Atrial selective effect of amiodarone to increase threshold of excitation.

Increases of pacing threshold stimulation are well documented with different antiarrhythmic drugs, but not with amiodarone. We report a case of a patient with dual-chamber pacing, with stable thresholds on repeated measurements on the last year, who presented severe increase of atrial pacing threshold resulting in loss of atrial capture after a year of treatment with amiodarone. Thresholds were normalized once amiodarone was removed.

Coupling modes of gold trimer superstructures.

An experimental and theoretical examination of the coupling modes within superstructures of gold nanorod trimers is presented. The experimentally determined spectrum of the nanorod trimers is reported and the modes are elucidated using an electrostatic eigenmode method based on the coupling of evanescent electric fields. The theory is able to reproduce the experimental spectrum well, and the nature of the modes and interactions are discussed.

Influence of particle-substrate interaction on localized plasmon resonances.

We present a theory for determining the localized surface plasmon resonance shifts of arbitrarily shaped metal nanoparticles on a substrate. Using a pseudoparticle concept, an expression for the particle-substrate interaction is derived, providing both physical insight and formulas to estimate the shifted plasmon resonance. The theory is verified against measured scattering spectra of nanorods on substrates.

Electrochemical charging of single gold nanorods.

Metal nanocrystals are commonly used to mediate important chemical reactions such as water splitting and CO oxidation. To investigate such redox reactions in detail, it would be useful to be able to carry out electrochemistry on single metal nanocrystals. We report here that the surface plasmon resonance of a single gold nanocrystal can be reversibly and rapidly tuned by tens of nanometers electrochemically.

Plasmon coupling of gold nanorods at short distances and in different geometries.

The experimentally determined scattering spectra of discrete, crystalline, gold nanorod dimers arranged side-to-side, end-to-end, at right angles in different orientations and also with longitudinal offsets are reported along with the electron micrographs of the individual dimers. The spectra exhibit both red- and blue-shifted surface plasmon resonances, consistent with the plasmon hybridization model. However, the plasmon coupling constant for gold dimers with less than a few nanometers separation between the particles does not obey the exponential dependence predicted by the Universal Plasmon Ruler equation.

Dark-field microscopy studies of single metal nanoparticles: understanding the factors that influence the linewidth of the localized surface plasmon resonance.

This article provides a review of our recent Rayleigh scattering measurements on single metal nanoparticles. Two different systems will be discussed in detail: gold nanorods with lengths between 30 and 80 nm, and widths between 8 and 30 nm; and hollow gold-silver nanocubes (termed nanoboxes or nanocages depending on their exact morphology) with edge lengths between 100 and 160 nm, and wall thicknesses of the order of 10 nm. The goal of this work is to understand how the linewidth of the localized surface plasmon resonance depends on the size, shape, and environment of the nanoparticles.

Direct observation of chemical reactions on single gold nanocrystals using surface plasmon spectroscopy.

Heterogeneous catalysts have been pivotal to the development of the modern chemical industry and are essential for catalysing many industrial reactions. However, reaction rates are different for every individual catalyst particle and depend upon each particle's morphology and size, crystal structure and composition. Measuring the rates of reaction on single nanocrystals will enable the role of catalyst structure to be quantified.

Modelling the optical response of gold nanoparticles.

This tutorial review presents an overview of theoretical methods for predicting and understanding the optical response of gold nanoparticles. A critical comparison is provided, assisting the reader in making a rational choice for each particular problem, while analytical models provide insights into the effects of retardation in large particles and non-locality in small particles. Far- and near-field spectra are discussed, and the relevance of the latter in surface-enhanced Raman spectroscopy and electron energy-loss spectroscopy is emphasized.

Charge-induced Rayleigh instabilities in small gold rods.

It is demonstrated that the addition of electrons to gold nanorods with aspect ratios ranging from 2 to 4 leads to an initial blue-shift in the absorption spectrum due to the increasing surface plasmon frequency of the electron gas. However, at longer times, there are changes in particle morphology induced by the surface charge. In the case of smaller injected electron densities, the surface plasmon band red-shifts as the end caps of the rods undergo increased faceting and develop {111} faces.

Contributions from radiation damping and surface scattering to the linewidth of the longitudinal plasmon band of gold nanorods: a single particle study.

The scattering spectra of single gold nanorods with aspect ratios between 2 and 4 have been examined by dark field microscopy. The results show that the longitudinal plasmon resonance (electron oscillation along the long axis of the rod) broadens as the width of the rods decreases from 14 to 8 nm. This is attributed to electron surface scattering.