Characterizing nanostructured films using phase sensitive vibrational sum frequency spectroscopy

Area of Science:

• Surface Science
• Spectroscopy
• Nanomaterials

Background:

• Nanoparticle films are crucial catalysts but difficult to study in situ.
• Vibrational sum-frequency generation (vSFG) spectroscopy is sensitive and surface-specific.
• Phase-resolved vSFG has been challenging for disordered nanoparticle systems.

Purpose of the Study:

• To develop a phase-resolved vSFG spectroscopy method for nanoparticle films.
• To enable operando characterization of catalytic interfaces on dielectric supports.
• To overcome limitations in applying vSFG to disordered systems.

Main Methods:

• Utilized z-cut α-quartz as an internal reference for phase measurement.
• Applied phase-resolved vSFG spectroscopy to an octadecyltrichlorosilane film.
• Analyzed a film of Mn-doped Co3O4 nanoparticles using the developed protocol.

Main Results:

• Demonstrated quantitative detection of absolute phase for surface films.
• Resolved two distinct OH species on the nanoparticle surface.
• Determined the orientation of OH species relative to the surface (H-up).

Conclusions:

• Developed a practical, internally referenced phase-resolved vSFG methodology.
• Enabled operando access to catalytic interfaces of nanoparticle ensembles.
• Expanded the applicability of vSFG beyond metallic or plasmonic systems.