Theoretical Calculations and Experimental Measurements of the Vibrational Response of p-NTP SAMs: An Orientational Analysis

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• 作者：Francesca Cecchet ; Dan Lis ; Julien Guthmuller ; Benot Champagne ; Gregory Fonder ; Zineb Mekhalif ; Yves Caudano ; Alaa Addin Mani ; Paul A. Thiry ; Andr Peremans
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：March 11, 2010
• 年：2010
• 卷：114
• 期：9
• 页码：4106-4113
• 全文大小：326K
• 年卷期：v.114,no.9(March 11, 2010)
• ISSN：1932-7455

文摘

The vibrational response of p-nitrothiophenol (p-NTP) self-assembled monolayers (SAMs), on Pt and on Au, has been investigated by combining theoretical methods with vibrational spectroscopies. Experimentally, the vibrational signatures have been measured using infrared spectroscopy (IR), polarization-modulation reflection absorption infrared spectroscopy (RAIRS), and with sum frequency generation spectroscopy (SFG). Theoretically, density functional theory calculations (DFT) have predicted the molecular vibrations and have estimated their IR vectors and Raman tensors, necessary to simulate the spectra and therefore to interpret the vibrational signatures as well as to retrieve the molecular orientation. So, a tilt angle () of 60° for the molecular 1,4-axis of p-NTP has been directly estimated for both Pt and Au SAMs by the polarization-dependent SFG data. Then, combining these results with RAIRS measurements has allowed to determine rotation angles (ξ) of 56° and 66° for p-NTP SAMs on Pt and Au, respectively.