Recent topics on single-molecule fluctuation analysis using blinking in surface-enhanced resonance Raman scattering: clarification by the electromagnetic mechanism

Itoh, Tamitake; Yamamoto, Yuko S.

doi:10.1039/c6an00936k

Cited by 42 publications

(28 citation statements)

References 126 publications

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“…Extensive microscopy results presented in this manuscript (Figures and S5) established that SCs are clusters of nanoparticles with well‐defined size and nano‐crevices. Such nano‐crevices provide high electromagnetic field intensity and are thus responsible for electromagnetic enhancement of the analytes localized in such hot spots. Compared with other reports that show fluctuating SERS signal at subnanometer concentration, the analyte localized in SCs experiences uniform and high electromagnetic filed intensity.…”

Section: Resultsmentioning

confidence: 99%

Surface‐enhanced Raman scattering platform operating over wide pH range with minimal chemical enhancement effects: Test case of tyrosine

Moronshing

Bhaskar

Mondal

et al. 2019

J Raman Spectroscopy

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Decoupling the contributions of electromagnetic and chemical enhancements in surface-enhanced Raman scattering (SERS) would lead to greater reliability and applicability in biological systems that involve large, localized pH gradients. However, suppressing short-range, chemical enhancement effects in SERS has proved challenging due to unavoidable charge-transfer interactions between analyte and the SERS platforms. This extends to both lithographically fabricated top-down and self-assembled bottom-up SERS platforms. Here, we employ a Soret effect-driven monodisperse nanoparticle assembly (Soret colloids [SCs]) with negligible surface charge (ξ < 16 mV) that provides exceptional SERS enhancement (analytical enhancement factor~10 6 ) contributed predominantly by excitation of localized surface plasmon resonance (electromagnetic enhancement) with minimal electrostatic or charge-transfer-based short-range interactions. Significantly, the low ξ of SCs is invariant over a wide pH range (pH 4-7) indicating minimal electrostatic surface charge. The interaction of such SCs with ionic analytes such as tyrosine leads to uniform SERS dictated by electromagnetic enhancement mechanism. The absence of contribution from chemical enhancement is clearly established by the vibrational fingerprints of tyrosine that are devoid of any spectral shifts originating from charge transfer between tyrosine and SCs. Accordingly, all features of the tyrosine that are independent of pH such as C-H stretch (2,700-3,000 cm −1 ) and C-C stretch (1,440 cm −1 ) and C-C-C bending (1,010 cm −1 ) are completely preserved without any spectral shifts. Simultaneously, pH-dependent vibrational features of tyrosine such as N-H stretch (1,545 cm −1 ), C¼O stretch (1,700 cm −1 ), COO − stretch (1,640 cm −1 ), C-O stretch (1,240 cm −1 ), and amide III bands (1,246 and 1,260 cm −1 ) are clearly observed. The intensities of such bands correspond exactly to the ionic state of tyrosine as dictated by the pH of the medium. This is reinforced by the crossover in the intensity of the pH-dependent vibrational modes (C-O vs. COOstretch, COO − vs. NH 3 + stretch) that coincides with the isoelectric pH of tyrosine. Finally, reliable quantification of the charge and concentration of tyrosine using SCs

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Section: Resultsmentioning

confidence: 99%

Surface‐enhanced Raman scattering platform operating over wide pH range with minimal chemical enhancement effects: Test case of tyrosine

Moronshing

Bhaskar

Mondal

et al. 2019

J Raman Spectroscopy

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“…This inelastic scattering can be understood as the annihilation or creation of a quantum vibronic or a rotation excitation in the molecule, resulting in a red-or blue-shift in frequency of the scattered photons known as Stokes/anti-Stokes scattering respectively. [15][16][17] Raman spectroscopy provides a very powerful, non-invasive technique for material studies, however, it is limited by low Raman cross sections ~10 -26 cm 2 [18] and ~10 -29 cm 2 for single molecules [19] (equivalent to quantum yields of 10 -6 -10 -8 [20] ). It is therefore fundamentally necessary to enhance this factor in order to detect trace quantities of materials.…”

Section: Introductionmentioning

confidence: 99%

Determining molecular orientationviasingle molecule SERS in a plasmonic nano-gap

et al. 2017

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In this work, plasmonic nano-gaps consisting of a silver nanoparticle coupled to an extended silver film have been fully optimized for single molecule Surface-Enhanced Raman Scattering (SERS) spectroscopy. The SERS signal was found to be strongly dependent on the particle size and the molecule orientation with respect to the field inside the nano-gap. Using Finite Difference Time Domain (FDTD) simulations to complement the experimental measurements, the complex interplay between the excitation enhancement and the emission enhancement of the system as a function of particle size were highlighted. Additionally, in conjunction with Density Functional Theory (DFT), the well-defined field direction in the nano-gap enables to recover the orientation of individual molecules.

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“…On a shorter time scale (as displayed in Fig.4), clear fluctuations of the signals are observed, which correspond to SERS blinking. 4,[29][30][31] One example are the bands at 1537 and 1509 cm -1 : For the first 70 s, the band at 1537 cm -1 is clearly stronger than the band at 1509 cm -1 , while the band at 1537 cm -1 almost disappears between 70 s and 100 s, and subsequently the original intensity ratio is restored. Both bands are assigned to C-C stretching vibrations, 32 the intensity of which varies according to thermal movements of the molecule within the SERS hot spot, giving rise to SERS blinking.…”

Section: Resultsmentioning

confidence: 99%

A versatile DNA origami based plasmonic nanoantenna for label-free single-molecule SERS

Tapio

Mostafa

Kanehira

et al. 2020

Preprint

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DNA origami technology allows for the precise nanoscale assembly of chemical entities that give rise to new functional materials. We have created a versatile DNA Origami Nanofork Antenna (DONA) by assembling Au or Ag nanoparticle dimers with 1.17 ± 0.67 nm gap size, enabling signal enhancements in surface-enhanced Raman scattering (SERS) of up to 1011. This allows for single-molecule SERS measurements, which can even be performed with larger gap sizes to accommodate differently sized molecules, and at various excitation wavelengths. A general scheme is presented to place single analyte molecules into the SERS hot spots using the DNA origami structure exploiting covalent and non-covalent coupling schemes. By using Au and Ag dimers, single-molecule SERS measurements of three dyes and cytochrome c and horseradish peroxidase proteins are demonstrated even under non-resonant excitation conditions, thus providing long photostability during time-series measurement, and enabling unprecedented optical monitoring of single molecules and DNA origami based nanomachines.

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Recent topics on single-molecule fluctuation analysis using blinking in surface-enhanced resonance Raman scattering: clarification by the electromagnetic mechanism

Cited by 42 publications

References 126 publications

Surface‐enhanced Raman scattering platform operating over wide pH range with minimal chemical enhancement effects: Test case of tyrosine

Surface‐enhanced Raman scattering platform operating over wide pH range with minimal chemical enhancement effects: Test case of tyrosine

Determining molecular orientationviasingle molecule SERS in a plasmonic nano-gap

A versatile DNA origami based plasmonic nanoantenna for label-free single-molecule SERS

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