Approaching nanoxerography: The use of electrostatic forces to position nanoparticles with 100 nm scale resolution

er. The experimental SPR reflectance curves of the polymer film were fitted with the full Fresnel equations in the six-phase model using the Nelder-Mead algorithm of minimization [36]. Cyclic voltammetry and constant potential electrolysis experiments were performed using an electrochemical analyzer (EG&G, VersaStat) linked to a computer (EG&G software #270/250). An open electrochemical cell (230 lL) enabled the easy and rapid removal and exchange of solution above the polymer films. Argon was passed through the funnel placed above the open cell to create an inert atmosphere. Glass supports (TF-1 glass, 20 mm ” 20 mm) coated with a Cr sublayer (5 nm) and polycrystalline Au layer (50 nm) supplied by Analytical-lSystem, Germany, were used for the in-situ electrochemical/SPR measurements [37,38]. The Au-coated glass plate was used as a working electrode (1.5 cm 2 area exposed to the solution), an auxiliary Pt and a quasi-reference Ag electrode were made from wires 0.5 mm in diameter and added to the cell. The Ag-quasi-reference electrode was calibrated [39] by referencing to the potential of dimethylviologen, E = ±0.687 V vs. SCE, measured by cyclic voltammetry, and the potentials are reported vs. SCE. The SPR-reflectance curves and their time-dependent changes were measured in situ upon application of an external potential to the working electrode. A polyacrylic acid film was electrochemically produced on the Au-SPR electrode [25±27]. The electropolymerization was performed in an aqueous solution composed of acrylic acid, 2 M, bis-acrylamide, 0.04 M, and ZnCl 2 , 0.2 M (pH 7.0 adjusted with NaOH). The electrode was preconditioned at the potential of ±1.5 V for 10 s, then five potential cycles were applied between ±1.5 V and 0.1 V (50 mV s ±1) and the cycling was finished at a potential of 0.1 V. The polyacrylic acid modified electrode was treated with HCl, 0.1 M, for 2 min to ensure complete dissolution of Zn 0 produced upon polymerization, the electrode was carefully washed with distilled water to remove excess monomer and Zn 2+ ions, and subsequently treated with CuSO 4 solution, 0.2 M, for 30 min. The CuSO 4 solution was removed from the cell and the polymeric film, saturated with Cu 2+ ions, was washed with water and 0.1 M tris-buffer (tris = tris(hy-droxymethyl)aminomethane), pH 5.5, and was added to the cell as electrolyte solution. The potential-controlled absorption features of the Cu 0 /Cu 2+ /PAA-modified Au electrode were measured with a Uvikon …