Harry O. Finklea

Bio: Harry O. Finklea is an academic researcher from West Virginia University. The author has contributed to research in topics: Electron transfer & Redox. The author has an hindex of 24, co-authored 61 publications receiving 2658 citations. Previous affiliations of Harry O. Finklea include University of Virginia.

Electron-transfer kinetics in organized thiol monolayers with attached pentaammine(pyridine)ruthenium redox centers

Abstract: Thiols with pendant redox centers (HS(CH 2 ) n CONHCH 2 pyRu(NH 3 ) 5 2+ , n=10, 11, 15) adsorb from acetonitrile solutions onto gold electrodes to form electroactive monolayers. Mixed monolayers can be formed when the electroactive thiols are co-adsorbed with alkanethiols (HS(CH 2 ) n CH 3 , n=11, 15) and ω-mercaptoalkanecarboxylic acids (HS(CH 2 ) n COOH, n=10, 11, 15); the diluent thiol in each case is slightly shorter than the electroactive thiol

Multiple electron tunneling paths across self-assembled monolayers of alkanethiols with attached ruthenium(ii/iii) redox centers

Abstract: Alkanethiol monolayers with pendant redox centers are deposited on gold electrodes by self-assembly. The monolayers are composed of both an electroactive thiol, HS(CH2)nC(O)NHCH2pyRu(NH3)52+/3+, with 10−15 methylene groups, and a diluent thiol, HS(CH2)mCOOH, also with 10−15 methylene groups. The monolayers are classified as “matched” (n = m), “exposed” (n = 15, m = 10−14), and “buried” (n = 10, m = 11−15) according to the relative position of the redox center. Cyclic voltammograms in aqueous Na2SO4 indicate that the monolayers are close-packed with the redox centers residing in the aqueous phase in all but the most buried cases. Measurements of electron transfer kinetics by several methods (cyclic voltammetry, ac impedance spectroscopy, chronoamperometry) yield an internally consistent set of kinetic parameters, the standard rate constant k°, and the reorganization energy λ of the redox centers. The reorganization energies are in good agreement with the theoretically predicted value of 1.0 eV for the pyRu...

Passivation of pinholes in octadecanethiol monolayers on gold electrodes by electrochemical polymerization of phenol

Abstract: An organized monolayer of octadecanethiol on a gold electrode strongly inhibits faradaic reactions except at pinholes in the monolayer. For simple outer-sphere redox couples, the monolayer-coated electrode behaves like a microelectrode array, with pinholes acting as the microelectrodes. The average size and separation of the pinholes can be estimated by fitting the experimental cyclic voltammograms with simulated voltammograms for a microarray electrode. The pinholes are selectively and permanently passivated by electrochemical polymerization of phenol in dilute sulfuric acid.

Formation and Structure of Self-Assembled Monolayers.

Abstract: The field of self-assembled monolayers (SAMs) has witnessed tremendous growth in synthetic sophistication and depth of characterization over the past 15 years.1 However, it is interesting to comment on the modest beginning and on important milestones. The field really began much earlier than is now recognized. In 1946 Zisman published the preparation of a monomolecular layer by adsorption (self-assembly) of a surfactant onto a clean metal surface.2 At that time, the potential of self-assembly was not recognized, and this publication initiated only a limited level of interest. Early work initiated in Kuhn’s laboratory at Gottingen, applying many years of experience in using chlorosilane derivative to hydrophobize glass, was followed by the more recent discovery, when Nuzzo and Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfides from dilute solutions.3 Getting away from the moisture-sensitive alkyl trichlorosilanes, as well as working with crystalline gold surfaces, were two important reasons for the success of these SAMs. Many self-assembly systems have since been investigated, but monolayers of alkanethiolates on gold are probably the most studied SAMs to date. The formation of monolayers by self-assembly of surfactant molecules at surfaces is one example of the general phenomena of self-assembly. In nature, self-assembly results in supermolecular hierarchical organizations of interlocking components that provides very complex systems.4 SAMs offer unique opportunities to increase fundamental understanding of self-organization, structure-property relationships, and interfacial phenomena. The ability to tailor both head and tail groups of the constituent molecules makes SAMs excellent systems for a more fundamental understanding of phenomena affected by competing intermolecular, molecular-substrates and molecule-solvent interactions like ordering and growth, wetting, adhesion, lubrication, and corrosion. That SAMs are well-defined and accessible makes them good model systems for studies of physical chemistry and statistical physics in two dimensions, and the crossover to three dimensions. SAMs provide the needed design flexibility, both at the individual molecular and at the material levels, and offer a vehicle for investigation of specific interactions at interfaces, and of the effect of increasing molecular complexity on the structure and stability of two-dimensional assemblies. These studies may eventually produce the design capabilities needed for assemblies of three-dimensional structures.5 However, this will require studies of more complex systems and the combination of what has been learned from SAMs with macromolecular science. The exponential growth in SAM research is a demonstration of the changes chemistry as a disciAbraham Ulman was born in Haifa, Israel, in 1946. He studied chemistry in the Bar-Ilan University in Ramat-Gan, Israel, and received his B.Sc. in 1969. He received his M.Sc. in phosphorus chemistry from Bar-Ilan University in 1971. After a brief period in industry, he moved to the Weizmann Institute in Rehovot, Israel, and received his Ph.D. in 1978 for work on heterosubstituted porphyrins. He then spent two years at Northwestern University in Evanston, IL, where his main interest was onedimensional organic conductors. In 1985 he joined the Corporate Research Laboratories of Eastman Kodak Company, in Rochester, NY, where his research interests were molecular design of materials for nonlinear optics and self-assembled monolayers. In 1994 he moved to Polytechnic University where he is the Alstadt-Lord-Mark Professor of Chemistry. His interests encompass self-assembled monolayers, surface engineering, polymers at interface, and surfaces phenomena. 1533 Chem. Rev. 1996, 96, 1533−1554

Proton-Coupled Electron Transfer

Abstract: ▪ Abstract Proton-coupled electron transfer (PCET) is an important mechanism for charge transfer in a wide variety of systems including biology- and materials-oriented venues. We review several are...

Electrochemical Quantitation of DNA Immobilized on Gold

Abstract: We have developed an electrochemical method to quantify the surface density of DNA immobilized on gold. The surface density of DNA, more specifically the number of nucleotide phosphate residues, is calculated from the amount of cationic redox marker measured at the electrode surface. DNA was immobilized on gold by forming mixed monolayers of thiol-derivitized, single-stranded oligonucleotide and 6-mercapto-1-hexanol. The saturated amount of charge-compensating redox marker in the DNA monolayer, determined using chronocoulometry, is directly proportional to the number of phosphate residues and thereby the surface density of DNA. This method permits quantitative determination of both single- and double-stranded DNA at electrodes. Surface densities of single-stranded DNA were precisely varied in the range of (1−10) × 1012 molecules/cm2, as determined by the electrochemical method, using mixed monolayers. We measured the hybridization efficiency of immobilized single-stranded DNA to complementary strands as a...

Thermochemistry of Proton-Coupled Electron Transfer Reagents and its Implications

Abstract: Many, if not most, redox reactions are coupled to proton transfers. This includes most common sources of chemical potential energy, from the bioenergetic processes that power cells to the fossil fuel combustion that powers cars. These proton-coupled electron transfer or PCET processes may involve multiple electrons and multiple protons, as in the 4 e–, 4 H+ reduction of dioxygen (O2) to water (eq 1), or can involve one electron and one proton such as the formation of tyrosyl radicals from tyrosine residues (TyrOH) in enzymatic catalytic cycles (eq 2). In addition, many multi-electron, multi-proton processes proceed in one-electron and one-proton steps. Organic reactions that proceed in one-electron steps involve radical intermediates, which play critical roles in a wide range of chemical, biological, and industrial processes. This broad and diverse class of PCET reactions are central to a great many chemical and biochemical processes, from biological catalysis and energy transduction, to bulk industrial chemical processes, to new approaches to solar energy conversion. PCET is therefore of broad and increasing interest, as illustrated by this issue and a number of other recent reviews.