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ZnO Nanoparticle Formation from the Molecular Precursor [MeZnO t Bu] 4 by Ozone Treatment in Ionic Liquids: in‐situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment
Author(s) -
Bauer Tanja,
Voggenreiter Markus,
Xu Tao,
Wähler Tobias,
Agel Friederike,
PohakoEsko Kaija,
Schulz Peter,
Döpper Tibor,
Görling Andreas,
Polarz Sebastian,
Wasserscheid Peter,
Libuda Jörg
Publication year - 2017
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201600345
Subject(s) - ozonolysis , ozone , infrared spectroscopy , ozonide , chemistry , methanethiol , ionic bonding , absorption spectroscopy , spectroscopy , analytical chemistry (journal) , photochemistry , organic chemistry , ion , sulfur , physics , quantum mechanics
As reported previously, novel ZnO nanostructures can be grown by oxidation of [MeZnO t Bu] 4 “building blocks” with O 3 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 t Bu] 4 and [C 2 C 1 Im][OTf] were (co‐)deposited as thin films by physical vapor deposition (PVD) onto Au(111), separately or simultaneously. The IR spectrum of [MeZnO t Bu] 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 t Bu] 4 in [C 2 C 1 Im][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 [C 2 C 1 Im][OTf] is observed. Spectroscopically we identify the primary ozonide formed by addition of O 3 to [C 2 C 1 Im] + and suggest a reaction mechanism, which leads to a biuret derivative. Upon ozone treatment of mixed [MeZnO t Bu] 4 /[C 2 C 1 Im][OTf] films, ZnO aggregates are formed at the IL/vacuum interface. Ozonolysis of [C 2 C 1 Im][OTf] is suppressed. Upon annealing to 320 K, further ZnO aggregates are formed, leading to enclosure of [C 2 C 1 Im][OTf] in the ZnO film. At 380 K the IL is released from the mixed film. The pure [C 2 C 1 Im][OTf] desorbs at 420 K, leaving behind the ZnO phase.