Preparation Of Luminescent Quantum Dots And Their Applications In Chemical And Biological Analysis

Compared with conventional organic fluorescent dyes, quantum dots have a lot of unique optical properties, which make them appealing as a new class of fluorescent probes. In recent years, quantum dots have gained increasing attention and played important roles in the fields of biochemistry, cell biology and molecular biology, etc. Aiming at this important research direction, the development of quantum dots was summarized, and then the following several works have mainly performed by taking quantum dots preparation, quantum dots characterization and quantum dots applications in chemical and biological analysis as the line of this dissertation.1. Water-soluble CdTe quantum dots were synthesized directly and used for the detection of Cu2+.Water-soluble CdTe quantum dots were prepared in aqueous solution by using thioglycolic acid as the stabilizer and then characterized by fluorescence spectroscopy, UV-Visible spectroscopy, AFM and TEM, respectively. The results show that these quantum dots have good optical properties, such as narrow spectral line widths and continuous absorption profiles, which provide a powerful foundation for further applications. With this kind of water-soluble quantum dots as fluorescence probes, a novel approach was developed for sensitive and selective detection of copper ions based on fluorescence quenching. The mechanism of fluorescence quenching caused by copper ions was further studied. Meanwhile, different influence factors to the detection were investigated, including buffer concentration, quantum dots concentration, pH values and reaction time. Under the optimized conditions, the relative fluorescence intensity decreased linearly with the copper ions concentration in the range from 2 to 200μg·L-1 and the detection limit could reach 0.29μg·L-1. Compared with traditional fluorescence methods for copper ions detection, this quantum dots-based approach is more stable and effective and could be used as a new technique for the detection of copper ions.2. A novel method was developed for the detection of human IgG based on water-soluble CdTe quantum dots.By using the above-prepared water-soluble CdTe quantum dots, a new method was established to detect human IgG based on the fluorescence resonance energy transfer between functional quantum dots and Au nanoparticles. Quantum dots have size-dependent emission spectrum, which can be overlapped easily by the absorbance spectrum of Au nanoparticles and thus facilitates the fluorescence resonance energy transfer. Based on this method, human IgG can be detected easily and specifically without expensive instrument. The relative fluorescence intensity increased linearly with human IgG concentration in the range from 0.5 to 10μg·mL-1 and the detection limit could reach 0.21μg·mL-1. Therefore, this method could be used as a novel technique in the detection of human IgG.3. A novel fluorescence labeling method was developed to characterize the expression of P-gp at cellular level based on water-soluble CdTe quantum dots.Aiming at the advance research field related to cellular characterization by nanotechnology, the above-prepared water-soluble CdTe quantum dots were successfully conjugated with biotin and polyethylene glycol and further used for immunofluorescent labeling of multi-drug resistance related protein P-gp of toque cancer cells (Tca8113 and Tca8113/BLM). The results demonstrate that luminescence in Tca8113/BLM cells is brighter than that in Tca8113 cells, indicating that p-gp are over-expressed in BLM-induced Tca8113 cells (Tca8113/BLM). Compared with traditional fluorescent labeling methods, this approach has good stability against photobleaching, which would play an important role in the field of cellular and subcellular characterizations.4. CdTe quantum dots doped silica nanoparticles with excellent photostability were prepared and used to recognize liver cells.Based on the reverse microemulsion technique, luminescent quantum dots doped core-shell nanoparticles were prepared at moderate conditions by employing water-soluble CdTe quantum dots as the core and silica as the shell of the nanoparticles. In comparison with the pure water-soluble CdTe quantum dots, these nanoparticles showed superiority in photostability. This method is useful and simple for obtaining uniform quantum dots-doped nanoparticles without other rigorous experimental conditions and the nanoparticles have a good dispersibility. Moreover, these nanoparticles were modified with amine groups and phosphonate groups in one step, and further labeled with galactose receptor. With the function of galactose receptor, living liver cells were recognized by galactose receptor-modified quantum dots-doped nanoparticles successfully.5. Semiconductor nanocrystal with blue emission was synthesized, which accelerates the development of short-wavelength-emitting nanomaterials.As is known to all, treatment of quantum dots by silica coating can further improve their photochemical stability. However, quantum dots preparation and silanization are separated in the reported methods. In order to simplify the operation, we designed another synthesizing route to prepare silica-coated CdTe quantum dot directly by using (3-mercaptopropyl)-trimeth-oxysilane as the stabilizer. Accidentally, a novel blue-light-emitting nanomaterials were obtained during this process. Aiming at the advance research field of short-wavelength-emitting nanomaterials, these products were further characterized by fluorescence spectroscopy, TEM, HRTEM and selected area electron diffraction (SAED) pattern, respectively. Nanorod structures can be seen distinctly from the TEM and HRTEM image. Furthermore, the results show that these nanorods have good luminescent characteristics with emission maximum at ~410 nm, exhibit good photostability and have a number of potential advantages, which could be used as a novel blue-emitting nanomaterials.6. By using low-price heat-transfer fluid oil as solvent, hydrophobic CdSe quantum dots were synthesized successfully.According to the high temperature colloidal chemistry synthetic procedures, hydrophobic CdSe quantum dots were prepared successfully in heat-transfer fluid oil, which is very cheap and often used in industry. To further characterize these quantum dots, fluorescence spectroscopy, UV-Visible spectroscopy, TEM and HRTEM were performed, respectively. The results show that these hydrophobic CdSe quantum dots, with good dispersibility and uniformity, have excellent optical properties including continuous absorption profiles and narrow spectral line widths with the full width at half maximum (FWHM) at 26~30 nm. Moreover, no obvious change of fluorescence intensity of quantum dots was observed after it was excited for 3600 seconds by successive intense irradiation, which demonstrates that these quantum dots have excellent photostability. This approach is low-cost and safe for the synthesis of hydrophobic CdSe quantum dots and offered the possibility to produce other kind of hydrophobic quantum dots.