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Brunello GF, Epting WK, de Silva J, Salvador PA, Litster S, Finklea HO, Lee YL, Gerdes KR, Mebane DS. Quantitative interpretation of impedance spectroscopy data on porous LSM electrodes using X-ray computed tomography and Bayesian model-based analysis. Phys Chem Chem Phys 2017; 19:25334-25345. [PMID: 28890971 DOI: 10.1039/c7cp04533f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is broadly understood that strontium-doped lanthanum manganate (LSM) cathodes for solid oxide fuel cells (SOFCs) have two pathways for the reduction of oxygen: a surface-mediated pathway culminating in oxygen incorporation into the electrolyte at the triple-phase boundary (TPB), and a bulk-mediated pathway involving oxygen transfer across the electrode-electrolyte interface. Patterned electrode and thin film experiments have shown that both pathways are active in LSM. Porous electrode geometries more commonly found in SOFCs have not been amenable for precise measurement of active electrode width because of the difficulty in precisely measuring the electrode geometry. This study quantitatively compares a reaction-diffusion model for the oxygen reduction reaction in LSM to the impedance spectrum of an experimental LSM porous electrode symmetric button cell on a yttria-stabilized zirconia (YSZ) electrolyte. The porous microstructure was characterized using computed tomography (nano-CT) and Bayesian model-based analysis (BMA) was used to estimate model parameters. BMA produced good fits to the data, with higher than expected values for the interfacial capacitance at the LSM-YSZ interface and vacancy diffusion activation energy; these results may indicate that the active width of the electrode is on a similar scale with that of the space-charge width at the LSM-YSZ interface. The analysis also showed that the active width and proportion of current moving through the bulk pathway is temperature dependent, in accordance with patterned electrode results.
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Affiliation(s)
- Giuseppe F Brunello
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506, USA.
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Sun J, Finklea HO, Liu Y. Characterization and electrolytic cleaning of poly(methyl methacrylate) residues on transferred chemical vapor deposited graphene. Nanotechnology 2017; 28:125703. [PMID: 28163262 DOI: 10.1088/1361-6528/aa5e55] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Poly(methyl methacrylate) (PMMA) residue has long been a critical challenge for practical applications of the transferred chemical vapor deposited (CVD) graphene. Thermal annealing is empirically used for the removal of the PMMA residue; however experiments imply that there are still small amounts of residues left after thermal annealing which are hard to remove with conventional methods. In this paper, the thermal degradation of the PMMA residue upon annealing was studied by Raman spectroscopy. The study reveals that post-annealing residues are generated by the elimination of methoxycarbonyl side chains in PMMA and are believed to be absorbed on graphene via the π-π interaction between the conjugated unsaturated carbon segments and graphene. The post-annealing residues are difficult to remove by further annealing in a non-oxidative atmosphere due to their thermal and chemical stability. An electrolytic cleaning method was shown to be effective in removing these post-annealing residues while preserving the underlying graphene lattice based on Raman spectroscopy and atomic force microscopy studies. Additionally, a solution-gated field effect transistor was used to study the transport properties of the transferred CVD graphene before thermal annealing, after thermal annealing, and after electrolytic cleaning, respectively. The results show that the carrier mobility was significantly improved, and that the p-doping was reduced by removing PMMA residues and post-annealing residues. These studies provide a more in-depth understanding on the thermal annealing process for the removal of the PMMA residues from transferred CVD graphene and a new approach to remove the post-annealing residues, resulting in a residue-free graphene.
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Affiliation(s)
- Jianbo Sun
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, United States of America
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Greenawald LA, Snyder JL, Fry NL, Sailor MJ, Boss GR, Finklea HO, Bell S. Development of a cobinamide-based end-of-service-life indicator for detection of hydrogen cyanide gas. Sens Actuators B Chem 2015; 221:379-385. [PMID: 26213448 PMCID: PMC4511729 DOI: 10.1016/j.snb.2015.06.085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We describe an inexpensive paper-based sensor for rapid detection of low concentrations (ppm) of hydrogen cyanide gas. A piece of filter paper pre-spotted with a dilute monocyanocobinamide [CN(H2O)Cbi] solution was placed on the end of a bifurcated optical fiber and the reflectance spectrum of the CN(H2O)Cbi was monitored during exposure to 1.0-10.0 ppm hydrogen cyanide gas. Formation of dicyanocobinamide yielded a peak at 583 nm with a simultaneous decrease in reflectance from 450-500 nm. Spectral changes were monitored as a function of time at several relative humidity values: 25, 50, and 85% relative humidity. With either cellulose or glass fiber papers, spectral changes occurred within 10 s of exposure to 5.0 ppm hydrogen cyanide gas (NIOSH recommended short-term exposure limit). We conclude that this sensor could provide a real-time end-of-service-life alert to a respirator user.
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Affiliation(s)
- Lee A. Greenawald
- Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health/National Personal Protective Technology Laboratory (CDC/NIOSH/NPPTL), 1095 Willowdale Road, Morgantown, WV 26505, USA
- Corresponding author. (L.A. Greenawald)
| | | | - Nicole L. Fry
- Department of Chemistry and Biochemistry, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093, USA
| | - Michael J. Sailor
- Department of Chemistry and Biochemistry, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093, USA
| | - Gerry R. Boss
- Department of Medicine, 9500 Gilman Drive, University of California, San Diego, La Jolla, CA 92093, USA
| | - Harry O. Finklea
- C. Eugene Bennett Department of Chemistry, 217 Clark Hall, West Virginia University, Morgantown, WV 26506, USA
| | - Suzanne Bell
- C. Eugene Bennett Department of Chemistry, 217 Clark Hall, West Virginia University, Morgantown, WV 26506, USA
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Cai R, Yan W, Bologna MG, de Silva K, Ma Z, Finklea HO, Petersen JL, Li M, Shi X. Synthesis and characterization of N-2-aryl-1,2,3-triazole based iridium complexes as photocatalysts with tunable photoredox potential. Org Chem Front 2015. [DOI: 10.1039/c4qo00281d] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
N-2-Aryl chelated 1,2,3-triazole-Ir(iii) complexes with various substituents were prepared for the first time.
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Affiliation(s)
- Rong Cai
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Wuming Yan
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Matthew G. Bologna
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Kaushalya de Silva
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Zhao Ma
- Department of Medicinal Chemistry
- School of Pharmacy
- Shandong University
- Jinan
- China
| | - Harry O. Finklea
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Jeffrey L. Petersen
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Minyong Li
- Department of Medicinal Chemistry
- School of Pharmacy
- Shandong University
- Jinan
- China
| | - Xiaodong Shi
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
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Finklea HO, Ravenscroft MS. Temperature and Overpotential Dependence of Long-Range Electron Transfer across a Self-Assembled Monolayer with Pendant Ruthenium Redox Centers. Isr J Chem 2013. [DOI: 10.1002/ijch.199700022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Madhiri N, Finklea HO. Potential-, pH-, and isotope-dependence of proton-coupled electron transfer of an osmium aquo complex attached to an electrode. Langmuir 2006; 22:10643-51. [PMID: 17129042 DOI: 10.1021/la061103j] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
An osmium complex, [OsII(bpy)2(4-aminomethylpyridine)(H2O)]2+, is attached to a mixed self-assembled monolayer on a gold electrode. The complex exhibits 1-electron, 1-proton redox chemistry (OsIII(OH)/OsII(H2O)) at pHs and potentials that are experimentally accessible with gold electrodes in aqueous electrolytes. The thermodynamic behavior and kinetic behavior of the system are investigated as a function of pH in both H2O and D2O. The two formal potentials and two pKa values are relatively constant for two chain lengths in H2O and in D2O. The standard rate constants at all pHs are strongly and uniformly affected by chain length, indicating that electronic coupling is the dominant factor controlling the rate of electron transfer. In both H2O and D2O, the standard rate constant is weakly dependent on the pH, exhibiting a minimum value midway between the pKa values. The kinetic isotope effect is small; standard rate constants decrease by roughly a factor of 2 in D2O over a wide range of pHs, but not at the more acidic pHs. The Tafel plots and plots of the transfer coefficient vs overpotential are asymmetrical at all pHs. These results are interpreted in terms of a larger reorganization energy for the OsII species and a smaller reorganization energy for the OsIII species. The OsIII reorganization energy is constant at all pHs in both H2O and D2O. The pH dependence of the OsII reorganization energy accounts for some or all of the pH dependence of the standard rate constant in H2O and D2O. The data deviate substantially from predictions of the stepwise proton-coupled electron-transfer mechanism. The observation of a kinetic isotope effect supports the concerted mechanism.
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Affiliation(s)
- Nicholas Madhiri
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, USA
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Affiliation(s)
- Robert M. Haddox
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Harry O. Finklea
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
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Abstract
Molecularly imprinted polymers on quartz crystal microbalances (QCM) are examined for their ability to detect vapors of small organic molecules with greater sensitivity and selectivity than the traditional amorphous polymer coatings. Hydroquinone and phenol serve as noncovalently bound templates that generate shape-selective cavities in a poly(acrylic) or poly(methacrylic) polymer matrix. The imprinted polymers are immobilized on the piezoelectric crystal surface via a precoated poly(isobutylene) layer. The behavior of the imprinted polymer films is characterized by the dynamic and steady-state response of the QCM frequency to pulses of organic vapors in dry air. The apparent partition coefficients are determined for imprinted and nonimprinted polymers prepared by two synthetic methods and for varying mole ratios of template to monomer. The hydroquinone-imprinted polymers and, to a lesser extent, the phenol-imprinted polymers exhibit greater sensitivity and higher selectivity than the nonimprinted polymers toward organic vapors that are structurally related to the templates. These results indicate that molecularly imprinted polymers are promising for the development of selective piezoelectric sensors for organic vapor detection.
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Affiliation(s)
- Yi Fu
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, USA
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Smalley JF, Finklea HO, Chidsey CED, Linford MR, Creager SE, Ferraris JP, Chalfant K, Zawodzinsk T, Feldberg SW, Newton MD. Heterogeneous electron-transfer kinetics for ruthenium and ferrocene redox moieties through alkanethiol monolayers on gold. J Am Chem Soc 2003; 125:2004-13. [PMID: 12580629 DOI: 10.1021/ja028458j] [Citation(s) in RCA: 266] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The standard heterogeneous electron-transfer rate constants between substrate gold electrodes and either ferrocene or pentaaminepyridine ruthenium redox couples attached to the electrode surface by various lengths of an alkanethiol bridge as a constituent of a mixed self-assembled monolayer were measured as a function of temperature. The ferrocene was either directly attached to the alkanethiol bridge or attached through an ester (CO(2)) linkage. For long bridge lengths (containing more than 11 methylene groups) the rate constants were measured using either chronoamperometry or cyclic voltammetry; for the shorter bridges, the indirect laser induced temperature jump technique was employed to measure the rate constants. Analysis of the distance (bridge length) dependence of the preexponential factors obtained from an Arrhenius analysis of the rate constant versus temperature data demonstrates a clear limiting behavior at a surprisingly small value of this preexponential factor (much lower than would be expected on the basis of aqueous solvent dynamics). This limit is independent of both the identity of the redox couple and the nature of the linkage of the couple to the bridge, and it is definitely different (smaller) from the limit derived from an equivalent analysis of the rate constant (versus temperature) data for the interfacial electron-transfer reaction through oligophenylenevinylene bridges between gold electrodes and ferrocene. There are a number of possible explanations for this behavior including, for example, the possible effects of bridge conformational flexibility upon the electron-transfer kinetics. Nevertheless, conventional ideas regarding electronic coupling through alkane bridges and solvent dynamics are insufficient to explain the results reported here.
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Affiliation(s)
- John F Smalley
- Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
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Penn JH, Owens WH, Petersen JL, Finklea HO, Snider DA. Mixed anhydrides: physical properties influenced by molecular structure. J Org Chem 2002. [DOI: 10.1021/jo00060a032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Finklea HO, Hanshew DD. Electron-transfer kinetics in organized thiol monolayers with attached pentaammine(pyridine)ruthenium redox centers. J Am Chem Soc 2002. [DOI: 10.1021/ja00035a001] [Citation(s) in RCA: 558] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Charney LM, Finklea HO, Schultz FA. Electrochemistry, spectroelectrochemistry, and electron paramagnetic resonance spectroscopy of aqueous molybdenum(VI), -(V), -(IV), and -(III) catechol complexes. Stabilization of reduced monomers in weakly alkaline solution. Inorg Chem 2002. [DOI: 10.1021/ic00132a017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Smith DA, McDonald JW, Finklea HO, Ott VR, Schultz FA. Eight-coordinate complexes of molybdenum with 1,1-dithio ligands. Synthesis, electrochemistry, and spectroscopic properties. Inorg Chem 2002. [DOI: 10.1021/ic00140a045] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ravenscroft MS, Finklea HO. Kinetics of electron transfer to attached redox centers on gold electrodes in nonaqueous electrolytes. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100065a047] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Finklea HO, Boggess RK, Trogdon JW, Schultz FA. Thin-layer spectroelectrochemistry cell with demountable gold or mercury-gold minigrid electrodes. Anal Chem 2002. [DOI: 10.1021/ac00258a047] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Rice LE, Boston MC, Finklea HO, Suder BJ, Frazier JO, Hudlicky T. Regioselectivity in the Reformatskii reaction of 4-bromocrotonate. Role of the catalyst and the solvent in the normal vs. abnormal modes of addition to carbonyl substrates. J Org Chem 2002. [DOI: 10.1021/jo00184a042] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Finklea HO. Theory of Coupled Electron−Proton Transfer with Potential-Dependent Transfer Coefficients for Redox Couples Attached to Electrodes†. J Phys Chem B 2001. [DOI: 10.1021/jp010768l] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Harry O. Finklea
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
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Finklea HO. Consequences of a potential-dependent transfer coefficient in ac voltammetry and in coupled electron–proton transfer for attached redox couples. J Electroanal Chem (Lausanne) 2001. [DOI: 10.1016/s0022-0728(00)00399-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Brevnov DA, Finklea HO. Second harmonic ac voltammetry study of a fast faradaic process in the presence of the uncompensated resistance. J Electroanal Chem (Lausanne) 2000. [DOI: 10.1016/s0022-0728(00)00204-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Affiliation(s)
- Michael R. Jarrett
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Harry O. Finklea
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
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Finklea HO, Phillippi MA, Lompert E, Grate JW. Highly Sorbent Films Derived from Ni(SCN)2(4-picoline)4 for the Detection of Chlorinated and Aromatic Hydrocarbons with Quartz Crystal Microbalance Sensors. Anal Chem 1998; 70:1268-76. [PMID: 21644723 DOI: 10.1021/ac970652e] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Harry O. Finklea
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Mark A. Phillippi
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Elisabeth Lompert
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Jay W. Grate
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352
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Finklea HO, Liu L, Ravenscroft MS, Punturi S. Multiple Electron Tunneling Paths across Self-Assembled Monolayers of Alkanethiols with Attached Ruthenium(II/III) Redox Centers. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp962831q] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Harry O. Finklea
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | - Luna Liu
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
| | | | - Sesto Punturi
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506-6045
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Finklea HO, Hanshew DD. Preparation and reversible behavior of organized thiol monolayers with attached pentaminepyridineruthenium redox centers. J Electroanal Chem (Lausanne) 1993. [DOI: 10.1016/0022-0728(93)80098-3] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Sullivan B, Abruna H, Finklea HO, Salmon DJ, Nagle JK, Meyer TJ, Sprintschnik H. Multiple emissions from charge transfer excited states of ruthenium(II)—polypyridine complexes. Chem Phys Lett 1978. [DOI: 10.1016/0009-2614(78)85059-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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