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

Journal Reference

ACS Nano. 2015;9(8):7968-75.

Khatib O¹, Wood JD², McLeod AS, Goldflam MD, Wagner M, Damhorst GL, Koepke JC, Doidge GP, Rangarajan A, Bashir R, Pop E³, Lyding JW, Thiemens MH,Keilmann F⁴, Basov DN.

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1. Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
2. Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
3. Department of Electrical Engineering, Stanford University , Stanford, California 94305, United States.
4. Ludwig-Maximilians-Universität and Center for Nanoscience , 80539 München, Germany.

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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).

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