Elastic scattering measurements show that isolated nanometric holes in optically thin Au films exhibit a localized surface plasmon resonance in the red to near-infrared region. The hole plasmon red shifts with increasing hole diameter or increasing refractive index of the surrounding medium, analogous to a dipolar particle plasmon. A pronounced blue shift is observed when the distance between holes is decreased, indicating an enhanced coupling between holes mediated by surface plasmon polaritons of the intervening flat film surface.

We present a sensitive and easily regenerated nano-optical sensor based on immobilization of avidincoated colloidal gold particles on a biotin-modified planar lipid bilayer supported on the walls of a quartz cuvette. The so constructed sensing template, being specific for capturing of biotinylated biomacromolecules, is analyzed using optical spectroscopy combined with Mie theory calculations for quantification of the colorimetric changes induced by biorecognition events in the interfacial region of the particles. By further utilizing de Feiter's formalism, which correlates changes in effective refractive index and thickness with adsorbed mass, a good agreement between the Mie theory and experiments is demonstrated. Furthermore, the template is proven sensitive enough to follow the hybridization kinetics of 15-mer fully complementary DNA strands without the introduction of labels or secondary signal amplification.

Gold surfaces and structures modified with octanedithiol were reacted with dithiothreitol prior to immersion in buffered solutions of charge stabilized gold nanoparticles. The procedure gives a dithiol layer with adequate properties for a homogeneous octanedithiol monolayer and uniform and reproducible gold nanoparticle binding. The distance between the adsorbing particles is controlled by the particle electrostatic interactions and can be carefully tuned by variation of ionic strength. To some extent, long-range ordering occurs among the adsorbed particles. This behavior is facilitated by the particles' small size compared to the Debye screening but also by the homogeneity of the surface modification. The simple character of the system makes it attractive for fabrication of controlled nanoparticle arrays where further chemical and biological modifications are required.

A single-electron tunneling transistor was made by capturing a chemically synthesized gold cluster between two gold electrodes. The transistor had a quasiperiodic modulation of the current–voltage characteristics as a function of a gate voltage applied to an oxidized aluminum electrode at 4.2 K. The Coulomb blockade voltage for this device was 50 mV observed at 4.2 K and room temperature. The maximum observed blockade voltage was 200 mV for devices without gate.

Single‐electron tunneling devices were made by self‐assembly of colloidal ligand‐stabilized gold clusters in the small gap between two gold electrodes, which were covered with a self‐assembled monolayer of 1,8‐octanedithiol. With this method we control the size of the active part of the device which is smaller than the traditional lithographic resolution, with chemical methods and use self‐positioning of the particle by weak forces between the substrate and the particle. The current voltage characteristic of the devices exhibit a Coulomb staircase and gate effect at 4.2 K, and a prominent Coulomb blockade at room temperature.

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