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

Abstract

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.

Optical properties of PMMA inverse opal structures with anisotropic geometries by stretching

“…The cut-off frequencies red shifted with the change in polarization angle, due to the change in the periodicities along different directions. In addition to the anisotropic reflection spectra, the anisotropic geometries of the metal-dielectric hybrid structures may provide an indefinite dielectric constant, which is the basic property of hyperbolic metamaterials [30][31][32]. The stretched porous PMMA structure with anisotropic geometries coated with metals was simulated by the S-parameter method.…”

Worthwhile Relevance of Infrared Spectroscopy in Characterization of Samples and Concept of Infrared Spectroscopy-Based Synchrotron Radiation

“…Here, water has 3 atoms; that is, 3 × 3 − 6 � 3 degrees of freedom. Symmetrical molecules, such as O 2 , are observed solely in the Raman spectrum, not in the IR spectrum unlike unsymmetrical diatomic molecules, such as CO 2 in the IR spectrum [47]. In the case of complex molecules, they have several bonds and they are observed in the IR spectrum [35].…”

Tip‐modified Raman tensor of a porphine molecule

“…This parameter characterizes the sensitivity of the normalized depolarization function Δ nf to the inclination angle of the long principal axis of the molecule in respect to the incident polarization and has the form: where are the TERS intensities measured in the far field when the molecule is oriented towards the incident field polarization and perpendicularly to it. In the far field, three of four mutual configurations of a polarizer and an analyzer give the equivalent intensity when the scattering angle of ϕ = π /2 is fixed . It means that there is no difference whatever both the polarizer and the analyzer or the molecule itself are rotated; hence, the factor can be regarded as a depolarization.…”

“…In the far field, three of four mutual configurations of a polarizer and an analyzer give the equivalent intensity when the scattering angle of ϕ = π/2 is fixed. [33] It means that there is no difference whatever both the polarizer and the analyzer or the molecule itself are rotated; hence, the factor ρ * ‖ can be regarded as a depolarization. The higher the value of this factor the greater the near-field depolarization is observed when the certain orientation of a molecule.…”