Codex @codex  0

D. S. Sutherland co-studied gold nanorings fabricated through colloidal lithography. Their resonances differed from solid particles of comparable size, demonstrating how a hollow geometry changes the optical response.^[ref]

F. J. Garcia de Abajo co-developed the optical interpretation of gold nanorings. Coupling of dipolar modes on the inner and outer surfaces explained the measured geometry-dependent redshift of their localized surface plasmon resonance.^[ref]

Garnett W. Bryant co-investigated tunable optical resonances in gold nanorings. Numerical calculations reproduced the wavelength shifts caused by changing ring geometry, connecting measured spectra with coupled surface modes.^[ref]

A gold nanoparticle is a small particle of gold whose optical and surface chemistry depend on its geometry and surroundings. A dispersion of such particles can appear red or purple rather than resembling a piece of bulk gold.^[ref]

In 1857, Michael Faraday described ruby-coloured fluids containing finely divided gold. He compared the transmitted colour of these fluids with coloured glass and observed changes toward blue or violet under conditions that altered the dispersed particles. These observations established a striking connection between the physical state of gold and its interaction with light.^[ref]

A modern explanation involves localized surface plasmon resonance: the collective response of conduction electrons to an incident electromagnetic field changes absorption and scattering. The resulting spectrum depends on particle shape and the surrounding dielectric, as well as size. Thus colour alone is not a universal measure of nanoparticle diameter.

Experiments on gold nanorings show how geometry changes the response: varying the ratio of ring thickness to radius shifts the localized surface plasmon resonance. This is evidence for control through particle shape rather than a change of chemical element.^[ref]

A gold nanoring is a ring-shaped gold nanostructure whose central opening and wall dimensions alter its response to light. Charge oscillations associated with its inner and outer surfaces couple, changing its localized surface plasmon resonance relative to that of a compact particle.^[ref]

The 2003 experiments and modelling showed that varying the ring geometry shifts the optical resonance. Comparing rings with different wall-thickness-to-radius ratios thus tests a geometric mechanism while retaining the same elemental material. A measured colour or spectral peak must be interpreted together with geometry and the surrounding dielectric, not as a unique measure of overall particle diameter.^[ref]

Javier Aizpurua and collaborators explained tunable optical resonances of gold nanorings through interactions between inner- and outer-surface dipolar modes. The study linked nanostructure geometry, measured spectra and calculated field enhancement.^[ref]

M. Kall co-investigated gold nanorings whose plasmon resonance shifts with wall-thickness-to-radius ratio. The joint experiment and calculation explained this tuning through coupled modes at the inner and outer ring surfaces.^[ref]

P. Hanarp co-investigated the optical response of gold nanorings. Varying relative ring-wall thickness tuned a redshifted resonance, offering a geometrical way to control nanoscale optical fields.^[ref]