Synthesis and Performance of Ag/TiO2,MS/TiO2 and CsPbX3/TiO2 Composites

Author:Xia Hong Bo

Supervisor:wu su li


Degree Year:2019





TiO2 with different morphologies has been widely studied in photocatalysis or luminescence regulation due to its excellent photoelectric chemical property,high refractive index,non-toxic and low cost.In the field of photocatalysis,the wide band gap of TiO2 restrict its response to visible light.At present,the synthesis of a composite of noble metal or sulfide semiconductor with TiO2 is a very effective approach to enhance the visible light responsivity.However,the organic ligands which benefit for anchoring noble metal or sulfide semiconductor on TiO2 also affect the electron transfer between them,which can influence the photocatalytic effect of catalysts.In the field of luminescence regulation,inverse opal structure has been demonstrated to be an effective means for enhancing fluorescent emission.However,the electron transfer between TiO2 and perovskite quantum dot will quench the luminescence of quantum dots due to the higher conduction band of perovskite quantum dot.Thus,the luminescence properties of quantum dot will be influenced by the energy transfer and the modulation of inverse opal when perovskite quantum dot is combined with TiO2 inverse opal and it is difficult to study the effect of inverse opal on the luminescence properties of quantum dots.To solve the above problems,the new methods are proposed to combine TiO2 with noble metals or sulfide semiconductors with few organic ligands between them based on the reducibility of sulfydryl and the break of C-S bond;Based on the viewpoint that organic ligands can inhibit the electron transfer between quantum dots and TiO2,the perovskite quantum dots with high surface ligand density is synthesized by using ligand with strong binding ability to the surface of quantum dot.The effect of inverse opal on the luminescence property of quantum dots has been studied under the premise of inhibiting the electron transfer between TiO2 and quantum dots.Based on the complexation ability and reduction capacity of sulfydryl for Ag+,the Ag/TiO2 with 1.1 wt%,2.8 wt%and.4.2 wt%loading amount of Ag were generated by adsorption-heating reduction process using TiO2 microspheres containing thioglycolic acid as raw materials.Meanwhile,the Ag can be combined with TiO2 directly with few organic ligands as stabilizer due to the dissociation of thioglycolic acid in the process of thermal reduction.The catalytic active of Ag/TiO2 for the degradation of methyl orange is tested and Ag/TiO2(2.8 wt%)show highest photocatalytic activity among them due to the local surface plasmon resonance effect of Ag.When Ag/TiO2(2.8 wt%)is used as photocatalyst,the degradation rate is near 95%after 70 minutes which is 3 times than the pure TiO2.Based on the characteristic of the C-S bond is easy to break when the sulfhydryl is coexisting with Pb21,Cd2+ and Cu2+ under heating condition,PbS/TiO2,CdS/TiO2 and CuS/TiO2 are obtained by adsorption-thermal decomposition process.The ligands in the origin TiO2 are dissociated during the heating process which is beneficial to electron transfer between sulfide semiconductor and TiO2.In the catalytic reduction of Cr6+,PbS/TiO2,CdS/TiO2 and CuS/TiO2 show enhanced visible-light catalytic activity due to the narrow band gap of sulfide semiconductor.The reduction rate is near 100%after 140 minutes when PbS/TiO2 is used as photocatalyst which is 5 times than the pure TiO2.The CsPb(Cl0.4Br0.6)3-P and CsPb(Cl0.4Br0.6)3-O quantum dot with high and low surface ligand density respectively were synthesized by using palmitic acid and oleic acid as ligands.The fluorescence intensity of CsPb(Cl0.4Br0.6)3-P could be enhanced by 6.4 times when CsPb(Cl0.4Br0.6)3-P is combined with inverse opal with the pore size of 250 nm.The fluorescence intensity of CsPb(Cl0.4Br0.6)3-O could be enhanced by 2.2 times when CsPb(Cl0.4Br0.6)3-O,which has low sueface ligand density,is combined with inverse opal with the pore size of 250 nm.These results proved that the high surface ligand density of quantum dots can inhibit the electron transfer between TiO2 and quantum dots indeed.