Dixon Matthew C, Daniel Thomas A, Hieda Mitsunori, Smilgies Detlef M, Chan Moses H W, Allara David L
Department of Chemistry and The Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA.
Langmuir. 2007 Feb 27;23(5):2414-22. doi: 10.1021/la062313z. Epub 2007 Jan 24.
Thin nanoporous gold (np-Au) films, ranging in thickness from approximately 40 to 1600 nm, have been prepared by selective chemical etching of Ag from Ag/Au alloy films supported on planar substrates. A combination of scanning electron microscopy (SEM) imaging, synchrotron grazing incidence small angle X-ray scattering, and N2 adsorption surface area measurements shows the films to exhibit a porous structure with intertwined gold fibrils exhibiting a spectrum of feature sizes and spacings ranging from several to hundreds of nanometers. Spectroscopic ellipsometry measurements (300-800 nm) reveal the onset of surface plasmon types of features with increase of film thicknesses into the approximately 200 nm film thickness range. Raman scattering measurements for films functionalized with a self-assembled monolayer formed from 4-fluorobenzenethiol show significant enhancements which vary sharply with film thickness and etching times. The maximum enhancement factors reach approximately 10(4) for 632.8 nm excitation, peak sharply in the approximately 200 nm thickness range for films prepared at optimum etching times, and show high spot to spot reproducibility with approximately 1 microm laser spot sizes, an indication that these films could be useful as durable, highly reproducible surface-enhanced Raman substrates.
通过对支撑在平面衬底上的Ag/Au合金膜进行选择性化学蚀刻，制备出了厚度约为40至1600nm的薄纳米多孔金（np-Au）膜。扫描电子显微镜（SEM）成像、同步辐射掠入射小角X射线散射和N2吸附表面积测量相结合，表明这些膜呈现出一种多孔结构，其中交织的金纤维展现出一系列特征尺寸和间距，范围从几纳米到几百纳米。光谱椭偏测量（300 - 800nm）揭示，随着膜厚度增加到约200nm的膜厚范围，出现了表面等离子体类型的特征。对用4-氟苯硫醇形成的自组装单分子层功能化的膜进行拉曼散射测量，结果显示出显著增强，且增强程度随膜厚度和蚀刻时间急剧变化。对于632.8nm激发，最大增强因子达到约10(4)，在最佳蚀刻时间制备的膜中，在约200nm厚度范围内急剧峰值，并且在约1μm激光光斑尺寸下显示出高的点与点之间的重现性，这表明这些膜可作为耐用、高度可重现的表面增强拉曼基底。
