http://www.researchonline.mq.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9300 The diffractive properties of gold films with a periodic lattice of sub-micron voids beneath the surface are investigated. It has been shown that nanoporous metal surfaces exhibit frequency-selective non-dispersive diffraction enhanced by Mie plasmons in nanovoids, which leads to absolute angular tolerance of the diffracted beam intensity that can be useful for a variety of applications covering angle-tolerant optical filters, deflectors, absorbers, and beam splitters. Diffraction spectra are measured and calculated to support these conclusions, showing good qualitative agreement. 2011-01-18T01:21:30.702Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9301 We study the optical plasmonic properties of metal surfaces which have a periodic lattice of voids buried immediately beneath their flat upper surface. Light reflection spectra calculated in the framework of a self-consistent electromagnetic multiple-scattering layer-KKR approach exhibit two types of plasmon resonances originating from the excitation of different plasmon modes: surface plasmon-polaritons propagating on the planar surface of metal and Mie plasmons localized in the buried voids. Coupling between these two types of plasma oscillation leads to an enhancement of the surface plasmon-polariton resonances even for close-packed void lattices. Our theoretical model quantitatively agrees with experimental results, demonstrating that planar surfaces can exhibit strong plasmonic field enhancements. 2011-01-18T01:21:30.507Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9302 Templated electrodeposition of gold to produce thin (<1 μm) films containing a close packed hexagonal array of uniform sphere segment voids is shown to give surfaces which show strong surface enhancement for Raman scattering from molecules adsorbed at the surface. The magnitude of this is enhancement is determined by the precise geometry of the surface and depends on the choice of void diameter and film thickness. The resulting SER active surfaces are stable, reusable, give reproducible surface enhancement and can be used for in situ electrochemical SERS studies. 2010-08-29T12:10:10.103Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9304 Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface. 2010-08-29T09:23:03.173Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9143 Surface-enhanced Raman scattering is an ideal tool for identifying molecules from the “fingerprint” of their molecular bonds; unfortunately, this process lacks a full microscopic understanding and, practically, is plagued with irreproducibility. Using nanostructured metal surfaces, we demonstrate strong correlations between plasmon resonances and Raman enhancements. Evidence for simultaneous ingoing and outgoing resonances in wavelength and angle sheds new light on the Raman enhancement process, allowing optimization of a new generation of reproducible Raman substrates. 2010-08-10T08:50:55.764Z ]]> http://www.researchonline.mq.edu.au/vital/access/manager/Repository/mq:9142 In this study we report results for a systematic study of the wetting of structured gold surfaces formed by electrodeposition through monolayer templates of close-packed uniform submicrometer spheres. Removal of the template after deposition leaves a regular hexagonal array of sphere segment pores where the depth of the pores and, thus, the topography of the surface are controlled by the thickness of gold deposited through the template. We find that, as the thickness of the porous film increases up to the radius of the pores, the apparent contact angle for water on the surface increases from 70° on the flat surface to more that 130°, and then with increasing thickness above the radius of the pores the apparent contact angle decreases back toward 70°. We show that these changes in the apparent contact angle agree with the model of Cassie and Baxter for nonwetted surfaces even though the gold itself is hydrophilic. We also show that the apparent contact angle is independent of the diameter of the pores over the range 400−800 nm. This is the first reported example showing the change of a hydrophilic surface (θ < 90°) into a hydrophobic surface (θ* > 90°) purely by control of the surface topography. The role of the pore shape and size in stabilizing the nonwetting (Cassie−Baxter) droplet on the surface is discussed. 2010-08-09T09:00:22.909Z ]]>