xperimental results of photo-catalytic activity of Ag-Au nano-composites on different type of titania are compared with numerical simulations. The action spectra of photo-catalyzed oxidation and the extinction (absorption together with scattering) spectra are compared for similar shape and size nanoparticles. Different shell-core composites using Ag and Au are numerically modeled for qualitative understanding of the light enhancement and its localization on the nanoparticle-titania substrate. We show that the electrical field component perpendicular to the interface between nanoparticle and substrate contributes the major field enhancement portion. Light enhancement at hot-spots and its scaling with gap size are revealed by surface enhanced Raman spectroscopy (SERS). Alloying of Ag and Au on nanoscale is demonstrated. The sp-to-d band transition of electrons in the plasmonic Ag and Au is proposed as a model of photo-catalysis at the wavelengths longer that the fundamental optical transition in titania (approximately 3.1 eV or 400 nm). Surface-enhanced infrared absorption (SEIRA) spectroscopy, is applied to highlyselective metal hole arrays (MHA), enhancing specific molecular vibrations for molecule fingerprinting, with up to 10 times enhancement of the absorption peaks within the 200-2000 cm−1 band. Selective IR band enhancement can be used for identification of specific molecules within complex mixtures and can be extended to longer wavelengths to probe the THz molecular bands. Discussed systems can bemodeled with a high fidelity using finite-difference timedomain (FDTD) methods. Sensing applications with microparticles can also be modeled providing insight in applications in far-IR (10-50 μm) and towards THz spectral range. The very same principles are applicable for broadband light energy harvesting.
Silver-gold nano-composites for photo-catalytic and sensing applications / Kowalska, E; Nishijima, Y; Rosa, Lorenzo; Juodkazis, S.. - (2013), pp. 219-244.