Ultrabroadband infrared nanospectroscopic imaging

Abstract

Characterizing and ultimately controlling the heterogeneity underlying biomolecular functions, quantum behavior of complex matter, photonic materials, or catalysis requires large-scale spectroscopic imaging with simultaneous specificity to structure, phase, and chemical composition at nanometer spatial resolution. However, as with any ultrahigh spatial resolution microscopy technique, the associated demand for an increase in both spatial and spectral bandwidth often leads to a decrease in desired sensitivity. We overcome this limitation in infrared vibrational scattering-scanning probe near-field optical microscopy using synchrotron midinfrared radiation. Tip-enhanced localized light-matter interaction is induced by low-noise, broadband, and spatially coherent synchrotron light of high spectral irradiance, and the near-field signal is sensitively detected using heterodyne interferometric amplification. We achieve sub-40-nm spatially resolved, molecular, and phonon vibrational spectroscopic imaging, with rapid spectral acquisition, spanning the full midinfrared (700-5,000 cm) with few cm −1 spectral resolution. We demonstrate the performance of synchrotron infrared nanospectroscopy on semiconductor, biomineral, and protein nanostructures, providing vibrational chemical imaging with subzeptomole sensitivity.any properties and functions of natural or synthetic materials are defined by chemically or structurally distinct phases, domains, or interfaces on length scales of a few nanometers to micrometers. Characterizing these heterogeneities has long driven the development of advanced microscopy techniques, with notable advances in electron (1), photoemission (2), X-ray (3), and superresolution (4) microscopies. Although extremely effective, these techniques have strict sample requirements: either they operate in vacuum, are limited by electron or X-ray beam damage, or rely on labeling with exogenous fluorophores.In contrast, infrared (IR) vibrational spectroscopic imaging is minimally invasive, requires little sample preparation, is applicable in situ and under ambient conditions, and provides intrinsic chemical contrast and spectroscopic identification for a wide range of materials (5), including living cells (6) and tissues (7,8). The spatial resolution, however, is diffraction-limited to 2-10 μm, depending on wavelength. Moreover, high signal-to-noise spectra even at this low resolution are only possible with a source of high spectral irradiance (9). Subwavelength imaging has been achieved to some extent through point-spread function deconvolution (10, 11) and attenuated total reflection techniques (12). However, the micrometer-size wavelength of IR radiation, in general, has fundamentally limited its application for the characterization of essentially any mesoscopic, heterogeneous material where chemical information at the nanoscale is desired.Infrared scattering-scanning near-field microscopy (IR s-SNOM) overcomes the diffraction limit by scattering incident light with the typically metallic tip of an atomic for...

Phase transition in bulk single crystals and thin films ofVO2by nanoscale infrared spectroscopy and imaging

“…For nano-IR with the broadband synchrotron source the integrated infrared power (700 -5000 cm -1 ) is ~0.5 mW, so that we obtain all the broadband nano-IR spectrum with second harmonic demodulation (S 2 ) [51].…”

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

“…Yet, for a better evaluation of the capability of this approach additional experiments are required involving more challenging samples are required, which is subject of the present study. A recent study demonstrated the capability of this approach for characterizing biological samples [43].…”

Nanoimaging of Electronic Heterogeneity in Bi2Se3 and Sb2Te3 Nanocrystals

“…[27,33,34] Considering that IR s-SNOM is sensitive to low-energy intra-and interband transitions, Drude conductivity, and related surface excitations, we performed broadband spectroscopic nanoimaging using synchrotron near-field infrared nanospectroscopy (SINS) [35] from 750 to 2000 cm −1 . (Figure 1d).…”