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The Synthesis and Photocatalytic Activity of Photocatalyst

Author: LiNing
Tutor: WeiMingKun
School: Wuhan University of Technology
Course: Applied Chemistry
Keywords: Ag3PO4 Ag2S modified rhodamine B ZnO nanowires E.coli
CLC: O643.36
Type: Master's thesis
Year: 2011
Downloads: 173
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Abstract

In recent years,it has been attracting people’s attention that semiconductors can photodegradate the organic pollutants by using sunlight.We prepared Ag3PO4,Ag3PO4 modified by Ag2S and ZnO nanowires.We studied photodegradation of the solution of rhodamine B under irradiation of Ag3PO4, Ag3PO4 modified by Ag2S and the degradation of E.coli by ZnO nanowires under the UV illuminated process.We got conclusions as followed.(1)The Ag3PO4 photocatalyst was prepared by the precipitation method,and then,XRD,SEM and UV-vis were used to characterize the photocatalyst. The solution of rhodamine B, was selected as the degradation object in the study of its photocatalytic activity. The graph of UV-Vis approved that Ag3PO4 had obviously absorption of visible light at the range lower than 525nm.Compared with N-TiO2,s rate of degradation 8.1%,that of Ag3PO4 was 93.9% in the photodegradation experiments of 45 minutes with the solution of rhodamine B under irradiation,which was of high efficiency.It also had high efficiency after 5 times photocatalyzed,and the graphs of XRD and SEM indicateed that, Ag3PO4,which was of cubic structure type,had no changes after 5 times photocatalyzed, and all these results above showed that Ag3PO4 was of stability. Therefore, Ag3PO4 was a kind visible-light photocatalyst of high efficiency and stability.(2) We prepared Ag2S/Ag3PO4 samples of different content of Ag2S,which were 0.0248%、0.124%、0.248%、1.24%和2.48%. The graphs of UV-Vis approved that the absorption threshold of 2.48%-Ag2S/Ag3PO4 redshifted about 10 nm. Compared with Ag3PO4’s rate of degradation 75.55%,those of 2.48%-Ag2S/Ag3PO4、1.24%-Ag2S/Ag3PO4、0.248%-Ag2S/Ag3PO4、0.124%-Ag2S/Ag3PO4 and 0.0248%-Ag2S/Ag3PO4,were 61.33%、63.92%、65.58%、68.97% and 77.37% in the photodegradation experiments of 30 minutes with the solution of rhodamine B under irradiation.There were no obvious differences among the 5 times photocatalyzations,and the degradation rate of the fifth photocatalyzation also reached 62.5%. the graphs of XRD and SEM indicateed that the samples were of Ag3PO4 primarily,with different content of Ag2S.Therefore,a small amount of Ag2S could enhance the photocatalytic activity of Ag3PO4,but with the increasing content of Ag2S, the photocatalytic activity of Ag3PO4 was reduced.(3) We studied the damage of membrane of E.coli treated with ZnO nanowires and UV light. Under the UV illuminated process, ZnO was activated to generate a conduction electron (e-) and a hole (h+), which behaves as an oxidizing agent. The reaction of the cell wall organics with h+ leaded to formation of free radicals, which are easy to oxidize organic groups such as CH2, CH3, amide groups and PO2 of the phospho-lipid phospho-diester, in the hydrophobic end exposed to the outer layer of E.coli. The shape of E.coli experienced seriously twisted and QDs could enter the cells or be absorbed on the cell surface because of the damaged cells not absorbing the extracellular materials selectively. These above conclusions suggest that ZnO nanowires might be potential materials for photocatalytic degradation of micro-ganisms.

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