Revealing unconventional host-guest complexation at nanostructured interface by surface-enhanced Raman spectroscopy

Area of Science:

• Nanomaterials Science
• Supramolecular Chemistry
• Surface Chemistry

Background:

• Interfacial host-guest complexation is key for functionalizing nanomaterials.
• Studying interfacial complexation is challenging due to complex environments and trace components.

Purpose of the Study:

• To investigate the interfacial complexation between cucurbit[7]uril (CB[7]) and methyl viologen (MV2+).
• To elucidate the mechanism of cooperative adsorption and complexation at the gold nanoparticle (Au NP) interface.
• To propose a novel host-guest complexation model at the nanostructured interface.

Main Methods:

• Utilizing surface-enhanced Raman spectroscopy (SERS) for near-single-molecule sensitivity and molecular fingerprinting.
• Employing gold nanoparticles (Au NPs) as a model system for interfacial studies.
• Conducting control experiments with varying cucurbituril cavity sizes (CB[n]s).

Main Results:

• A cooperative adsorption effect involving halide anions (I-), methyl viologen (MV2+), and cucurbit[7]uril (CB[7]) was identified on Au NP surfaces.
• Similar SERS peak shifts across different cucurbiturils (CB[5], CB[6], CB[7]) indicated guest complexation with MV2+.
• An unconventional exclusive complexation model between CB[7] and MV2+ on Au NPs was proposed, differing from solution-phase models.

Conclusions:

• SERS provides crucial insights into host-guest interactions at nanostructured interfaces.
• The proposed interfacial complexation model expands the understanding of supramolecular chemistry on nanomaterials.
• Findings may inform applications in host-guest chemistry within engineered nanomaterials.