Study On Photo-Properties Of Single Quantum Dots And Its Application Of Super-Localization

As novel fluorescent nanomaterials, quantum dots have played important roles in many fileds, such as chemical analysis, biology sensor, molecular imaging, owing to their excellent optical properties. Studies on the properties of single quantum dot can help to find new experimental phenomenology, which can’t be found in the ensemble-approach; provide a mentality to improve the properties of quantum dots; contribute to a better application of QDs in various fields. Utilizing the wide-field fluorescence microscopy as the main study approach and taking single QD as research object, this dissertation showed photobleaching of QDs by non-excitation light, presented the influence factor of oxidation process, and applied the QDs to single molecule counting and super-resolution localization. The main work were as follows:1. Photobleaching of Quantum Dots by Non-excitation LightCore/shell quantum dots are found to be photobleached by non-excitation wavelength light at the single molecule level and ensemble level. That means even the provided photons have not enough energy to pump electrons into conductive band, the photoreaction of QD for photobleaching still occurs but with slower rate comparing with photobleaching by excitation light. The photodynamic of photobleaching under the non-excitation illumination also follows the consecutive elementary reactions as the behavior of excitation wavelength irradiation.2. Oxidation Dynamic of Single CdSe/ZnS Quantum DotsQDs photo-spectal blue shift are caused by an overall size reduction of the QDs due to photooxidation. In this chapter, we utilized the spectral imaging to monitor the process of bule shift, that equals to monitor the QDs oxidation process. After investigated the influence of excitation wavelengh and intensity on Core/shell CdSe/ZnS qauntum dots photo-spectral blue shift, we found that the extent of the blue shift strongly depends on the excitation wavelength and QDs initial size, but not depends on the excitaion intensity. The core oxidation rate is almost proportional to the excitation intensity, shorter excitation wavelength induces faster oxidation rate.3. A meathod for measuring extent of QDs aggregationReal-time measurement of the extent of nanopaticle aggregation is a difficult technical problem. In this chapter, we described a simple and accurate stoichiometry method to count the number of QDs among aggregated QDs by recording the process of its spectral buling and photobleaching. Observing aggregated QDs first-order spectral split, the number of spectral split displays the number of QDs.4. Superlocalization Technique of Multi-color and same-color Quantum Dot ComplexSuperlocalization technique of multicolor quantum dot complex is baesd on different spectral position at different color QDs to monitor the QDs blinking. Tracing the first order spectral of multicolor and dualcolor QDs complex, we realized different color QDs localization, separately, and measured the distance between the two QDs, that is less than diffraction limit distance.Baesd on the QDs spectral bule shift and photobleaching asynchronism, a simple superlocalization technique of same-color QDs complex were developed by identifying QDs blinking.