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Miami University
Dr. James A. Cox

Professor
Department of Chemistry and Biochemistry
Phone: 513-529-2493
Fax: 513-529-5715
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Dr. James A. Cox
Dr. James A. Cox "Electrodes are being modified with nanoparticles and nanostructured composites with the goals of overcoming slow electron-transfer kinetics, passivation by adsorption of macromolecules, and/or blocking unwanted reaction pathways. New sensors, conservation of expensive metals, and new fabrication routes are among the objectives."


Description of Research
Present studies are based on three recent developments in our laboratory. First, a new method of synthesizing charged, monolayer-protected metal nanoparticles with near-monodisperse size distribution has been developed. The mean size can be systematically varied. Preliminary studies suggest that synergistic catalysis is achieved. That is, the protecting group and the nanoparticle both catalyze electrode reactions, but when both are present, the catalytic activity is greater than with either alone. Second, a means of electrochemical deposition of nm-layers of silica that have controlled, nanoscale pores perpendicular to the electrode surface has been devised. A ship-in-the-bottle synthesis of nanoparticles within these pores is projected to provide a catalytic surface that is not passivated by adsorption of macromolecules in the sample. Third, layer-by-layer electrostatic assembly of rigid films on surfaces has been developed. These films have quasi-pores that facilitate mass transfer within the assembly. Functionalization of nanoparticles in the films can lead to catalytic systems or to selective traps for targeted analytes. In combination, this development is being used to devise selective sensors.

Among the outcomes of these initiatives are the following. Highly dispersed nanoparticles on a non-catalytic electrode surface provided the same level of catalysis as a monolayer or bulk electrode. The templated silica resulted in an electrode at which the first reported electrochemical oxidation of a phospholipid was achieved. The layer-by-layer approach was used to fabricate a surface at which a phospholipid was selectively trapped from a sample and subsequently oxidized. Extensions to biological sensors, fuel cell electrodes, and detectors for liquid chromatography are underway.

Undergraduate researcher's roles in your lab
Undergraduates have been involved in the applications of templated silica, particularly to the use of this material to mimic biological membranes in terms of directing the pathways of reactions toward kinetically unfavored products that are implicated in certain diseases. Applications of sensors are also suited to undergraduate researchers.

Graduate student's role in your lab
Graduate students are involved in all aspects of the studies.

Presentations

D.V. Ca and J.A. Cox, Crystal Growth and Fiber Extrusion with Sol-Gel Matrices, Pittcon 2006, Orlando, FL, March 2006, Abstract 1600-18P

Funding
$100.000 Grant from the State of Ohio
Nanomaterials in our Environment

$100.000 Grant from the State of Ohio
Nanomaterials in our Environment
Publications

M.M Wandstrat and J.A. Cox, Preconcentration and Determination of a Phospholipid at a Surface Modified by Layer-by-Layer Assembly, Electroanalysis, in press.

D.V. Ca, L. Sun, J.A. Cox, Optimization of the Dispersion of Gold and Platinum Nanoparticles on Indium Tin Oxide for the Electrocatalytic Oxidation of Cysteine and Arsenite, Electrochimica Acta, 51, 2188-2194, 2006.

M.M. Wandstrat and J.A. Cox, Acceleration of the Densification of a Silica Sol-Gel by Inclusion of Generation-Zero Poly(amidoamine) Dendrimer, Journal of Non-Crystalline Solids, 351, 3667-3670, 2005.

A. Walcarius, D. Mandler, J.A. Cox, M. Collinson, O. Lev, Exciting New Directions in the Intersection of Functionalized Sol-Gel Materials with Electrochemistry (feature article), Journal of Materials Chemistry, 15, 3663-3689, 2005.

L. Sun, D.V. Ca, J.A. Cox, Electrocatalysis of the Hydrogen Evolution Reaction by Nanocomposites of Poly(amidoamine)-Encapsulated Platinum Nanoparticles and Phosphotungstic Acid, Journal of Solid State Electrochemistry, 9, 816-822, 2005.

M. Giorgetti, M. Berrettoni, S. Zamponi, P.J. Kulesza, J.A. Cox, Cobalt Hexacyanoferrate in PAMAM Doped Silica Matrix. 2. Structural and Electronic Characterization, Electrochimica Acta, 51, 511-516, 2005.

J.A. Cox, K.W. Kittredge, D.V. Ca, Measurement Platforms Fabricated by Layer-by-Layer Assembly of Crown Ether Functionalized Gold Nanoclusters, Journal of Solid State Electrochemistry, 8, 722-726, 2004.

J.L. Cohen, J.A. Cox, Role of Pore Size on the Electrochemical Oxidation of 5-Hydroxytryptophan in a Silica Sol-Gel Matrix, Journal of Solid State Electrochemistry, 8, 886-891, 2004.

Nano is HUGE at Miami University
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