Fluorescence Emission Characteristics Of Single Quantum Dots Based On Interfacial Electron Transfer Dynamics

Colloidal quantum dots are nanoscale single photon emitters with excellent optical properties,including high quantum yield,long fluorescence lifetime,good light stability,desirable biocompatibility,and continuously adjustable spectroscopy,which have a wide range of applications in the fields of biomedicine,lighting display,and quantum information.Especially for the optoelectronic devices,the study of the interfacial electron transfer dynamics between single quantum dots and conductors,semiconductors and other nanomaterials is of great significance for the practical application of quantum dots.Single quantum dots are very sensitive to the nano-environment in which they are located,some near-field interactions such as electron transfer,energy transfer,and dielectric effect between single quantum dots and their local environment will change the optical radiation characteristics of quantum dots.The single quantum dots completely remove the ensemble averaging effect,thereby obtaining the dynamics of the single quantum dot in the nano-environment and the variations of microscopic information.The interfacial electron transfer dynamics will affect the optical properties of single quantum dot contacted with other materials,such as fluorescence lifetime,blinking behavior,dipole orientation,and exciton emission characteristics.Our main work includes three aspects as follows:1.The interfacial electron transfer dynamics between single quantum dots and semiconductor nanomaterials.We investigated the interfacial electron transfer dynamics of single near-infrared CdSeTe/ZnS_3ML quantum dots encased in N-type semiconductor nanoparticles indium tin oxide（ITO）. ITO with higher Fermi level than that of CdSeTe/ZnS_3ML quantum dots,when a single quantum dot was encased in a thin film formed of ITO nanoparticles,the electrons in ITO will be transferred to the quantum dot to ill in its trap states of the surface,thus,suppressing fluorescence blinking f single quantum dots.In addition,ITO can modulate the fine structure of he band-edge exciton of a single quantum dot,which leads to linearly olarized fluorescence emission property of a single quantum dot.2.Enhancing two-photon emission of the biexciton state in a single quantum ot.When single near-infrared emitting CdSeTe/ZnS_3ML core/multishell uantum dots are encased in N-type semiconductor ITO nanoparticles,the TO nanoparticles with high electron density can increase the dielectric creening of single quantum dots,to reduce the Coulomb interactions etween carriers,thus suppressing the nonradiative Auger recombination of iexcitons.It is observed that an average g^（2）（0）=0.57 in the second-order orrelation function curves which indicates the effective creation of iexciton and subsequent two-photon emission from single quantum dots ncased in ITO nanoparticles.The fluorescence quantum yield ratio of the iexciton to single-exciton emission is increased to⁴.8 times while the uger recombination rate reduces by roughly an order of magnitude, ndicating the significantly enhanced two-photon emission of single uantum dots.3.Fluorescence emission properties of single near-infrared CdSeTe/ZnS_3ML uantum dots on a new type of two-dimensional material.Electron transfer ccurs when single quantum dots are spin-coated on thin layers MoS₂ due o the high charge carrier mobility of MoS₂ and the higher Fermi level than hat of CdSeTe/ZnS_3ML quantum dots.Experimental studies indicate that he fluorescence blinking rate of single quantum dots on MoS₂ decreases y nearly one order of magnitude.In addition,the fluorescence lifetime of ingle quantum dots significantly reduces from 90 ns to 23 ns since the dditional non-radiative channels introduced by MoS₂.