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标题:In situ Raman spectroscopy of bias-induced structural changes in nitroazobenzene molecular electronic junctions.
时间:2020-02-14 23:53:52
DOI:10.1021/ja045763r
PMID:15600368
作者:Nowak, Aletha M.; McCreery, Richard L.
关键词:In Situ Raman Spectroscopy of Bias-Induced Structural Changes in Nitroazobenzene Molecular Electronic Junctions, Artículo
出版源: 《Journal of the American Chemical Society》 ,126 (50) :16621-16631
摘要:Carbon/nitroazolbenzene (NAB)/titanium/gold molecular electronic junctions with active thicknesses of 7-8 nm were constructed having partially transparent Ti/Au top contacts, which permitted in situ monitoring of molecular structure with Raman spectroscopy for applied biases between +3 and -3 V. Deposition of the Ti/Au top contacts resulted in spectral changes similar to those accompanying NAB reduction in a conventional spectroelectrochemical experiment. Upon application of +3 V (carbon relative to Ti), the spectrum indicated reoxidation of the NAB reduction product, and this redox cycle could be repeated at least three times. When a voltage excursion to -2 or -3 V occurred, the spectra indicated irreversible loss of the nitro group, and a dramatic but reversible decrease in Raman intensity over the entire shift range examined. Negative applied voltage causes formation of reduced NAB and a high oxidation state of titanium, while positive voltage forms oxidized NAB and injects electrons into the titanium oxide layer. The spectral changes were correlated with current/voltage curves in order to probe the mechanism of rectification and conductance switching reported previously. Overall, the combination of spectroscopic and voltammetric results implies a conduction mechanism involving both NAB and titanium oxide, possibly mediated by the injection of carriers into the semiconducting titanium oxide, or by reduction of an insulating titanium oxide to a more conductive form.
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