Electrochemical Preparation And Characterization Of CdSe Nanomaterials

Compared with organic and inorganic elctroluminescence materials, nano semiconductor has a higher electronic affinity and a narrower emitting spectrum. The grains of the nano semiconductor, which can affect its electronic affinity and ionization potential, may be changed by the conditions of the synthesis. The absorption and emitting spectrum would have a blue-shifed when the nanofilms get more small grains. Therefor, the stronger emitting edge can be adjusted in the range of visible area by changing the grains of nanoconductor. In this thesis, cadmium selenide nano semiconductor material was prepared by electrochemistry, which made great contribution to the assembly of the polymer/ nanocrystals composition EL devices.The reduction process of the SeO2 was analyzed by the electrochemistry method in the alkaline electrolyte and the CdSe nanocrystals films was prepared successfully by constant potential deposition and pulse current deposition methods. The morphology, structure and optic properties of the nanofilm were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), ultraviolet-visible (UV-VIS) spectrometer and Fluorescence spectroscopy. The XRD experiment results indicate that the CdSe prepared by constant potential is a cubic phase polycrystalline film. Compared with CdSe bulk materil, the peaks of CdSe nanofilm have an obvious blue-shifted in the absorption and emitting spectra. And with the increase of the reaction time, the absorption and the PL spectra are slightly red-shifted because of the quanta effect.As for the CdSe film prepared by pulse current deposition method, the SEM image described that the nanocrystals appears rod structure which the diameter is 30~50nm and the length is 100~300nm. The UV-VIS spectra revealed that the absorption edge of the CdSe film focused on the range from 300nm to 550nm, which has an obvious blue-shifted than that of the body of the CdSe material. The PL spectra indicate that the CdSe nanocrystal film have a characteristic of photoluminescence and the emitting peak located in a range of 460nm~470nm.The anodic aluminum oxide membranes were prepared by two-step oxidation in the solution of oxalic acid when the voltages are 60V and 40V, and stripped from the aluminum substrate adopting strip against electricity technique. The oxide barrier layer was chemically dissolved from bottom side of the film in phosphoric acid. The diameters of AAO's holes are 120nm and 80nm. The nanowire arrays of CdSe were deposited into AAO by single-bath method. In the SEM image, the nanowires have a length of 4μm and a diameter of 120nm. X-ray diffraction (XRD) result demonstrates that the structure of CdSe nanowires is hexagonal phase.