Near IR Scanning Angle Total Internal Reflection Raman Spectroscopy at Smooth Gold Films
Near IR Scanning Angle Total Internal Reflection Raman Spectroscopy at Smooth Gold Films
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DOI：
10.1021/ac203355a
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发表时间：
2012-05-15
影响因子：
7.4
通讯作者：
Smith, Emily A.
中科院分区：
文献类型：
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作者：
McKee, Kristopher J.;Meyer, Matthew W.;Smith, Emily A.
收集非共振分析物的全内反射（TIR）拉曼和反射率光谱，作为蓝宝石或蓝宝石/光滑50 nm金界面处的入射角的函数，使用785 nm激发。对于两个界面，作为入射角的函数的拉曼信号通过相对于入射场乘以在拉曼测量（D-RS）中探测的层的厚度的计算的界面均方电场（MSEF）来良好地建模。的拉曼散射可再现地增强在界面处含有金膜相对于蓝宝石界面的系数为4.3-4.6的含水吡啶或2.2-3.7的纯硝基苯，这取决于分析的振动模式。增加的拉曼信号的机制是在入射角处增强的MSEF，其中在金属膜中激发传播的表面等离子体。加入金膜后，TIR棱镜的背景降低了89-95%，硝基苯1347 cm（-1）峰面积的相对不确定度从15%降低到1.7%。本文用全反射（TIR）拉曼光谱法测量了苯乙烷（S/N = 6.8）和4-巯基吡啶（S/N = 16.5）在金膜上的单分子膜，激发光为785 nm（210 mW），1 min内无共振增强。
Total internal reflection (TIR) Raman and reflectivity spectra were collected for nonresonant analytes as a function of incident angle at sapphire or sapphire/smooth 50 nm gold interfaces using 785 nm excitation. For both interfaces, the Raman signal as a function of incident angle is well-modeled by the calculated interfacial mean square electric field (MSEF) relative to the incident field times the thickness of the layer being probed in the Raman measurement (D-RS). The Raman scatter was reproducibly enhanced at the interface containing a gold film relative to the sapphire interface by a factor of 4.3-4.6 for aqueous pyridine or 2.2-3.7 for neat nitrobenzene, depending on the analyzed vibrational mode. The mechanism for the increased Raman signal is the enhanced MSEF at incident angles where propagating surface plasmons are excited in the metal film. The background from the TIR prism was reduced by 89-95% with the addition of the gold film, and the percent relative uncertainty in peak area was reduced from 15 to 1.7% for the 1347 cm(-1) mode of nitrobenzene. Single monolayers of benzenethiol (S/N = 6.8) and 4-mercaptopyridine (S/N = 16.5) on gold films were measured by TIR Raman spectroscopy with 785 rim excitation (210 mW) without resonant enhancement in 1 min.