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- Title
ZnO Nanoparticle Formation from the Molecular Precursor [MeZnO tBu]<sub>4</sub> by Ozone Treatment in Ionic Liquids: in-situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment.
- Authors
Bauer, Tanja; Voggenreiter, Markus; Xu, Tao; Wähler, Tobias; Agel, Friederike; Pohako ‐ Esko, Kaija; Schulz, Peter; Döpper, Tibor; Görling, Andreas; Polarz, Sebastian; Wasserscheid, Peter; Libuda, Jörg
- Abstract
As reported previously, novel ZnO nanostructures can be grown by oxidation of [MeZnO tBu]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). [MeZnO tBu]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 [MeZnO tBu]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 [MeZnO tBu]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 [MeZnO tBu]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.
- Subjects
ZINC oxide; NANOPARTICLES; IONIC liquids; VIBRATIONAL spectra; OZONE
- Publication
Zeitschrift für Anorganische und Allgemeine Chemie, 2017, Vol 643, Issue 1, p31
- ISSN
0044-2313
- Publication type
Article
- DOI
10.1002/zaac.201600345