Preparation And Photocatalytical Properties Of ZnO Quantum Dots

ZnO quantum dots were prepared by liquid phase synthesis method.The structure and photoluminescence were characterized by the complex means such as XRD,HRTEM,XPS,PL etc.;the effect of ZnO quantum dots on photocatalytic treatment of dye wastewater were investigated;The influences of several factors including the ratio of raw materials,different dye wastewater,calcination HRTEMperature on photocatalytic properties of the ZnO quantum dots were explored.Polyethylene glycol(PEG 2000),methyl acrylamide(MAC),thiourea(THU)were used to modify the surface of ZnO quantum dots,and the effect of surface modification on the photocatalytic performance and structural properties were studied by combined characterization and photocatalytic experiments to check the effect of the surface modification on the photocatalytic properties of ZnO quantum dot.Four elements including Co,Cu,S,Cd were used for doping the PEG-modified ZnO quantum dots,and the effect of doping with different elements on the photocatalytic properties of ZnO quantum dots were examined by combined characterization and photocatalytic experiments.The main conclusions were as follows:(1)ZnO quantum dots prepared by means of liquid phase had very considerable photocatalytic activity.The optimal material ratio(n(Zn(C4H6O4)/n(LiOH))of preparing ZnO quantum dots was 1:5.0.1g of ZnO quantum dot powder were used to examine the effect of the chroma degradation,the experimental result showed 50 mL of 0.1g/L reactive yellow X-R dye wastewater rate of degradation rate in 40 min was 89.8%,rate of COD degradation rate was 63.32%.The ZnO quantum dot performed strong surface activity and prone to agglomeration;high-HRTEMperature calcination treatment on ZnO quantum dot could reduce the agglomeration,but could not significantly enhance its photocatalytic properties.ZnO quantum dots showed significant differences on the photocatalytic degradation and adsorption effects to treat different dye wastewater;the number of color rendering group and their location in the dye molecules determined the degree of difficulty of dye degradation.(2)PEG2000,MAC and THU modification did not alter the crystal structure and configuration of the surface of ZnO quantum dot,but improved its surface defects and reduced its agglomeration to some extent.As the increasing of surface modifying agent addition,the particle size of ZnO quantum dots of PEG-2000 surface modified got smaller;the particle size of ZnO quantum dots showed decreased initially and then increased when modified by MAC and THU surface.The photocatalytic performance of ZnO quantum dot surface modified by PEG promoted most significantly and its optimal quality percentage content was 6%.0.1g of this ZnO quantum dot powder were used to examine the effect of the chroma degradation,the experimental result showed 50 mL of 0.1g/L reactive yellow X-R dye wastewater rate of degradation rate in 40 min was 99.21%,rate of COD degradation rate was 70.26%.(3)Four elements including Co,Cu,S,Cd were used for doping 6% PEG-modified ZnO quantum dots,the particle size and the degree of agglomeration of ZnO quantum dots all reduced in vary degrees,but the hexagonal wurtzite structure did not change and crystals swelling and distortion of ZnO quantum dot did not result in obviously.The best photocatalytic performance was doping ZnO quantum dot with Cd,and the optimal doping amount was 0.9%.0.05 g of this ZnO quantum dot powder were used to examine the effect of the chroma degradation,the experimental result showed 50 mL of 0.1g/L reactive yellow X-R dye wastewater rate of degradation rate in 40 min was 96.72%,rate of COD degradation rate was 63.47%.