Scanning electrochemical microscopy assessment of rates of molecular transport through mesoporous thin-films of porphyrinic "molecular squares"

Mary Elizabeth Williams, Joseph T Hupp

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Scanning electrochemical microscopy (SECM), in combination with electrode platform micropatterning, has been used for qualitative characterization of molecular sieving and exceptionally precise quantitative measurement of molecular permeation through thin films of meso- and microporous materials composed of porphyrinic "molecular squares". SECM measurements reveal that modification of the squares, to reduce cavity sizes and alter the size cutoff for permeation, has only a modest effect upon the permeabilities of those probe molecules small enough to pass through the modified films. Additional experiments as a function of electrolyte composition show that the ability to observe sieving behavior electrochemically is determined not only by the relative sizes of redox-active permeant molecules and film-based cavity openings, but also by the steric properties of ions needed for charge compensation - even when the permeant molecule is initially neutral. As expected, when the size of the opening is altered the steric requirements for the charge-compensating ion are similarly altered. The experiments also show that charge-compensating ion transport can be convoluted to a small but measurable extent with the probe-molecule transport measurement. The identity of the component of the electrolyte not required for charge compensation, however, does not detectably affect the SECM-based permeation measurement.

Original languageEnglish
Pages (from-to)8944-8950
Number of pages7
JournalJournal of Physical Chemistry B
Volume105
Issue number37
DOIs
Publication statusPublished - Sep 20 2001

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Microscopic examination
Permeation
microscopy
Scanning
Thin films
Molecules
scanning
ion charge
Ions
thin films
Electrolytes
molecules
electrolytes
Microporous materials
cavities
Mesoporous materials
probes
permeability
cut-off
platforms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Scanning electrochemical microscopy assessment of rates of molecular transport through mesoporous thin-films of porphyrinic "molecular squares". / Williams, Mary Elizabeth; Hupp, Joseph T.

In: Journal of Physical Chemistry B, Vol. 105, No. 37, 20.09.2001, p. 8944-8950.

Research output: Contribution to journalArticle

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