Surface Enhanced Vibrational Spectroscopy of Proteins with Plasmonic Nanoantenna Arrays

2010 ◽  
Vol 1248 ◽  
Author(s):  
Ronen Adato ◽  
Ahmet A. Yanik ◽  
Jason J. Amsden ◽  
David Kaplan ◽  
Fiorenzo Omenetto ◽  
...  
Keyword(s):  
Single Molecule ◽  
Cross Sections ◽  
Near Field ◽  
Molecular Layer ◽  
Direct Access ◽  
Functional Studies ◽  
Intrinsic Absorption ◽  
Surface Enhanced ◽  
Infrared Spectral ◽  
Fluorescent Molecules

AbstractInfrared absorption spectroscopy is a powerful tool for structural and functional studies of biomolecules. The technique enables direct access to the vibrational fingerprints of molecular bonds in the mid-infrared spectral region (3-20μm). Although intrinsic absorption cross-sections are nearly ten orders of magnitude greater than corresponding Raman cross-sections, they are still small in comparison with those of fluorescent molecules. Sensitivity improvements are therefore required for the method to be applicable to single molecule / molecular layer studies. In this work, we demonstrate the use of lithographically patterned arrays of nanoantennas to enhance the absorption signature of the protein amide-I and II backbone vibrations. Strong absorption signals from monolayer thickness films are obtained. By arranging ensembles of tailored antennas in specific lattices, higher quality factor resonances and increased near-field intensities are possible. These features are leveraged to obtain 104-105 fold signal enhancements and the direct measurement of vibrational spectra of proteins at zepto-mole sensitivity levels.

scholarly journals Non-Radiative Processes and Vibrational Pumping in Surface-Enhanced Raman Scattering

2021 ◽  
Author(s):  
◽  
Christopher Galloway
Keyword(s):  
Cross Section ◽  
Single Molecule ◽  
Cross Sections ◽  
Plasmon Resonance ◽  
Additional Contribution ◽  
Vibrational Modes ◽  
Silver Colloids ◽  
Surface Enhanced ◽  
Vibrational Population ◽  
Anti Stokes

<p><b>The main focus of this thesis was the physical interpretation of the pumping cross-section. This was achieved by performing a statistical analysis of single molecule vibrational pumping events in which both the SERS and pumping cross-sections could be measured simultaneously. Samples were constructed in which small aggregates of silver colloids were evenly distributed on a dry surface.</b></p> <p>The sample was then cooled to 77K so that the main mechanism for creating a vibrational population was through Stokes scattering. Spatial mappings were then performed which measured how the SERS spectrum varied with positionon the sample and the single molecule events were identified. The SERS cross-sections were determined from the Stokes intensity while the pumping cross-sections were determined from the ratio of the anti-Stokes and Stokes peaks. It was observed that the pumping cross-section was often significantly larger than the SERS cross-section, as much as four orders of magnitude in some cases. Several attempts were made to explain this discrepancy including the possibility ofthe surface plasmon resonance favouring anti-Stokes scattering, underestimated lifetimes for the vibrational modes, and additional pumping from fluorescence. However, the most likely candidate was non-radiative Stokes scattering by the observed molecule which would increase the vibrational population but would not increase the Stokes intensity. To estimate the proportion of scattered light that is radiative or non-radiative,single molecule measurements were performed under both surface-enhanced and unmodified conditions. By comparing the fluorescence and Raman intensities under these scenarios, it was possible to estimate the radiative and non-radiative enhancement factors. It was found that the non-radiative SERS cross-section was typically much larger than the radiative cross-section for samples consisting of aggregated silver colloids. The discrepancy between the pumping and SERS cross-section (which is the radiative cross-section) could therefore be explained by non-radiative scattering dominating the creation of the vibrational population, along with an additional contribution due to the plasmon resonance favouring certain vibrational modes. Furthermore, the lifetime of a molecule after it has been excited to the first electronic state was estimated to be as short as 25 fs. It would be impossible to measure lifetimes of this order of magnitude in single molecules using time-resolved techniques. Furthermore, to the very best of our knowledge, this is the first time that an experimental determination of the non-radiative SERS cross-section has been made.</p>

scholarly journals Non-Radiative Processes and Vibrational Pumping in Surface-Enhanced Raman Scattering

2021 ◽  
Author(s):  
◽  
Christopher Galloway
Keyword(s):  
Cross Section ◽  
Single Molecule ◽  
Cross Sections ◽  
Plasmon Resonance ◽  
Additional Contribution ◽  
Vibrational Modes ◽  
Silver Colloids ◽  
Surface Enhanced ◽  
Vibrational Population ◽  
Anti Stokes

<p><b>The main focus of this thesis was the physical interpretation of the pumping cross-section. This was achieved by performing a statistical analysis of single molecule vibrational pumping events in which both the SERS and pumping cross-sections could be measured simultaneously. Samples were constructed in which small aggregates of silver colloids were evenly distributed on a dry surface.</b></p> <p>The sample was then cooled to 77K so that the main mechanism for creating a vibrational population was through Stokes scattering. Spatial mappings were then performed which measured how the SERS spectrum varied with positionon the sample and the single molecule events were identified. The SERS cross-sections were determined from the Stokes intensity while the pumping cross-sections were determined from the ratio of the anti-Stokes and Stokes peaks. It was observed that the pumping cross-section was often significantly larger than the SERS cross-section, as much as four orders of magnitude in some cases. Several attempts were made to explain this discrepancy including the possibility ofthe surface plasmon resonance favouring anti-Stokes scattering, underestimated lifetimes for the vibrational modes, and additional pumping from fluorescence. However, the most likely candidate was non-radiative Stokes scattering by the observed molecule which would increase the vibrational population but would not increase the Stokes intensity. To estimate the proportion of scattered light that is radiative or non-radiative,single molecule measurements were performed under both surface-enhanced and unmodified conditions. By comparing the fluorescence and Raman intensities under these scenarios, it was possible to estimate the radiative and non-radiative enhancement factors. It was found that the non-radiative SERS cross-section was typically much larger than the radiative cross-section for samples consisting of aggregated silver colloids. The discrepancy between the pumping and SERS cross-section (which is the radiative cross-section) could therefore be explained by non-radiative scattering dominating the creation of the vibrational population, along with an additional contribution due to the plasmon resonance favouring certain vibrational modes. Furthermore, the lifetime of a molecule after it has been excited to the first electronic state was estimated to be as short as 25 fs. It would be impossible to measure lifetimes of this order of magnitude in single molecules using time-resolved techniques. Furthermore, to the very best of our knowledge, this is the first time that an experimental determination of the non-radiative SERS cross-section has been made.</p>

scholarly journals High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures

Nanophotonics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1457-1467 ◽  
Author(s):  
Georg Ramer ◽  
Mohit Tuteja ◽  
Joseph R. Matson ◽  
Marcelo Davanco ◽  
Thomas G. Folland ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Cross Sections ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
High Q ◽  
Surface Phonon Polaritons ◽  
Previous Hypothesis ◽  
Phonon Polaritons ◽  
Field Reflectance ◽  
Strong Confinement

AbstractThe anisotropy of hexagonal boron nitride (hBN) gives rise to hyperbolic phonon-polaritons (HPhPs), notable for their volumetric frequency-dependent propagation and strong confinement. For frustum (truncated nanocone) structures, theory predicts five, high-order HPhPs, sets, but only one set was observed previously with far-field reflectance and scattering-type scanning near-field optical microscopy. In contrast, the photothermal induced resonance (PTIR) technique has recently permitted sampling of the full HPhP dispersion and observing such elusive predicted modes; however, the mechanism underlying PTIR sensitivity to these weakly-scattering modes, while critical to their understanding, has not yet been clarified. Here, by comparing conventional contact- and newly developed tapping-mode PTIR, we show that the PTIR sensitivity to those weakly-scattering, high-Q (up to ≈280) modes is, contrary to a previous hypothesis, unrelated to the probe operation (contact or tapping) and is instead linked to PTIR ability to detect tip-launched dark, volumetrically-confined polaritons, rather than nanostructure-launched HPhPs modes observed by other techniques. Furthermore, we show that in contrast with plasmons and surface phonon-polaritons, whose Q-factors and optical cross-sections are typically degraded by the proximity of other nanostructures, the high-Q HPhP resonances are preserved even in high-density hBN frustum arrays, which is useful in sensing and quantum emission applications.

High resolution scanning near field mapping of enhancement on SERS substrates: comparison with photoemission electron microscopy

2016 ◽  
Vol 18 (14) ◽  
pp. 9405-9411 ◽  
Author(s):  
C. Awada ◽  
J. Plathier ◽  
C. Dab ◽  
F. Charra ◽  
L. Douillard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Near Field ◽  
Spectroscopic Technique ◽  
Proof Of Concept ◽  
Sers Substrates ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Photoemission Electron

The need for a dedicated spectroscopic technique with nanoscale resolution to characterize SERS substrates pushed us to develop a proof of concept of a functionalized tip–surface enhanced Raman scattering (FTERS) technique.

scholarly journals Improving SERS Detection of Bacillus thuringiensis Using Silver Nanoparticles Reduced with Hydroxylamine and with Citrate Capped Borohydride

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Hilsamar Félix-Rivera ◽  
Roxannie González ◽  
Gabriela Del Mar Rodríguez ◽  
Oliva M. Primera-Pedrozo ◽  
Carlos Ríos-Velázquez ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Surface Charge ◽  
Near Field ◽  
Medical Diagnostics ◽  
Biological Warfare Agents ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Sers Detection ◽  
Warfare Agents ◽  
Enhanced Raman Scattering

The development of techniques that could be useful in fields other than biological warfare agents countermeasures such as medical diagnostics, industrial microbiology, and environmental applications have become a very important subject of research. Raman spectroscopy can be used in near field or at long distances from the sample to obtain fingerprinting information of chemical composition of microorganisms. In this research, biochemical components of the cell wall and endospores of Bacillus thuringiensis (Bt) were identified by surface-enhanced Raman scattering (SERS) spectroscopy using silver (Ag) nanoparticles (NPs) reduced by hydroxylamine and borohydride capped with sodium citrate. Activation of “hot spots”, aggregation and surface charge modification of the NPs, was studied and optimized to obtain signal enhancements from Bt by SERS. Slight aggregation of the NPs as well as surface charge modification to a more acidic ambient was induced using small-size borohydride-reduced NPs in the form of metallic suspensions aimed at increasing the Ag NP-Bt interactions. Hydroxylamine-reduced NPs required slight aggregation and no pH modifications in order to obtain high spectral quality results in bringing out SERS signatures of Bt.

Sign in / Sign up

Export Citation Format

Share Document