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Tadashi Watanabe - One of the best experts on this subject based on the ideXlab platform.
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spectroelectrochemical determination of the redox potentials of pheophytin a and primary quinone q a in photosystem ii from thermosynechococcus elongatus
2013Co-Authors: Yuki Kato, Tadao Shibamoto, Miwa Sugiura, Tadashi WatanabeAbstract:Thin-layer cell Spectroelectrochemistry was applied for the first time to measure the redox potentials of pheophytin (Phe) a and the primary quinone QA in photosystem (PS) II core complexes from a thermophilic cyanobacterium Thermosynechococcus elongatus. The determined potentials for oxygen-evolving PS II from a T. elongatus wild type strain were −522 ± 3 mV and −140 ± 2 mV for Phe a and QA, respectively. Based on the determined values together with kinetic analytical data in literature, a renewed diagram is proposed for the energetics in PS II, and further, modification of the redox properties for acclimation to cultivate conditions is also discussed.
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species dependence of the redox potential of the primary quinone electron acceptor qa in photosystem ii verified by Spectroelectrochemistry
FEBS Letters, 2010Co-Authors: Tadao Shibamoto, Yuki Kato, Ryo Nagao, Takuya Yamazaki, Tatsuya Tomo, Tadashi WatanabeAbstract:Abstract The redox potentials Em(QA/ Q A − ) of the primary quinone electron acceptor QA in oxygen-evolving photosystem II complexes of three species were determined by Spectroelectrochemistry. The Em(QA/ Q A − ) values were experimentally found to be −162 ± 3 mV for a higher plant spinach, −171 ± 3 mV for a green alga Chlamydomonas reinhardtii and −104 ± 4 mV vs. SHE for a red alga Cyanidioschyzon merolae. On the basis of possible deviations for the experimental values, as estimated to differ by 9–29 mV from each true value, plausible causes for such remarkable species-dependence of Em(QA/ Q A − ) are discussed, mainly by invoking the effects of extrinsic subunits on the delicate structural environment around QA.
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redox potential of the primary plastoquinone electron acceptor qa in photosystem ii from thermosynechococcus elongatus determined by Spectroelectrochemistry
Biochemistry, 2009Co-Authors: Tadao Shibamoto, Miwa Sugiura, Yuki Kato, Tadashi WatanabeAbstract:The redox potential of the primary plastoquinone electron acceptor QA, Em(QA/QA−), in an oxygen-evolving photosystem (PS) II complex from a thermophilic cyanobacterium Thermosynechococcus elongatus was determined to be −140 ± 2 mV vs. SHE by thin-layer cell Spectroelectrochemistry for the first time. The Em(QA/QA−) value obtained here together with the recently determined redox potential of pheophytin (Phe) a [Kato et al. (2009) Proc. Natl. Acad. Sci. U.S.A. 106, 17365−17370] yields −330 to −370 mV for the free energy change by electron transfer from Phe a− to QA and provides a renewed picture for the energetics on the electron acceptor side in PS II.
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Spectroelectrochemistry of cytochrome b559 in the d1 d2 cyt b559 complex from spinach
FEBS Letters, 2008Co-Authors: Tadao Shibamoto, Yuki Kato, Tadashi WatanabeAbstract:Abstract The redox potential of cytochrome b559 (Cyt b559) in the D1–D2–Cyt b559 complex from spinach has been determined to be +90 ± 2 mV vs. SHE at pH 6.0, by thin-layer cell Spectroelectrochemistry for the first time. The redox potential, corresponding uniquely to the so-called “low-potential form”, exhibited a sigmoidal pH-dependence from pH 4.0 to 9.0, ranging from +115 to +50 mV. An analysis of the pH-dependence based on model equations suggests that two histidine residues coordinating to the heme iron in the protein subunits may exert electrostatic influence on the redox potential of Cyt b559.
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Spectroelectrochemistry of p700 in native photosystem i particles and diethyl ether treated thylakoid membranes from spinach and thermosynechococcus elongatus
FEBS Letters, 2008Co-Authors: Yanrong Zhang, Yuki Kato, Akimasa Nakamura, Yoshinori Kuroiwa, Tadashi WatanabeAbstract:The redox potentials (E � 0 ) of P700 in intact and diethyl ether-treated thylakoid membranes as well as native pho- tosystem (PS) I particles from spinach and Thermosynechococ- cus elongatus have been measured by a Spectroelectrochemistry with an error range of ±2-3 mV. Stepwise removal of antenna pigments by ether treatment caused distinct shifts of the E � 0 va- lue with increasing degree of water saturation in ether; negatively from +471 to +428 mV for spinach, but positively from +423 to +436 mV for T. elongatus. Such a contrasting behavior is dis- cussed by invoking the mode of action of ether on the microenvi- ronments around P700. 2008 Federation of European Biochemical Societies. Pub- lished by Elsevier B.V. All rights reserved.
Lotha Dunsch - One of the best experts on this subject based on the ideXlab platform.
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unraveling the electron spin resonance pattern of nonsymmetric radicals with 30 fluorine atoms electron spin resonance and vis near infrared Spectroelectrochemistry of the anion radicals and dianions of c60 cf3 2n 2n 2 10 derivatives and density func
Journal of the American Chemical Society, 2010Co-Authors: Alexey A Popov, Iva E Kareev, Natalia Shustova, Steve H Strauss, Olga V Oltalina, Lotha DunschAbstract:The charged states of C(60)(CF(3))(2n) (2n = 2-10) derivatives have been studied by electron spin resonance (ESR) and vis-near-infrared (NIR) Spectroelectrochemistry. The anion radicals and diamagnetic dianions were furthermore described by theoretical calculations. The ESR spectra of anion radicals exhibit complex patterns due to multiple CF(3) groups. Their interpretation is accomplished by DFT calculations with B3LYP functional. It is shown that calculations provide reliable results when the extended aug-cc-pCVTZ basis set is used for fluorine atoms; however, specially tailored basis sets such as EPR-III also give very similar results with only a fraction of the computational cost. Absorption spectra of the anions exhibit NIR absorption bands, whose assignment is provided by time-dependent DFT calculations.
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in situ nmr Spectroelectrochemistry of higher sensitivity by large scale electrodes
Analytical Chemistry, 2009Co-Authors: Sabrina Klod, Frank Ziegs, Lotha DunschAbstract:The combination of NMR spectroscopy and electrochemistry provides an in situ method to measure structural changes of the redox components in an electrochemical reaction by proton NMR experiments. As the use of metal thin film radio frequency (RF) transparent electrodes in NMR spectroelectrochemical studies is limited by layer thickness and electrodes size, we present a new spectroelectrochemical NMR cell design consisting of nearly metal free symmetrically arranged large scale carbon fiber electrodes. Due to the advantages of modern NMR spectroscopy, a cell rotation is not necessary for high resolution measurements. This makes the presented cell for in situ spectroelectrochemical NMR measurements easy to prepare. The cell design is universal for a large variety of NMR spectrometers and frequencies used for detection of different nuclei. The feasibility of this new in situ NMR spectroelectrochemical cell is demonstrated in a detailed study of the electrochemical behavior of p-benzoquinone in different aque...
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Spectroelectrochemistry of carbon nanostructures
ChemPhysChem, 2007Co-Authors: Ladislav Kava, Lotha DunschAbstract:This review is focused on charge-transfer reactions at carbon nanotubes and fullerenes. The Spectroelectrochemistry of fullerenes deals with the spin states of fullerenes, the role of mono-anions and the reactivity of higher charged states in C60. The optical (Vis–NIR) Spectroelectrochemistry of single-walled carbon nanotubes (SWNTs) follows changes in the allowed optical transitions among the Van Hove singularities. The Raman Spectroelectrochemistry of SWNT benefits from strong resonance enhancement of the Raman scattering. Here, both semiconducting and metallic SWNTs are analyzed using the radial breathing mode (RBM) and G-modes as well as the second order (D, G′) and intermediate frequency modes. Raman Spectroelectrochemistry of SWNT allows the addressing of index-identified tubes and even single isolated nanotubes. Optical and Raman Spectroelectrochemistry of fullerene peapods, C60@SWNT and C70@SWNT indicates effective shielding of the intratubular fullerene (peas). The most striking effect in the Spectroelectrochemistry of peapods is the so-called “anodic Raman enhancement” of intratubular C60. Double-walled carbon nanotubes (DWNTs) give a specific spectroscopic response in Vis–NIR Spectroelectrochemistry for the inner and the outer tube. They are better distinguishable by Raman Spectroelectrochemistry which allows a precise tracing of the specific doping response of outer/inner tubes.
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ionic liquid for in situ vis nir and raman Spectroelectrochemistry doping of carbon nanostructures
ChemPhysChem, 2003Co-Authors: Ladislav Kava, Lotha DunschAbstract:1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) is an advantageous electrolyte for the study of charge-transfer reactions at single-walled carbon nanotubes (SWCNTs) and fullerene peapods (C60@SWCNT). Compared to traditional electrolyte solutions, this medium offers a broader window of electrochemical potentials to be applied, and favorable optical properties for in situ Vis/NIR and Raman Spectroelectrochemistry of nano-carbon species. The electrochemistry of both nanotubes and peapods is dominated by their capacitive double-layer charging. Vis/NIR Spectroelectrochemistry confirms the charging-induced bleaching of transitions between Van Hove singularities. At high positive potentials, new optical transitions were activated in partly filled valence band. The bleaching of optical transitions is mirrored by the quenching of resonance Raman scattering in the region of tube-related modes. The Raman frequency of the tangential displacement mode of SWCNT shifts to blue upon both anodic and cathodic charging in the ionic liquid. The Raman modes of intratubular C60 exhibit a considerable intensity increase upon anodic doping of peapods.
Lothar Dunsch - One of the best experts on this subject based on the ideXlab platform.
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structure dependence of charged states in linear polyaniline as studied by in situ atr ftir Spectroelectrochemistry
Journal of Physical Chemistry B, 2012Co-Authors: Andrea Kellenberger, Evgenia Dmitrieva, Lothar DunschAbstract:The electrochemical doping of emeraldine salt and emeraldine bases with different weight average molecular weights was studied by in situ Fourier transform infrared (FTIR) Spectroelectrochemistry using attenuated total reflection (ATR) technique. The formation and stabilization of charge carriers in polyaniline during p-doping was followed in dependence of the chain branching. The potential dependence of the IR bands during the oxidation of the polymer clearly demonstrates the formation of the different charged polymer structures (π-dimers, polarons, and bipolarons). It is shown that IR bands usually attributed to a semiquinoid polaron lattice correspond in fact to doubly charged species, π-dimers, which are face-to-face complexes of two polarons. Bands corresponding exclusively to polarons have been identified at 1266, 1033, and 1010 cm–1, suggesting that polarons are predominantly stabilized on the linear segments near the polymer branches by phenazine.
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Recent Advances in in situ multi-Spectroelectrochemistry
Journal of Solid State Electrochemistry, 2011Co-Authors: Lothar DunschAbstract:To consider the past, present and future of in situ Spectroelectrochemistry, a review on the recent state of modern Spectroelectrochemistry and trends in the development of spectroelectrochemcial techniques is presented for the combined application of different in situ spectroelectrochemcial methods like ESR Spectroelectrochemistry, NMR Spectroelectrochemistry, Raman Spectroelectrochemistry or IR Spectroelectrochemistry to electrode systems. Starting with a discussion of the first steps in Spectroelectrochemistry in the past, the main part of this review is focused on the advantages of the combined application of spectroelectrochemical techniques in the analysis of electrode reactions. The spectroelectrochemical methods are demonstrated to be successful in electrode reactions both for solid structures like polymers or carbon nanotubes and for molecular structures like fullerenes and oligothiophenes. The final outlook is attributed to future developments in Spectroelectrochemistry.
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the reaction mechanism of p toluenediamine anodic oxidation an in situ esr uv vis nir spectroelectrochemical study
ChemPhysChem, 2007Co-Authors: Aurelie Goux, Dominic Pratt, Lothar DunschAbstract:In situ ESR-UV/Vis Spectroelectrochemistry is applied to obtain new insights into the intermediates and reaction products of the anodic oxidation of p-toluenediamine in aqueous solution at different pH values. A strong pH dependence of the stability of the cation radical is found. While the absence of a stable radical was proved by ESR spectroscopy at pH 2 and 10, this radical is detected at medium pH values and assigned to the semiquinonediimine structure. The UV/Vis absorption of the radical is observed at these pH values as well. The p-toluenediimine intermediate and the trimeric reaction product were followed during the electrode reaction by UV/Vis spectroscopy at all pH values.
William R Heinema - One of the best experts on this subject based on the ideXlab platform.
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optically transparent carbon nanotube film electrode for thin layer Spectroelectrochemistry
Analytical Chemistry, 2015Co-Authors: Tingting Wang, Daoli Zhao, Noe T Alvarez, Vesseli Shanov, William R HeinemaAbstract:Carbon nanotube (CNT) film was evaluated as an optically transparent electrode (OTE) for thin layer Spectroelectrochemistry. Chemically inert CNT arrays were synthesized by chemical vapor deposition (CVD) using thin films of Fe and Co as catalysts. Vertically aligned CNT arrays were drawn onto a quartz slide to form CNT films that constituted the OTE. Adequate conductivity and transparency make this material a good OTE for Spectroelectrochemistry. These properties could be varied by the number of layers of CNTs used to form the OTE. Detection in the UV/near UV region down to 200 nm can be achieved using these transparent CNT films on quartz. The OTE was characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, UV-visible spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and thin layer Spectroelectrochemistry. Ferricyanide, tris(2,2'-bipyridine) ruthenium(II) chloride, and cytochrome c were used as representative redox probes for thin layer Spectroelectrochemistry using the CNT film OTE, and the results correlated well with their known properties. Direct electron transfer of cytochrome c was achieved on the CNT film electrode.
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electrochemistry and Spectroelectrochemistry of europium iii chloride in 3licl 2kcl from 643 to 1123 k
Analytical Chemistry, 2013Co-Authors: Cynthia A Schroll, Sayandev Chatterjee, Tatiana G Levitskaia, William R HeinemaAbstract:The electrochemical and spectroelectrochemical behavior of europium(III) chloride in a molten salt eutectic, 3LiCl–2KCl, over a temperature range of 643–1123 K using differential pulse voltammetry, cyclic voltammetry, potential step chronoabsorptometry, and thin-layer Spectroelectrochemistry is reported. The electrochemical reaction was determined to be the one-electron reduction of Eu3+ to Eu2+ at all temperatures. The redox potential of Eu3+/2+ shifts to more positive potentials, and the diffusion coefficient for Eu3+ increases as temperature increases. The results for the number of electrons transferred, redox potential, and diffusion coefficient are in good agreement between the electrochemical and spectroelectrochemical techniques. This research extends our ability to develop a spectroelectrochemical sensor for lanthanides and actinides into molten salt media.
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semi infinite linear diffusion Spectroelectrochemistry on an aqueous micro drop
Analytical Chemistry, 2011Co-Authors: Cynthia A Schroll, Sayandev Chatterjee, William R HeinemaAbstract:We report a technique for conducting semi-infinite diffusion Spectroelectrochemistry on an aqueous micro-drop as an easy and economic way of investigating spectroelectrochemical behavior of redox active compounds and correlating spectroscopic properties with thermodynamic potentials on a small scale. The chemical systems used to demonstrate the aqueous micro-drop technique were an absorbance based ionic probe [Fe(CN)6]3–/4– and an emission based ionic probe [Re(dmpe)3]2+/+. These chemical systems in a micro-drop were evaluated using cyclic voltammetry and UV–visible absorbance and luminescence spectroscopies.
Alvaro Colina - One of the best experts on this subject based on the ideXlab platform.
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quantitative raman Spectroelectrochemistry using silver screen printed electrodes
Electrochimica Acta, 2018Co-Authors: Daniel Martinyerga, Aranzazu Heras, Alvaro Colina, A Perezjunquera, Maria Begona Gonzalezgarcia, Jua V Peralesrondo, David Hernandezsantos, Pablo FanjulboladoAbstract:Abstract Surface enhanced Raman scattering (SERS) is a powerful technique based on the intensification of the Raman signal because of the interaction of a molecule with a nanostructured metal surface. Electrochemically roughened silver has been widely used as SERS substrate in the qualitative detection of analytes at the ultra-trace level. However, its potential for quantitative analysis has not been widely exploited yet. In this work, the combination of time-resolved Raman Spectroelectrochemistry with silver screen-printed electrodes (SPE) is proposed as a novel methodology for the preparation of SERS substrates. The in situ activation of a SERS substrate is performed simultaneously with the analytical detection of a probe molecule, controlling the process related to the preparation of the substrate and performing the analytical measurement in real time. The results show the good performance of silver SPE as electrochemically-induced surface-enhanced Raman scattering substrates. Raman spectra were recorded at fairly low integration times (250 ms), obtaining useful spectroelectrochemical information of the processes occurring at the SPE surface with excellent time-resolution. By recording the microscopic surface images at different times during the experiment, we correlated the different data obtained: structural, optical and electrochemical. Finally, the in situ activation process was used to obtain a suitable in situ SERS signal for ferricyanide and tris(bipyridine)ruthenium (II) quantification. The detection of the analytes at concentrations of a few tens of nM was possible with a low integration time (2 s) and good precision, demonstrating the exceptional performance of the Raman spectroelectrochemical method and the possibility to use cost-effective screen-printed electrodes for applications where a high sensitivity is needed.
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direct determination of ascorbic acid in a grapefruit paving the way for in vivo Spectroelectrochemistry
Analytical Chemistry, 2017Co-Authors: Jesus Garozruiz, Aranzazu Heras, Alvaro ColinaAbstract:The study of real samples is more complicated than the study of other systems. However, the inherent advantages of UV–vis absorption Spectroelectrochemistry should overcome some difficulties related to direct measurements in complex matrices. For this reason, a singular Spectroelectrochemistry device has been fabricated and validated. The novel cell is based on single-walled carbon nanotubes, which are filtered and subsequently press-transferred on a polyethylene terephthalate support using a stencil with a custom design. With this new methodology, working, counter, and reference electrodes are completely flat on the surface, where two optical fibers are fixed in a long optical path length configuration. To demonstrate the usefulness of this device and the power of Spectroelectrochemistry techniques to solve problems of the current world, this device is used to quantitatively detect the concentration of ascorbic acid in a complex matrix such as a fruit, directly, without any previous sample pretreatment. ...
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development of a novel bidimensional Spectroelectrochemistry cell using transfer single walled carbon nanotubes films as optically transparent electrodes
Analytical Chemistry, 2015Co-Authors: Jesus Garozruiz, Aranzazu Heras, Susana Palmero, Alvaro ColinaAbstract:A really easy method to transfer commercial single-walled carbon nanotubes (SWCNTs) to different substrates is proposed. In this paper, a homogeneous transference of SWCNTs films to nonconductor and transparent supports, such as polyethylene terephthalate, glass, and quartz, and to conductor supports, such as indium tin oxide, aluminum, highly ordered pyrolytic graphite, and glassy carbon, was achieved using a very fast, reproducible, and clean methodology. In order to test these transferences, SWCNTs films transferred on quartz were used as working optically UV–vis transparent electrodes due to their optimal electrical and optical properties. A new easy-to-use, homemade optical fiber based cell for bidimensional Spectroelectrochemistry was developed, offering the possibility to measure in normal and parallel configuration. The cell was tested with ferrocenemethanol, a compound widely used in electrochemistry but scarcely studied by Spectroelectrochemistry, covering the UV–vis spectral region.
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Spectroelectrochemistry at screen printed electrodes determination of dopamine
Analytical Chemistry, 2012Co-Authors: Noelia Gonzalezdieguez, Jesus Lopezpalacios, Alvaro Colina, Aranzazu HerasAbstract:A new device to perform spectroelectrochemical measurements in the UV/visible spectral region using screen-printed electrodes has been developed. Neurotransmitter dopamine has been selected as a proof of concept of the capabilities of the new device. The results obtained have allowed us both to study the oxidation mechanism of dopamine and to carry out the spectroelectrochemical detection of this neurotransmitter. Differences in dopamine oxidation mechanism have been observed depending on the initial concentration. Thus, dopamine concentrations lower than 10–3 M led to a higher generation of dopaminochrome and its derivatives with a band centered at 305 nm, which was the best wavelength to determine dopamine spectrophotometrically at these concentrations. However, if dopamine concentration is higher than 10–3 M, dopaminoquinone is stable enough to use its maximum of absorbance, 395 nm, to detect this neurotransmitter. Dopamine concentration can also be calculated from the electrochemical data in spectroel...
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flexible optically transparent single walled carbon nanotube electrodes for uv vis absorption Spectroelectrochemistry
Electrochemistry Communications, 2009Co-Authors: Aranzazu Heras, Alvaro Colina, Jesus Lopezpalacios, Antti Kaskela, Albe G Nasibuli, Virginia Ruiz, Esko I KauppineAbstract:Abstract We present a simple and reproducible method to produce single-walled carbon nanotube (SWCNT) optically transparent electrodes (OTEs) for optical transmission Spectroelectrochemistry on flexible and insulating Polyethylene terephthalate (PET) supports. SWCNTs grown by aerosol chemical vapor deposition (CVD) and collected directly from the gas phase on filters were transferred to PET substrates by simple pressing the filter against PET. Despite their high transparency (up to 92% transmittance at 550 nm), the resulting SWCNT/PET/OTEs exhibited excellent electrochemical properties for a series of redox couples covering a wide potential window. For low density SWCNT networks, the electroactive surface area calculated from the voltammetric response represents roughly the whole surface coverage of SWCNTs as determined by FESEM. Highly transparent SWCNT/PET/OTEs also showed very good performance for Ru ( bipy ) 3 3 + / 2 + Spectroelectrochemistry, enabling an accurate estimation of characteristic electrochemical parameters for this redox couple.
