Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLimits to surface-enhanced Raman scattering near arbitrary-shape scatterers
193
0
0.0
(
0
)
Added by
J\\'er\\^ome Michon
Publication date
2019
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
The low efficiency of Raman spectroscopy can be overcome by placing the active molecules in the vicinity of scatterers, typically rough surfaces or nanostructures with various shapes. This surface-enhanced Raman scattering (SERS) leads to substantial enhancement that depends on the scatterer that is used. In this work, we find fundamental upper bounds on the Raman enhancement for arbitrary-shaped scatterers, depending only on its material constants and the separation distance from the molecule. According to our metric, silver is optimal in visible wavelengths while aluminum is better in the near-UV region. Our general analytical bound scales as the volume of the scatterer and the inverse sixth power of the distance to the active molecule. Numerical computations show that simple geometries fall short of the bounds, suggesting further design opportunities for future improvement. For periodic scatterers, we use two formulations to discover different bounds, and the tighter of the two always must apply. Comparing these bounds suggests an optimal period depending on the volume of the scatterer.
rate research
Read More
The Dipole-Quadrupole theory of Surface Enhanced Hyper Raman Scattering (SEHRS), created by the authors is expounded in details. Peculiarities of the behavior of electromagnetic field on rough metal surfaces are considered. It is demonstrated that there is an enhancement of the dipole and quadrupole light-molecule interaction near the places with a large curvature. The expression for the SEHRS cross-section of symmetrical molecules, which consists of several contributions is obtained. Selection rules for the scattering contributions are obtained and a qualitative classification of the contributions after an enhancement degree is performed. Analysis of experimental spectra of pyrazine and phenazine, and also some another molecules is performed too. It is demonstrated a full coincidence of experimental regularities in these spectra with the theory suggested.
We derive shape-independent limits to the spectral radiative heat-transfer rate between two closely spaced bodies, generalizing the concept of a black body to the case of near-field energy transfer. Through conservation of energy and reciprocity, we show that each body of susceptibility $chi$ can emit and absorb radiation at enhanced rates bounded by $|chi|^2 / textrm{Im} chi$, optimally mediated by near-field photon transfer proportional to $1/d^2$ across a separation distance $d$. Dipole--dipole and dipole--plate structures approach restrict
Recently, studies have been carried out on attempts to combine surface-enhanced Surface-enhanced Raman spectroscopy (SERS) substrates that can be based on either localized surface plasmon (LSP) or surface plasmon polaritons (SPP) structures. By combining these two systems, the drawbacks of each other can be solved. However, the manufacturing methods involved so far are sophisticated, labor-intensive, expensive, and also technically demanding. We propose a facile method for the fabrication of a flexible plasmonic nanoslit SERS sensor. We utilized the pattern on periodic optical disks (DVD-R) as a cheap substitute for printing the periodic pattern on PDMS with soft imprint lithography. Ag nanoslit (AgNS) was fabricated by serial bideposition using a dynamic oblique angle deposition (DOD) technique. The nanoslit structures were physically and optically characterized, and the experimental results were compared to the numerical simulation studies; Monte Carlo and the finite-difference time-domain (FDTD) simulation. The Ag nanoslit structure showed an excellent SERS enhancement, and its biosensing capability was demonstrated by the sensing of bilirubin.
We report that rhomb-shaped metal nanoantenna arrays support multiple plasmonic resonances, making them favorable bio-sensing substrates. Besides the two localized plasmonic dipole modes associated with the two principle axes of the rhombi, the sample supports an additional grating-induced surface plasmon polariton resonance. The plasmonic properties of all modes are carefully studied by far-field measurements together with numerical and analytical calculations. The sample is then applied to surface-enhanced Raman scattering measurements. It is shown to be highly efficient since two plasmonic resonances of the structure were simultaneously tuned to coincide with the excitation and the emission wave- length in the SERS experiment. The analysis is completed by measuring the impact of the polarization angle on the SERS signal.
Surface-enhanced Raman spectroscopy is a powerful and versatile sensing method with a detection limit down to the single molecule level. In this article, we demonstrate how topology optimization (TopOpt) can be used for designing surface enhanced Raman scattering (SERS) substrates adhering to realistic fabrication constraints. As an example, we experimentally demonstrated a SERS enhancement factor of 5*10e4 for the 604 cm-1 Raman line of rhodamine 6G using metal nanostructures with a critical dimension of 20 nm. We then show that, by relaxing the fabrication constraints, TopOpt may be used to design SERS substrates with orders of magnitude larger enhancement factor. The results validate topology optimization as an effective method for engineering nanostructures with optimal performance and fabrication tolerance.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
