Frequency Modulated Raman Spectroscopy

Greco, Silvio Mario Luciano; Zilio, Simone Dal; Bek, Alpan; Lazzarino, Marco; Naumenko, Denys

doi:10.1021/acsphotonics.7b01026

Cited by 6 publications

(6 citation statements)

References 29 publications

(46 reference statements)

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“…The glancing angle at which the deposited material encounters the surface produces an array of posts all oriented toward the evaporation source. These nanoposts were demonstrated to be efficient SERS substrates for analytical applications, showing an EF of 10 8 . , In addition, to generate a large SERS enhancement, the anisotropic and ordered nature of the nanorod structures make them sensitive to the polarization of the incident light. , Other reports have demonstrated the polarization response of SERS signals in various structures, such as nanogaps (e.g., nanoparticles dimers) and anisotropic nanoparticles. − Previous work by Brolo’s group has used the SERS polarization response of plasmonic microarrays to subtract unwanted background from Raman spectra. − …”

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confidence: 99%

SERS in Plain Sight: A Polarization Modulation Method for Signal Extraction

et al. 2019

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Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical spectroscopy offering advantages ranging from "vibrational fingerprints" to multiplexed detection. However, the use of this technique in real-world applications has been limited due to difficulties in detecting inherently weak Raman signals often embedded in strong interfering background signals. A variety of plasmonics-active platforms have been developed to increase Raman signals but are not sufficient to extract weak SERS signals from intense interfering background signals. Herein, we describe a practical method, referred to as polarization modulation-SERS (PM-SERS), which utilizes the polarization dependence of anisotropic SERS-active nanostructures to modulate the plasmonic effect to extract SERS signals and remove background. The modulation is obtained by switching the polarization of the excitation source at a specific frequency involving addition of only few optical components such as liquid crystal polarizers to a typical Raman setup. In this work, we characterized the polarization-dependent response of the SERS substrates fabricated using the oblique angle evaporation (OAV) technique and their response under laser excitation using a polarization modulated source. We demonstrated that the PM-SERS method can extract the analyte weak SERS signals from the strong interfering background signal in different situations, involving a fluorescent sample and a strong background light, and we show the possibility of using PM-SERS at a quasi-real time rate (0.5 Hz). We believe that the PM-SERS method will help expand the translation of applications that utilize SERS-substrates to realworld settings.

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confidence: 99%

SERS in Plain Sight: A Polarization Modulation Method for Signal Extraction

et al. 2019

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“…A similar approach was recently used. Greco et al reported on the exploitation of mechanical resonances in a cantilever to study the plasmonic amplification of a single hotspot with modulated Raman spectroscopy …”

Section: Resultsmentioning

confidence: 99%

“…Greco et al reported on the exploitation of mechanical resonances in a cantilever to study the plasmonic amplification of a single hotspot with modulated Raman spectroscopy. 27 Spatial Resolution below 10 nm. The spatial resolution of this system is obtained from the cross-sectional analysis in Figure 2.…”

Section: Acs Photonicsmentioning

confidence: 99%

Optical Absorption Imaging by Photothermal Expansion with 4 nm Resolution

et al. 2018

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For quite a long time, people thought of the diffraction limit of light as a fundamental unbreakable barrier that prevents seeing objects with sizes smaller than half the wavelength of light. Super-resolution optical methods and near-field optics enabled overcoming this limitation. Here we report an alternative approach based on tracking the photothermal expansion that a nano-object experiences upon visible light absorption, applied successfully in the characterization of samples with a spatial/lateral resolution down to 4 nm. Our device consists of an atomic force microscope coupled with a solid-state laser and a mechanical chopper synchronized with the natural oscillation mode of an in-house-made gold tip cantilever system. This configuration enhances the detection of nanostructures due to the intermittent light excitation and the consequent intermittent thermal expansion of the sample under investigation. The sensitivity and spatial resolution are further improved by the electric field enhancement due to the excitation of localized surface plasmons at the tip apex. Our concept is demonstrated by the analysis of a two-dimensional material (GaSe) on crystalline sp2 carbon (graphite) and by an array of multiwalled carbon nanotubes lithographically designed in a SiO2 matrix. The photothermal expansion originating from light absorption leads to an unprecedented spatial resolution for an optical absorption event imaged below 10 nm.

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“…As a widely used and powerful characterization method, Raman spectroscopy can preliminarily understand the phono information of synthetic crystals [21] . We characterized the NbAs crystals by Raman spectroscopy, shown in Figure 2(b) of bulk NbAs crystals, which mainly displayed three prominent Raman peaks in the range of 180-330 cm -1 .…”

Section: Materials Characterizationmentioning

confidence: 99%

Preparation of NbAs Single Crystal by the Seed Growth Process

Sun¹,

Zhao²,

Huo³

et al. 2022

Preprint

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A Weyl semimetal is a novel crystal with low-energy electronic excitations that behave as Weyl fermions. It has received worldwide interest and was believed to have opened the next era of condensed matter physics after graphene and three-dimensional topological insulators. Howev-er, it is not easy to obtain a single large-size crystal because there are many nucleations in the preparation process. Here, a bottom-seed CVT growth method is proposed in this paper, and we acquired the large-size, high-quality NbAs single crystals up to 5x4x4 mm3 finally. X-ray diffrac-tion and STEM confirmed that they are tetragonal NbAs, which the key is to use seed crystal in vertical growth furnace. Notably, the photoelectric properties of the crystal are obtained under the existing conditions, which paves the way for the follow-up work.

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Frequency Modulated Raman Spectroscopy

Cited by 6 publications

References 29 publications

SERS in Plain Sight: A Polarization Modulation Method for Signal Extraction

SERS in Plain Sight: A Polarization Modulation Method for Signal Extraction

Optical Absorption Imaging by Photothermal Expansion with 4 nm Resolution

Preparation of NbAs Single Crystal by the Seed Growth Process

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