Mengxin Ge

Topic

SERS Study of N-heterocyclic Carbenes Absorbed on a Silver Electrode

Department of Chemistry

Date & location

• Tuesday, August 23, 2022
• 1:30 P.M.
• Virtual Defence

Reviewers

Supervisory Committee

• Dr. Alexandre Brolo, Department of Chemistry, University of Victoria (Supervisor)
• Dr. Dennis Hore, Department of Chemistry, UVic (Member)

External Examiner

• Dr. Tao Lu, Department of Electrical and Computer Engineering, UVic

Chair of Oral Examination

• Dr. Kieka Mynhardt, Department of Mathematics and Statistics, UVic

Abstract

SERS (surface-enhanced Raman spectroscopy) has the potential to be used in a variety of commercial and basic applications, which often rely on molecules that are bound to a nanostructured metal surface. Thiols are usually used as the intermediate to modify the substrate surface for SERS. In recent years, N-heterocyclic carbene (NHC) has been introduced as an alternative approach for metal surface modification. Nanostructured gold surfaces suitable for SERS had been modified by NHC species. Those studies showed the promising of the NHC modification route for the fabrication of robust platform for SERS.

The objective of this work is to explore the SERS characteristics of NHC species on silver surfaces. The interactions between two different NHC molecules and a nanostructured silver surface, instead of a gold surface, were studied for the first time. The experiments were realized in electrochemical conditions, using a three-electrodes system, to fully test the stability of the NHC modified surfaces. The SERS spectra were compared to theoretical calculations and normal Raman in order to identify the vibrational characteristics of the NHC molecules. The effects of different NHC molecules substituents on the electrochemical stability of the surface were also discussed. The results showed that NHC molecules can be decomposed on the silver surface easily under electrochemical conditions. This contrast to the observations in gold, where the NHC monolayers showed a high level of stability.

This work also discusses potential side products which may be derived from the decomposition of the NHC molecules. Raman spectra of potential side products were collected and compared to the NHC SERS collected under electrochemical control at different potentials.

This study provides insights into the influence of the substituents at the NHC on their stability under the electrochemical condition, which should guide the development of future applications.