Walljet electrochemistry: Quantifying molecular transport through metallopolymeric and zirconium phosphonate assembled porphyrin square thin films

Aaron M. Massari, Richard W. Gurney, Craig P. Schwartz, SonBinh T. Nguyen, Joseph T Hupp

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

By employing redox-active probes, condensed-phase molecular transport through nanoporous thin films can often be measured electrochemically. Certain kinds of electrode materials (e.g. conductive glass) are difficult to fabricate as rotatable disks or as ultramicroelectrodes - the configurations most often used for electrochemical permeation measurements. These limitations point to the need for a more materials-general measurement method. Herein, we report the application of walljet electrochemistry to the study of molecular transport through model metallopolymeric films on indium tin oxide electrodes. A quantitative expression is presented that describes the transport-limited current at the walljet electrode in terms of mass transport through solution and permeation through the film phase. A comparison of the film permeabilities for a series of redox probes measured using the walljet electrode and a rotating disk electrode establishes the accuracy of the walljet method, while also demonstrating similar precision for the two methods. We apply this technique to a system consisting of zirconium phosphonate assembled films of a porphyrinic molecular square. Transport through films comprising three or more layers is free from significant contributions from pinhole defects. Surprisingly, transport through films of this kind is 2-3 orders of magnitude slower than through films constructed via interfacial polymerization of nearly identical supramolecular square building blocks (Keefe; et al. Adv. Mater. 2003, 15, 1936). The zirconium phosphate assembled films show good size exclusion behavior. The details of the observed dependence of permeation rates on probe molecule size can be rationalized with a model that assumes that the walls of the squares are slightly tilted from a strictly vertical geometry, consistent with atomic force microscopy measurements, and assumes that the individual wall geometries are locked by rigid interlayer linkages.

Original languageEnglish
Pages (from-to)4422-4429
Number of pages8
JournalLangmuir
Volume20
Issue number11
DOIs
Publication statusPublished - May 25 2004

Fingerprint

Organophosphonates
Porphyrins
Electrochemistry
electrochemistry
Zirconium
porphyrins
Thin films
thin films
Electrodes
Permeation
electrodes
probes
Conductive materials
Geometry
rotating disks
Rotating disks
pinholes
electrode materials
geometry
Tin oxides

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

Cite this

Walljet electrochemistry : Quantifying molecular transport through metallopolymeric and zirconium phosphonate assembled porphyrin square thin films. / Massari, Aaron M.; Gurney, Richard W.; Schwartz, Craig P.; Nguyen, SonBinh T.; Hupp, Joseph T.

In: Langmuir, Vol. 20, No. 11, 25.05.2004, p. 4422-4429.

Research output: Contribution to journalArticle

Massari, Aaron M. ; Gurney, Richard W. ; Schwartz, Craig P. ; Nguyen, SonBinh T. ; Hupp, Joseph T. / Walljet electrochemistry : Quantifying molecular transport through metallopolymeric and zirconium phosphonate assembled porphyrin square thin films. In: Langmuir. 2004 ; Vol. 20, No. 11. pp. 4422-4429.
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