Brewster-Angle Variable Polarization Spectroscopy of Colloidal Au-Nanospheres and -Nanorods at the Silicon Surface

Abstract

Colloidal Au-nanospheres and -nanorods were chemically synthesized from chloroauric acid containing solutions and adsorbed to hydrogen-terminated p-Si(111) surfaces. A comparative analysis of the respective plasmon resonance modes, in solution and at the silicon surface, was carried out by in situ optical transmission and surface reflection techniques. In solution, the absorbance was determined by VIS transmission spectroscopy and compared to Mie theory as well as finite difference time domain calculations. At the p-Si(111) surface, the reflectance was analyzed for the first time by Brewster-angle variable polarization spectroscopy (BA-VPS) and discussed in terms of anisotropic uniaxial thin-film properties. With BA-VPS, the strengths of parallel and orthogonal electric field components of the incident wave can be varied relative to the surface plane. Consequently, opposite changes of transverse and longitudinal resonance strengths are detected upon gradually incremented light polarization angles. Model considerations confirm that spherical and elongated particles can thereby be distinguished. The influence of particle–surface interaction and the dielectric environment is finally discussed.

Surface sensitivity of optical and magneto-optical and ellipsometric properties in magnetoplasmonic nanodisks

“…The high sensitivity of the p-BA to small changes in absorption of thin films has been used before to explore defects in materials 19,20 and for plasmonic characterization of adsorbed nanoparticles. 21 Our results open the door to the use of this technique on nanostructured transducers for biochemical sensing purposes. Noteworthy, this approach may collect most of the desired features for this application.…”

Efficient plasmonic scattering of colloidal silver particles through annealing-induced changes

“…Therefore MNPs produced from a wet chemical approach are advantageous [7], which allows precise control over the morphology of MNPs and thus their optical properties [17]. It is well known that LSPRs are very sensitive to shape and material used and hence influence the absorption and light scattering of the MNPs [7,9,18,19]. MNP synthesis has advanced in recent years dramatically and diverse possibilities of shapes and metals exist to match the needs for optical applications like PSC [9].…”