A Comparative Plasmonic Study of Nanoporous and Evaporated Gold Films

Previously, we have reported that nanoporous gold (NPG) films prepared by a chemical dealloying method have distinctive plasmonic properties, i.e., they can simultaneously support localized and propagating surface plasmon resonance modes (l-SPR and p-SPR, respectively). In this study, the plasmonic properties of NPG are quantified through direct comparison with thermally evaporated gold (EG) films. Cyclic voltammetry and electrochemical impedance spectroscopy experiments reveal that the NPG films have 4–8.5 times more accessible surface area than EG films. Assemblies of streptavidin–latex beads generate p-SPR responses on both NPG and EG films that correlate well with the bead density obtained from scanning electron microscopy (SEM) images. A layer-by-layer assembly experiment on NPG involving biotinylated anti-avidin IgG and avidin, studied by l-SPR and SEM, shows that the l-SPR signal is directly linked to the accessibility of the interior of the NPG porosity, an adjustable experimental parameter that can be set by the dealloying condition and time

Reactivity of electrogenerated superoxide ion. Part 3. Oxidative cleavage and reduction of some cyclohexanones

The structure modifications induced by electrogenerated superoxide ion in 4-substituted cyclohexanones are related to the reactivity of O2 - as base, and electron-donor. The formation of dicarboxylic acids (50-70% yield, after 8 F per mole of substrate had flowed) implies the participation of unreduced O2. Redox cycles involving O2/O2 - , O2/O2H. and ketone/alcohol systems may be considered as an hypothesis