Investigation of organic monoradicals reactivity using surface-enhanced Raman spectroscopy

Area of Science:

• Chemical Spectroscopy
• Photochemistry
• Materials Science

Background:

• Organic monoradicals are reactive intermediates with significant roles in chemical synthesis and biological processes.
• Understanding their reactivity, particularly with common solvents like methanol, is crucial for controlling chemical reactions.
• Surface-enhanced Raman spectroscopy (SERS) and self-assembled monolayers (SAMs) offer powerful tools for studying surface-confined reactions at the molecular level.

Purpose of the Study:

• To investigate the generation and subsequent reaction of organic monoradicals with methanol.
• To explore the influence of precursor chemical structure on monoradical generation efficiency.
• To evaluate the impact of SERS substrates and experimental conditions on reaction outcomes.

Main Methods:

• Generation of monoradicals from substituted thiophenols and phenylmethanethiols via UV irradiation.
• Formation of self-assembled monolayers (SAMs) of radical precursors on SERS substrates.
• Exposure of SAMs to methanol under controlled UV irradiation conditions.
• Analysis of pre- and post-reaction samples using confocal Raman microscopy for SERS spectra acquisition.

Main Results:

• Successful generation of organic monoradicals from various substituted precursors.
• Demonstrated dependence of monoradical generation efficiency on the specific chemical structure of the precursor (e.g., halogen or nitro substituents).
• Observed significant influence of the SERS substrate material and experimental parameters (irradiation time, methanol concentration) on the observed SERS spectra and reaction pathways.

Conclusions:

• The efficiency of generating organic monoradicals for reaction with methanol is critically determined by the precursor's molecular design.
• Both the choice of SERS substrate and the precise experimental conditions play a vital role in the successful detection and characterization of radical reactions.
• This study highlights the synergistic application of SERS and SAMs for probing complex surface-mediated radical chemistry.