Syntheses of nanostructured Cu- and Ni-based micro-assemblies with selectable 3-D hierarchical biogenic morphologies

Abstract

A combined layer-by-layer (LbL) surface amine amplification and electroless deposition process has been developed to convert biologically replicable three-dimensional (3-D) nanostructured micro-assemblies (such as siliceous diatom frustules) into freestanding Cu-bearing or Ni-bearing structures that retain the starting biogenic microscale 3-D shapes and nanoscale patterns. After reacting the hydroxyl-bearing surfaces of these biotemplates with an aminosilane, a LbL polyacrylate/polyamine deposition process was used to dendritically amplify the surface amine concentration. Subsequent binding of metal chloride catalysts to these amine-enriched surfaces enabled the rapid electroless deposition of thin, conformal, continuous, and nanocrystalline or amorphous metallic coatings on the 3-D biotemplates. Selective removal of the underlying templates then yielded freestanding Cu-bearing or Ni-bearing structures. The conformality and continuity of the thin coatings, and the fidelity with which the biogenic shape and fine features were preserved in the freestanding structures, were significantly enhanced by the amplification of surface amines (and the associated enrichment of catalytic sites) resulting from the LbL polyacrylate/polyamine treatment. Monolithic and multicomponent structures (e.g., Cu, multilayer Au/Cu, CuO, and Ni–P alloy) with bio-derived morphologies have been synthesized utilizing this approach. This readily-scalable process may be used to convert self-assembled rigid templates (of biological or synthetic origin) into nanostructured transition metal-based micro-assemblies with a wide variety of selectable 3-D hierarchical morphologies for use in numerous functional and structural applications.