bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Insights into the Formic Acid Oxidation Mechanism on Platinum Electrodes
Authors: Herrero Enrique , Perales Juan V. , Feliu Juan 
Published: February 2020

In the formic acid oxidation reaction only two electrons are exchanged. Despite the apparent simplicity of this reaction, the oxidation mechanism is still a subject of debate. The major issue is the role of formic acid, solution formate and adsorbed formate in the oxidation mechanism. In order to shed light into this issue, formic acid oxidation on platinum single crystal electrodes has been studied to determine the effects of pH and specific anion adsorption in the oxidation mechanism. It has been found that the solution pH has an important effect in the oxidation currents. As has been already observed for polycrystalline electrodes [1], currents are proportional to the solution pH. Thus, it can be proposed that the active species in the oxidation mechanism is formate. On the other hand, the specific adsorption of sulfate on the Pt(111) electrode has a catalytic effect on the oxidation since the onset potential is displaced towards more negative values. This unexpected result indicates that the adsorbed anions have an important role in the oxidation mechanism as DFT calculations suggest [2]. In order to get further insight into the oxidation mechanism, activation energies have been calculated, both for the route through the active intermediate and for the route through CO. The activation energy of the process diminishes in the presence of adsorbed sulfate, which confirms the active participation of the adsorbed anion in the oxidation mechanism. Using previous data obtained with fast voltammetry [3], an oxidation mechanism is proposed for the direct route. In this mechanism, the oxidation through the active intermediate route requires an adsorbed anion (formate or sulfate) and a free platinum site where a solution formate species can bond. The currents calculated with this mechanism are compared with the experimental currents. An excellent agreement is found between both results, which supports the validity of the proposed oxidation mechanism.

References

1. Joo J, Uchida T, Cuesta A, Koper MTM, Osawa M (2013) J Am Chem Soc 135:9991-9994
2. Wang H-F, Liu Z-P (2009) J Phys Chem C 113:17502-17508
3. Grozovski V, Vidal-Iglesias FJ, Herrero E, Feliu JM (2011) ChemPhysChem 12:1641-1644
Facet-Controlled Metal Alloy Electrocatalysts for Oxygen Reduction Reaction
Authors: Yang Hong 
Published: February 2020

Recent advancement of low-temperature proton-exchange membrane (PEM) fuel cell technology can be attributed in part to the rapid development of electrocatalysts for reduction of oxygen. Such electrocatalysts can now be prepared with very high level of precision in size, shape and composition to meet the increasingly stringent performance targets in activity and durability [1]. The new synthetic methods are based predominately on the solution phase approach where the control of reaction kinetics can be more precise than that for the impregnation method [2].
In this talk, I will present the recent progress on the design and synthesis of metal alloy nanostructures. I will discuss the approach to the preparation of facet-controlled Pt alloy nanoparticles based on the gas reducing agent in liquid solution (GRAILS) method [3-4] and how this method is used in the development of structurally tuneable electrocatalysts for reduction of oxygen. A range of plutonic shapes including {111} faceted octahedron, icosahedron and twin defect-regulated morphologies can now be made (see the TEM images). I will illustrate the relationship between size, composition, structure (including surface strain) and catalytic property (activity and stability) of these bimetallic and multimetallic nanostructured catalysts for oxygen reduction reaction (ORR) and present the likely venues for the scaled-up production.

References:
(1) Peng, Z. M.; Yang, H. Nano Today, 2009, 4, 143-164; Wu, J. B.; Yang, H. Acc. Chem. Res., 2013, 46, 1848-1857.
(2) You, H. J.; Yang, S. C.; Ding, B. J.; Yang, H. Chem. Soc. Rev., 2013, 42, 2880-2904.
(3) Wu, J. B.; Qi, L.; You, H. J.; Gross, A. Li, J. Yang, H. J. Am. Chem. Soc., 2012, 134, 11880-11883.
(4) Wu, J. B.; Gross, A.; Yang, H. Nano Lett.,
2011, 11, 798-802.
The Expression and Electroochemical Characterization of Fructose Dehydrogenase
Authors: Kawai Shota , Kitazumi Yuki , Shirai Osamu , Kano Kenji 
Published: February 2020

Redox enzymes and proteins are related to the many vital processes, such as tricarboxylic cycle and respiratory chain. There are only a limited number of redox enzymes and proteins that enable to couple enzyme reaction and electrode reaction without any mediators. In other words, they can transfer the electron to (or from) electrodes directly. This reaction is called direct electron transfer (DET)-type bioelectrocatalysis reaction. DET reaction has received considerable attention for construction of electrochemical applications, such as biosensors and biofuel cells. There must be several factors governing the DET reaction, but the details have not yet clearly elucidated.
D-Fructose dehydrogenase (FDH; EC 1.1.99.11) from Gluconobacter japonicus NCBR 3260 is a heterotrimeric membrane-bound enzyme. Subunits I and II have covalently bound flavin adenine dinucleotide (FAD) and three heme C moieties, respectively. FDH shows strict substrate specificity to D-fructose and is used in diagnosis and food analysis. FDH is one of the DET-type enzymes. FDH has high DET activity. DET reaction of FDH occurs at a large variety of electrodes. The FAD in subunit I is the catalytic site to accept electrons form the substrate, and the electrons are transferred to the electrode through the heme C in subunit II.
For the first step to explore the mechanisms of the DET reaction of FDH, we sequenced the genes encoding each subunit of the FDH complex from G. japonicus NBRC3260 and constructed an expression system to highly produce FDH in a G. oxydans strain. We also constructed derivatives modified in subunit I/III subcomplex (ΔcFDH) lacking of the heme C subunit. The recombinant FDH reacts with electrode directly. However, ΔcFDH catalyzes the oxidation of D-fructose with several artificial electron acceptors, but loses the DET ability. The formal potentials (E˚') of the three heme C moieties of FDH have been determined to be –10 ± 4, 60 ± 8 and 150 ± 4 mV (vs. Ag|AgCl|sat. KCl) at pH 5.0, while the onset potential of FDH-catalyzed DET-type bioelectrocatalytic wave is –100 mV. Judging from these results, we conclude that FDH communicates electrochemically with electrodes via the heme C.
Enzyme-Metal Oxide Composite As Catalysts for Enzymatic Oxygen Reduction
Authors: Zhou Yan , Umasankar Yogeswaran , Ramasamy Ramaraja P 
Published: February 2020

Laccase is widely used in enzymatic fuel cell as cathode catalyst. There has been a lot of work using carbon nanostructures as immobilization support for laccase to demonstrate bio-electrocatalytic activity towards oxygen reduction reaction.1,2,3 The metal oxide nanoparticles studied were TiO2, ZnO and SnO2. The immobilization of laccase on these metal oxide nanoparticles were achieved. The coupling agent was silane and the crosslinking agents were dithiobis[succinimidyl propionate] (DSP), 1,5-Difluoro-2,4-dinitrobenzene (DFDNB) and succinimidyl iodoacetate (SIA). Attenuated total resonance fourier transform infrared spectroscopy (ATR-FTIR) was performed on the nanocomposites and the results confirmed that laccase was attached on to the metal oxide nanoparticles through the molecular crosslinkers. The resulting laccase-metal oxide nanocomposites were deposited onto screen printed carbon electrode and tested for oxygen reduction electro-catalysis in an electrochemical cell using 0.2 M sodium acetate buffer as the electrolyte. The composite modified electrode showed an open circuit potential of 0.61V vs Ag/AgCl. Cyclic voltammograms showed a clear difference between unmodified and laccase modified TiO2 in the oxygen reduction region with an onset potential of 0.57 V. In comparison the laccase physisorbed onto TiO2without the molecular crosslinkers showed no obvious electrocatalytic activity. The work adds significant value to the biofuel cell community as it introduces a new class of material as enzymatic support for bio-electrochemical reactions.

Fig. 1: Schematic representation of Laccase immobilized onto metal oxide nanoparticles through molecular crosslinkers.

Fig. 2
: Cyclic voltammetry of crosslinked and physisorbed laccase on TiO2 nanoparticle electrodes in O2 saturated sodium acetate buffer electrolyte.

Acknowledgements:

The authors would like to thank University of Georgia for providing seed funds to carry out this research.

References:

1. Ramasamy, R. P.; Luckarift, H. R.; ivnitski, D. M.; Atanassov, P. B.; Johnson, G. R., High electrocatalytic activity of tethered multicopper oxidase- carbon nanotube conjugates. Chemical Communications
2010, 46 (33), 5977-6188.
2. Naga S. Parimi; Yogeswaran Umasankar; Plamen Atanassov; Ramasamy, R. P., Kinetic and Mechanistic Parameters of Laccase Catalyzed Direct Electrochemical Oxygen Reduction Reaction. ACS Catalysis
2012, 2, 38-44.
3. Umasankar, Y.; Brooks, D. B.; B., B.; Zhou, Z.; Ramasamy, R. P., Three dimensional carbon nanosheets as novel catalyst support for enzymatic bioelectrodes. Advanced Energy Materials
2013 (accepted paper).
From Twitching to Nanowires Toward a Holistic Understanding of Motility Structures and Extracellular Electron Transfer in Shewanella Oneidensis
Authors: Ista Linnea K , Cornejo Jose A , Babanova Sofia , Schuler Andrew J , Atanassov Plamen 
Published: February 2020

Extracellular electron transfer (EET) in dissimilatory metal reducing bacteria, such as Shewanella oneidensis and Geobacter spp., is thought to be mediated by nanowires composed of type IV pili encased in membrane-bound cytochromes. 1,2 Type IV pili are also required for EET competent biofilm formation in these organisms. 3 Although the necessity for the involvement of T4P in biofilm formation has been established, surface motility has not been observed in these organisms, 3,4 whereas it is required in other g-proteobacteria. 5

Using self-assembled monolayers (SAMs) of ω-substituted alkanethiolates on gold, we have recently demonstrated that twitching motility occurs in Shewanella oneidensis MR1 and that it is responsive to the chemistry of the substratum. In addition, using deletion mutants, we are eludicating the roles of the two classes of T4P present (PilA and Msh) in S. oneidensis in surface motility and their significance in biofilm formation. (Figure 1) We have found that while both types of pili are required for wild-type early biofilm formation, either pilus on its own is sufficient for twitching surface motility. We are also exploring the formation of nanowires and subsequent EET for this set of mutants.
In this presentation, we discuss the known and possible interrelationships between surface motility, nanowire production, biofilm formation and EET, including mechanisms for their molecular coordination. We predict that manipulation of engineerable parameters can modulate these cellular activities for better design of microbial biofuel cells.

References

(1) El-Naggar, M. Y.; Finkel, S. E. Scientist
2013, 27, 38.
(2) Lovley, D. R. Energy & Environmental Science
2011, 4, 4896.
(3) Saville, R. M.; Dieckmann, N.; Spormann, A. M. FEMS Microbiol Lett
2010, 308, 76.
(4)Thormann, K. M.; Saville, R. M.; Shukla, S.; Pelletier, D. A.; Spormann, A. M. J Bacteriol
2004, 186, 8096.
(5)O'Toole, G. A.; Kolter, R. Mol Microbiol
1998, 30, 295.

Acknowledgements

This work was supported through ARO grant W911NF-12-1-0208.
Sub-1 V Electrolyte-Gated Polymer Transistors with Ionic Liquid Electrolyte and High-Surface Area Carbon Gate Electrode
Authors: Soavi Francesca , Sayago Jonathan , Cicoira Fabio , Santato Clara 
Published: February 2020

Electrolyte-gated (EG) transistors permit to achieve current modulations of several orders of magnitude at relatively modest gate voltages, by exploiting the exceptionally high capacitance of electrical double layer forming at the electrolyte/transistor channel interface. Different doping mechanisms have been proposed to explain the gating process in EG transistors. For organic polymers, the common doping mechanism is faradic, depends on the channel electrical potential and the doping charge is about two orders of magnitude larger than for electrostatically doped non-porous materials. Moreover, organic channel and electrolyte have to be selected taking into account that channel modulation has to be performed by applying gate-source voltages (Vgs) which are compatible with the electrochemical stability window of the electrolyte. Ionic liquid electrolytes, for their exceptionally high chemical and electrochemical stability and good conductivity at room temperature are of interest as electrolyte gating media in EG transistor. The faradic nature of the polymer channel doping also requires the use of gate electrode materials that are non-limiting in terms of their capability to supply the charge required for channel modulation within the electrochemical stability window of the electrolyte.
We targeted the use of high surface area carbons as gate electrode materials because of their capability to electrostatically supply the charge required to dope organic polymer transistor channels, within narrow electrode potential excursion.
Here, we report on a new generation of low voltage EG transistors making use of a low-cost, high surface area gate electrode, an organic electronic polymer, like MEH-PPV (poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene), as the channel material and ionic liquid, like [EMIM][TFSI] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), as the electrolyte gating medium. Using such configuration, is it possible to apply Vgs biases lower than 1.0 V to achieve effective channel modulations (ON/OFF ratio larger than 103) and hole mobility of about 10-3 cm2V-1s-1.

Acknowledgement

This work was financially supported by NSERC (Discovery grants, CS and FC) and FQRNT (Nouveau Chercheur, CS). JS acknowledges financial support by CONACYT.

References

[1] J. Sayago, F. Soavi, F. Cicoira, C. Santato, Adv. Mater., submitted.
Photoluminescence Investigation of Fundamental Charge Transfer Processes in Stable Nitroxyl Radical-Containing Polymers
Authors: Hughes Barbara Katherine , Ferguson Andrew , Braunecker Wade A. , Gennett Thomas 
Published: February 2020

The electrochemical redox reactions of stable organic polymer materials with unpaired electrons is a relatively new and exciting area of battery research. Specifically, stable nitroxyl radical-containing polymers have displayed excellent characteristics as the cathode-active material and have presented themselves as low-cost and environmentally friendly alternative to the current Li-ion battery technologies. However, with the advancement of organic-radical battery technology there is a lack of fundamental understanding of the dynamics of charge transfer processes, electronic and ionic, within organic radical-containing polymers. In order to elucidate the mechanisms further, we have conducted an extensive photoluminescence investigation of the polymers in various oxidation states
Since nitroxyl radicals are known fluorescence quenchers, we probed the charge transport in this system by the incorporation of fluorescent perylene markers into the radical-containing polymer matrix. We have investigated the interplay between collisional and static quenching processes using steady-state and time-resolved photoluminescence quenching studies of perylene by TEMPO (2,2,6,6-tetramethylpiperidinyloxyl), radical-containing species. Quenching studies for these model systems, including both free TEMPO monomers and non cross-linked, solution-phase PTMA-nitroxy polymers, (poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) have allowed us to calculate optimal synthetic parameters for construction of polymer cathode systems. We have determined how such polymer properties as average chain length, spacing between pendant groups, proclivity for polymer folding, and solvent swelling affect both the mechanism of quenching as well as the efficiency of charge transfer. As a function of polymer length, we observe a change in quenching mechanism, while the density of radical moieties has significant affects on quenching/charge transfer efficiency. The quenching sphere of action and thus the optimal distance between radical moieties and fluorophores for the most efficient charge transfer has also been determined and will be discussed at length.
Standard Potential of Ion-Sensors
Authors: Lewenstam Andrzej 
Published: February 2020

The potentiometric measurement of ions belongs to the most frequently applied electroanalytical methods. It is owing to the need of routine determinations of the main blood electrolytes (Na+, K+, Cl-, and HCO3
-), pH and PCO2. Growing demand for improved reliability of the sensors response and manageable response time is associated with their fundamental properties characterized by sensitivity, selectivity, detection limit and standard potential [1]. The latter should be preferably stable over certain time, and in this way not to be a source of analytical error.
The interpretation of the standard (resp. formal) potential is often ignored owing to the application of internal electrode solution, i.e. symmetric ion-sensor systems. However, the present wave in ion-sensor technology typically utilizes all-solid-state sensor architecture, in which the internal liquid contact is substituted by a solid contact, with resulting assymetricion-sensors. This type of contact was first used for ion-selective electrodes with a solid-state (crystalline) membrane, and made by platinum, silver, carbon. More recently, conducting polymer as a solid-contact material for the ion-selective electrodes with plastic membranes was proposed [2]. Very recently the application of nanostructured materials was offered [3]. Beyond any doubt, the understanding of the reason(s) of standard potential stability of the asymmetric solid-contact ion-sensors is of a primary importance, but rarely undertaken.
Thermodynamic interpretation the standard potential of the asymmetric all-solid-state ion-selective sensors will be presented. This interpretation is related to the fundamental concepts metallic electrodes and all-solid-state electrodes presented by Trasatti [4] and Buck & Koebel [5], and extended by Lewenstam [6] for the solid contacts made of conducting polymers. The applicability of the interpretation for the whole family of all-solid-state ion-selective sensors will be discussed.

References

[1] A. Lewenstam, Clinical analysis of blood gases and electrolytes by ion-sensitive sensors, in: S. Alegret, A. Merkoci (eds.), Electrochemical Sensor Analysis (Comprehensive Analytical Chemistry vol. 49), Chapter 1, Elsevier, Amsterdam 2007.
[2] A.Cadogan, Z.Gao, A.Lewenstam, A.Ivaska and D.Diamond; Analytical Chemistry, 64 (1992) 2496; A. Lewenstam, in: G. Inzelt, A. Lewenstam, F. Scholz (Eds.), Handbook of Reference Electrodes, Springer, Heidelberg New York Dordrecht London, 2013, pp. 279-288.
[3] G.A. Crespo, S. Macho, F.X Ruis, Anal. Chem. 50 (2008) 1316-1322.
[4] R.P. Buck, V.R. Shepard, Anal. Chem. 46 (1974) 2097-2109; M. Koebel, Anal. Chem.,46 (1974) 1559–1563.
[5] A. De Battisi, S. Trasatti, 79 (1977) 251-258.
[6] A. Lewenstam, J. Bobacka, A. Ivaska, J. Electroanal. Chem., 368 (1994) 23-31.
Traceability of pH Measurements
Authors: Camoes Maria Filomena , Spitzer Petra 
Published: February 2020

The free acidity of an aqueous solution is usually expressed in terms of its pH, a measure of the hydrogen ions activity. Being the most often measured chemical parameter, pH values are meant to be used either in the assessment of other chemical species or in comparison exercises. The validity of conclusions requires that the values of pH measurements are linked through common references. Measurements are performed in pH meters submitted to prior calibration with reference pH buffers whose pH values have been established against conventionally assigned pH values of primary pH buffer standards. This chain of operations is supported on the quality associated with, namely, buffers, electrodes, procedures, calculations and model assumptions.
An overview will be given on recent fundamental and applied studies addressing these various issues, for the particular case of highly saline waters approaching the complex composition of seawater.
Electrochemical Sensors for Measurement of Glucose in Tiny Volumes of Tear Fluid
Authors: Meyerhoff Mark E. , Cha Kyoung-Ha , Qin Yu , Cohan Bruce C. , Balijepalli Anant , Jensen Gary C. 
Published: February 2020

Tear glucose measurements have been suggested as a potential non-invasive alternative to blood glucose monitoring for diabetic patients [1,2]. While previous work has demonstrated a correlation between blood and tear glucose values in humans using complex LC-MS and capillary electrophoresis methods, this correlation has not been thoroughly established and additional clinical studies with a much larger patient population are sorely needed. This requires the availability of a very simple device that can quantitate the levels of glucose in tiny volumes (1 uL or less) of human tear fluid at the point of testing. Further, given the low levels of glucose found in tear fluid (10-300 µM), compared to blood plasma (3-15 mM), this creates a challenge for the conventional electrochemical measurement technologies typically employed for blood glucose measurements.
In preliminary efforts toward achieving this goal, we utilized miniaturized needle type amperometric glucose enzyme electrodes that can be inserted into a microliter glass capillary tube to measure the levels of glucose in tear fluid obtained from anesthetized rabbits and proved that there was a reasonable correlation between blood and tear glucose levels [3,4]. However, the sensors employed in these first studies required 3 µL or more of tear fluid and the capillary tube was used to conveniently sample such volumes.
A more attractive approach for determining glucose in < 1 µL tear volumes from human subjects is to use commercial electrochemical blood glucometer test strips in association with a laboratory quality, high current sensitivity potentiostat. Of many commercial blood glucose test strips evaluated, only one device has been found to be capable of achieving the low detection limits (< 10 µM) required for human tear glucose measurements. Using such strips, calibration data in the range of 0-300 μM glucose yield excellent precision and good selectivity over potential redox species found in tears (e.g., ascorbic and uric acids). Multiple measurements of glucose in tear fluid obtained from normal (non-diabetic) human subjects using commercial strips in conjunction with a laboratory potentiostat yield fasting tear glucose concentrations for non-diabetics within the range of 20-160 µM, similar to the values found by others using more complex LC-MS methods [1]. This glucometer strip based method could greatly facilitate more in depth clinical studies with a large number of patients (both normal and diabetic), to determine definitively whether tear glucose and blood glucose levels correlate well enough to enable routine measurements in tear fluid to supplement blood glucose testing.

References

[1] Lane JD, et al. Curr. Eye Research 31 (2006), 895–901.
[2] Baca JT, et al. Clin. Chem. 53 (2007), 1370-1372.
[3] Yan Q, et al. Anal. Chem. 83 (2011), 8341-8346.
[4] Peng B, et al. Biosens. Bioelectron. (2013) 49, 204-209.