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FABRICATION OF SOL-GEL FILMS BASED ON ELECTROCHEMICALLY ASSISTED DEPOSITION PROCESSING

Mehdi, Beata Layla
http://rave.ohiolink.edu/etdc/view?acc_num=miami1367543075

Abstract Details

2013, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
Electrochemical measurements in complex media are complicated by the adsorption to the electrode of macromolecules or products of electrode reactions, which are the most common causes of electrode passivation. In this study, we are addressing the above concerns by employing electrochemically-assisted deposition of sol-gel films that contain pores in the nanometer range to obtain size-exclusion electrodes. In this case, the pores must be larger than the diameter of the analyte but smaller than the size of potential interferent. These films also are capable of immobilizing electron-transfer catalysts and of providing effective charge transport to the electrode surface. Pores normal to the electrode surface are obtained by passivating a controlled array of sites on the electrode. For example, adsorption of a generation-4 polyamidoamine dendrimer (G4-PAMAM) blocks the generation of hydroxide at negative potentials or the generation of hydrogen ion at positive potentials at the sites of the adsorbed material. The sol-gel reaction occurs at the bare electrode-sol interface only; at the bare surface, hydrogen ion or the hydroxide is electrochemically generated. Sol-gel processing is catalyzed by the generation of hydrogen ion or hydroxide ion. Hence, the actual pore hypothesized to be a “shadow” of adsorbed material in an otherwise-continuous film of sol-gel. By potential and electrolysis-time control, films with a thickness of 100 nm and 10 ± 5 nm pores are formed. Perhaps more effective is the modification of the electrode surface by controlled array of 50-nm polystyrene sulfate (PSS) beads. First, the electrode is modified by a sub-monolayer of an amine, which upon protonation serves as a host for the PSS. Next, the deposition described above is performed. Nanoporous sol-gels (npSG) derived from tetraethylorthosilicate precursors contain negative silanol sites that perturb the electrochemistry of charged species at pH values above the isoelectric point of silica, ca. pH 2. We showed that application of sufficiently high ionic strength supporting electrolyte (e.g. >1.5 M KCl electrolyte), eliminated the effect of these sites on voltammetry of ionic species by causing a breakdown of the Donnan Exclusion Principle. Previously, it was shown that the influence of the negative sites of npSGs was eliminated by silanization. A more conventional alternative that was developed was, to deposit organically modified sol-gel (ormosil) film. These films were made porous by the same methods as mentioned above. A key to their development was to use solvent extraction to remove the dendrimer or PSS. Of importance was that the ormosil films with template pores blocked adsorption of test interferences, bovine serum albumin (BSA) and a phospholipid. A feature of the electrode system that was developed was inclusion of electrochemical catalysts, electrodeposited ruthenium oxide stabilized with cyano-crosslinks and a dirhodium-substituted polyoxometalate attached to gold nanoparticles, at the electrode surface at the base of the pore to mediate oxidation of phospholipids. In this regard, cyclic voltammetry and flow injection amperometry were used to demonstrate the electrocatalytic oxidation of phosphatidylocholine and cardiolipin (CL). This was the first report of the electrochemical oxidation of CL. Response from concentrations at the µM level was obtained.
James Cox, Dr (Advisor)
Andre Sommer, Dr (Committee Member)
Neil Danielson, Dr (Committee Chair)
165 p.
Chemistry; Materials Science
Sol-gel; electrochemistry; phospholipids; dendrimer;

Recommended Citations

Citations

  • Mehdi, B. L. (2013). FABRICATION OF SOL-GEL FILMS BASED ON ELECTROCHEMICALLY ASSISTED DEPOSITION PROCESSING [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1367543075

    APA Style (7th edition)

  • Mehdi, Beata. FABRICATION OF SOL-GEL FILMS BASED ON ELECTROCHEMICALLY ASSISTED DEPOSITION PROCESSING. 2013. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1367543075.

    MLA Style (8th edition)

  • Mehdi, Beata. "FABRICATION OF SOL-GEL FILMS BASED ON ELECTROCHEMICALLY ASSISTED DEPOSITION PROCESSING." Doctoral dissertation, Miami University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1367543075

    Chicago Manual of Style (17th edition)

miami1367543075
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© 2013, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.