Studies On Aqueous Synthesis And Application Of CdTe Semiconductor Nanocrystals

Due to the unique size-dependent optical and electronic properties, high quality semiconductor nanocrystals (NCs) have widely applied in the fields of optoelectronic conversion, immune sensor and, especially, biological imaging. According to the practical requirements, these NCs need to be improved in some properties or construction. In this paper, we had synthesized high quality CdTe NCs in water by some special methods, such as microwave-asistant, ultrasonic wave-assistant, ultrasonic-microwave-assistant, or microwave- hydrothermal. And a new green synthesis way of CdTe NCs was developed. In this way, the growth of NCs was accelerated by one reagent instead of energy. We also received the composites of CdTe NCs and SiO₂ by different methods. Finally, the CdTe NCs and CdTe/SiO₂ were applied to the microorganism imaging and latent fingerprint detection.Firstly, high quality CdTe NCs was synthesized by microwave-, ultrasonic wave-, ultrasonic-microwave-, microwave-hydrothermal- assistant procedures. In these methods, not only the quantum yield was improved greatly (max. ⁸0%), but also the spectra of fluorescence emission covered the region from visible to near infrared (500⁸30nm). It only took less than 55 seconds to synthesize NCs, which saved a great deal of time (72 hours in other methods) and energy. Moreover, it was shown that there was some effect on growth of CdTe NCs that was not reported before when using different mode of microwave instruments. For instance, fluorescence emission of CdTe NCs would split when a multimode microwave instruments is used.Secondly, a new chemical reagent other than energy was found to accelerate the growth of semiconductor nanocrystals (cadmium telluride), which was applied to the synthesis of high quality CdTe nanocrystals at room temperature and under ambient conditions for several hours. Under the mild conditions the mercapto-stabilizers were not destroyed, and the CdTe nanocrystals particle sizes with narrow and uniform distribution over the largest possible range was guaranteed. CdTe nanocrystals synthesized in this way had very good spectral properties. For example, the highest photoluminescence quantum yield up to 60% was obtained.Thirdly, the composites of CdTe NCs and SiO₂ were prepared by immersed self-assembled, in-situ methods and reverse microemulsion, respectively. These methods had their own merits. The immersed self-assembled means was so simple that CdTe NCs and MCM-41 were mixed together without any pretreatments. In reverse microemulsion, the size of silica nanoparticles of CdTe/SiO₂ was uniform and tunable. Moreover, we could disperse CdTe NCs into glass through sol-gel processing and a devised luminescent-glass was obtained.Finally, we had succeeded to detect the living Borrelia burgdorferi of Lyme disease by its photoluminescence image of microorganism. Since the CdTe NCs could form a photoluminescent nanocomposite with amino acid of fingerprints, a feasible and rapid detection procedure of latent fingerprints adapted well to collection of fingerprints in the location of a crime. We also studied on four medicines including Caffein, Berberine Hydrochloride, Cefalexin and Chloramphenicol, the spectra of fluorescence emission of the composites of these medicines with the CdTe NCs were affected differently.