We image 4-mercaptobenzonitrile-functionalized silver nanowires (∼20 nm diameter) through tip-enhanced Raman scattering (TERS). The enhanced local optical field–molecular interactions that govern the recorded hyperspectral TERS images are dissected through hybrid finite-difference time-domain density functional theory simulations. Our forward simulations illustrate that the recorded spatiospectral profiles of the chemically functionalized nanowires may be reproduced by accounting for the interaction between orientationally averaged molecular polarizability derivative tensors and enhanced incident/scattered local fields polarized along the tip axis. In effect, we directly map the enhanced optical fields of the nanowire in real space through TERS. The simultaneously recorded atomic force microscopy (AFM) images allow a direct comparison between our attainable spatial resolution in topographic (13 nm) and TERS (5 nm) imaging measurements performed under ambient conditions. Overall, our described protocol enables local electric field imaging with few nm precision through molecular TERS, and it is therefore generally applicable to a variety of plasmonic nanostructures.

中文翻译：

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通过分子TERS成像功能化的银纳米线的光场

我们通过尖端增强拉曼散射（TERS）成像了4-巯基苯甲腈官能化的银纳米线（直径约20 nm）。通过混合有限差分时域密度泛函理论模拟来剖析控制记录的高光谱TERS图像的增强的局部光场-分子相互作用。我们的正向模拟表明，通过考虑取向平均分子极化率导数张量与沿尖端轴极化的增强的入射/散射局部场之间的相互作用，可以复制化学功能化纳米线的记录时空光谱图。实际上，我们通过TERS直接绘制了纳米线在现实空间中的增强光场。同时记录的原子力显微镜（AFM）图像可直接比较我们在环境条件下进行的地形（13 nm）和TERS（5 nm）成像测量中可获得的空间分辨率。总体而言，我们描述的协议可以通过分子TERS实现几纳米精度的局部电场成像，因此通常适用于各种等离子体纳米结构。