Noncovalent Deposition of Nanoporous Ni Membranes on Spatially Organized Poly(p-xylylene) Film Templates
✍ Scribed by M. C. Demirel; M. Cetinkaya; A. Singh; W. J. Dressick
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 378 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
Nickel metal is widely used in catalytic, [1,2] energy storage, [3,4] and optical applications [5,6] due to its favorable physicochemical properties. Although Ni morphology, topology, and surface chemistry are critically important for these applications, their control is limited by: 1) Ni deposition conditions and treatments, [7][8][9] and 2) properties and available architectures of sacrificial metallization templates, [1,6,[10][11][12][13] which are usually removed by (thermo)chemical treatments after plating. In this regard, we have been exploring poly(p-xylylene) nanostructured thin films (NTFs) formed through vaporphase polymerization and directed deposition of [2.2]paracyclophane derivatives [14,15] (Fig. 1A) as new metallization templates. Proper selection of the deposition geometry and conditions and the [2.2]paracyclophane derivative permits exquisite, simultaneous control of film morphology, topology, and surface chemistry, yielding NTFs with diverse, well-organized porous structures (Fig. 1B-C). Here, we present our initial results relating to the fabrication and characterization of nanoporous Ni membranes templated by conformal electroless (EL) metallization of poly(chloro-p-xylylene) (PPX-C) NTFs.
EL metallization of polymer films is typically a multistep process [16] involving: 1) chemical or mechanical surface microroughening to promote metal adhesion; 2) adsorption of Pd/Sn core/shell colloids to the surface; 3) selective dissolution of the Sn II/IV b-hydroxy shell segment not anchoring the colloid to the surface to expose the catalytic Pd 0 core; and finally 4) solution deposition of EL metal. For NTFs, however, the need to minimize potential damage to film nanoarchitectures (Fig. 1), eliminate environmentally hazardous Sn salts, and reduce process steps and costs necessitates consideration of an alternate EL plating procedure. In one such process, [17][18][19][20][21] solvent-templated sites tailored to adsorb catalyst-binding pyridine ligands are first created at a polymer surface during film formation. Partitioning of pyridine from aqueous solution into these sites, driven by maximization of hydrophobic van der Waals and p-p interactions with the polymer aromatic functional groups that define the sites, noncovalently binds pyridine ligands at the polymer surface. Because the hydrophilic N site of the adsorbed pyridine remains accessible to aqueous solution, covalent binding of Pd II EL COMMUNICATION