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The Morphology Control of PbSe Nanocrystals under the Near-critical Conditions

Author: LiuDongHua
Tutor: ChenLiXue；ChenHaiYong
School: Jilin University
Course: Condensed Matter Physics
Keywords: near-critical conditions PbSe nanowires corrosion enthylenediamine nanoshells
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 41
Quote: 0
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Abstract

Nanocrystal semiconductors have attracted much attention due to their particular electrical and optical properties. As an important semiconductor, PbSe can be used in optoelectronic、biophysics and fluorescence microscope. For the narrow band-gap, PbSe can also be used to produce optical detector.、light resistors、optical transmitter and so on. PbSe can also be used as mid-infrared、far-infrared diode laser source、atmospheric pollution detection and automatically detection in pollution.In our experiment, we introduce a chemical method to prepare PbSe nanowires under the near-critical conditions. Near-critical conditions in our experiment is defined like this :put the solvent prepared by dissolving selenium in ethylenediamine and solvent prepared by dissolving lead actate in ethylenediamine into a three-flask bottle and then heated to certain temperature under refluxing and vigorous stirring. In the process of the reaction, there will be a critical temperature, when the temperature is higher than the critical temperature, the precipitation existed; when the temperature is lower than the critical temperature, no precipitation occurred. In our experiment, we control the temperature from the lower point to the higher point, and we named the critical temperature as the near-critical condition. Moreover, when the reaction is under the near-critical condition, because of the competition between the occurred of precipitation and the dissolving of the precipitation, more monomer will occur, this will provide a good condition to synthesize nanowires. In our experiment, we choose enthylenediamine as solvent, The lead selenide(PbSe) nanowires with an average of 200nm and high crystallinity were synthesized under the near-critical conditions via a green chemical route. The synthesized PbSe nanowires were further characterized by using Transmission Electron Microscope (TEM), X-ray diffraction (XRD). Finally, the growth mechanism of PbSe nanowires was discussed. We aslo report on the relation between corrosion of precipation and reaction-time. And we can control the reaction-time to increase or decrease the corrosion .Meanwhile we can use this method to prepare different nanostructures with different atomic ratio between lead and selenium. nanoflowers, nanocubic structure with holes, selenium nanotube with different concentration and ratio were aslo synthesized under refluxing and vigorous magnetic stirring. We aslo synthesize nanowires with an average of 30nm containing lead, selenium and other element .The product can be used as precursors to synthesize PbSe nanowires. The synthesized products were further characterized by using X-ray diffraction pattern (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM). Finally, the growth mechanism of the product were also discussed.

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