Time dependent spectral change upon potential step perturbation for Au nanoparticles immobilized on an organic monolayer-modified ITO electrode

Time-dependent scattering of ultrathin gold film under potential perturbation

Shifts of the plasmon scattering band of ultrathin gold films under the effect of dynamic applied potential were studied in single wavelength measurements. The effect on scattering of applied potential was ascribed to electronic charging and discharging of the gold film. Scattering transients in response to square-wave potential modulation had an exponential form which depended on the potential step width, the modulation frequency and the nature of the ions. The presence of an AC signal component induced by ±10 mV potential modulated at 2 kHz indicated the capability of very thin gold film to respond to high frequency voltage.

Morphology-dependent voltage sensitivity of a gold nanostructure

Gold nanostructures of various morphologies, including nanospheres, nanorods, nanoprisms, and thin films, were immobilized on ITO-coated coverslips in order to investigate the response of their scattering to potential. Shifts in the plasmon band obtained by potential-modulated spectroscopic imaging indicated that the voltage sensitivity of the gold nanostructure is dependent on its morphology, with nanospheres exhibiting the lowest sensitivity and ultrathin gold films exhibiting the highest. The effects of potential on gold nanoparticles are in qualitative agreement with Mie and Gans' theories in which the shift of the gold plasma frequency is due to the charging-discharging of the nanoparticles.