Far-field nanoscale infrared spectroscopy of vibrational fingerprints of molecules with graphene plasmons

Abstract

Infrared spectroscopy, especially for molecular vibrations in the fingerprint region between 600 and 1,500 cm−1, is a powerful characterization method for bulk materials. However, molecular fingerprinting at the nanoscale level still remains a significant challenge, due to weak light–matter interaction between micron-wavelengthed infrared light and nano-sized molecules. Here we demonstrate molecular fingerprinting at the nanoscale level using our specially designed graphene plasmonic structure on CaF2 nanofilm. This structure not only avoids the plasmon–phonon hybridization, but also provides in situ electrically-tunable graphene plasmon covering the entire molecular fingerprint region, which was previously unattainable. In addition, undisturbed and highly confined graphene plasmon offers simultaneous detection of in-plane and out-of-plane vibrational modes with ultrahigh detection sensitivity down to the sub-monolayer level, significantly pushing the current detection limit of far-field mid-infrared spectroscopies. Our results provide a platform, fulfilling the long-awaited expectation of high sensitivity and selectivity far-field fingerprint detection of nano-scale molecules for numerous applications.

Terahertz Biochemical Molecule‐Specific Sensors

“…In this section, we provide overviews and highlight the key concepts of the next generation of mid-IR absorption www.advopticalmat.de spectroscopies in designing various IR resonant antennas with different geometries [36,[42][43][44] and new materials, including aluminum, [45,46] graphene, [47,48] and dielectric materials. [49,50] In Figure 3a, Fano-resonant asymmetric metamaterials show strong near-field enhancement at the gap as well as sharp spectral features, operating in the mid-IR range.…”

Dynamical Tuning of Graphene Plasmonic Resonances by Ultraviolet Illuminations

“…[11][12][13][14][15][16][17][18][19][20][21] To tune graphene plasmonic resonances, electrical gating has been dominantly used. [22][23][24][25][26][27][28][29] For instance, plasmonic resonances in graphene ribbon arrays [25] could be tuned in a range over 500 cm −1 with a gate voltage varying from −20 to −130 V. By using an ion gel, [30] a broad tunable range around 1000 cm −1 was realized with a low gate voltage of about 4 V.…”

“…By utilizing the gate-controlled dynamical tuning, graphene plasmonic resonances could have potential applications in optoelectronics [31][32][33][34] such as tunable sensors [25,26] and modulators. [25,30] Nevertheless, the method of electrical gating www.advopticalmat.de…”

“…However, it is especially difficult and challenging for isolated graphene structures such as graphene disks. [22][23][24][25][26][27][28][29] For instance, plasmonic resonances in graphene ribbon arrays [25] could be tuned in a range over 500 cm −1 with a gate voltage varying from −20 to −130 V. By using an ion gel, [30] a broad tunable range around 1000 cm −1 was realized with a low gate voltage of about 4 V.By utilizing the gate-controlled dynamical tuning, graphene plasmonic resonances could have potential applications in optoelectronics [31][32][33][34] such as tunable sensors [25,26] and modulators. Thus, to find a way to tune plasmonic resonances in all kinds of graphene structures without the introduction of electrical connections is of great significance.…”

Near‐Field Characterization of Graphene Plasmons by Photo‐Induced Force Microscopy

“…With respect to the propagating SPPs on metals, the short propagation distance may pose a major impediment to real applications . Recently, there have been considerable efforts dedicated to investigating SPPs on graphene, which is known as graphene plasmons (GPs) . Graphene is a 2D material that can support SPPs subject to infrared and THz frequencies.…”