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Facilitating Tip-Enhanced Raman Scattering on Dielectric Substrates via Electrical Cutting of Silver Nanowire Probes
摘要： TERS is a powerful tool for nanoscale optical characterization of surfaces. However, even after 20 years of development, the parameters for optimal TERS tips are still up for debate. As a result, routine measurements on bulk or dielectric substrates remain exceptionally challenging. Herein we help to alleviate this by using electrical cutting to strategically modify silver nanowire TERS probes. Following cutting, the tips present a large, spherical apex and are often nanostructured with numerous nanoparticles, which we argue improve light collection and optical coupling. This doubles TERS signals on a highly-enhancing, gap-mode substrate compared to our standard nanowire tips, whilst maintaining a high reproducibility and resolution. More interestingly, on a dielectric substrate (graphene on SiO2) the tips give ~7x higher signals than our standard tips. Further investigations point to the non-local nature of the enhancement using standard, smooth, TERS probes without gap-mode, making such nanostructuring highly beneficial in these cases.
关键词： electrical cutting,silver nanowire,TERS,Tip-Enhanced Raman Scattering,nanoscale optical characterization,dielectric substrates
更新于2025-09-23 15:21:01
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Imaging the Optical Fields of Functionalized Silver Nanowires through Molecular TERS
摘要： 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 spatio-spectral 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 nano-structures.
关键词： silver nanowires,TERS,nanoscale imaging,optical fields,tip-enhanced Raman scattering
更新于2025-09-09 09:28:46