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Ghithan JH, Moreno M, Keynton RS, O'Toole MG, Mendes SB. Adsorption Properties and Electron-transfer Rates of a Redox Probe at Different Interfaces of an Immunoassay Assembled on an Electro-active Photonic Platform. ANAL SCI 2021; 37:1391-1399. [PMID: 33896878 DOI: 10.2116/analsci.21p010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Physical and chemical properties of a redox protein adsorbed to different interfaces of a multilayer immunoassay assembly were studied using a single-mode, electro-active, integrated optical waveguide (SM-EA-IOW) platform. For each interface of the immunoassay assembly (indium tin oxide, 3-aminopropyl triethoxysilane, recombinant protein G, antibody, and bovine serum albumin) the surface density, the adsorption kinetics, and the electron-transfer rate of bound species of the redox-active cytochrome c (Cyt-C) protein were accurately quantified at very low surface concentrations of redox species (from 0.4 to 4% of a full monolayer) using a highly sensitive optical impedance spectroscopy (OIS) technique based on measurements obtained with the SM-EA-IOW platform. The technique is shown here to provide quantitative insights into an important immunoassay assembly for characterization and understanding of the mechanisms of electron transfer rate, the affinity strength of molecular binding, and the associated bio-selectivity. Such methodology and acquired knowledge are crucial for the development of novel and advanced immuno-biosensors.
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Affiliation(s)
- Jafar H Ghithan
- Department of Physics and Astronomy, University of Louisville
| | - Monica Moreno
- Department of Bioengineering, University of Louisville
| | | | | | - Sergio B Mendes
- Department of Physics and Astronomy, University of Louisville
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2
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Zheng Y, Giordano AJ, Marder SR, Saavedra SS. Potential-Modulated Total Internal Reflection Fluorescence for Measurement of the Electron Transfer Kinetics of Submonolayers on Optically Transparent Electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6728-6735. [PMID: 32453577 DOI: 10.1021/acs.langmuir.0c00817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
An electroreflectance method to determine the electron transfer rate constant of a film of redox-active chromophores immobilized on an optically transparent electrode when the surface coverage of the film is very low (<0.1 monolayer) is described herein. The method, potential-modulated total internal reflection fluorescence (PM-TIRF) spectroscopy, is a fluorescence version of potential-modulated attenuated total reflection (PM-ATR) spectroscopy that is applicable when the immobilized chromophores are luminescent. The method was tested using perylene diimide (PDI) molecules functionalized with p-phenylene phosphonic acid (PA) moieties that bind strongly to indium-tin oxide (ITO). Conditions to prepare PDI-phenyl-PA films that exhibit absorbance and fluorescence spectra characteristic of monomeric (i.e., nonaggregated) molecules were identified; the electrochemical surface coverage was approximately 0.03 monolayer. The tilt angle of the long axis of the PDI molecular plane is 58° relative to the ITO surface normal, 25° greater than the tilt angle of aggregated PDI-phenyl-PA films, which have a surface coverage of approximately one monolayer. The more in-plane orientation of monomeric films is likely due to the absence of cofacial π-π interactions present in aggregated films and possibly a difference in PA-ITO binding modes. The electron transfer rate constant (ks,opt) of monomeric PDI-phenyl-PA films was determined using PM-TIRF and compared with PM-ATR results obtained for aggregated films. For PDI monomers, ks,opt = 3.8 × 103 s-1, which is about 3.7-fold less than ks,opt for aggregated films. The slower kinetics are attributed to the absence of electron self-exchange between monomeric PDI molecules. Differences in the electroactivity of the binding sites on the ITO electrode surface also may play a role. This is the first demonstration of PM-TIRF for determining electron transfer rate constants at an electrode/organic film interface.
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Affiliation(s)
- Yilong Zheng
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Anthony J Giordano
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Seth R Marder
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - S Scott Saavedra
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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3
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Ehamparam R, Oquendo LE, Liao MW, Brynnel AK, Ou KL, Armstrong NR, McGrath DV, Saavedra SS. Axially Bound Ruthenium Phthalocyanine Monolayers on Indium Tin Oxide: Structure, Energetics, and Charge Transfer Properties. ACS APPLIED MATERIALS & INTERFACES 2017; 9:29213-29223. [PMID: 28795562 DOI: 10.1021/acsami.7b07394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The efficiency of charge collection at the organic/transparent conducting oxide (TCO) interface in organic photovoltaic (OPV) devices affects overall device efficiency. Modifying the TCO with an electrochemically active molecule may enhance OPV efficiency by providing a charge-transfer pathway between the electrode and the organic active layer, and may also mitigate surface recombination. The synthesis and characterization of phosphonic acid-ruthenium phthalocyanine (RuPcPA) monolayer films on indium tin oxide (ITO), designed to facilitate charge harvesting at ITO electrodes, is presented in this work. The PA group was installed axially relative to the Pc plane so that upon deposition, RuPcPA molecules were preferentially aligned with the ITO surface plane. The tilt angle of 22° between the normal axes to the Pc plane and the ITO surface plane, measured by attenuated total reflectance (ATR) spectroscopy, is consistent with a predominately in-plane orientation. The effect of surface roughness on RuPcPA orientation was modeled, and a correlation was obtained between experimental and theoretical mean tilt angles. Based on electrochemical and spectroelectrochemical studies, RuPcPA monolayers are composed predominately of monomers. Electrochemical impedance spectroscopy (EIS) and potential modulated-ATR (PM-ATR) spectroscopy were used to characterize the electron-transfer (ET) kinetics of these monolayers. A rate constant of 4.0 × 103 s-1 was measured using EIS, consistent with a short tunneling distance between the chromophore and the electrode surface. Using PM-ATR, ks,opt values of 2.2 × 103 and 2.4 × 103 s-1 were measured using TE and TM polarized light, respectively; the similarity of these values is consistent with a narrow molecular orientation distribution and narrow range of tunneling distances. The ionization potential of RuPcPA-modified ITO was measured using ultraviolet photoelectron spectroscopy and the results indicate favorable energetics for hole collection at the RuPcPA/ITO interface, indicating that this type of TCO modification may be useful for enhancing charge collection efficiency in OPV devices.
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Affiliation(s)
- Ramanan Ehamparam
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Luis E Oquendo
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Michael W Liao
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Ambjorn K Brynnel
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Kai-Lin Ou
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Neal R Armstrong
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Dominic V McGrath
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - S Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
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ZHENG Y, SAAVEDRA SS. Characterization of Charge-Transfer Kinetics at Organic/Electrode Interfaces Using Potential-modulated Attenuated Total Reflectance (PM-ATR) Spectroscopy. ANAL SCI 2017; 33:427-433. [DOI: 10.2116/analsci.33.427] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yilong ZHENG
- Department of Chemistry & Biochemistry, University of Arizona
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5
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Zheng Y, Jradi FM, Parker TC, Barlow S, Marder SR, Saavedra SS. Influence of Molecular Aggregation on Electron Transfer at the Perylene Diimide/Indium-Tin Oxide Interface. ACS APPLIED MATERIALS & INTERFACES 2016; 8:34089-34097. [PMID: 27960436 DOI: 10.1021/acsami.6b10731] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Chemisorption of an organic monolayer to tune the surface properties of a transparent conductive oxide (TCO) electrode can improve the performance of organic electronic devices that rely on efficient charge transfer between an organic active layer and a TCO contact. Here, a series of perylene diimides (PDIs) was synthesized and used to study relationships between monolayer structure/properties and electron transfer kinetics at PDI-modified indium-tin oxide (ITO) electrodes. In these PDI molecules, one of the imide substituents is a benzene ring bearing a phosphonic acid (PA) and the other is a bulky aryl group that is twisted out of the plane of the PDI core. The size of the bulky aryl group and the substitution of the benzene ring bearing the PA were both varied, which altered the extent of aggregation when these molecules were absorbed as monolayer films (MLs) on ITO, as revealed by both attenuated total reflectance (ATR) and total internal reflection fluorescence spectra. Polarized ATR measurements indicate that, in these MLs, the long axis of the PDI core is tilted at an angle of 33-42° relative to the surface normal; the tilt angle increased as the degree of bulky substitution increased. Rate constants for electron transfer (ks,opt) between these redox-active modifiers and ITO were determined by potential-modulated ATR spectroscopy. As the degree of PDI aggregation was reduced, ks,opt declined, which is attributed to a reduction in the lateral electron self-exchange rate between adsorbed PDI molecules, as well as the heterogeneous conductivity of the ITO electrode surface. Photoelectrochemical measurements using a dissolved aluminum phthalocyanine as an electron donor showed that ITO modified with any of these PDIs is a more effective electron-collecting electrode than bare ITO.
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Affiliation(s)
- Yilong Zheng
- Department of Chemistry & Biochemistry, University of Arizona , Tucson, Arizona 85721-00041, United States
| | - Fadi M Jradi
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States
| | - Timothy C Parker
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States
| | - Stephen Barlow
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States
| | - Seth R Marder
- School of Chemistry & Biochemistry and the Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States
| | - S Scott Saavedra
- Department of Chemistry & Biochemistry, University of Arizona , Tucson, Arizona 85721-00041, United States
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Coelectrodeposition of Ternary Mn-Oxide/Polypyrrole Composites for ORR Electrocatalysts: A Study Based on Micro-X-ray Absorption Spectroscopy and X-ray Fluorescence Mapping. ENERGIES 2015. [DOI: 10.3390/en8088145] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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Agrisuelas J, Gabrielli C, García-Jareño J, Perrot H, Sel O, Vicente F. Electrochemically induced free solvent transfer in thin poly(3,4-ethylenedioxythiophene) films. Electrochim Acta 2015. [DOI: 10.1016/j.electacta.2015.02.133] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Wu LP, Zhang L, Lu LM, Duan XM, Xu JK, Nie T. Graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene): enhanced sensitivity for electrochemical determination of rutin and ascorbic acid. CHINESE JOURNAL OF POLYMER SCIENCE 2014. [DOI: 10.1007/s10118-014-1484-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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9
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Han X, Mendes SB. Optical impedance spectroscopy with single-mode electro-active-integrated optical waveguides. Anal Chem 2014; 86:1468-77. [PMID: 24417718 PMCID: PMC3983008 DOI: 10.1021/ac4030736] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An optical impedance spectroscopy (OIS) technique based on a single-mode electro-active-integrated optical waveguide (EA-IOW) was developed to investigate electron-transfer processes of redox adsorbates. A highly sensitive single-mode EA-IOW device was used to optically follow the time-dependent faradaic current originated from a submonolayer of cytochrome c undergoing redox exchanges driven by a harmonic modulation of the electric potential at several dc bias potentials and at several frequencies. To properly retrieve the faradaic current density from the ac-modulated optical signal, we introduce here a mathematical formalism that (i) accounts for intrinsic changes that invariably occur in the optical baseline of the EA-IOW device during potential modulation and (ii) provides accurate results for the electro-chemical parameters. We are able to optically reconstruct the faradaic current density profile against the dc bias potential in the working electrode, identify the formal potential, and determine the energy-width of the electron-transfer process. In addition, by combining the optically reconstructed faradaic signal with simple electrical measurements of impedance across the whole electrochemical cell and the capacitance of the electric double-layer, we are able to determine the time-constant connected to the redox reaction of the adsorbed protein assembly. For cytochrome c directly immobilized onto the indium tin oxide (ITO) surface, we measured a reaction rate constant of 26.5 s(-1). Finally, we calculate the charge-transfer resistance and pseudocapacitance associated with the electron-transfer process and show that the frequency dependence of the redox reaction of the protein submonolayer follows as expected the electrical equivalent of an RC-series admittance diagram. Above all, we show here that OIS with single-mode EA-IOW's provide strong analytical signals that can be readily monitored even for small surface-densities of species involved in the redox process (e.g., fmol/cm(2), 0.1% of a full protein monolayer). This experimental approach, when combined with the analytical formalism described here, brings additional sensitivity, accuracy, and simplicity to electro-chemical analysis and is expected to become a useful tool in investigations of redox processes.
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Affiliation(s)
- Xue Han
- Department of Physics and Astronomy, University of Louisville , Louisville, Kentucky 40292, United States
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10
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Wu L, Lu L, Zhang L, Xu J, Zhang K, Wen Y, Duan X, Yang F. Electrochemical Determination of the Anticancer Herbal Drug Shikonin at a Nanostructured Poly(hydroxymethylated-3,4-ethylenedioxythiophene) Modified Electrode. ELECTROANAL 2013. [DOI: 10.1002/elan.201300247] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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11
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Yu W, Chen J, Fu Y, Xu J, Nie G. Electrochromic property of a copolymer based on 5-cyanoindole and 3,4-ethylenedioxythiophene and its application in electrochromic devices. J Electroanal Chem (Lausanne) 2013. [DOI: 10.1016/j.jelechem.2013.04.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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12
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Electrosynthesis and characterization of poly(hydroxy-methylated-3,4-ethylenedioxythiophene) film in aqueous micellar solution and its biosensing application. CHINESE JOURNAL OF POLYMER SCIENCE 2012. [DOI: 10.1007/s10118-012-1195-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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13
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Lin HC, Polaske NW, Oquendo LE, Gliboff M, Knesting KM, Nordlund D, Ginger DS, Ratcliff EL, Beam BM, Armstrong NR, McGrath DV, Saavedra SS. Electron-Transfer Processes in Zinc Phthalocyanine-Phosphonic Acid Monolayers on ITO: Characterization of Orientation and Charge-Transfer Kinetics by Waveguide Spectroelectrochemistry. J Phys Chem Lett 2012; 3:1154-1158. [PMID: 26288050 DOI: 10.1021/jz3002426] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Using a monolayer of zinc phthalocyanine (ZnPcPA) tethered to indium tin oxide (ITO) as a model for the donor/transparent conducting oxide (TCO) interface in organic photovoltaics (OPVs), we demonstrate the relationship between molecular orientation and charge-transfer rates using spectroscopic, electrochemical, and spectroelectrochemical methods. Both monomeric and aggregated forms of the phthalocyanine (Pc) are observed in ZnPcPA monolayers. Potential-modulated attenuated total reflectance (PM-ATR) measurements show that the monomeric subpopulation undergoes oxidation/reduction with ks,app = 2 × 10(2) s(-1), independent of Pc orientation. For the aggregated ZnPcPA, faster orientation-dependent charge-transfer rates are observed. For in-plane-oriented Pc aggregates, ks,app = 2 × 10(3) s(-1), whereas for upright Pc aggregates, ks,app = 7 × 10(2) s(-1). The rates for the aggregates are comparable to those required for redox-active interlayer films at the hole-collection contact in organic solar cells.
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Affiliation(s)
- Hsiao-Chu Lin
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Nathan W Polaske
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Luis E Oquendo
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | | | | | - Dennis Nordlund
- #Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | | | - Erin L Ratcliff
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Brooke M Beam
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Neal R Armstrong
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Dominic V McGrath
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - S Scott Saavedra
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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14
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Surface Intiated Atom Transfer Radical Polymerizations from Indium Tin Oxide Electrodes: Electrochemistry of Polymer Brushes. ACTA ACUST UNITED AC 2012. [DOI: 10.1021/bk-2012-1101.ch013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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15
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Poly(3,4-ethylenedioxythiophene methanol)/ascorbate oxidase/nafion-single-walled carbon nanotubes biosensor for voltammetric detection of Vitamin C. CHINESE JOURNAL OF POLYMER SCIENCE 2012. [DOI: 10.1007/s10118-012-1140-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Wang X, Bernard M, Deslouis C, Joiret S, Rousseau P. A new transfer function in electrochemistry: Dynamic coupling between Raman spectroscopy and electrochemical impedance spectroscopy. Electrochim Acta 2010. [DOI: 10.1016/j.electacta.2009.11.079] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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17
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Kim BY, Ratcliff EL, Armstrong NR, Kowalewski T, Pyun J. Ferrocene functional polymer brushes on indium tin oxide via surface-initiated atom transfer radical polymerization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:2083-2092. [PMID: 19968255 DOI: 10.1021/la902590u] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The synthesis and electrochemical characterization of ferrocene functional polymethacrylate brushes on indium tin oxide (ITO) electrodes using surface-initiated atom transfer radical polymerization (SI-ATRP) is reported. SI-ATRP of ferrocene-containing methacrylate (FcMA) monomers from a phosphonic acid initiator-modified ITO substrate yielded well-defined homo- and block (co)polymer brushes of varying molar mass (4,000 to 37,000 g/mol). Correlation of both electrochemical properties and brush thicknesses confirmed controlled SI-ATRP from modified ITO surfaces. The preparation of block copolymer brushes with varying sequences of FcMA segments was conducted to interrogate the effects of spacing from the ITO electrode surface on the electrochemical properties of a tethered electroactive film.
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Affiliation(s)
- Bo Yun Kim
- Department of Chemistry, University of Arizona, 1306 E. University Boulevard, Tucson, Arizona 85721, USA
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18
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Beaujuge PM, Reynolds JR. Color Control in π-Conjugated Organic Polymers for Use in Electrochromic Devices. Chem Rev 2010; 110:268-320. [DOI: 10.1021/cr900129a] [Citation(s) in RCA: 1408] [Impact Index Per Article: 100.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Pierre M. Beaujuge
- The George and Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science and Engineering, Department of Chemistry, University of Florida, Gainesville, Florida 32611
| | - John R. Reynolds
- The George and Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science and Engineering, Department of Chemistry, University of Florida, Gainesville, Florida 32611
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Deepa M, Bhandari S, Kant R. A comparison of charge transport behavior in functionalized and non-functionalized poly 3,4-(ethylenedioxythiophene) films. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2008.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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20
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Beam BM, Armstrong NR, Mendes SB. An electroactive fiber optic chip for spectroelectrochemical characterization of ultra-thin redox-active films. Analyst 2009; 134:454-9. [DOI: 10.1039/b814338b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Araci ZO, Runge AF, Doherty WJ, Saavedra SS. Correlating Molecular Orientation Distributions and Electrochemical Kinetics in Subpopulations of an Immobilized Protein Film. J Am Chem Soc 2008; 130:1572-3. [DOI: 10.1021/ja710156d] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zeynep Ozkan Araci
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - Anne F. Runge
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - Walter J. Doherty
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
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Marrikar FS, Brumbach M, Evans DH, Lebrón-Paler A, Pemberton JE, Wysocki RJ, Armstrong NR. Modification of indium-tin oxide electrodes with thiophene copolymer thin films: optimizing electron transfer to solution probe molecules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:1530-42. [PMID: 17241084 DOI: 10.1021/la061840f] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We describe the modification of indium-tin oxide (ITO) electrodes via the chemisorption and electropolymerization of 6-{2,3-dihydrothieno[3,4-b]-1.4-dioxyn-2-yl methoxy}hexanoic acid (EDOTCA) and the electrochemical co-polymerization of 3,4-ethylenedioxythiophene (EDOT) and EDOTCA to form ultrathin films that optimize electron-transfer rates to solution probe molecules. ITO electrodes were first activated using brief exposure to strong haloacids, to remove the top approximately 8 nm of the electrode surface, followed by immediate immersion into a 50:50 EDOT/EDOTCA co-monomer solution. Potential step electrodeposition for brief deposition times was used to grow copolymer films of thickness 10-100 nm. The composition of these copolymer films was characterized by solution depletion studies of the monomers and atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy (reflection-absorption infrared spectroscopy (RAIRS)) of the product films. The spectroscopic data suggest that the composition of the copolymer approaches 80% EDOTCA when electropolymerization occurs from concentrated (10 mM) solutions. AFM characterization shows that electrodeposited poly(EDOT)/poly(EDOTCA) (PEDOT/PEDOTCA) films are quite smooth, with texturing on the nanometer scale. RAIRS studies indicate that these films consist of a combination of EDOTCA units with noninteracting -COOH groups and adjacent hydrogen-bonded -COOH groups. The EDOTCA-containing polymer chains appear to grow as columnar clusters from specific regions, oriented nearly vertically to the substrate plane. As they grow, these columnar clusters overlap to form a nearly continuous redox active polymer film. ITO activation and formation of these copolymer films enhances the electroactive fraction of the electrode surface relative to a nonactivated, unmodified "blocked" ITO electrode. Outer-sphere solution redox probes (dimethylferrocene) give standard rate coefficients, kS > or = 0.4 cm.s-1, at 10 nm thick copolymer films of PEDOT/PEDOTCA, which is 3 orders of magnitude greater than that on the unmodified ITO surface and approaches the values for kS seen on clean gold surfaces.
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23
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Araci ZO, Runge AF, Doherty WJ, Saavedra SS. Potential Modulated Attenuated Total Reflectance Spectroscopy of Prussian Blue Films on ITO. Isr J Chem 2006. [DOI: 10.1560/ijc_46_3_249] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Carter C, Brumbach M, Donley C, Hreha RD, Marder SR, Domercq B, Yoo S, Kippelen B, Armstrong NR. Small Molecule Chemisorption on Indium−Tin Oxide Surfaces: Enhancing Probe Molecule Electron-Transfer Rates and the Performance of Organic Light-Emitting Diodes. J Phys Chem B 2006; 110:25191-202. [PMID: 17165963 DOI: 10.1021/jp064061g] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Indium-tin oxide (ITO) surfaces have been modified by chemisorption of carboxylic acid functionalized small molecules: ferrocene dicarboxylic acid (1), 3-thiophene acetic acid (2), and 6-{4-[{4'-[[4-(5-carboxy-pentyloxy)-phenyl]-(4-methoxy-phenyl)-amino]-biphenyl-4-yl}-(4-methoxy-phenyl)-amino]-phenoxy}-hexanoic acid (p-OMe)2-TPD-(C5-COOH)2) (3). Voltammetrically determined surface coverages of 1-3 increased in two stages, the first stage completing in minutes, the latter stage taking several hours. Electron-transfer rate coefficients, kS, for the probe molecule ferrocene in acetonitrile likewise increased in two stages with increasing surface coverages of 1, 2, and 3. Fourier transform infrared spectroscopy of In2O3 powders, exposed for long periods to ethanol solutions of each modifier, confirmed the formation of indium oxalate-like surface species. X-ray photoelectron spectroscopy of carboxy-terminated alkanethiol-modified gold surfaces, exposed to these same In2O3(powder)/small molecule modifier solutions, showed the capture of trace levels of indium as a result of the chemisorption of these small molecules, suggesting that slow etching of the ITO surface also occurs during the chemisorption event. Conventional aluminum quinolate/bis-triarylamine organic light-emitting diodes (OLEDs) created on ITO surfaces modified with 1, 2, and 3, with and without an overlayer of PEDOT:PSS (a poly(thiophene)/poly(stryenesulfonate) ITO modifier), showed leakage currents lowered by several orders of magnitude and an increase in OLED device efficiency.
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Affiliation(s)
- Chet Carter
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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Ozkan Z, Runge A, Doherty W, Saavedra S. Potential Modulated Attenuated Total Reflectance Spectroscopy of Prussian Blue Films on ITO. Isr J Chem 2006. [DOI: 10.1560/j311-g807-47t3-2318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Doherty WJ, Wysocki RJ, Armstrong NR, Saavedra SS. Electrochemical Copolymerization and Spectroelectrochemical Characterization of 3,4-Ethylenedioxythiophene and 3,4-Ethylenedioxythiophene−Methanol Copolymers on Indium−Tin Oxide. Macromolecules 2006. [DOI: 10.1021/ma052322z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Walter J. Doherty
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Ronald J. Wysocki
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Neal R. Armstrong
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
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