Graphene-Based Platform for Infrared Near-Field Nanospectroscopy of Water and Biological Materials in an Aqueous Environment

TL;DR

This paper introduces a graphene-based liquid cell platform enabling infrared near-field nanospectroscopy of biological materials in water, allowing detailed molecular analysis of viruses in aqueous environments.

Contribution

The work presents a novel IR-compatible liquid cell architecture using graphene, facilitating nanoscale IR spectroscopy of biological samples in water.

Findings

Successful imaging of tobacco mosaic virus in water using s-SNOM.

Identification of amide I and II bands of TMV at nanoscale resolution.

Verification of water presence via characteristic IR absorption features.

Abstract

Scattering scanning near-field optical microscopy (s-SNOM) has emerged as a powerful nanoscale spectroscopic tool capable of characterizing individual biomacromolecules and molecular materials. However, applications of scattering-based near-field techniques in the infrared (IR) to native biosystems still await a solution of how to implement the required aqueous environment. In this work, we demonstrate an IR-compatible liquid cell architecture that enables near-field imaging and nanospectroscopy by taking advantage of the unique properties of graphene. Large-area graphene acts as an impermeable monolayer barrier that allows for nano-IR inspection of underlying molecular materials in liquid. Here, we use s-SNOM to investigate the tobacco mosaic virus (TMV) in water underneath graphene. We resolve individual virus particles and register the amide I and II bands of TMV at ca. 1520 and 1660 cm$^{-1}$, respectively, using nanoscale Fourier transform infrared spectroscopy (nano-FTIR). We verify the presence of water in the graphene liquid cell by identifying a spectral feature associated with water absorption at 1610 cm$^{-1}$.