Measurement And Controlling For Interfacial Electron Transfer Of Quantum Dots

Semiconductor nanocrystals have been widely used in optical detection, super-resolution fluorescence imaging and optical electronics because of its unique physical characteristics, such as stable, strong fluorescence radiation, no easy bleaching and broadband absorption spectrum. The process of electron transfer between quantum dots and semiconductor or insulator materials interface is very important for the preparation of quantum optical devices such as nano-conductor, solid-state light quantum devices and so on. Interfacial electron transfer process is highly dependent on the local nanoenvironment. The fluorescence and spectrum of single quantum dot can eliminate the effect of average, which can also provide us dynamic information of nanoenvironment. It has became an advanced tool in complex systems.Single quantum dot is an excellent tool which can be used to insight into the microscopic dynamics process of interfacial electron transfer. The optical properties of quantum dot, including fluorescence intensity, lifetime, blinking, can be influenced by interfacial electron transfer when quantum dots contacted with other materials. These changes can help us quantify the properties of interfacial electron transfer. The studying of the interaction between quantum dots and other materials, such as insulators, semiconductors, can provide theoretical foundation and technical reserves for the fabrication of quantum optical devices and nano optoelectronic devices. Our main work is as follows:1. The confocal and wide field fluorescence microscopy systems based on single molecule probes have been established. The methods for sample preparation, detection and data processing were given.2. We studied the optical properties of single quantum dots on glass interface with the presence of interfacial electron transfer. The statistical distribution of the fluorescence intensity on glass interface in different laser power was also studied, the distribution of dipole orientation on glass interface by defocused imaging in wide field, the single quantum dot shows a two-dimensional polarization orientation, measured the fluorescence lifetime on glass interface by the method of time resolution of photon statistics, the distribution of quantum dots fluorescence lifetime obey biexponential function, researched the fluorescence blinking of single quantum dot on glass interface by confocal microscope system. Furthermore, we find that the on time and off time distribution following the power law.3. Compared the behavior of blinking of quantum dot on glass, polymer film and semiconductor nanoparticles ITO. We found that the blinking behaviors are different with the different interface environment, it can be attributed to different interfacial electron transfer between quantum dots and local nanoenvironment. The fluorescence properties of quantum dots on glass interface under the external electric field were also studied, and we found that the fluorescence intensity can be modulated by electric field. This modulation effect can be attributed to the changes of electron transfer at the quantum dot surface or internal atoms. The deeply captured charges induced internal electric field which can shift the energy level difference between excited state and the charges transfer state. The changing of charges transfer rate leads to the change of fluorescence intensity.