[Luminescence Mechanism of Near-Infrared Quantum Dots].

Near-infrared quantum dots have unique optical properties, such as high fluorescence quantum yield, long fluorescent life, tunable fluorescence emission wavelength, half peak width and large stokes shift, resisting light bleaching etc. The advantage of "near infrared biological window" gives them great potential application value in biological fluorescent tags, solar cells, quantization calculation, photocatalysis, chemical analysis, food detection, vivo imaging and other fields. At present, the luminescence mechanism research of near-infrared quantum dots is still not comprehensive enough. In this paper, the luminescent principle of three different types of near-infrared quantum dots is summarized, including core/shell structure quantum dots (CdTe/CdSe, CdSe/CdTe/ZnSe, etc), ternary quantum dots (Cu-In-Se, CuInS2, etc) and doped quantum dots (Cu∶InP, etc). The luminescence mechanism of Type Ⅱ core/shell structure is most likely to attribute to the interband recombination luminescence, the ternary structure of quantum dots light emitting mechanism is considered to be due to the intrinsic structure defects, and the luminescence mechanism of doped quantum dots is deemed to result from the impurity defects. The existing problems of near-infrared luminescent principle of quantum dots are also discussed and their development tendency is explored t in this review. A systematic study of luminescence mechanism of near-infrared quantum dots will not only help to understand the luminescent properties of near infrared quantum dots, but also contribute to improve the synthesis methods of quantum dots with similarly high quality.

[Research of the photoelectrocatalysis degradation of methylene blue of TiO2 nanotube array films annealed in oxygen atmospheres].

Well-aligned and uniform titanium dioxide nanotube arrays were fabricated in situ on titanium substrate by electrochemical anodic oxidation. SEM images indicate that the TiO2 nanotubes are well organized into high-density uniform arrays,with diameter ranging in size from 70 to 100 nm. The XRD patterns show that the sample fabricated by anodic oxidation is amorphous without being annealed. As the 500 degrees C annealed sample crystallized in the anatase phase, which is in good photocatalytic activity. In quartz glass reactor, the photoelectrocatalytic degradation of MB in aqueous solutions as well as the effect factors and then to 0.1 mol/L NaCl as the electrolyte, under with in oxygen atmospheres annealed the applied bias is 0.5 V and has a pH = 3.25, light intensity is 1 000 microW/cm2 and the surface area of nano-tube array film conditions, will help to improve the TiO2 nanotubes array film photoelectrocatalysis degradation of MB degradation efficiency is 99.56%. The results of EIS analyses revealed that the surface reaction step was the only rate limiting step either for the photoelectrocatalytic process. The extra bias potential could decrease the values of the electron-transfer resistance and increase the separation efficiency of photogenerated electron-hole pairs.

[Photochemical preparation of Au nanoparticles with polyethyelene glycol and its resonance scattering spectral study].

The nano-photochemical reaction of polyethyelene glycol (PEG)-Au3+ was studied by resonance scattering and absorption spectrophotometry, and transmission electron microscopy. Influence of various factors on the preparation of gold nanoparticles was considered. There is a correlation between the molecular mass of PEG and the size of gold nanoparticles. A new photochemical method was proposed for the preparation of gold nanoparticles in size of 6-60 nm, using different molecular mass of PEG. The cause of obtaining gold nanoparticle with different size is the different space effect and hydrophobic property of PEG. A reasonable nano-reaction mechanism was developed.