Abstract
We report the use of dielectrophoresis to fabricate in-situ probes for tip-enhanced Raman spectroscopy (TERS) based on Au nanoparticles. A typical conductive atomic force microscope (AFM) was used to functionalize iridium-coated conductive silicon probes with Au nanoparticles of 10-nm diameter. Suitable TERS probes can be rapidly produced (30 to 120 s) by applying a voltage of 10 Vpp at a frequency of 1 MHz. The technique has the advantage that the Au-based probes are ready for immediate use for TERS measurements, minimizing the risks of tip contamination and damage during handling. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to confirm the quality of the probes, and used samples of p-ATP monolayers on silver substrates were used to demonstrate experimentally TERS measurements.
Highlights
Tip-enhanced Raman spectroscopy (TERS) is a powerful tool for nanoscale chemical analysis.[1,2] This Raman spectroscopy technique is based on the same mechanism as the surface-enhanced Raman spectroscopy (SERS) effect;[3] local electric fields are strongly enhanced in the vicinity of a metallic surface due to the coupling of its plasmon resonances with the excitation light
This was the clearest indication from any atomic force microscopy (AFM) measurements that DEP was being established and reproducibly functionalizing the probes inserted into the setup
These force spectroscopy results were supported by a number of imaging parameters that were monitored over the course of these experiments
Summary
Tip-enhanced Raman spectroscopy (TERS) is a powerful tool for nanoscale chemical analysis.[1,2] This Raman spectroscopy technique is based on the same mechanism as the surface-enhanced Raman spectroscopy (SERS) effect;[3] local electric fields are strongly enhanced in the vicinity of a metallic surface due to the coupling of its plasmon resonances with the excitation light. In TERS, this metallic surface takes the form of a sharp metal tip, usually an atomic force microscopy (AFM) or scanning tunneling microscopy probe coated in silver or gold. One of the key features of TERS is that chemical information can be obtained without requiring any special sample preparation, meaning the sample can be measured in situ. TERS can achieve excellent spatial resolution, which, in principle, is only limited by the size and shape of the scanning probe microscopy (SPM) probe tip apex. The setup of TERS ensures there is no variation of enhancement across a sample and automatically allows correlation of surface topography with chemical information
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