Preparation Of Near-infrared Quantum Dots In A Quasi-Biological System And Their Electrochemiluminescence Applications

In the last decades, there has been a rapid development of nanaotechnology. Ineed, the physical, chemical, optical, electronic and structural of nanomaterials differ markedly from the corresponding bulk materials, and are also different from molecule and atom. The unique physicochemical properties of nanomaterials, such as large surface-to-volume ratios, high hardness and magnetic susceptibility, good conductivity and excellent chemical and catalytic activity, etc. have received much attention in the fields of materials science, applied physics, chemistry and medicine. Due to minimal autofluorescence and negligible tissue scattering in the near-infrared region, near-infrared quantum dots (QDs) has played importat roles in the field of nanomedice. Therefore, to prepare better near infrared QDs for bioimaging and biodetection is our aim.In our previous work, fluorescent CdSe QDs were controllable synthesized in living yeast cells by a novel process which coupling irrelevant intracellular biochemical reactions in a proper space and time sequence. Such method not only successfully avoided to use explosive, inflammable and toxic organic reagents but also made the complicated chemistry reaction simple and safe. However, as the internal environment of cell is complicated, it is very difficult to obtain puried products. To solve the problem, we artificially construct a system to synthesis QDs in vitro by simulating the synthesis of fluorescent CdSe QDs in yeast cells. The main work in this thesis is as follows:(1) A strategy is proposed that involves coupling Na2SeO3reduction using glutathione, reduced nicotinamide adenine dinucleotide phosphate, and glutathione reductase with the binding of silver ions and alanine in a quasi-biological system to obtain near-infrared Ag2Se QDs with tunable fluorescence at90?in aqueous solution. This strategy successfully avoided high temperature, high pressure, and organic solvents and water-dispersible Ag2Se QDs can be directly obtained. The photoluminescence (PL) of the Ag2Se QDs was size-dependent. The Ag2Se QDs are less cytotoxic than other nanomaterials used for similar applications.(2) The near-infrared electrogenerated chemiluminescence (ECL) mechanism of water-dispersed Ag2Se QDs have been studied in detail. Dopamine was chosen as a model analyte to study the potential of Ag2Se QDs for analytical application based on ECL. The ECL signal of Ag2Se QDs can also be used for the detection of the practical drug (dopamine hydrochloride injection). The Ag2Se QDs could be a promising candidate emitter for ECL biosensors in the future.(3) Based on the Ag2Se QDs synthesized in a quasi-biological system, we developed a method to prepare doped Ag2Se QDs. The doped QDs were gained just by mixing metal ions with as-prepared Ag2Se QDs, which is simple and controllable. Doped QDs exhibited unique optical and magnetic properties, which is different from the host QDs. The quantum yield (QY) is significantly improved from3%to14%by introducing IIB transition metal ions. Moreover, magnetic-fluorescent QDs with QY up to14%and saturation magnetization of0.4emu/g were prepared by doping magnetic metal ions. The above method offers a new strategy for prepare near-infrared QDs with excellent properties.