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Mid-infrared plasmonic biosensing with graphene

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Science  10 Jul 2015:
Vol. 349, Issue 6244, pp. 165-168
DOI: 10.1126/science.aab2051

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Graphene-based biosensors

The mid-infrared (mid-IR) range is particularly well suited for biosensing because it encompasses the molecular vibrations that identify the biochemical building blocks of life, such as proteins, lipids, and DNA. However, the resulting optical signal is extremely weak and often requires complex techniques to enhance the biological detection. Rodrigo et al. present a graphene-based biosensor that they dynamically tuned over a broad spectral range through electrical gating. The authors selectively probed protein molecules at different mid-IR frequencies using a single device.

Science, this issue p. 165

Abstract

Infrared spectroscopy is the technique of choice for chemical identification of biomolecules through their vibrational fingerprints. However, infrared light interacts poorly with nanometric-size molecules. We exploit the unique electro-optical properties of graphene to demonstrate a high-sensitivity tunable plasmonic biosensor for chemically specific label-free detection of protein monolayers. The plasmon resonance of nanostructured graphene is dynamically tuned to selectively probe the protein at different frequencies and extract its complex refractive index. Additionally, the extreme spatial light confinement in graphene—up to two orders of magnitude higher than in metals—produces an unprecedentedly high overlap with nanometric biomolecules, enabling superior sensitivity in the detection of their refractive index and vibrational fingerprints. The combination of tunable spectral selectivity and enhanced sensitivity of graphene opens exciting prospects for biosensing.

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