Abstract:

The sensitivity of plasmon-enhanced spectroscopy (PES) fundamentally arises from the near-field

enhancements within plasmonic nanocavities. To further advance PES, we utilized a molecule with

exciton modes that are sensitive to the excitation wavelength to functionalize the metal tip. Our

findings reveal that exciton modes play a dominant role in shaping the near-field patterns. Specifi-

cally, "hot spots" within the exciton mode contribute positively to the near-field enhancements, while

"dark spots" provide negative contributions. The functionalized tip exhibits pronounced field gradi-

ent effects compared to the bare tip, significantly improving sensitivity and selectivity in near-field

spectroscopy. Moreover, both the field enhancement and field gradient effects of the functionalized

tip can be effectively tuned by adjusting the excitation energy and tilt angle. These results provide

crucial insights into near-field modulation for molecules resonating with plasmonic nanocavities. The

developmentofmolecule-functionalizedtipsoffersapromisingpathwaytoadvancingPEStechnology,

enabling enhanced sensitivity and selectivity for molecular characterization.