McFarland Adam D, Young Matthew A, Dieringer Jon A, Van Duyne Richard P
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
J Phys Chem B. 2005 Jun 9;109(22):11279-85. doi: 10.1021/jp050508u.
A detailed wavelength-scanned surface-enhanced Raman excitation spectroscopy (WS SERES) study of benzenethiol adsorbed on Ag nanoparticle arrays, fabricated by nanosphere lithography (NSL), is presented. These NSL-derived Ag nanoparticle array surfaces are both structurally well-characterized and extremely uniform in size. The WS SERES spectra are correlated, both spatially and spectrally, with the corresponding localized surface plasmon resonance (LSPR) spectra of the nanoparticle arrays. The surface-enhanced Raman scattering (SERS) spectra were measured in two excitation wavelength ranges: (1) 425-505 nm, and (2) 610-800 nm, as well as with the 532-nm line from a solid-state diode-pumped laser. The WS SERES spectra have line shapes similar to those of the LSPR spectra. The maximum SERS enhancement factor is shown to occur for excitation wavelengths that are blue-shifted with respect to the LSPR lambda(max) of adsorbate-covered nanoparticle arrays. Three vibrational modes of benzenethiol (1575, 1081, and 1009 cm(-1)) are studied simultaneously on one substrate, and it is demonstrated that the smaller Raman shifted peak shows a maximum enhancement closer to the LSPR lambda(max) than that of a larger Raman shifted peak. This is in agreement with the predictions of the electromagnetic (EM) enhancement mechanism of SERS. Enhancement factors of up to approximately 10(8) are achieved, which is also in good agreement with our previous SERES studies.
本文介绍了对通过纳米球光刻（NSL）制备的吸附在银纳米颗粒阵列上的苯硫酚进行的详细波长扫描表面增强拉曼激发光谱（WS SERES）研究。这些由NSL衍生的银纳米颗粒阵列表面在结构上具有良好的表征，并且尺寸极其均匀。WS SERES光谱在空间和光谱上都与纳米颗粒阵列相应的局域表面等离子体共振（LSPR）光谱相关。表面增强拉曼散射（SERS）光谱在两个激发波长范围内测量：（1）425 - 505 nm，以及（2）610 - 800 nm，同时还使用了固态二极管泵浦激光器的532 nm谱线。WS SERES光谱的线形与LSPR光谱相似。结果表明，对于相对于被吸附物覆盖的纳米颗粒阵列的LSPR λ(max)发生蓝移的激发波长，SERS增强因子最大。在一个基底上同时研究了苯硫酚的三种振动模式（1575、1081和1009 cm(-1)），结果表明，拉曼位移较小的峰比较大拉曼位移的峰在更接近LSPR λ(max)处显示出最大增强。这与SERS的电磁（EM）增强机制的预测一致。实现了高达约10(8)的增强因子，这也与我们之前的SERES研究结果高度吻合。
