Comparing Commercial Metal-Coated AFM Tips and Home-Made Bulk Gold Tips for Tip-Enhanced Raman Spectroscopy of Polymer Functionalized Multiwalled Carbon Nanotubes.

Antonino Foti,Razvigor Ossikovski,Bérengère Lebental,Suriya Venkatesan,Gaël Zucchi

doi:10.3390/nano12030451

Abstract

Tip-enhanced Raman spectroscopy (TERS) combines the high specificity and sensitivity of plasmon-enhanced Raman spectroscopy with the high spatial resolution of scanning probe microscopy. TERS has gained a lot of attention from many nanoscience fields, since this technique can provide chemical and structural information of surfaces and interfaces with nanometric spatial resolution. Multiwalled carbon nanotubes (MWCNTs) are very versatile nanostructures that can be dispersed in organic solvents or polymeric matrices, giving rise to new nanocomposite materials, showing improved mechanical, electrical and thermal properties. Moreover, MWCNTs can be easily functionalized with polymers in order to be employed as specific chemical sensors. In this context, TERS is strategic, since it can provide useful information on the cooperation of the two components at the nanoscale for the optimization of the macroscopic properties of the hybrid material. Nevertheless, efficient TERS characterization relies on the geometrical features and material composition of the plasmonic tip used. In this work, after comparing the TERS performance of commercial Ag coated nanotips and home-made bulk Au tips on bare MWCNTs, we show how TERS can be exploited for characterizing MWCNTs mixed with conjugated fluorene copolymers, thus contributing to the understanding of the polymer/CNT interaction process at the local scale.

Highlights

Introduction iationsPlasmonic nanotips can focus and amplify optical fields into nanosized volumes, in the so-called near-field region [1,2], far below the diffraction limit
This is possible owing to the resonant excitation of the localized surface plasmon (LSP) of the nanostructured tip, which acts as a nanoantenna that strongly enhances the electromagnetic field at the tip apex, turning it into a highly efficient light nanosource, i.e., a hot-spot [2,3]
When a Tip-enhanced Raman spectroscopy (TERS) tip is integrated into a scanning probe microscope (SPM), such as scanning tunnelling microscopy (STM), atomic force microscopy (AFM) or shear-force microscopy (ShFM), the hot-spot

Summary

Introduction

Plasmonic nanotips can focus and amplify optical fields into nanosized volumes, in the so-called near-field region [1,2], far below the diffraction limit This is possible owing to the resonant excitation of the localized surface plasmon (LSP) of the nanostructured tip (or probe), which acts as a nanoantenna that strongly enhances the electromagnetic field at the tip apex, turning it into a highly efficient light nanosource, i.e., a hot-spot [2,3]. This is the basic principle behind tip-enhanced Raman spectroscopy (TERS) [4,5], where a nanotip made of gold or silver squeezes the far-field components of a laser beam into the near-field region and vice versa. When a TERS tip is integrated into a scanning probe microscope (SPM), such as scanning tunnelling microscopy (STM), atomic force microscopy (AFM) or shear-force microscopy (ShFM), the hot-spot

Methods

Results

Conclusion