Surface-enhanced near-infrared absorption (SENIRA) spectroscopy

We present first experimental demonstration of surface-enhanced near-infrared absorption (SENIRA) spectroscopy of molecular overtone and combination bands in the 1-2.5 μm wavelength range. The plasmonic enhancement platform of choice is nanoporous gold (NPG) disks which feature high-density plasmonic hot-spots of localized electric field amplification. With a self-assembled monolayer (SAM) of octadecanethiol (ODT), an enhancement factor (EF) of up to ~10
⁴
has been demonstrated for the 1st C-H overtone at 1725 nm using NPG disk with 600 nm diameter. Together with localized surface plasmon resonance (LSPR) extinction spectroscopy, simultaneous sensing of sample refractive index has been achieved for the first time.