Molecular Orientation and Optical Properties of 3,3′-Diethylthiatricarbocyanine Iodide Adsorbed to Gold Surfaces: Consequences for Surface-Enhanced Resonance Raman Spectroscopy
Molecular Orientation and Optical Properties of 3,3′-Diethylthiatricarbocyanine Iodide Adsorbed to Gold Surfaces: Consequences for Surface-Enhanced Resonance Raman Spectroscopy
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DOI：
10.1021/acs.jpcc.5b02686
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发表时间：
2015-05-07
影响因子：
3.7
通讯作者：
Mathies, Richard A.
中科院分区：
文献类型：
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作者：
Dietze, Daniel R.;Mathies, Richard A.
3，3 '-二乙基硫代三碳菁碘化物（DTTC）是一种重要的近红外拉曼报告分子和荧光标记物，在生物医学成像方面具有很高的应用潜力。通常假设染料分子在吸附到金表面时保持其单体光学性质，并且表面增强拉曼光谱（Sers）实验通常被设计为利用使用785 nm光的单体共振增强的最佳优势。为了验证这一假设，我们研究了DTTC碘化物薄膜的光学性质的透明金基板上使用偏振和角度依赖的紫外-可见光谱。表面吸收光谱表明，DTTC分子形成强烈的耦合二聚体的金表面，蓝移的吸收带的跃迁偶极矩是平行于金属表面对齐。这些结果澄清了最近Sers实验中遇到的不一致，并提出了提高基于DTTC的生物医学成像信号质量的方法。
3,3'-Diethylthiatricarbocyanine iodide (DTTC) is an important near-infrared Raman reporter and fluorescence marker showing high potential for biomedical imaging. It is commonly assumed that the dye molecules retain their monomeric optical properties when adsorbed to gold surfaces, and surface-enhanced Raman spectroscopy (SERS) experiments are typically designed to take optimal advantage of the monomer resonance enhancement using 785 nm light. To test this assumption, we investigated the optical properties of DTTC iodide thin films on transparent gold substrates using polarized and angle-dependent UV-vis spectroscopy. The surface absorption spectra demonstrate that DTTC molecules form strongly coupled dimers on gold surfaces, with blue-shifted absorption bands where the transition dipole moment is aligned parallel to the metal surface. These results clarify inconsistencies encountered in recent SERS experiments and suggest ways to enhance signal quality in DTTC-based biomedical imaging.