# Differential extinction of Vibrational Molecular Overtone Transitions with Gold Nanorods and Non-Trivial Surface Enhanced Near-IR Absorption (SENIRA)

## TL;DR

This paper demonstrates how coupling plasmonic gold nanorods with molecular vibrational overtone transitions significantly enhances near-infrared absorption, enabling advanced sensing applications.

## Contribution

It introduces the first observation of differential extinction of forbidden vibrational overtones coupled to localized surface plasmons, revealing a novel interplay that boosts detection sensitivity.

## Key findings

- Orders of magnitude enhancement in differential extinction.
- Non-trivial interplay between absorption enhancement and suppression.
- Potential for new surface-enhanced near-infrared sensors.

## Abstract

Resonant coupling between plasmonic nanoantennas and molecular vibrational excitations is employed to amplify the weak overtone transitions that reside in the near-infrared. We explore for the first time the differential extinction of forbidden molecular overtone transitions coupled to the localized surface plasmons. We show that a non-trivial interplay between the molecular absorption enhancement and suppression of plasmonic absorption in a coupled system gives rise to orders of magnitude enhancement of the probe molecule differential extinction. Our results pave a road toward a new class of surface-enhanced near-infrared absorption-based sensors.