Electrodeposition of Three-Dimensionally Periodic Metal Meshes and Spheres
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Electrodeposition of Three-Dimensionally Periodic Metal Meshes and Spheres Lianbin Xu,§,‡ Weilie L. Zhou,‡ Ray H. Baughman,† Anvar A. Zakhidov,† and John B. Wiley*,§,‡ § Department of Chemistry and the ‡Advanced Materials Research Institute, University of New Orleans, New Orleans, LA 70148-2820 † Honeywell Int., Materials Laboratory, Morristown, NJ 07962-1021 E-mail: [email protected] ABSTRACT Electrochemical methods have been used to produce three-dimensionally periodic metal meshes and spheres. Nickel is initially deposited into porous opal sheets. The opals themselves consist of close-packed silica spheres, which serve as a template for the growth of the nickel arrays within the void space between SiO2 spheres. Dissolution of the SiO2 spheres results in open, three-dimensionally periodic nickel mesh structures. The metal meshes can then be oxidized in air to produce nonconducting NiO meshes. This results in an inverse template that can be used for the growth of three-dimensionally periodic metal sphere arrays. Details on the preparation and characterization of these materials are presented. INTRODUCTION Three-dimensionally ordered arrays of nanospheres and their replicas (porous networks) are of great interest for applications in a variety of areas, including catalysis, separations, photonics, magnetics, and thermoelectrics. Opal nanosphere arrays (colloidal crystals) [1] of silica or latex spheres have been used as templates for the formation of inverse mesh replicas of a variety of materials by metal alkoxide hydrolysis [2, 3], particle infusion [4, 5], polymerization [6], chemical vapor deposition (CVD) [7, 8], melt infiltration [9], salt precipitation [10], electroless deposition [11] and electrodeposition [12-15]. Dissolution of the templates then produces open three-dimensional mesh structures. More recently, ordered nanosphere arrays have also been acquired by the subsequent use of the fabricated mesh materials as templates [16, 17]. Herein we describe the production of metal meshes and spheres by the electrochemical deposition approach. In this method, by the use of poorly conducting oxide sphere or mesh arrays as molds, well-defined metal meshes and spheres can be readily obtained. EXPERIMENTAL Electrode Fabrication. Synthetic opals were prepared by the methods described previously [18]. The opal used here was composed of 290 nm silica spheres. Figure 1 shows the fabrication procedure for the opal sheet electrode. We first sputtered a Au film (ca. 1 µm thick) onto one side of an opal piece (typically 7×10×1.5 mm), then Ag paste (Ted Pella, Inc.) was used to attach a length of Cu wire to the Au film, and finally the Au/wire side of the electrode, as well as the edges, were covered with an insulating glue (3M). Sample Preparation. Using the opal membrane as the working electrode, versus a Pt wire counter electrode, Ni was deposited galvanostatically into the opal template [13] at a current density of 0.12 mA/cm2. The Ni electroplating solution was obtained commercially (Technic, D9.16.1
Figure 1. Schematic
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