Noncovalent Deposition of Nanoporous Ni Membranes on Spatially Organized Poly(p‐xylylene) Film Templates

Abstract

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] (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

Catalytic activity of cobalt deposited on nanostructured poly(p-xylylene) films

“…The metallization of the nanostructured PPX film has a potential impact on the development of new materials for coatings, catalyst supports, medical implants, and sensor platforms. Recently, we showed that the pyridine can non-covalently bind to the poly(chloro-p-xylylene) (PPX-Cl) film and subsequently covalently bind a Pd colloid to initiate the electroless deposition of nickel at the surface [18].…”

Bio-organism sensing via surface enhanced Raman spectroscopy on controlled metal/polymer nanostructured substrates

“…The deposition of columnar poly͑chloro-p-xylylene͒ ͑PPX-Cl͒ films by oblique angle polymerization has been described in our previous work. [20][21][22][23] Briefly, the dimer precursor dichloro-͓2.2͔paracyclophane was placed in a deposition cell in the vacuum chamber and fixed to allow a deposition area of ϳ1 cm 2 on the substrate. The chamber was evacuated and the precursor then converted to a reactive gas of monomers by pyrolysis ͑690°C͒.…”

“…Recently, with a view to overcoming these problems, we developed a new class of nonlithographically prepared SERS substrates based on vacuum deposited polymer films with highly controllable columnar nanostructures [20][21][22][23] which were further coated with a vacuum deposited Au or Ag thin film. The novel concept was to ͑1͒ first build tunable nanomorphology substrates by varying processing conditions and the polymer materials and ͑2͒ then metalize the nanostructured surfaces by carefully selected, controlled metalization processes such that the final structure was optimized for a useful combination of EFs, reproducibility and analyte selectivity.…”

Bridging Experiments and Simulations in Oblique Angle Polymerization

“…[1] Recently, we reported a novel process for depositing nanostructured polymers by oblique angle polymerization (OAP). [8][9][10] OAP is a vapor deposition polymerization (VDP) method that creates a porous and low-density film of nanostructured columns. OAP starts with a monomer or a dimer, which is converted to a polymer during the growth process.…”