Optical Properties of Disulfide-Functionalized Diacetylene Self-Assembled Monolayers on Gold: a Spectroscopic Ellipsometry Study
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- 作者：Mirko Prato ; Marina Alloisio ; Sushilkumar A. Jadhav ; Andrea Chincarini ; Tiziana Svaldo-Lanero ; Francesco Bisio ; Ornella Cavalleri ; Maurizio Canepa
- 刊名：Journal of Physical Chemistry C
- 出版年：2009
- 出版时间：December 3, 2009
- 年：2009
- 卷：113
- 期：48
- 页码：20683-20688
- 全文大小：244K
- 年卷期：v.113,no.48(December 3, 2009)
- ISSN：1932-7455
文摘
Spectroscopic ellipsometry (SE) has been applied to study the optical properties of thiolate polydiacetylene (PDA) self-assembled monolayers (SAMs) deposited on low-roughness polycrystalline gold. A systematic investigation of methyl-terminated diacetylene (dihexacosa-7,9-diyn disulfide, DS9) SAMs is presented. The results have been compared with experiments on carbazolyl-derivatized diacetylene (14-(9H-9-carbazolyl)tetradeca-10,12-diyn-1-yl disulfide, CDS9) SAMs and with findings recently obtained on SAMs of alkanethiols. The SE measurements have been complemented with X-ray photoelectron spectroscopy and atomic force microscopy data. The difference between SE spectra measured after and before the monolayer assembly (δΨ = ΨSAM − ΨAu and δΔ = ΔSAM − ΔAu) showed specific absorptions of the adsorbed molecules, including narrow features in the 500−700 nm wavelength range which have been interpreted as markers of the SAM polymerization state. To our knowledge, these results represent the first unambiguous optical detection of polymer-induced absorptions in the case of diacetylene SAMs. Polymerization mainly occurred in the so-called red phase (absorption peak around 550 nm) on very flat surface regions obtained by flame-annealing the sample. The polymeric phase was stable against moderate UV irradiance. The detection of the blue phase was questionable as specific absorptions (around 640 nm) overlap with an absorption band related to the formation of the S−Au interface.