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Abstract Cr2+and Cr3+ions are shown to mediate the formation, morphology, and organization of arachidic acid (AA) Langmuir‐Blodgett (LB) monolayers. This finding, based on cyclic voltammetry (CV), linear sweep voltammetry (LSV) and fluorescence recovery after photobleaching (FRAP) measurements, show that Langmuir monolayer formation depends on subphase pH and metal ion concentration. Following monolayer deposition on indium tin oxide (ITO), the LB monolayer organization can be modified reversibly through control of the Cr oxidation state, which has not been shown before by other monolayers formed with other divalent metal ions. The dynamics and the mobility of a chromophore (perylene) incorporated into the monolayer sense changes in Cr oxidation state‐dependent organization of the LB monolayer. Demonstrating reversible changes in monolayer organization provides an opportunity to control chemical and electron access to the interface support.
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Permeability and Dynamics of a Monolayer are Mediated by ITO Support Surface-Modification
Indium tin oxide (ITO) has been extensively used as a transparent conductor. The surface chemistry of ITO is amenable to reactions similar to those used to modify silica, but a long-standing issue has been understanding the density and robustness of the ITO surface-modification. We report on the formation of chemically bound Cd2+-complexed octadecylphosphonic acid (ODPA) monolayer formed on a Langmuir trough and deposited using Langmuir−Blodgett (LB) methodology onto an ITO surface, either in its native form or functionalized with phosphonate (RPO3^2−). The organization of the Langmuir monolayer depends on the pH and presence of Cd2+ in the aqueous subphase on which it is formed and on the functionalization of the ITO surface. We probe the permeability of the resulting LB−support interface electrochemically and the motional freedom characteristic of chromophores contained within the monolayer using fluorescence recovery after photobleaching (FRAP). Our data demonstrate that without modification of the ITO surface the monolayer is significantly permeable by the electrophores used (ferrocene and Ru3+), and surface modification to produce covalently bound phosphonate functionality results in a monolayer that is impermeable to the electrophores. FRAP studies reveal a relatively rigid monolayer aliphatic chain region for deposition on either native or modified ITO, suggesting direct Cd2+−ITO interactions.
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- Award ID(s):
- 2150173
- PAR ID:
- 10475870
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry B
- Volume:
- 127
- Issue:
- 36
- ISSN:
- 1520-6106
- Page Range / eLocation ID:
- 7785 to 7795
- Subject(s) / Keyword(s):
- Indium tin oxide, Langmuir-Blodgett films, alkyl phosphonate monolayers and electrochemical properties.
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.jpcb.3c02803
