UV-SERS monitoring of plasmons photodegradation of biomolecules on Aluminum platforms decorated with Rhodium nanoparticles

TL;DR

This study investigates UV plasmonic platforms made of nanoporous aluminum decorated with rhodium nanoparticles for enhanced Raman spectroscopy of biomolecules, focusing on photodegradation and oxidation effects at different UV wavelengths.

Contribution

It extends previous work by exploring a new UV excitation wavelength and improved molecule access to hot spots, providing detailed spectroscopic analysis of biomolecule stability.

Findings

Raman intensity decreases with higher rhodium nanoparticle concentration at 266 nm.

Enhanced molecule access at 325 nm improves spectroscopic performance.

Evidence of biomolecule photodegradation and oxidation driven by rhodium nanoparticles.

Abstract

In the search for novel nanostructured materials for UV plasmonics a limited number of choices can be done. Materials such as aluminum, rhodium, gallium and few others can be used. One of the most interesting application for UV plasmonics is Surface Enhanced Raman Spectroscopy. It can be extended to this spectral range to explore spectral properties of biomolecules that have only a small cross section in the visible spectral range. We have recently reported on a functional substrates based on nanoporous aluminum decorated with rhodium nanoparticles. This system showed an interesting behavior for UV excitation at 266 nm, with an unexpected decreasing Raman intensity for increasing rhodium nanoparticles concentrations. We proposed that this effect can be due to the difficult access to the hot spots for the molecules deposited via thermal evaporation. Here we extend this study exploring the performance of the system at another UV excitation wavelengths (325 nm) reporting on experimental results obtained using a deposition process that can bring the molecules at the hot-spots in a more efficient way. Extensive spectroscopic acquisitions, combined with 3D maps, allow to shade a more clear view on the performance of this plasmonic platform. In particular, the photodegration and the potential oxidation of biomolecules driven by the hot-electron/hot-holes produced by the rhodium nanoparticles will be reported.