Antenna-enhanced sensor geometries.
(A) Optical scattering measurements and plasmon resonance shifts for a single palladium-gold triangle antenna during two hydrogen uptake and release cycles. (B) Hydrogen-dependent measurements for a single palladium-gold rod antenna (A–B reprinted by permission from Macmillan Publishers Ltd: Nature Materials , copyright 2011). (C) Numerically calculated single particle scattering spectra for different diameters of the Pd disk next to the triangular Au antenna (initial gap size g=7 nm). (D) Resonance shifts due to the Pd/PdH transition and the growing of the Pd disk for different initial gap sizes g (C–D reprinted with permission from . Copyright 2012 Optical Society of America). (E) SEM image and schematic depiction of a 120 nm high, truncated Au nanocone with a 15 nm SiO2 spacer layer and a Pd particle on the tip. (F) Dark-field optical image of a single nanocone (left) and its spectral response to 100 vol.% Ar, 10 vol.% H2 in Ar, and 100 vol.% Ar (right). (G) Corresponding optical isotherm of the nanocone system during hydrogenation (E–G reprinted with permission from . Copyright 2011, John Wiley & Sons, Ltd.).