Gold nanoelectrode arrays and their evaluation by impedance spectroscopy and cyclic voltammetry.

A sol-gel strategy is developed to fabricate highly regular Au nanoelectrode arrays (NEAs) consisting of a nanoperforated ultrathin membrane of ZrO(2), which exhibits a well-ordered array of pores (65+/-5) nm in diameter with a mean center-to-center distance of (110+/-10) nm, on a polycrystalline gold surface. The structural properties are investigated by field-emission scanning electron microscopy (FE-SEM), while grazing incidence small-angle X-ray scattering (GISAXS) is used to assess the thickness homogeneity and the period of the array of electrodes. In addition, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are carried out to describe quantitatively the accessibility, electrochemical behavior, and diffusion processes of the gold NEA. A model applying parameters obtained from FE-SEM, CV, and EIS analyses is proposed to simulate the experimental results. A fairly good agreement between the experimental and the simulated data is obtained, thus allowing the deconvolution of the different diffusion regimes at the NEA.

In situ growth of gold colloids within alginate films.

Gold-alginate bionanocomposite films were prepared by impregnation of alginate films with HAuCl(4) followed by reduction with glucose. The mannuronate over guluronate ratio (M/G) of the polymer as well as the initial polymer concentration were shown to influence the film thickness, the amount of trapped Au(3 + ) ions, and the volume fraction of Au(0) nanoparticles but not the size of these colloids (about 4 nm). The homogeneity of the gold colloid dispersion within the alginate gels was studied by transmission electron microscopy (TEM) and confirmed by simulation of the surface plasmon resonance (SPR) spectra using the Maxwell-Garnett model. The calculated spectra also provided fruitful information about the gold colloid/alginate interface. Overall, the whole process is controlled by the balance between the M/G ratio, defining the polymer affinity for Au(III) species, and the solution viscosity, controlling the diffusion phenomena.