| In this thesis we studied the applications of colloidal nanocrystal quantum dots (QD) in bio-medical studies. We investigate the synthesis of QD and report a relatively simple method for synthesizing QD. To produce QDs that are more stable and have higher fluorescent quantum efficiency than those produced by other methods (typically CdSe/ZnS core/shell structures), we developed a CdSe/ZnSe/ZnS (core/shell/shell) nanocrystal complex, capped with the small molecule mercaptoacetic acid (MAA) for aqueous solubilization and low toxicity. These MAA-capped QDs can be used as the visualization aid for a multi-functional probe combining the functions of viruses and carbon nanotubes (CNT). A mild method of tagging virus through a polycationic solution, Polybrene, at 4°C is developed. This method can preserve most viral infectivity. The probes can be used to induce higher death rate in cells under near-infrared laser irradiation than in the cells without them, and thus, after additional improvements, may find applications in the study of cancer therapy. The optical properties of MAA-capped QDs are pH dependent. In particular, the fluorescence intensity increases with pH (pH between 4 and 10) of the environment. The results lead to a new venue to exploit QD as nano-scale sensors for localized physical and chemical properties in cells. |
