Nurturing Plasmonic Properties of Nanocomposite Thin Films: The Importance of Optimum Oblate Shape

Abstract

Metal nanoparticles (MNPs) embedded dielectric thin films are very crucial for many optoelectronic applications. This report investigates various ways of tuning the plasmonic properties of such nanocomposite thin films. For this, the well-known plasmon resonance condition was first generalized to include the shape and volume fraction of MNPs. This was followed by deriving an empirical formula for the resonance position (λR) which was worked out to be the positive root of a quadratic equation. The coefficients of the deduced quadratic relation involve the parameters obtained from the empirical fit to some of the experimental dielectric functions of MNPs available in literature. The derived working formula enables research community to tune the LSPR of nanocomposites in the whole range of visible wavelengths. The derived formula also concluded that with known lower volume fractions, shape of MNPs affects λR the most, compared to the other parameters. The derived formula was validated by calculating the full extinction spectra. It was shown for the first time that there exists an optimum value of oblate shape to give maximum resonance for a given nanocomposite.

Surface enhanced Raman scattering in thin films: the importance of Raman analyte-plasmonic particle inverse geometry

“…It is very crucial to know the aspect ratio which is defined as the ratio of the in-plane diameter to the height of the prepared spheroidal AuNPs in order to understand the optical absorbance spectra which in turn determines how effective the AuNPs are for the SERS activity at a particular excitation laser wavelength. It has been shown in earlier works [25,26] that an oblate shape has more extinction cross-section at a redshifted wavelength compared to its spherical counterpart of equivalent volume.…”

“…Comparing the observed positions and relative intensities of the LSPR peaks with both theoretical and experimental literature facts, some of the statistical nature of AuNPs can be inferred. For example, the LSPR position for a given shape and metal-dielectric pair is fixed [25,26]. Whereas the deviations from shape and materials are indicated by the shifts in LSPR position, the deviation in size (change in volume of AuNPs) is indicated by the change in intensity of the LSPR peak.…”

Bioactive Gelatin-based Date By-Product for Packaging Applications: Physico-Chemical and Biological Characterization

“…In general, the protein-based films have moderate mechanical properties and good oxygen barrier properties, but they are sensitive to water. Some physical or chemical post-treatment methods can be applied to make the properties of protein-based films improved for specific applications [10,11]. Herein the DBP was used to elaborate active packaging formulations as substitutions for synthetic additives.…”