The Study Of Several Semiconductor Metal Oxides Emission Spectra

Scholars have studied a lot of the emission spectra properties of CeO₂,TiO₂,ZnO and SnO₂, also very in-depth, but there are few studies comparing thesesemiconductor metal oxides emission spectra. By our preliminary test, there are somecommon characteristics and differences in their fluorescence spectra. So this articlestudied the emission spectra of several semiconductor metal oxides and the evolutionof the soectra.The study respectively uses heat precipitation method, sol-coagulation method,direct precipitation method, solid-phase chemical reaction-hydrothermal synthesismethod to synthesis CeO₂powders and respectively designated the products asTP-CeO₂、SA-CeO₂、DC-CeO₂、G-CeO₂. The synthesis of ZnO and SnO₂powdersuseed solid-phase chemical reaction-hydrothermal method, the products weredesignated as YG-ZnO and G-SnO₂, respectively. Sol-hydrothermal method was usedin the synthesis of TiO₂Powder, which was designated as S-TiO₂. The400℃heatedproducts of these semiconductor powders are nanocrystals proved by FWHM andHRTEM.We can divide the emission spectra of the semiconductor metal oxides which areabove-mentioned into three categories. The first category emission spectra is onbehalf of TP-CeO₂, whose intensity of330nm emission peak is significantlyincreased with the rising of the heat treatment temperature, other PL peaks remainbasically unchanged and their peak intensity increases gradually but less than330nmemission peak. The second category emission spectrum is on behalf of S-TiO₂. Withthe rising of the heat treatment temperature, the positiones of all PL peaks in thevisible region remain basically unchanged, but their peak intensity increases gradually,their maximum intensity occurred at600°C and then gradually decreased. The third category emission spectra is on behalf of G-SnO₂. With the rising of the heattreatment temperature, the position of PL peak is essentially the same, but the peakintensity increases gradually, UV-section of its PL spectra always maintains higherrelative strength.We determine the Egdirand Egindirvalues of DC-CeO₂powders heated at differenttemperatures based on their UV-Vis absorption spectra. Applying them to the relevantemission spectra of the powderes, we can calculate Sindir/Sdirand SVi/SUVratios.Comparing the Sindir/Sdir rof those DC-CeO₂powders heated at different temperatures,we can find that the contribution of the direct transition to the intensity of theemission spectrum of UV-near-UV region bigger than that of the indirect transition.By linear regression analysis, it was found that a significant positive correlationrelationship existed between the Sindir/Sdirvalues and SVi/SUVvalues of those DC-CeO₂powders heated at different temperatures. It showed us that the SVi/SUVratio willsupply a clue to the knowing of the contribution of direct transition to the intensity ofUV-near-UV region of the emission spectrum.It was found that a significant positive correlation relationship was existedbetween the Sindir/Sdirand SVi/SUVratios of several semiconductor metal oxides bylinear regression analysis.It was found that the SVi/SUVratio of CS1-350is smaller than that ofSA-CeO₂-400by emission spectra measuring and Gaussian fitting of the emissionspectra. Considering that the capacity of methylene blue decolorization of CS1isstronger than that of SA-CeO₂, we could recognize that the size of the SVi/SUVratiocertainly reflects the capacity of the methylene blue decolorization.