glass.The distribution of the amplitude weighted average lifetime of single QDs in ITO and its full width at half maximum(FWHM)is shown here.It is found that electrons of ITO transfer to QDs and fill the trap states on the surface of QDs shell.We studied the photon statistical properties of single QDs in ITO by using second order correlation function.3.We measured the distribution of CdSe/ZnS single QDs in the semiconductor nanoparticles ITO by the wide-field defocus imaging techniques and found that two-dimension dipole moments of most single QDs have been changed to a single dipole moment.We used linearly polarized rotary laser to excite single QDs inside ITO and found that the average degree of polarization of single QDs could reach to be 0.55.The result showed nanoparticles ITO could effectively modify the polarization properties of single QDs and produce single-dipole QDs.