ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instabl...ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instable and after several days the color of the ZnSe nanocrystals-doped SiO 2 glass changed from yellow to red. According to the analysis results of XRD, UV-Vis transmission spectra and XPS, the existence of many zinc vacancies in the ZnSe nanocrystals was considered as the reason of the instability. Based on this reason, the synthesis process was improved by introducing much larger amount of zinc to the precursor sol and this made the stability of the ZnSe nanocrystals improved greatly from several days to more than 6 months.展开更多
Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme hetero...Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies(VO,Zn-ZnO/ZnS)is rationally constructed via ion-exchange and calcination treatments.In such a photocatalytic system,the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption.Moreover,the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes,respectively,which are beneficial for promoting the photo-induced carrier separation.Meanwhile,the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity.As expected,the optimized VO,Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H_(2) production rate of 160.91 mmol g^(-1)h^(-1),approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS,respectively.Simultaneously,the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier.This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar-to-fuel energy conversion.展开更多
采用密度泛函理论计算的方法研究了Zn空位缺陷下ZnO的电子结构性质。结果表明,所有ZnO材料均为直接带隙型材料,含有Zn空位缺陷的ZnO禁带宽度由0.78 e V分别增加至1.62 e V和1.58 e V。所有ZnO的总态密度曲线具有相似的形状,含有Zn空位...采用密度泛函理论计算的方法研究了Zn空位缺陷下ZnO的电子结构性质。结果表明,所有ZnO材料均为直接带隙型材料,含有Zn空位缺陷的ZnO禁带宽度由0.78 e V分别增加至1.62 e V和1.58 e V。所有ZnO的总态密度曲线具有相似的形状,含有Zn空位缺陷的ZnO的总态密度曲线极值点数量减少,局域化能量点数量减少。含有Zn空位缺陷的ZnO费米能上的态密度降低。随着Zn空位缺陷浓度的增加,ZnO费米能上的p态电子数量逐渐增加,这主要由来自于Op态电子的贡献。展开更多
The effects of Ce doping on the structure,optical,oxidation,thermal and magnetic properties of ZnS:Ce nanorods synthesized by a chemical co-precipitation method were reported.The crystalline phase transformation from ...The effects of Ce doping on the structure,optical,oxidation,thermal and magnetic properties of ZnS:Ce nanorods synthesized by a chemical co-precipitation method were reported.The crystalline phase transformation from cubic to hexagonal structure was observed upon doping ZnS with Ce.Magnetic measurements showed the existence of room temperature ferromagnetism in Ce-doped ZnS nanorods.X-ray photoelectron spectroscopic(XPS)measurements provided evidence for Zn-S bonds and oxidation state of Ce in the near-surface region.Raman spectrum provided evidence for the presence of defects as well as hexagonal structure of 5 wt.%Ce doped ZnS nanorods.Ce substitution induced shape evolution was studied by using TEM.DRS spectra further validated the incorporation of Ce^3+ions.The present study reveals that Ce doped ZnS nanorods may find applications in spintronic devices.展开更多
文摘ZnSe nanocrystals doped in silica were prepared by using sol-gel process and in situ growth technique. It was found that when n(Zn)∶n(Se)=1∶1 in the sol precursor, the resultant ZnSe nanocrystals were rather instable and after several days the color of the ZnSe nanocrystals-doped SiO 2 glass changed from yellow to red. According to the analysis results of XRD, UV-Vis transmission spectra and XPS, the existence of many zinc vacancies in the ZnSe nanocrystals was considered as the reason of the instability. Based on this reason, the synthesis process was improved by introducing much larger amount of zinc to the precursor sol and this made the stability of the ZnSe nanocrystals improved greatly from several days to more than 6 months.
文摘Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies(VO,Zn-ZnO/ZnS)is rationally constructed via ion-exchange and calcination treatments.In such a photocatalytic system,the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption.Moreover,the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes,respectively,which are beneficial for promoting the photo-induced carrier separation.Meanwhile,the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity.As expected,the optimized VO,Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H_(2) production rate of 160.91 mmol g^(-1)h^(-1),approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS,respectively.Simultaneously,the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier.This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar-to-fuel energy conversion.
文摘采用密度泛函理论计算的方法研究了Zn空位缺陷下ZnO的电子结构性质。结果表明,所有ZnO材料均为直接带隙型材料,含有Zn空位缺陷的ZnO禁带宽度由0.78 e V分别增加至1.62 e V和1.58 e V。所有ZnO的总态密度曲线具有相似的形状,含有Zn空位缺陷的ZnO的总态密度曲线极值点数量减少,局域化能量点数量减少。含有Zn空位缺陷的ZnO费米能上的态密度降低。随着Zn空位缺陷浓度的增加,ZnO费米能上的p态电子数量逐渐增加,这主要由来自于Op态电子的贡献。
文摘The effects of Ce doping on the structure,optical,oxidation,thermal and magnetic properties of ZnS:Ce nanorods synthesized by a chemical co-precipitation method were reported.The crystalline phase transformation from cubic to hexagonal structure was observed upon doping ZnS with Ce.Magnetic measurements showed the existence of room temperature ferromagnetism in Ce-doped ZnS nanorods.X-ray photoelectron spectroscopic(XPS)measurements provided evidence for Zn-S bonds and oxidation state of Ce in the near-surface region.Raman spectrum provided evidence for the presence of defects as well as hexagonal structure of 5 wt.%Ce doped ZnS nanorods.Ce substitution induced shape evolution was studied by using TEM.DRS spectra further validated the incorporation of Ce^3+ions.The present study reveals that Ce doped ZnS nanorods may find applications in spintronic devices.
