Optomechanic Coupling in Ag Polymer Nanocomposite Films

Abstract

Particle vibrational spectroscopy has emerged as a new tool for the measurement of elasticity, glass transition, and interactions at a nanoscale. For colloid-based materials, however, the weakly localized particle resonances in a fluid or solid medium renders their detection difficult. The strong amplification of the inelastic light scattering near surface plasmon resonance of metallic nanoparticles (NPs) allowed not only the detection of single NP eigenvibrations but also the interparticle interaction effects on the acoustic vibrations of NPs mediated by strong optomechanical coupling. The “rattling” and quadrupolar modes of Ag/polymer and polymer-grafted Ag NPs with different diameters in their assemblies are probed by Brillouin light spectroscopy (BLS). We present thorough theoretical 3D calculations for anisotropic Ag elasticity to quantify the frequency and intensity of the “rattling” mode and hence its BLS activity for different interparticle separations and matrix rigidity. Theoretically, a liquidlike environment, e.g., poly(isobutylene) (PIB) does not support rattling vibration of Ag dimers but unexpectedly hardening of the extremely confined graft melt renders both activation of the former and a frequency blue shift of the fundamental quadrupolar mode in the grafted nanoparticle Ag@PIB film.

Sub-Rouse Dynamics in Poly(isobutylene) as a Function of Molar Mass

“…18−20 Results have shown PIB-induced nanoparticle asphericity and anisotropic grafting in one-component PIB-g-Ag in dilute solution, 19 as well as a pronounced laser light stimulated phonon response in thin films. 20 In addition, metal sputtering-competing water vapor blocking values were shown by one-layer PIB coatings onto thin and flexible PET substrates. 18 In this work, the effect of PIB molecular mass in packing and dynamics is examined, through a combination of techniques, including XRD, DSC, DS, and rheology.…”

“…The gel permeation chromatography (GPC) traces of the synthesized homopolymers are shown in Figure . The behavior of PIB nanocomposites in dilute solution and in thin films, as well as the performance of PIB as water vapor barrier coatings onto thin flexible films, has recently been studied. − Results have shown PIB-induced nanoparticle asphericity and anisotropic grafting in one-component PIB- g -Ag in dilute solution, as well as a pronounced laser light stimulated phonon response in thin films . In addition, metal sputtering-competing water vapor blocking values were shown by one-layer PIB coatings onto thin and flexible PET substrates .…”

Phonon transport in the gigahertz to terahertz range: Confinement, topology, and second sound

“…The OM-coupling and BLS signal of nanomaterials can be enhanced through the plasmonic near fields of metallic nanostructures 12,13,[55][56][57] . However, we believe that the enhancement factor for BLS cannot reach that of surfaceenhanced Raman scattering (SERS), in which the signal of molecular vibrations is enhanced by over 10 8 times with plasmons 58 .…”

“…Such phenomena are relevant for molecules but cannot be exploited for the confined acoustic modes of entire nanostructures. One the other hand, the BLS signal comes from volume (PE) and surface (MI) integrals that take into account the entire distribution of atomic displacements and their overlap with the electromagnetic fields 57 . This means that if there is a considerable spatial separation between the maximum atomic displacement and the maximum electromagnetic field, then the OM-coupling and the BLS enhancement will be limited.…”

Influence of Surfactant-Mediated Interparticle Contacts on the Mechanical Stability of Supraparticles

“…To shed light on changes in the interparticle contacts by the presence of surfactants, we employ the noncontact, noninvasive, and zero-strain Brillouin Light Spectroscopy (BLS) − to record the primary particle mechanical vibrations in the supraparticles. The vibration spectrum is highly sensitive to the interparticle contacts − and thus allows correlating the mechanical properties of the supraparticles under compression with the micromechanics of the interparticle contacts. This correlation helps to rationalize the changes observed in the supraparticle mechanical stability and showcases the possibility of mechanical property design for particulate materials via surfactants.…”