News & Events

Tip-Enhanced Raman Spectroscopy: Fundamental Investigations and Application to 2D Organic Materials

Date: 
Thursday, March 28, 2019 - 17:00 to 18:00
Speaker: 
Dr. Marie Richard-Lacroix
Affiliation: 
Friedrich-Schiller-University of Jena et Leibniz Institute of Photonic Technology
Event Category: 
APT - Analytical, Physical & Theoretical Seminar
Location: 
Chemistry D215

Abstract:

With the emergence of a wide variety of nanomaterials in several field of chemistry, physics and even biology, there is an obvious requirement for the development of characterization tools giving access to information at the scale of the material under investigation. Tip-enhanced Raman spectroscopy (TERS) combines the rich chemical and structural information brought by Raman spectroscopy with the imaging capabilities of atomic force microscopy (AFM) and this, with a sensitivity and a lateral resolution that reach the single molecule level. As for surface-enhanced Raman spectroscopy (SERS), TERS is based on the excitation of localized surface plasmons, arising from the collective oscillation of the electrons of the conduction bands of metals such as silver or gold, that cause a strong enhancement and confinement of the electric field. Simultaneously to field enhancement, plasmon formation can promote the transfer of electrons from the metal to the molecules (or vice versa). Those “hot electrons” are now increasingly recognized as efficient catalyst for inducing specific chemical reactions in ambient conditions, i.e. in conditions in which they are otherwise impossible, showing the potential of TERS to create site specific desired reactions. Currently, our lack of comprehension of the critical parameters affecting routine TERS measurements still greatly limits its widespread application as a common analytical tool. Spatial resolution, plasmon resonance frequency of the tip and local heating due to near-field temperature rise are undoubtedly three of the most challenging (though also most critical) experimental factor to determine. Here, our recent efforts to overcome those issues will be presented. Simultaneous measurement of the Stokes and anti-Stokes spectral ranges of self-assembled monolayers, time-resolved probing of blinking lines and near-field simulations are combined to extract quantitative and reproducible information of those parameters. Specific examples of plasmon-assisted chemical reactions to form well-defined 2D materials and application of TERS mapping to the nanoscale characterization of functionalized 2D carbon nanosheets will also be presented.