Preparation And Application Of The Mn-Doped ZnSe And Otherwise Fluorescent Quantum Dots

Cadmium chalcogenides QDs such as CdS, CdSe, and CdTe are widely explored. All of these have highly toxic elements Cd. What's more, a large number of problems such as low reaction temperature, long reaction time, and low-dispensability were existed in the aqueous phase synthesis for the QDs. To these problems, a green and rapid synthetic procedure is introduced for the low-toxic luminescent Mn-doped ZnSe QDs (Mn:ZnSe), Mn:ZnSe/ZnS QDs, and CuInS2 QDs in aqueous phase by microwave irradiation in the thesis. The as-prepared QDs are characterized by XRD, TEM, PL spectra, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and EPR. The applications for the prepared QDs were also explored.The results were summarized as follows:1. A successful rapid and green synthesis procedure is reported for the high-quality Mn2+ doped ZnSe nanocrystals under microwave-assisted hydrothermal conditions in aqueous phase. The as-prepared QDs had high crystallinity and mono dispersiblity. It was confirmed to the Mn impurities were embedded inside the nanocrystals with EPR spectral. Fluorescence life time of the Mn-doped ZnSe QDs was extended as long as 400μs, which was 10000 times higher than that of conventional QDs such as CdS, CdSe, and CdTe. Mn-doped ZnSe nanocrystals have highly photostability in 37℃water under continues irradiation at 260nm using a 150w xenon lamp. 2. Based on the long life-time and high-quality Mn-doped ZnSe QDs and sensitive quenching effect due to a anti-cancer drug 5-Fluorouracil, a time-resolved fluorescence detection of 5-FU with the detection limit of 128 nM is established. The relative standard deviation for seven independent measurements of 1.5μM 5-FU was 3.8% and the recovery ranged from 93% to 106%.3. A two-step synthesis was used for the low toxic Mn:ZnSe/ZnS core/shell quantum dots. The Mn:ZnSe/ZnS core/shell nanocrystals exhibited increased PL intensity compared with the Mn:ZnSe core nanocrystals, and the PL quantum yield(QY) of the Mn:ZnSe/ZnS core/shell nanocrystals was up to 25%. A novel sensing system based on the fluorescence resonance energy transfer (FRET) between Mn:ZnSe/ZnS QDs and Au nanoparticals (AuNPs) was established for the detection of human IgG. The calibration graph was linear over the range of 0.2 to 3.2μM of human IgG under optimal conditions.4. A microwave-assisted hydrothermal synthesis is reported for the CuInS2 QDs. The prepared CuInS2 QDs not only posses high crystallinity and monodispersity, but also exhibit excellent water-solubility and photoluminescence. Moreover, the CuInS2 QDs showed a high electrogenerated luminescence (ECL) signal.