Preparation of Graded Materials by Laterally Controlled Template Synthesis

Abstract

A novel scheme is presented for the synthesis of graded materials by electrodeposition in porous insulating templates. Lateral control of copper electrodeposition in nanoporous alumina membranes is achieved by application of a lateral potential gradient on a thin Au film evaporated on the membrane, used as the cathode. Formation of metal gradients in the membranes is shown to occur under conditions where essentially no gradient is formed on similar bare electrodes. This is attributed to the permanent resistivity of the thin Au film between the pores, which does not disappear upon Cu deposition, allowing a potential gradient to be maintained. Formation of a copper gradient in porous alumina membranes by uniform deposition followed by gradient dissolution is also demonstrated. These results establish the feasibility of controlled electrodeposition and gradient formation in nanoporous insulating templates.

Au–Pd Alloy Gradients Prepared by Laterally Controlled Template Synthesis

“…4 mm along the membrane. With the present cell design and Au cathode thickness, potential gradients of several hundred millivolts can be sustained by current injection into the thin Au film on the alumina membrane, [24] such that deposition of graded alloys with sizeable lateral composition gradients can be achieved under wellcontrolled conditions. Graded materials produced by this method may be designed to display gradients of mechanical, chemical, electrical, optical, magnetic, or catalytic properties, in various geometries determined by the geometry of the gradient-inducing electrodes.…”

“…0.02 lm diameter. In this work, as in previous work [24], the Au was evaporated on the 0.02 lm side.) The membranes were then used as templates for Au-Pd electrodeposition in the pores, such that the open side of the pores is bathed in the solution and the inner side of the evaporated Au serves as the cathode.…”

“…[5][6][7]10,[21][22][23] Application of the latter scheme to template electrodeposition in insulating nanoporous alumina membranes (NAMs) resulted in graded materials comprising an ensemble of metal nanowires of continuously variable lengths. [24] Lateral gradients of tens of micrometers in nanowire length were obtained by template electrodeposition or electrodissolution of Cu in NAMs under an applied lateral voltage gradient. [24] The ability to obtain graded materials spanning the entire membrane width is attributed to the insulating nature of the template, which enables the sustainment of substantial voltage drops on the thin, gold working electrode without being affected by the metal deposited in the pores.…”

Facile Route to Laterally Graded Nanotemplate

“…Nanostructures based on the AAO template entail a highly-ordered array in high density. Although lateral control of the electrodeposition of a metal into the pores of an AAO template by applying a potential gradient to the Au electrode deposited on one side of the AAO membrane has been reported, 11 to our knowledge lateral control of the template itself has so far not been demonstrated.…”

Template Synthesis of Sc@C82(I) Nanowires and Nanotubes at Room Temperature

“…[1] Compare to artificial templates, biological materials are hierarchical, abundant, complex, renewable, and environmentally benign. So far, several types of biological materials such as diatoms, [2] bacteria, [3,4] pollen, [5] cornstarch, [6] chitin, [7] and wood [8,9] have been utilized in order to prepare hierarchical inorganic materials.Among them, wood has highly anisotropic cellular structures, which can be used as a hierarchical template to generate novel ceramics with micro-, meso-, and macrostructures. Con-…”