The Excellent Performance Of Water-soluble Quantum Dots And Quantum Dot - Polymer Nanospheres Preparation Of Microwave Radiation And Research

With comparison to traditional organic dyes, quantum dots (QDs) possess unique advantages such as broad absorption spectra coupled to narrow photoluminescent emission spectra, size-tunable luminescent color, strong fluorescence, and high resistance to photobleaching. Therefore, QDs, which are considered as the novel fluorescent probes, have elicited a great deal of attentions in the past decade. QDs can be synthesized through two representative strategies: one is the organometallic method; the other is the aqueous method. Sufficient progresses have been achieved for preparation of high-quality QDs through the organometallic routes up to the present. However, complicated manipulations are often required in the organic route. In addition, expensive and toxic reagents are used for synthesizing QDs in organic phase. In contrast, the aqueous synthesis procedure is simpler, cheaper, and less toxic. The biggest problem is that the QDs prepared through conventional aqueous method possess relatively poor spectral properties, poor photostability, and severe cytotoxiciy, which is adverse to the further study and wide applications of QDs in nano-biological research.For the purpose of conquering the shortcomings mentioned above, different kinds of high-quality QDs and QDs-polymer nanospheres were successfully prepared directly in aqueous phase assisted by microwave irradiation. Furthermore, the cytotoxicity of as-prepared QDs and nanospheres were systematically studied. Afterwards, cells and vivo were imaged by these QDs and nanospheres. The details are as follows:1. A method named "program process of microwave irradiation (PPMI)" was developed. Water-dispersed CdTe QDs with PLQY of 68% were prepared, since the conditions of both nuclear formation and growth were optimized in PPMI method;2. CdS shell was successfully epitaxial growth on the surface of CdTe core QDs assisted by microwave irradiation. The PLQY of as-prepared CdTe/CdS core-shell structure QDs was enhanced to 75%;3. The water-dispersed CdTe QDs with both high PLQY (82%) and narrow fwhm (27 nm) were obtained through further improving and optimizing synthesis conditions. The PLQY reached remarkable 98% after amelioration of illumination method;4. The CdTe/CdS/ZnS core-shell-shell structure QDs, which possess high PLQY, narrow fwhm, outstanding photostability, and excellent biocompatibility, were firstly prepared in aqueous phase via the method of core-shell epitaxial growth assisted by microwave irradiation;5. The surface of as-prepared quantum dots was modified by use of poly(allylamine) via electrostatic attraction. On the basis of this research, two different emission wavelength of the quantum dots-poly(allylamine) composite can be observed in PL spectrum while excited by a single excitation wavelength;6. A general approach to surface modification of quantum dots named "synchronous formation of quantum dots-polymer nanospheres (SFQN)" was developed, which is completely different from traditional method of surface modification. The QDs-polymer nanospheres rapidly prepared through SFQN method possessed not only the favorable spectral properties, but also excellent photostability and good compatibility;7. The cytotoxicity of as-prepared QDs and QDs-polymer nanospheres were systematically studied. Furthermore, these QDs and QDs-polymer nanospheres were primarily applied for cells and vivo imaging.These researches provided useful evidence for further nano-biological applications of quantum dots as fluorescent probes.