物理化学学报 >> 2020, Vol. 36 >> Issue (7): 1906069.doi: 10.3866/PKU.WHXB201906069

所属专题: 纳米复合材料

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贵金属在Ag2S纳米颗粒中由内向外的迁移现象

刘丹叶1,2,陈东1,刘卉1,*(),杨军1,2,*()   

  1. 1 中国科学院过程工程研究所,多相复杂系统国家重点实验室,北京 100190
    2 中国科学院大学,北京 100049
  • 收稿日期:2019-06-24 录用日期:2019-07-26 发布日期:2020-03-21
  • 通讯作者: 刘卉,杨军 E-mail:liuhui@ipe.ac.cn;jyang@ipe.ac.cn
  • 基金资助:
    国家自然科学基金(21506225);国家自然科学基金(21573240);国家自然科学基金(21706265)

Inside-Out Migration of Noble Metals in Ag2S Nanoparticles

Danye Liu1,2,Dong Chen1,Hui Liu1,*(),Jun Yang1,2,*()   

  1. 1 State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
    2 University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2019-06-24 Accepted:2019-07-26 Published:2020-03-21
  • Contact: Hui Liu,Jun Yang E-mail:liuhui@ipe.ac.cn;jyang@ipe.ac.cn
  • Supported by:
    the National Natural Science Foundation of China(21506225);the National Natural Science Foundation of China(21573240);the National Natural Science Foundation of China(21706265)

摘要:

纳米颗粒具有明显区别于块体材料的新奇特性,本文利用透射电镜观察,描述并讨论一种发生在贵金属(Au、Ag、Pd和Pt)和硫化银(Ag2S)构成的核壳结构纳米颗粒中的有趣现象,即贵金属在Ag2S纳米颗粒中由内向外的迁移。迁移可在室温下进行,其最终结果使最初的核壳结构颗粒演变成由贵金属和Ag2S构成的异质纳米二聚体结构,如Au-Ag2S、Ag-Ag2S、Pd-Ag2S和Pt-Ag2S。电镜表征表面实验条件下贵金属在Ag2S的迁移类似于一种整体迁移的模式且迁移过程中伴随着颗粒形貌结构的演变。贵金属在Ag2S中的经空位互换的扩散机制或半导体纳米颗粒的自纯化机制可以用来解释这种迁移现象。

关键词: 纳米颗粒, 贵金属, 硫化银, 核壳结构, 迁移

Abstract:

Materials such as metals, semiconductors, and oxides are attractive at nanometer scales due to the physical and chemical property differences with their bulk counterparts as induced by the quantum confinement effect and large surface-to-volume ratios. In particular, heterogeneous nanostructures consisting of semiconductors and noble metals are extremely important because of the synergistic effects occurring at the interfaces between their noble metal and semiconductor domains; these often equip the heterogeneous nanostructures with improved properties compared to those of isolated individual components. Thus far, heterogeneous nanostructures have garnered a considerable research interest, and tremendous development in achieving high degree control over these nanostructures with respect to their domain size, morphology, and composition has been realized. Their immense application potential in optics, catalysis, imaging, and biomedicine render them a field full of original innovation possibilities. Herein, we demonstrate a phenomenon observed in core-shell nanostructures composed of noble metals and silver sulfide (Ag2S): the inside-out migration of noble metals in Ag2S nanoparticles. We prepare core-shell nanostructures with noble metals and Ag2S residing at the core and shell regions, respectively, through various synthetic strategies including seed-mediated growth and galvanic replacement reactions followed by sulfidation. We then characterize the core-shell nanostructures before and after aging them in toluene at room temperature (e.g. 25 ℃) for a period of time up to 72 h. In contrast to the reported diffusion of Au from the outside to the inside of InAs or PbTe nanoparticles, which results in an Au core encapsulated by an amorphous InAs or PbTe shell, the noble metals (Au, Ag, Pd, or Pt) in core-shell nanostructures with noble metals and Ag2S residing at the core and shell regions, respectively, are found to diffuse from the inside to the outside through the Ag2S shell. Thus, heterogeneous nanodimers consisting of the corresponding noble metal and Ag2S are formed. Observations using an electron transmission microscope confirm that the inside-out migration of noble metals in Ag2S is carried out in a holistic manner. Due to the apparent interface mismatch between face-centered cubic noble metals and monoclinic Ag2S crystal phases, defects such as vacancies must exist at these interfaces. This makes the migration of noble metals in Ag2S possible by either a vacancy/substitutional mechanism or by the self-purification mechanism that occurs intrinsically in nanoscale semiconductors. As the migration rate of noble metals in Ag2S increases with the decrease in the size of the noble metal core and the radius of noble metal atoms, the inside-out migration rates of Ag, Pd, and Pt in Ag2S are found to be much higher than that of Au because of their smaller particle sizes or atom radii. This scientific phenomenon can be effective in the development of synthetic routes for heterogeneous nanostructures that might not be obtained by conventional methods.

Key words: Nanoparticle, Noble metal, Silver sulfide, Core-shell structure, Migration

MSC2000: 

  • O648