| Summary: | 碩士 === 臺北醫學大學 === 醫學科學研究所 === 98 === This study elucidates the high quantum efficiency of synthesized semiconductor nano-crystals including CdTe(core) and CdTe/CdS (core/shell) with 2-5nm and 10nm diameters, respectively. The analytical results from dynamic light scattering (DLS) show the zeta potential is in the –20 ~ -50mV range for these two quantum dots. CdTe is synthesized as model QDs by modifying the surface with 3-mercaptoproproionic acid (MPA) or thio-glycolic acid (TGA), respectively. MPA or TGA is used as stabilizers to protect the QDs and prevent precipitation due to QD particle aggregation. After surface modification treatment, the QDs are easy to connect with proteins or drugs such as bovine serum albumin (BSA). The photo-luminescence intensity can be efficiently enhanced with increasing BSA concentration.
We also carried out an experiment with metal doped into the CdTe/CdS to investigate the photo-stability and fluorescence property including Mn-doping CdTe/CdS and TiO2, ZnO-doping CdTe/CdS via microwave irradiation. The results of Mn-doping CdTe/CdS showed that enhanced PLQY was obtained to meet the requirement for highly quantum efficiency. Furthermore, internal doping of TiO2 and ZnO also possessed better ability to display high fluorescence intensity than CdTe/CdS without doping. Observing the elementary process including surface adsorption and lattice incorporation, it illustrated that Mn2+ had already incorporated into the CdTe/CdS zinc blend structure interior. According to EDX (energy-dispersive X-ray), it double confirmed that Mn2+ entered into the CdTe/CdS. However, once the temperature increased to 120oC, a decrease in photo-luminescence occurred. This result indicated that Mn2+ had been diffused out of the CdTe/CdS, namely lattice diffusion.
To understand the biocompatible properties, CdTe (core) and CdTe/CdS (core/shell) was added into neuro-2a cell (mouse neuro-blastoma cell) to evaluate the core and core/shell toxicity via MTT assay. It was found that CdS was capable of encapsulating CdTe possessing highly bio-compatibility and resulting in lower toxicity than CdTe. From the experimental results, we can conclude that surface-modified QDs have better photo-stability and fluorescence characteristics than bare QDs and are also suitable for further biomedicine applications.
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