ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]₄ by Ozone Treatment in Ionic Liquids: in-situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment

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• 作者：Tanja Bauer ; Markus Voggenreiter ; Tao Xu ; Tobias Wä ; hler ; Friederike Agel ; Kaija Pohako-Esko ; Peter Schulz ; Tibor Dö ; pper ; Andreas Gö ; rling ; Sebastian Polarz ; Peter Wasserscheid and Jö ; rg Libuda
• 刊名：Zeitschrift für anorganische und allgemeine Chemie
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：643
• 期：1
• 页码：31-40
• 全文大小：2327K
• ISSN：1521-3749

文摘

As reported previously, novel ZnO nanostructures can be grown by oxidation of [MeZnOtBu]₄ “building blocks” with O₃ in ionic liquids (ILs). In this study, we have explored the role of the IL during ZnO formation by in-situ infrared reflection absorption spectroscopy (IRAS) in ultrahigh vacuum (UHV). [MeZnOtBu]₄ and [C₂C₁Im][OTf] were (co-)deposited as thin films by physical vapor deposition (PVD) onto Au(111), separately or simultaneously. The IR spectrum of [MeZnOtBu]₄ was analyzed between 300 and 4000 cm^–1 based on calculated spectra from density-functional theory (DFT). Spectral changes in the IL-related bands during the thermal treatment of [MeZnOtBu]₄ in [C₂C₁Im][OTf] indicate the loss of the precursor ligands and the interaction of the IL with the growing ZnO aggregates. The films were treated with ozone (10^–6 mbar) in UHV and the spectral changes were monitored in-situ by IRAS. Slow ozonolysis of [C₂C₁Im][OTf] is observed. Spectroscopically we identify the primary ozonide formed by addition of O₃ to [C₂C₁Im]⁺ and suggest a reaction mechanism, which leads to a biuret derivative. Upon ozone treatment of mixed [MeZnOtBu]₄/[C₂C₁Im][OTf] films, ZnO aggregates are formed at the IL/vacuum interface. Ozonolysis of [C₂C₁Im][OTf] is suppressed. Upon annealing to 320 K, further ZnO aggregates are formed, leading to enclosure of [C₂C₁Im][OTf] in the ZnO film. At 380 K the IL is released from the mixed film. The pure [C₂C₁Im][OTf] desorbs at 420 K, leaving behind the ZnO phase.