Ultrafast Interfacial Charge Carrier Dynamics in ZnSe and ZnSe/ZnS Core/Shell Nanoparticles: Influence of Shell Formation

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• 作者：V. V. Matylitsky ; A. Shavel ; N. Gaponik ; A. Eychm&uuml ; ller ; J. Wachtveitl
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 21, 2008
• 年：2008
• 卷：112
• 期：7
• 页码：2703 - 2710
• 全文大小：215K
• 年卷期：v.112,no.7(February 21, 2008)
• ISSN：1932-7455

文摘

The post-preparative irradiation of water-soluble thiol-stabilized ZnSe colloidal nanocrystals (NCs) leads toa strong increase of the photoluminescence quantum yield of UV blue emission. The altered photoluminescenceproperties of the colloidal samples have been explained previously by changes in particle composition, size,and surface modification accompanying irradiation. In this work, the charge carrier dynamics in NCs beforeand after irradiation treatment has been examined via femtosecond transient absorbance spectroscopy in theUV-visible spectral region. Upon adsorption of the electron acceptor methylviologen (MV²⁺), an ultrafastheterogeneous electron transfer from the conduction band of the nanocrystals to MV²⁺ is observed and studied.Therefore, the employment of the MV²⁺ helps to assign the observed dynamics to electron or hole relaxationprocesses. It is shown that a ZnSe/ZnS core/shell structure is formed during the post-preparative treatment.The transient absorbance measurements of the MV²⁺/NC system indicate that the formation of a shell resultsin the confinement of the hole to the core, while the electron is still delocalized throughout the entire core/shell structure. The confinement of the hole to the core also explains the strong increase of thephotoluminescence quantum yield and the photostability of the NCs after post-preparative irradiation.