Noncovalent mechanism for the conformal metallization of nanostructured parylene films

Niranjan A. Malvadkar, Koray Sekeroglu, Walter J. Dressick, Melik C. Demirel

Research output: Contribution to journalArticle

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Abstract

We describe a rapid, reliable method of preparing nanoporous Ni or Co films using nanostructured poly(chlorop- xylylene) (nanoPPX) films as templates. The nanoPPX films are vapor deposited onto Si substrates using oblique angle polymerization (OAP), resulting in the formation of an obliquely aligned PPX nanorod array on the substrate. The nanoPPX films are then subjected to noncovalent functionalization using an aromatic ligand (i.e., pyridine) by means of treatment with either an aqueous solution of the ligand or ligand vapor. The results of quartz crystal microbalance and X-ray diffraction studies support a model in which pyridine adsorption is facilitated by the formation of p-p interactions with aromaticmoieties in the amorphous surface regions of nanoPPX. The physisorbed pyridine in the nanoPPXfilm can subsequently bind a catalytic Pd(II)-based colloidal seed layer. Continuous, conformal Ni or Co films, characterized by FIB/SEM and AFM, are grown on the Pd(II)-laden nanoPPX films using electroless metallization. Analogous metallization of a conventionally deposited planar PPX film results in noncontinuous or patchy metal deposits. Such behavior is attributed to the sluggish adsorption of pyridine in the planar PPX film, resulting in an ̃22-fold decrease in the quantity of pyridine adsorbed compared to that in a nanoPPX film. Consequently, the level of Pd(II) bound by pyridine on a planar PPX film is insufficient to catalyze continuous metallization. Results of a statistical two-level factorial design indicate that the morphology of the metal layer formed on a nanoPPX film is profoundly influenced by the ligand adsorption condition (i.e., aqueous ligand vs ligand vapor treatment) and is correlated to the catalytic activity of Co films for the production of hydrogen from sodium borohydride decomposition.

Original languageEnglish (US)
Pages (from-to)4382-4391
Number of pages10
JournalLangmuir
Volume26
Issue number6
DOIs
StatePublished - Mar 16 2010

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All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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