ZnO Nanoparticle Formation from the Molecular Precursor [MeZnOtBu]4 by Ozone Treatment in Ionic Liquids: in-situ Vibrational Spectroscopy in an Ultrahigh Vacuum Environment
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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DOI：
10.1002/zaac.201600345
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发表时间：
2017-01-01
影响因子：
1.4
通讯作者：
Libuda, Joerg
中科院分区：
文献类型：
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作者：
Bauer, Tanja;Voggenreiter, Markus;Libuda, Joerg
如前所述，新型ZnO纳米结构可以通过在离子液体（IL）中用O-3氧化[MeZnOtBu]（4）结构单元来生长。在这项研究中，我们已经探讨了在ZnO形成过程中的作用，通过原位红外反射吸收光谱（IRAS）在超高真空（UHV）。通过物理气相沉积（PVD）将[MeZnOtBu]（4）和[C（2）C（1）Im][OTf]作为薄膜单独或同时（共）沉积到Au（111）上。基于密度泛函理论（DFT）计算的光谱，分析了[MeZnOtBu]（4）在300和4000 cm（-1）之间的IR光谱。在[C（2）C（1）Im][OTf]中[MeZnOtBu]（4）热处理期间IL相关带的光谱变化表明前体配体的损失以及IL与生长的ZnO聚集体的相互作用。在超高真空中用臭氧（10（-6）mbar）处理薄膜，并用IRAS原位监测光谱变化。观察到[C（2）C（1）Im][OTf]的缓慢臭氧分解。通过光谱分析，我们确定了O-3与[C（2）C（1）Im]（+）加成形成的初级臭氧化物，并提出了一种反应机理，该反应机理导致缩二脲衍生物。在臭氧处理[MeZnOtBu]（4）/[C（2）C（1）Im][OTf]混合膜时，在IL/真空界面处形成ZnO聚集体。[C（2）C（1）Im][OTf]的臭氧分解被抑制。在退火到320 K时，进一步形成ZnO聚集体，导致[C（2）C（1）Im][OTf]在ZnO膜中的封闭。在380 K下，IL从混合膜中释放。纯的[C（2）C（1）Im][OTf]在420 K下脱附，留下ZnO相。
As reported previously, novel ZnO nanostructures can be grown by oxidation of [MeZnOtBu](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). [MeZnOtBu](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 [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 [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 [MeZnOtBu](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.