Polarization-dependent surface-enhanced Raman scattering (SERS) from microarrays

Hong, Koh Yiin; Brolo, Alexandre G.

doi:10.1016/j.aca.2017.04.003

Cited by 13 publications

(9 citation statements)

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“…Surface-enhanced Raman scattering (SERS) is an increase in Raman efficiency due to extremely localized electromagnetic fields at the surface of, for instance, Au and Ag nanoparticles . These fields can be excited using visible radiation and are tightly confined to only certain areas, known as “plasmonic hotspots”. − Molecules in these hotspots experience enhanced excitation and scattering when probed with the proper laser wavelength and/or polarization. , In recent years, there have been several spectroscopic studies of SERS hotspots consisting of either random structures − or nanofabricated plasmonic antennas. − Plasmonic hotspots are widely explored not only for chemical analysis via SERS, but also for particle/molecule trapping, , enhanced photochemistry, − and even nanolithography. , Images of plasmonic hotspots have been obtained with ∼10 nm resolution by near-field scanning optical microscopy − and with higher resolution by scanning (transmission) electron microscopes using electron energy-loss spectroscopy. − However, while many experiments concentrate on the average optical properties (e.g., the extinction spectrum from a nanoparticle suspension or the transmission spectrum from a nanofabricated substrate) to predict SERS performance, fewer experiments directly probe Raman scattering from single nanostructures (e.g., imaging of subnanoparticle interactions ,− ). Moreover, most reports do not completely explore the time evolution or local origin of fluctuations in the SERS signal.…”

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Dynamic Imaging of Multiple SERS Hotspots on Single Nanoparticles

et al. 2020

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Signal intensity fluctuations are a ubiquitous characteristic of single-molecule surface-enhanced Raman scattering (SERS). In this work, we observed SERS intensity fluctuations (SIFs) from single nanoparticles fully coated with an adsorbate layer. Fluctuations from dry, fully coated nanoparticles are assigned to a dynamic molecule/metal environment wherein atomic-scale reconstructions support SERS. Using super resolution imaging techniques, we were able to pinpoint the positions of the fluctuations with subparticle precision. We observed that the fluctuation events were separated spatially, temporally, and were unique to different laser excitation wavelengths and polarizations. Dual-wavelength super-resolution SERS imaging with green and red lasers reveal various classes of SIFs that occur either simultaneously or nonsimultaneously and from either the same or different location on a single nanoparticle. Similar results were seen when the particle is excited with different polarizations. This suggests that single molecule responses from several different hotspots in the same nanoparticle were readily probed. Furthermore, each nanoparticle contains multiple unique hotspots of different strengths, and resonance conditions, which are accessible by the different illumination conditions. The plasmon resonances localized by the roughness features at the nanoparticle's surface play a significant role in the fluctuation events. Our experiments show that SERS hotspots that support single molecules are not a static feature of the nanoparticle. This information should be useful to guide future single-molecule SERS experiments.

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Dynamic Imaging of Multiple SERS Hotspots on Single Nanoparticles

et al. 2020

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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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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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“…Considerations above can be analogously extended to many other plasmonic platforms possessing anisotropic morphology fabricated using various procedures [ 88 ]. For example, polarization properties of metallic nanocubes [ 89 , 90 , 91 ], arrays of silver NP rows [ 92 ], gold nanoassemblies [ 93 ], metallic gratings structures [ 94 ], half-shells [ 95 ] etc. were studied in literature.…”

Section: Polarization Effects For Molecules On Plasmonic Nanostrucmentioning

confidence: 99%

“…This aspect was usually resolved in the literature by applying a correction assuming exponential decay of the SERS signal with time [ 81 , 97 , 109 ]. Polarization-dependent properties of SERS microarrays also found use in elimination of the polarization insensitive spurious bands originating from the bulk material [ 94 ].…”

Section: Polarization Effects For Molecules On Plasmonic Nanostrucmentioning

confidence: 99%

“…For aligned silver NRs in [ 98 ], the magnitude of the SERS enhancement and of absorbance of the same polarization were almost a perfect match ( Figure 19 ) with the biggest response provided by polarization along the NRs. Counterintuitively, in the case of metallic grating structures [ 94 ], light polarization exhibiting the biggest transmission was also found to dominate in the SERS spectrum over perpendicular polarization for which the transmitted intensity was lower. Such trends were also found for silver NR arrays in [ 97 ], although a bigger SERS response was found for polarization perpendicular to the adjacent NRs.…”

Section: Polarization Effects For Molecules On Plasmonic Nanostrucmentioning

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Polarization- and Angular-Resolved Optical Response of Molecules on Anisotropic Plasmonic Nanostructures

Šubr

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2018

Nanomaterials

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A sometimes overlooked degree of freedom in the design of many spectroscopic (mainly Raman) experiments involve the choice of experimental geometry and polarization arrangement used. Although these aspects usually play a rather minor role, their neglect may result in a misinterpretation of the experimental results. It is well known that polarization- and/or angular- resolved spectroscopic experiments allow one to classify the symmetry of the vibrations involved or the molecular orientation with respect to a smooth surface. However, very low detection limits in surface-enhancing spectroscopic techniques are often accompanied by a complete or partial loss of this detailed information. In this review, we will try to elucidate the extent to which this approach can be generalized for molecules adsorbed on plasmonic nanostructures. We will provide a detailed summary of the state-of-the-art experimental findings for a range of plasmonic platforms used in the last ~ 15 years. Possible implications on the design of plasmon-based molecular sensors for maximum signal enhancement will also be discussed.

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Polarization-dependent surface-enhanced Raman scattering (SERS) from microarrays

Cited by 13 publications

References 43 publications

Dynamic Imaging of Multiple SERS Hotspots on Single Nanoparticles

Dynamic Imaging of Multiple SERS Hotspots on Single Nanoparticles

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

Polarization- and Angular-Resolved Optical Response of Molecules on Anisotropic Plasmonic Nanostructures

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