Artykuły w czasopismach: „Surface redox reduction”

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Hua, Chunxia, Shuliang Dou, Hongbo Xu, Shuai Hou, Hangchuan Zhang, Panpan Zhang, Yang Gan, Jiupeng Zhao i Yao Li. "A nanostructured Fc(COCH3)2film prepared using silica monolayer colloidal crystal templates and its electrochromic properties". Physical Chemistry Chemical Physics 19, nr 45 (2017): 30756–61. http://dx.doi.org/10.1039/c7cp05074g.

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Zhu, Yun Guang, Chuankun Jia, Jing Yang, Feng Pan, Qizhao Huang i Qing Wang. "Dual redox catalysts for oxygen reduction and evolution reactions: towards a redox flow Li–O2 battery". Chemical Communications 51, nr 46 (2015): 9451–54. http://dx.doi.org/10.1039/c5cc01616a.

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Bradley, Kieren, Kyriakos Giagloglou, Brian E. Hayden, Hugo Jungius i Chris Vian. "Reversible perovskite electrocatalysts for oxygen reduction/oxygen evolution". Chemical Science 10, nr 17 (2019): 4609–17. http://dx.doi.org/10.1039/c9sc00412b.

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Voylov, D. N., I. N. Ivanov, V. I. Bykov, S. B. Tsybenova, I. A. Merkulov, S. A. Kurochkin, A. P. Holt, A. M. Kisliuk i A. P. Sokolov. "Oscillatory behaviour of the surface reduction process of multilayer graphene oxide at room temperature". RSC Advances 6, nr 81 (2016): 78194–201. http://dx.doi.org/10.1039/c6ra14414d.

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Heyrovský, Michael, i Ladislav Novotný. "Interfacial interactions and the heterogeneous one-electron reduction of methyl viologen". Collection of Czechoslovak Chemical Communications 52, nr 5 (1987): 1097–114. http://dx.doi.org/10.1135/cccc19871097.

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The one-electron reversible electroreduction of methyl viologen to its radical cation in aqueous solutions on mercury electrodes proceeds, according to potential, concentration and time of electrolysis, in various ways. Methyl viologen is adsorbed in flat orientation at the electrode surface; it undergoes a surface redox process in π-interaction with the metal in a potential range positive by about 0.2 V of the beginning of the electroreduction. The actual reduction starts by electron transfer followed by adsorption of the radical cation and, at higher concentrations and in a narrow potential range, by crystallization at the electrode surface of a salt of the radical cation. In solution near the electrode the radical cation dimerizes and the dimer also adsorbs at the electrode. In the region of the standard redox potential and more negative the reduction proceeds by electron transfer from the electrode covered by a layer of the radical cation or of its dimer.

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Whittingham, Alexander W. H., Jordan Lau i Rodney D. L. Smith. "Mechanistic insights into the spontaneous reaction between CO2 and La2–xSrxCuO4". Canadian Journal of Chemistry 99, nr 9 (wrzesień 2021): 773–79. http://dx.doi.org/10.1139/cjc-2021-0059.

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Layered perovskites such as La2–xSrxCuO4 are active electrocatalysts for CO2 reduction, but they suffer from structural instability under catalytic conditions. This structural instability is found to arise from the reaction of CO2 with surface sites. Variable scan rate voltammetry shows the growth of a Cu-based redox couple when potentials cathodic of 0.6 V vs. RHE are applied in the presence of CO2. Electrochemical impedance spectroscopy identifies a redox active surface state at this voltage, whose concentration is increased by electrochemical reduction in the presence of CO2. In situ spectroelectrochemical FTIR identifies surface bound carbonates as being involved in the formation of these surface sites. The orthorhombic lattice for La2CuO4 is found to uniquely enable binding bidentate binding of carbonate ions to the surface through reaction with CO2. The incorporation of Sr(II) induces a transition to a tetragonal lattice, for which only monodentate carbonate ions are observed. It is proposed that the binding of carbonate ions in a bidentate fashion generates sufficient strain at the surface to result in amorphization at the surface, yielding the observed Cu(II)/Cu(I) redox couple.

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Andreeva, Donka Ch, Matey G. Kalchev i Atanas A. Andreev. "Surface Redox Strength and Catalytic Activity of the CuO/ZnO System". Collection of Czechoslovak Chemical Communications 57, nr 12 (1992): 2561–64. http://dx.doi.org/10.1135/cccc19922561.

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Information about the reduction properties and reactivity of surface hydroxyl groups has been obtained from the interaction of iodine with a series of CuO/ZnO samples in wide range of concentrations. The maximum capacity of iodine reduction and maximum catalytic activity in water gas shift reaction were observed with the sample containing 20 wt.% CuO. The correlation found gives evidence in favour of the associative mechanism of reaction.

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Gross-Wittke, A., G. Gunkel i A. Hoffmann. "Temperature effects on bank filtration: redox conditions and physical-chemical parameters of pore water at Lake Tegel, Berlin, Germany". Journal of Water and Climate Change 1, nr 1 (1.03.2010): 55–66. http://dx.doi.org/10.2166/wcc.2010.005.

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In the city of Berlin, artificial groundwater recharge techniques, such as bank filtration and infiltration ponds, are an important source for drinking water production. Climate change with increasing surface water temperatures can influence the water purification processes during bank filtration mainly due the intensification of metabolic processes leading to a decrease of oxygen and an increase of anaerobic conditions. In Lake Tegel a significant increase of water temperature in the epilimnion of 2.4°C within the last 30 years was recorded. For a better understanding of induced bank filtration at Lake Tegel, redox processes and physical-chemical conditions within the surface sediment layers (0–26 cm depth) at the littoral infiltration zone were investigated. The influence of temperature in the range of 0–25°C on microbial catalysis of redox processes, such as reduction of nitrate and sulphate, was examined during the period March 2004–June 2005. High water temperatures (16–25°C) were accompanied by negative redox potentials (EH=−47 mV) and decreasing Ninorg concentrations, while the amount of ammonia, Mn2 + and Fe2 + was rising. This indicates redox processes such as denitrification, Mn4 + reduction, nitrate respiration and ammonification, as well as Fe3 + reduction. The reduction of sulphate, however, has not yet become significant at Lake Tegel, but with increasing water temperature, sulphate reduction must be expected.

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Vecchietti, Julia, Sebastián Collins, Wenqian Xu, Laura Barrio, Darío Stacchiola, Mónica Calatayud, Frederik Tielens, Juan José Delgado i Adrian Bonivardi. "Surface Reduction Mechanism of Cerium–Gallium Mixed Oxides with Enhanced Redox Properties". Journal of Physical Chemistry C 117, nr 17 (24.04.2013): 8822–31. http://dx.doi.org/10.1021/jp400285b.

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Mason, Joseph, Christopher Batchelor-McAuley i Richard G. Compton. "Surface modification imparts selectivity, facilitating redox catalytic studies: quinone mediated oxygen reduction". Physical Chemistry Chemical Physics 15, nr 21 (2013): 8362. http://dx.doi.org/10.1039/c3cp50607j.

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Ceré, Silvia, Marcela Vazquez, Susana R. de Sánchez i David J. Schiffrin. "Surface redox catalysis and reduction kinetics of oxygen on copper–nickel alloys". Journal of Electroanalytical Chemistry 505, nr 1-2 (czerwiec 2001): 118–24. http://dx.doi.org/10.1016/s0022-0728(01)00469-7.

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Tammeveski, Kaido, Kyösti Kontturi, Richard J. Nichols, Robert J. Potter i David J. Schiffrin. "Surface redox catalysis for O2 reduction on quinone-modified glassy carbon electrodes". Journal of Electroanalytical Chemistry 515, nr 1-2 (listopad 2001): 101–12. http://dx.doi.org/10.1016/s0022-0728(01)00633-7.

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Fang, Wei-Chuan, i Wei-Lee Fang. "Fast and reversible surface redox reduction in V2O5 dispersed on CNx nanotubes". Chemical Communications, nr 41 (2008): 5236. http://dx.doi.org/10.1039/b809253b.

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Zhao, Lili, Chang Liu, Zhuangzhuang Qiao, Yan Yao i Jianbin Luo. "Reduction responsive and surface charge switchable polyurethane micelles with acid cleavable crosslinks for intracellular drug delivery". RSC Advances 8, nr 32 (2018): 17888–97. http://dx.doi.org/10.1039/c8ra01581c.

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Liu, Ting-Hang, Mohammad A. Yaghmour, Miin-Huey Lee, Thomas M. Gradziel, Johan H. J. Leveau i Richard M. Bostock. "An roGFP2-Based Bacterial Bioreporter for Redox Sensing of Plant Surfaces". Phytopathology® 110, nr 2 (luty 2020): 297–308. http://dx.doi.org/10.1094/phyto-07-19-0237-r.

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The reduction-oxidation (redox) environment of the phytobiome (i.e., the plant–microbe interface) can strongly influence the outcome of the interaction between microbial pathogens, commensals, and their host. We describe a noninvasive method using a bacterial bioreporter that responds to reactive oxygen species and redox-active chemicals to compare microenvironments perceived by microbes during their initial encounter of the plant surface. A redox-sensitive variant of green fluorescent protein (roGFP2), responsive to changes in intracellular levels of reduced and oxidized glutathione, was expressed under the constitutive SP6 and fruR promoters in the epiphytic bacterium Pantoea eucalypti 299R (Pe299R/roGFP2). Analyses of Pe299R/roGFP2 cells by ratiometric fluorometry showed concentration-dependent responses to several redox active chemicals, including hydrogen peroxide (H2O2), dithiothreitol (DTT), and menadione. Changes in intracellular redox were detected within 5 min of addition of the chemical to Pe299R/roGFP2 cells, with approximate detection limits of 25 and 6 μM for oxidation by H2O2 and menadione, respectively, and 10 μM for reduction by DTT. Caffeic acid, chlorogenic acid, and ascorbic acid mitigated the H2O2-induced oxidation of the roGFP2 bioreporter. Aqueous washes of peach and rose flower petals from young blossoms created a lower redox state in the roGFP2 bioreporter than washes from fully mature blossoms. The bioreporter also detected differences in surface washes from peach fruit at different stages of maturity and between wounded and nonwounded sites. The Pe299R/roGFP2 reporter rapidly assesses differences in redox microenvironments and provides a noninvasive tool that may complement traditional redox-sensitive chromophores and chemical analyses of cell extracts.

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Gandhi, Mansi, Desikan Rajagopal i Annamalai Senthil Kumar. "In situ electro-organic synthesis of hydroquinone using anisole on MWCNT/Nafion modified electrode surface and its heterogeneous electrocatalytic reduction of toxic Cr(vi) species". RSC Advances 11, nr 7 (2021): 4062–76. http://dx.doi.org/10.1039/d0ra10370e.

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Deng, Ying, Zuorui Wen, Guiling Luo, Hui Xie, Juan Liu, Yaru Xi, Guangjiu Li i Wei Sun. "Carbon Nitride Nanosheet and Myoglobin Modified Electrode for Electrochemical Sensing Investigations". Current Analytical Chemistry 16, nr 6 (13.08.2020): 703–10. http://dx.doi.org/10.2174/1573411015666190710223818.

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Background: Carbon-based nanomaterials, especially carbon nitride (C3N4) has attracted tremendous interest in biosensor applications. Meanwhile, the mechanism of redox protein sensing and related electrocatalytic reactions can provide a valid basis for understanding the process of biological redox reaction. Objective: The aim of this paper is to construct a new electrochemical enzyme sensor to achieve direct electron transfer of myoglobin (Mb) on CILE surface and display electrocatalytic reduction activity to catalyze trichloroacetic acid (TCA) and H2O2. Methods: The working electrode was fabricated based on ionic liquid modified Carbon Paste Electrode (CILE) and C3N4 nanosheets were modified on the CILE surface, then Mb solution was fixed on C3N4/CILE surface and immobilized by using Nafion film. The as-prepared biosensor displayed satisfactory electrocatalytic ability towards the reduction of TCA and H2O2 in an optimum pH 7.0 buffer solution. Results: The results indicated that C3N4 modified electrode retained the activity of the enzyme and displayed quasi-reversible redox behavior in an optimum pH 7.0 buffer solution. The electrochemical parameters of the immobilized Mb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.27, the charge transfer coefficient (α) as 0.53 and the electrontransfer rate constant (ks) as 3.32 s-1, respectively. The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction activity to catalyze trichloroacetic acid and H2O2. Conclusion: The Nafion/Mb/C3N4/CILE displayed outstanding electrocatalytic reduction, which demonstrated the promising applications of C3N4 nanosheet in the field electrochemical biosensing.

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Gorny, Josselin, Gabriel Billon, Catherine Noiriel, David Dumoulin, Ludovic Lesven i Benoît Madé. "Chromium behavior in aquatic environments: a review". Environmental Reviews 24, nr 4 (grudzień 2016): 503–16. http://dx.doi.org/10.1139/er-2016-0012.

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The fate of chromium (Cr) – a redox sensitive metal – in surface sediments is closely linked to early diagenetic processes. This review summarizes the main redox pathways that have been clearly identified over recent decades concerning the behavior of Cr(III,VI) in aquatic environments, and applies them to surface sediments where data for redox speciation remain limited. Overall, abiotic redox reactions that govern the speciation of Cr involve manganese (Mn) (III,IV) (hydr)-oxydes for Cr(III) oxidation, Cr(VI)-reducing species (dissolved iron (Fe) (II) and hydrosulfide (HS)−), and Cr(VI)-reducing phases (ferrous and sulfide minerals, as well as Fe(II)-bearing minerals). Bacterial activity is also responsible for the redox interconversion between Cr(III) and Cr(VI): biotic reduction of Cr(VI) to Cr(III) is observed through either detoxification or dissimilatory reduction. Whereas Mn(II)-oxidizing bacteria are known to promote indirect oxidation of Cr(III) to Cr(VI), the reaction mechanisms are unresolved. Conversely, oxygen (O2), nitrate (NO3−), and nitrite (NO2−) do not appear to play any role in Cr(III) oxidation. Additionally, Mn(II) and ammonium (NH4+) are not known to promote Cr(VI) reduction. Once reduced, the mobility of Cr(III) in sediments is significantly restricted and regulated by precipitation and sorption processes. Finally, even if the role of natural organic matter in sediment has been determined, further research is required to identify the complexation mechanisms.

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Zheleznyak, А. R., О. М. Bakalinska, А. V. Brichka, G. O. Kalenyuk i М. Т. Каrtel. "Properties, production methods and use of tin nanoxide". Surface 12(27) (30.12.2020): 193–230. http://dx.doi.org/10.15407/surface.2020.12.193.

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The prevalence of tin compounds, economic affordability and non-toxicity determine its wide range of applications. Modern scientific literature on the properties, methods of preparation and application of tin nanooxide is analyzes in review. Its main characteristics and structural features are described. The ability of tin cations to be in two oxidation states, the ease of reduction of Sn+4 to Sn+2 and reverse oxidation, determines the redox properties of the SnO2 surface. In addition to stable oxides Sn4+ and Sn2,+ the existence of a homologous series of Snn+1O2n metastable compounds is assumed. It is proved that four-coordinated Sn+2 cations on the SnO2 surface can coexist only with oxygen vacancies in the immediate environment. Such cationic sites have the properties of strong Lewis acids and are highly reactive. Computer simulation of the SnO2 crystal surface allows us to propose a number of catalytic activity of SnO2 surfaces: (110) < (001) < (100) < (101). Preparation methods and synthesis parameters (nature and type of precursor, stabilizing agent and solvent, duration and temperature of the reaction, pH of the reaction mixture, etc.) determine the physicochemical properties of nanoparticles (shape, size, morphology and degree of crystallinity). The main (sol-gel, precipitation and coprecipitation, CVD, spray pyrolysis, hydrothermal, “green”) and less common (detonation, electric discharge) methods of nano-SnO2 obtaining are analyzed in the work. A variety of methods of synthesis and conditions makes it possible to obtain SnO2 nanoparticles with desired properties, which determine the activity of tin oxide in redox reactions, namely: nanosize and morphology of particles with prevalence of the most reactive faces - (100) і (101). Among the methods that do not require complex hardware design, one can dwell on the methods of sol-gel, "green" and coprecipitation. Tin oxide is traditionally used as an abrasive for polishing metal, glass and ceramic products. The transition to nanosized particles allows this material to reversibly absorb and release oxygen, which has determined its use in the design of gas-sensitive and biosensors, the creation of solar cells, fuel cells, lithium-ion batteries, oxidation catalysts, transparent and photoconductors. The multivalence and the presence of oxygen vacancies on the surface of tin oxide nanoparticles, the ease and speed of penetration into the cell membrane give nano-SnO2 properties of medicinal preparations, which makes it possible to use it in biomedical technologies for the treatment of diseases associated with oxidative stress lesions. The size, concentration of nanoparticles and modification of their surface are the key factors of influence, which usually intensify the antimicrobial, antibacterial, antitumor and antioxidant activity of the material.

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Yu, Tong, i Paul L. Bishop. "Stratification of microbial metabolic processes and redox potential change in an aerobic biofilm studied using microelectrodes". Water Science and Technology 37, nr 4-5 (1.02.1998): 195–98. http://dx.doi.org/10.2166/wst.1998.0618.

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In this study we used oxygen, sulfide, redox potential and pH microelectrodes to examine the stratification of microbial metabolic processes and the change of redox potential within an aerobic biofilm used to treat azo dye containing wastewater. These microelectrodes have tip diameters of 3 to 20 μm and a high spatial resolution. They were used to measure the profiles of oxygen, total dissolved sulfide, redox potential and pH as a function of depth in the biofilm. These profiles demonstrated that oxygen was depleted at 550 μm from the surface and the deeper section of the biofilm was actually anaerobic. While aerobic oxidation took place only in a shallow layer near the surface, sulfate reduction occurred in the deeper anaerobic zone, even with a low concentration of sulfate (6.75 mg/l as SO2−) in the bulk solution. We discovered a sharp decrease of redox potential (271 mV) from a positive potential to a negative potential within a very narrow band of 50 μm near the interface between the aerobic zone and the sulfate reduction zone. The new experimental findings support the concept of stratification of the microbial metabolic processes in biofilms.

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Haidar, Fatima, Mathieu Maas, Andrea Piarristeguy, Annie Pradel, Sara Cavaliere i Marie-Christine Record. "Ultra-Thin Platinum Deposits by Surface-Limited Redox Replacement of Tellurium". Nanomaterials 8, nr 10 (15.10.2018): 836. http://dx.doi.org/10.3390/nano8100836.

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Platinum is the most employed electrocatalyst for the reactions taking place in energy converters, such as the oxygen reduction reaction in proton exchange membrane fuel cells, despite being a very low abundant element in the earth’s crust and thus extremely expensive. The search for more active electrocatalysts with ultra-low Pt loading is thus a very active field of investigation. Here, surface-limited redox replacement (SLRR) that utilizes the monolayer-limited nature of underpotential deposition (UPD) was used to prepare ultrathin deposits of Pt, using Te as sacrificial metal. Cyclic voltammetry and anodic potentiodynamic scanning experiments have been performed to determine the optimal deposition conditions. Physicochemical and electrochemical characterization of the deposited Pt was carried out. The deposit comprises a series of contiguous Pt islands that form along the grain interfaces of the Au substrate. The electrochemical surface area (ECSA) of the Pt deposit obtained after 5 replacements, estimated to be 18 m2/g, is in agreement with the ECSA of extended surface catalysts on flat surfaces.

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Ceré, Silvia, Marcela Vazquez, Susana R. de Sánchez i David J. Schiffrin. "Surface redox catalysis and reduction kinetics of hydrogen peroxide on copper–nickel alloys". Journal of Electroanalytical Chemistry 470, nr 1 (lipiec 1999): 31–38. http://dx.doi.org/10.1016/s0022-0728(99)00207-7.

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Moretti, Roberto, i Andri Stefánsson. "Volcanic and Geothermal Redox Engines". Elements 16, nr 3 (1.06.2020): 179–84. http://dx.doi.org/10.2138/gselements.16.3.179.

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The redox (reduction–oxidation) potential is an essential variable that controls the chemical reactions of fluids in magmatic and associated geothermal systems. However, the evolution of the redox potential is difficult to trace from a magma’s source at depth to the surface. The key is knowing that electron transfer is the twin face of the acid–base exchanges that drive charge transfer in the many reactions that occur in multiphase and chemically complex systems. The deduced redox reactivity can reveal many features about the evolution of a system’s composition and the external factors that control it. As such, redox potential analysis is an important geochemical tool by which to monitor volcanoes and to explore geothermal systems.

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Liu, Zhiming, Haiyan Liu, Hui Zeng i Qi Xu. "A novel Ce–Sb binary oxide catalyst for the selective catalytic reduction of NOx with NH3". Catalysis Science & Technology 6, nr 22 (2016): 8063–71. http://dx.doi.org/10.1039/c6cy01756h.

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Han, Young-Soo, Hoon Young Jeong, Sung Pil Hyun, Kim F. Hayes i Chul-Min Chon. "Beam-induced redox transformation of arsenic during AsK-edge XAS measurements: availability of reducing or oxidizing agents and As speciation". Journal of Synchrotron Radiation 25, nr 3 (14.03.2018): 763–70. http://dx.doi.org/10.1107/s1600577518002576.

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During X-ray absorption spectroscopy (XAS) measurements of arsenic (As), beam-induced redox transformation is often observed. In this study, the As species immobilized by poorly crystallized mackinawite (FeS) was assessed for the susceptibility to beam-induced redox reactions as a function of sample properties including the redox state of FeS and the solid-phase As speciation. The beam-induced oxidation of reduced As species was found to be mediated by the atmospheric O2and the oxidation products of FeS [e.g.Fe(III) (oxyhydr)oxides and intermediate sulfurs]. Regardless of the redox state of FeS, both arsenic sulfide and surface-complexed As(III) readily underwent the photo-oxidation upon exposure to the atmospheric O2during XAS measurements. With strict O2exclusion, however, both As(0) and arsenic sulfide were less prone to the photo-oxidation by Fe(III) (oxyhydr)oxides than NaAsO2and/or surface-complexed As(III). In case of unaerated As(V)-reacted FeS samples, surface-complexed As(V) was photocatalytically reduced during XAS measurements, but arsenic sulfide did not undergo the photo-reduction.

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Kung, Johannes W., Sven Baumann, Martin von Bergen, Michael Müller, Peter-Leon Hagedoorn, Wilfred R. Hagen i Matthias Boll. "Reversible Biological Birch Reduction at an Extremely Low Redox Potential". Journal of the American Chemical Society 132, nr 28 (21.07.2010): 9850–56. http://dx.doi.org/10.1021/ja103448u.

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Li, Chenglong, Zhitao Han, Yuqing Hu, Tingjun Liu i Xinxiang Pan. "Synthesis of W-modified CeO₂/ZrO₂ catalysts for selective catalytic reduction of NO with NH₃". RSC Advances 12, nr 42 (2022): 27309–20. http://dx.doi.org/10.1039/d2ra04862k.

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Liu, Chang, Yayuan Guan, Yuling Su, Lili Zhao, Fancui Meng, Yongchao Yao i Jianbin Luo. "Surface charge switchable and core cross-linked polyurethane micelles as a reduction-triggered drug delivery system for cancer therapy". RSC Advances 7, nr 18 (2017): 11021–29. http://dx.doi.org/10.1039/c7ra00346c.

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The core cross-linked polyurethane micelles with redox sensitive and pH-responsive surface charge switchable properties were prepared by using diisocyanates as crosslinkers and studied as anticancer drug carriers.

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Daniel, P., S. I. Shylin, H. Lu, M. N. Tahir, M. Panthöfer, T. Weidner, A. Möller, V. Ksenofontov i W. Tremel. "The surface chemistry of iron oxide nanocrystals: surface reduction of γ-Fe2O3 to Fe3O4 by redox-active catechol surface ligands". Journal of Materials Chemistry C 6, nr 2 (2018): 326–33. http://dx.doi.org/10.1039/c7tc04795a.

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Metcalfe, Clive, Peter Cresswell, Laura Ciaccia, Benjamin Thomas i A. Neil Barclay. "Labile disulfide bonds are common at the leucocyte cell surface". Open Biology 1, nr 3 (listopad 2011): 110010. http://dx.doi.org/10.1098/rsob.110010.

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Redox conditions change in events such as immune and platelet activation, and during viral infection, but the biochemical consequences are not well characterized. There is evidence that some disulfide bonds in membrane proteins are labile while others that are probably structurally important are not exposed at the protein surface. We have developed a proteomic/mass spectrometry method to screen for and identify non-structural, redox-labile disulfide bonds in leucocyte cell-surface proteins. These labile disulfide bonds are common, with several classes of proteins being identified and around 30 membrane proteins regularly identified under different reducing conditions including using enzymes such as thioredoxin. The proteins identified include integrins, receptors, transporters and cell–cell recognition proteins. In many cases, at least one cysteine residue was identified by mass spectrometry as being modified by the reduction process. In some cases, functional changes are predicted (e.g. in integrins and cytokine receptors) but the scale of molecular changes in membrane proteins observed suggests that widespread effects are likely on many different types of proteins including enzymes, adhesion proteins and transporters. The results imply that membrane protein activity is being modulated by a ‘redox regulator’ mechanism.

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Salusso, Davide, Silvia Mauri, Gabriele Deplano, Piero Torelli, Silvia Bordiga i Sergio Rojas-Buzo. "MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy". Nanomaterials 13, nr 2 (9.01.2023): 272. http://dx.doi.org/10.3390/nano13020272.

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The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium’s redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed.

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Philipossian, Ara, Yasa Sampurno, Fritz Redeker, Kiana A. Cahue i Jason J. Keleher. "Slurry Activation for Enhanced Surface Redox Reactions in CMP". Solid State Phenomena 346 (14.08.2023): 311–17. http://dx.doi.org/10.4028/p-zds0xu.

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A novel add-on hardware device is placed near the point of slurry dispense that can instantaneously activate slurry performance during polishing via megasonic irradiation. This new technology (Flucto-CMP® is able to overcome the inherent polisher-slurry weaknesses such as wafer-level defects, process vibrations, cost of ownership, slurry waste, remval rate (RR), and RR selectivity. Flucto-CMP® has been successfully applied to various types of CMP slurries resulting in significant increases in the removal rates of copper, SiC, borosilicate hard mask, ILD, TiN, and silicon carbide through chemical alteration of the passivation layer needed for material removal. Specifically, for copper CMP, using Flucto-CMP®, we see an up to 31% boost in RR which is well correlated with the amount of reactive oxidizing species generated through irradiation as well as the measured relative indentation depth of the passivation layer. In addition to boosts in RR, for copper, we see a 50X drop in the variance of shear force and a 5X drop in the variance of normal force when Flucto-CMP® is used. This dramatic reduction in process vibration for copper soft-landing processes ought to reduce wafer-level defects. Much greater rate improvements are observed when polishing SiC, and borosilicate hard masks.

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Fonseca, Juliana, Nicolas Bion, Yordy E. Licea, Cláudia M. Morais, Maria do Carmo Rangel, Daniel Duprez i Florence Epron. "Unexpected redox behaviour of large surface alumina containing highly dispersed ceria nanoclusters". Nanoscale 11, nr 3 (2019): 1273–85. http://dx.doi.org/10.1039/c8nr07898j.

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In CeO₂–Al₂O₃ prepared by the EISA route, Ce⁴⁺ can be totally reduced into Ce³⁺ between 400 and 500 °C with the participation of Al₂O₃ in the reversible reduction process.

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Wang, Zhao-Wen, Masayuki Nara, Yong-Xiao Wang i Michael I. Kotlikoff. "Redox Regulation of Large Conductance Ca2+-activated K+ Channels in Smooth Muscle Cells". Journal of General Physiology 110, nr 1 (1.07.1997): 35–44. http://dx.doi.org/10.1085/jgp.110.1.35.

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The effects of sulfhydryl reduction/oxidation on the gating of large-conductance, Ca2+-activated K+ (maxi-K) channels were examined in excised patches from tracheal myocytes. Channel activity was modified by sulfhydryl redox agents applied to the cytosolic surface, but not the extracellular surface, of membrane patches. Sulfhydryl reducing agents dithiothreitol, β-mercaptoethanol, and GSH augmented, whereas sulfhydryl oxidizing agents diamide, thimerosal, and 2,2′-dithiodipyridine inhibited, channel activity in a concentration-dependent manner. Channel stimulation by reduction and inhibition by oxidation persisted following washout of the compounds, but the effects of reduction were reversed by subsequent oxidation, and vice versa. The thiol-specific reagents N-ethylmaleimide and (2-aminoethyl)methanethiosulfonate inhibited channel activity and prevented the effect of subsequent sulfhydryl oxidation. Measurements of macroscopic currents in inside-out patches indicate that reduction only shifted the voltage/nPo relationship without an effect on the maximum conductance of the patch, suggesting that the increase in nPo following reduction did not result from recruitment of more functional channels but rather from changes of channel gating. We conclude that redox modulation of cysteine thiol groups, which probably involves thiol/disulfide exchange, alters maxi-K channel gating, and that this modulation likely affects channel activity under physiological conditions.

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Parvanian, Amir Masoud, Hamidreza Salimijazi, Mehdi Shabaninejad, Ulrike Troitzsch, Peter Kreider, Wojciech Lipiński i Mohammad Saadatfar. "Thermochemical CO2 splitting performance of perovskite coated porous ceramics". RSC Advances 10, nr 39 (2020): 23049–57. http://dx.doi.org/10.1039/d0ra02353a.

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A representative volume of LCMA coated porous SiC showing a maximum of 23% shrinkage when subject to high-temperature CO₂ conversion redox reactions. This results in significant structural changes including a reduction in specific surface area.

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Bernas, Tytus, i Jurek Dobrucki. "Extracellular Reduction of Cat1 Free Radical by Transformed Human Hepatocytes". Bioscience Reports 18, nr 6 (1.12.1998): 341–50. http://dx.doi.org/10.1023/a:1020213400556.

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Redox activities associated with plasma membranes of nonphagocytic animal and plant cells have been reported by several authors. However, the natural substrates, structure and biological role of these putative enzyme systems are not known. Data indicating extracellular reduction of a nitroxide free radical Cat1 (1-oxy-4-trimethylamine-2,2,6,6,tetramethyl-piperidine) by hepatocytes were thought to be artefactual. We report evidence in support of a notion that Cat1 as well as a tetrazolium salt, CTC (5-cyano-2,3-ditolyl tetrazolium chloride), are reduced extracellularly, probably at the cell surface, by human HepG2 hepatoma cells. These data provide evidence confirming the existence of a yet unidentified reducing activity associated with outer surface of plasma membranes of transformed human hepatocytes.

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Fukushi, Yuka, Yuichi Yokochi, Ken-ichi Wakabayashi, Keisuke Yoshida i Toru Hisabori. "Verification of the Relationship between Redox Regulation of Thioredoxin Target Proteins and Their Proximity to Thylakoid Membranes". Antioxidants 11, nr 4 (13.04.2022): 773. http://dx.doi.org/10.3390/antiox11040773.

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Thioredoxin (Trx) is a key protein of the redox regulation system in chloroplasts, where it modulates various enzyme activities. Upon light irradiation, Trx reduces the disulfide bonds of Trx target proteins (thereby turning on their activities) using reducing equivalents obtained from the photosynthetic electron transport chain. This reduction process involves a differential response, i.e., some Trx target proteins in the stroma respond slowly to the change in redox condition caused by light/dark changes, while the ATP synthase γ subunit (CF1-γ) located on the surface of thylakoid membrane responds with high sensitivity. The factors that determine this difference in redox kinetics are not yet known, although here, we hypothesize that it is due to each protein’s localization in the chloroplast, i.e., the reducing equivalents generated under light conditions can be transferred more efficiently to the proteins on thylakoid membrane than to stromal proteins. To explore this possibility, we anchored SBPase, one of the stromal Trx target proteins, to the thylakoid membrane in Arabidopsis thaliana. Analyses of the redox behaviors of the anchored and unanchored proteins showed no significant difference in their reduction kinetics, implying that protein sensitivity to redox regulation is determined by other factors.

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Wang, Zhao, Xinyu Guo, Lingyun Hao, Xiaojuan Zhang, Qing Lin i Ruilong Sheng. "Charge-Convertible and Reduction-Sensitive Cholesterol-Containing Amphiphilic Copolymers for Improved Doxorubicin Delivery". Materials 15, nr 18 (18.09.2022): 6476. http://dx.doi.org/10.3390/ma15186476.

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For achieving successful chemotherapy against cancer, designing biocompatible drug delivery systems (DDSs) with long circulation times, high cellular endocytosis efficiency, and targeted drug release is of upmost importance. Herein, a well-defined PEG-b-P(MASSChol-co-MANBoc) block copolymer bearing redox-sensitive cholesteryl-side group was prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization (with non-redox PEG-b-P(MACCChol-co-MAN-DCA) as the reference), and 1,2-dicarboxylic-cyclohexene acid (DCA) was then grafted onto the hydrophobic block to endow it with charge-convertible characteristics under a tumor microenvironment. The amphiphilic copolymer could be assembled into polymeric spherical micelles (SSMCs) with polyethylene glycol (PEG) as the corona/shell, and anti-cancer drug doxorubicin (DOX) was successfully encapsulated into the micellar core via strong hydrophobic and electrostatic interactions. This nanocarrier showed high stability in the physiological environment and demonstrated “smart” surface charge conversion from negative to positive in the slightly acidic environment of tumor tissues (pH 6.5~6.8), as determined by dynamic light scattering (DLS). Moreover, the cleavage of a disulfide bond linking the cholesterol grafts under an intracellular redox environment (10 mM GSH) resulted in micellar dissociation and accelerated drug release, with the non-redox-responsive micelles (CCMCs) as the control. Additionally, a cellular endocytosis and tumor proliferation inhibition study against MCF-7 tumor cells demonstrated the enhanced endocytosis and tumor cell inhibitory efficiency of dual-responsive SSMCs/DOX nanomedicines, revealing potentials as multifunctional nanoplatforms for effective oncology treatment.

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Yamashita, Yutaro, Shohei Tashiro, Yoshiki Ishii, Takayuki Uchihashi, Nobuyuki Matsushita, Ryou Kubota i Mitsuhiko Shionoya. "Shape-selective one-step synthesis of branched gold nanoparticles on the crystal surface of redox-active Pd^II-macrocycles". Dalton Transactions 51, nr 4 (2022): 1318–24. http://dx.doi.org/10.1039/d1dt03973c.

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Redox-active PdII3-macrocycle crystals were found to provide an excellent platform for gold reduction and growth of immobilized particles, leading to the one-step synthesis of stable, monodisperse, Konpeito-shaped gold nanoparticles.

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Trudgeon, David P., i Xiaohong Li. "Enhanced Surface Area Carbon Cathodes for the Hydrogen–Bromine Redox Flow Battery". Batteries 8, nr 12 (6.12.2022): 276. http://dx.doi.org/10.3390/batteries8120276.

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The hydrogen–bromine redox flow battery is a promising energy storage technology with the potential for capital costs as low as 220 $ kWh−1 and high operational power densities in excess of 1.4 W cm−2. In this work, enhanced surface area bromine electrodes incorporating carbon black (CB) and graphene nanoplatelets (GnPs) on carbon paper and carbon cloth substrates were investigated, and the effect of electrolyte concentration on performance of the electrodes was studied. Carbon-black-modified electrodes are found to possess the largest electrochemically active surface areas, i.e., up to 11 times that of unmodified materials, while GnP electrodes are shown to have superior kinetic activity towards the bromine electrode reaction. In terms of performance, lower electrolyte concentrations are found to favour the improved kinetic parameters associated with graphene nanoplatelet electrodes, while highly concentrated electrolytes favour the larger electrochemically active surface area of carbon black electrodes. The optimal performance was achieved on a carbon-black-modified carbon cloth electrode in a 6 M HBr/2 M Br2 electrolyte concentration, with polarisation current densities approaching 1.6 A cm−2 at overpotentials of ±400 mV, and mean overpotentials of 364 mV during oxidation and 343 mV during reduction, resulting from bromine oxidation/reduction cycling tests at ±1.5 A cm−2.

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Hadinugrahaningsih, Tritiyatma, Yuli Rahmawati i Elma Suryani. "An analysis of preservice Chemistry teachers’ misconceptions of reduction-oxidation reaction concepts". Journal of Technology and Science Education 12, nr 2 (7.07.2022): 448. http://dx.doi.org/10.3926/jotse.1566.

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This article describes a study of 149 of preservice chemistry teachers’ misconceptions of concepts related to an reduction-oxidation reaction. A mixed-method approach was used to obtain data through the ROXCI (Redox Concept Inventory) instrument and interviews. Results indicated that the highest misconceptions were for item number 10 (4.03% or only 6 of 149 students answered correctly) and the lowest misconception occurred on item number 1 (94.63% or 141 of 149 students answered correctly). These results were supported by the analysis of the interviews where the respondents produced misconceptions when explaining the process of electron transfer in redox reactions. The highest percentage of consistent answers in the six ROXCI categories was obtained in the surface feature concept category (6.71% or 10 out of 149 respondents consistently answered correctly). This shows that preservice chemistry teachers are not able to connect the three levels of chemical representation, macroscopic, microscopic, and symbolic in studying chemistry, especially for the redox concept. Analysis of the relationships between misconceptions and average student confidence shows that every distractor chosen by the respondents at every level was followed by a degree of confidence of between 50%-70%, indicating that misconceptions became stronger because the preservice chemistry teachers did not realize that a concept believed to be true is wrong.

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Šuligoj, Andraž, Iztok Arčon, Matjaž Mazaj, Goran Dražić, Denis Arčon, Pegie Cool, Urška Lavrenčič Štangar i Nataša Novak Tušar. "Surface modified titanium dioxide using transition metals: nickel as a winning transition metal for solar light photocatalysis". Journal of Materials Chemistry A 6, nr 21 (2018): 9882–92. http://dx.doi.org/10.1039/c7ta07176k.

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Ni and Zn show a winning combination of redox potential and band positions of TiO₂ supported metal-oxo-nanoclusters for enhanced solar-light activity. However, Ni is the only metal which has a positive effect on solar photoactivity in both oxidation and reduction reactions.

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Shan, Wenpo, Yang Geng, Yan Zhang, Zhihua Lian i Hong He. "A CeO2/ZrO2-TiO2 Catalyst for the Selective Catalytic Reduction of NOx with NH3". Catalysts 8, nr 12 (30.11.2018): 592. http://dx.doi.org/10.3390/catal8120592.

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In this study, CeZr0.5TiaOx (with a = 0, 1, 2, 5, 10) catalysts were prepared by a stepwise precipitation approach for the selective catalytic reduction of NOx with NH3. When Ti was added, all of the Ce-Zr-Ti oxide catalysts showed much better catalytic performances than the CeZr0.5Ox. Particularly, the CeZr0.5Ti2Ox catalyst showed excellent activity for broad temperature range under high space velocity condition. Through the control of pH value and precipitation time during preparation, the function of the CeZr0.5Ti2Ox catalyst could be controlled and the structure with highly dispersed CeO2 (with redox functions) on the surface of ZrO2-TiO2 (with acidic functions) could be obtained. Characterizations revealed that the superior catalytic performance of the catalyst is associated with its outstanding redox properties and adsorption/activation functions for the reactants.

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Revil, André, Zhaoyang Su, Zhongmin Zhu i Alexis Maineult. "Self-Potential as a Tool to Monitor Redox Reactions at an Ore Body: A Sandbox Experiment". Minerals 13, nr 6 (24.05.2023): 716. http://dx.doi.org/10.3390/min13060716.

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Ore bodies generate natural electrical fields that are measurable at the ground surface. The ground surface signature of this electrical field is called a self-potential anomaly. We developed a sandbox experiment to monitor the evolution of a self-potential anomaly associated with redox processes mediated by bacterial activity at the surface of a buried metallic object crossing the water table. A Bio-Electrochemical Cell (BEC) is formed by a metal bar connecting the upper, oxygen-rich, part of the tank and an aquifer containing an electron donor in the form of acetate. The self-potential response was observed during a period of 327 days. The tomography of the self-potential signature confirms that self-potential tomography is able to locate the metallic target acting as a BEC. In addition, we performed redox potential, pH, and electrical potential measurements over a vertical cross-section of the tank at several time steps to obtain an idea of where the redox front is located. The distributions of the redox potential and pH further demonstrated the development of the oxidation-reduction chemical processes facilitated by the BEC as bacterial communities developed around the metallic bar. The electrical potential anomaly shows that the bacterial communities followed a short period of exponential growth, then a longer period of a sustained population. These results demonstrate the usefulness of the self-potential method in monitoring redox processes at the surface of a buried ore body. Further works will need to combine such self-potential anomalies with induced polarization anomalies through joint inversion.

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Ma, Tianxiao, i Tianxiao Ma. "Measuring DNA Charge Transport on a Surface Using a Redox Modulated Fluorescence Intensity Strategy with DNA SAMs". ECS Meeting Abstracts MA2022-01, nr 55 (7.07.2022): 2323. http://dx.doi.org/10.1149/ma2022-01552323mtgabs.

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The double stranded DNA helix has drawn great attention across different research areas. Various types of platforms have been used to study DNA charge transfer (CT) system. Two types of DNA CT platforms are considered as the most effective: the photoinduced CT in solution with assembled donor and acceptor and electrochemistry on ground state CT in a DNA self-assembled monolayer (SAM)1. We will show a new approach for the study of DNA CT on gold surface by studying the redox modulated fluorescence signal of a co-deposited double-stranded DNA assemblies labeled with Methylene Blue (MB) or AlexaFluoro488 (AF488). We demonstrate a method that can optically distinguish between the two mechanisms of the MB redox on DNA-modified surface: namely either DNA CT mediated reduction or the direct reduction of MB by the gold surface2. Given the fact that the studies on DNA-mediated electrochemistry on surface has been mainly using electrochemical measurements and we still do not fully understand the full picture of the DNA CT, we believe that this study will provide a fresh opinion and facilitate understanding on the DNA CT mechanism on electrode surface. Reference: Arnold, A. R.; Grodick, M. A.; Barton, J. K. DNA Charge Transport: From Chemical Principles to the Cell. Cell Chem. Biol. 2016, 23 (1), 183–197. Pheeney, C. G.; Barton, J. K. DNA Electrochemistry with Tethered Methylene Blue. Langmuir 2012, 28 (17), 7063–7070. Muren, N. B.; Olmon, E. D.; Barton, J. K. Solution, Surface, and Single Molecule Platforms for the Study of DNA-Mediated Charge Transport. Chem. Chem. Phys. 2012, 14 (40), 13754–13771.

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Kirsch, R., A. C. Scheinost, A. Rossberg, D. Banerjee i L. Charlet. "Reduction of antimony by nano-particulate magnetite and mackinawite". Mineralogical Magazine 72, nr 1 (luty 2008): 185–89. http://dx.doi.org/10.1180/minmag.2008.072.1.185.

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AbstractThe speciation of antimony is strongly influenced by its oxidation state (V, III, 0, —III). Redox processes under anaerobic groundwater conditions may therefore greatly alter the environmental behaviour of Sb. Employing X-ray absorption and photoelectron spectroscopy, we show here that Sb(V) is reduced to Sb(III) by magnetite and mackinawite, two ubiquitous Fe(II)-containing minerals, while Sb(III) is not reduced further. At the surface of magnetite, Sb(III) forms a highly symmetrical sorption complex at the position otherwise occupied by tetrahedral Fe(III). The Sb(V) reduction increases with pH, and at pH values >6.5 Sb(V) is completely reduced to Sb(III) within 30 days. In contrast, at the mackinawite surface, Sb(V) is completely reduced across a wide pH range and within 1 h. The Sb(V) reduction proceeds solely by oxidation of surface Fe(II), while the oxidation state of sulphide is conserved. Independent of whether Sb(V) or Sb(III) was added, an amorphous or nano-particulate SbS3-like solid formed.

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Aliotta, Chiara, Maria Costa, Leonarda Francesca Liotta, Valeria La Parola, Giuliana Magnacca i Francesca Deganello. "Peculiar Properties of the La0.25Ba0.25Sr0.5Co0.8Fe0.2O3−δ Perovskite as Oxygen Reduction Electrocatalyst". Molecules 28, nr 4 (8.02.2023): 1621. http://dx.doi.org/10.3390/molecules28041621.

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The electrochemical reduction of molecular oxygen is a fundamental process in Solid Oxide Fuel Cells and requires high efficiency cathode materials. Two La0.25Ba0.25Sr0.5Co0.8Fe0.2O3−δ-based perovskite compounds were prepared by solution combustion synthesis, and characterized for their structural, microstructural, surface, redox and electrochemical properties as potential cathodes in comparison with Ba0.5Sr0.5Co0.8Fe0.2O3−δ and La0.5Sr0.5Co0.8Fe0.2O3−δ perovskites. Results highlighted that calcination at 900 °C led to a “bi-perovskite heterostructure”, where two different perovskite structures coexist, whereas at higher calcination temperatures a single-phase perovskite was formed. The results showed the effectiveness of the preparation procedures in co-doping the A-site of perovskites with barium and lanthanum as a strategy to optimize the cathode’s properties. The formation of nanometric heterostructure co-doped in the A-site evidenced an improvement in oxygen vacancies’ availability and in the redox properties, which promoted both processes: oxygen adsorption and oxygen ions drift, through the cathode material, to the electrolyte. A reduction in the total resistance was observed in the case of heterostructured material.

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Poulain, Alexandre J., Sinéad M. Ní Chadhain, Parisa A. Ariya, Marc Amyot, Edenise Garcia, Peter G. C. Campbell, Gerben J. Zylstra i Tamar Barkay. "Potential for Mercury Reduction by Microbes in the High Arctic". Applied and Environmental Microbiology 73, nr 7 (9.02.2007): 2230–38. http://dx.doi.org/10.1128/aem.02701-06.

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ABSTRACT The contamination of polar regions due to the global distribution of anthropogenic pollutants is of great concern because it leads to the bioaccumulation of toxic substances, methylmercury among them, in Arctic food chains. Here we present the first evidence that microbes in the high Arctic possess and express diverse merA genes, which specify the reduction of ionic mercury [Hg(II)] to the volatile elemental form [Hg(0)]. The sampled microbial biomass, collected from microbial mats in a coastal lagoon and from the surface of marine macroalgae, was comprised of bacteria that were most closely related to psychrophiles that had previously been described in polar environments. We used a kinetic redox model, taking into consideration photoredox reactions as well as mer-mediated reduction, to assess if the potential for Hg(II) reduction by Arctic microbes can affect the toxicity and environmental mobility of mercury in the high Arctic. Results suggested that mer-mediated Hg(II) reduction could account for most of the Hg(0) that is produced in high Arctic waters. At the surface, with only 5% metabolically active cells, up to 68% of the mercury pool was resolved by the model as biogenic Hg(0). At a greater depth, because of incident light attenuation, the significance of photoredox transformations declined and merA-mediated activity could account for up to 90% of Hg(0) production. These findings highlight the importance of microbial redox transformations in the biogeochemical cycling, and thus the toxicity and mobility, of mercury in polar regions.

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ZHEZHERYA, T. P., V. A. ZHEZHERYA i P. M. LYNNYK. "MIGRATION OF BIOGENIC ELEMENTS FROM BOTTOM SEDIMENTS AS AN ADDITIONAL INTERNAL LOAD OF NUTRIENTS ON THE WATER BODIES OF THE URBAN AREA". Hydrology, hydrochemistry and hydroecology, nr 3(65) (2022): 57–67. http://dx.doi.org/10.17721/2306-5680.2022.3.4.

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There were investigated the seasonal and spatial dynamics of the content of nutrients in the lakes of the Opechen’ system. It has been established that the content of nutrients in reservoirs of the urbanized territory, in addition to the external load, depends significantly on their migration from the bottom sediments under oxygen deficiency and reduction conditions. The concentration of dissolved oxygen and the value of the redox potential were within 0–16.2 mg/dm3 and -129÷295 mV. Dissolved oxygen deficiency (0–5.4 mg/dm3 and 0–44% saturation) and transitional redox or reduction conditions (-129÷69 mV) in the water of the bottom horizon were observed throughout the year. The increase in the concentration of dissolved oxygen (12.1–16.2 mg/dm3 and 107–175% saturation) occurred only in the surface water horizon during the spring-autumn period. The concentration of ammonium nitrogen, nitrite and nitrate ions varied within 0–13.17, 0.006–0.186 and 0.016–0.142 mg N/dm3. The content of inorganic phosphorus and dissolved silicon reached 0.010–3.121 mg P/dm3 and 0.03–6.4 mg/dm3. The concentration of ammonium nitrogen, inorganic nitrogen, inorganic phosphorus and dissolved silicon near the bottom was always higher than in the water of the surface horizon. This is due to the formation of oxygen deficiency, transitional redox or reduction conditions, which increase the migration of nutrients from bottom sediments. The N:P ratio decreased from winter to autumn on average in the range of 7,2–2,6, which indicates an increase in the concentration of phosphorus in the water relative to nitrogen and the formation of favorable conditions for the development of blue-green algae. Favorable conditions for the supply of inorganic nitrogen and phosphorus from the bottom sediments are formed when the concentration of dissolved oxygen is ≤4 mg/dm3 and the value of the redox potential is ≤100 mV. It was established that the concentration of oxygen and the value of the redox potential affect the content of inorganic nitrogen and phosphorus, but the relationship between the studied indicators is nonlinear. The oxygen regime and the value of the redox potential don’t affect the content of dissolved silicon, and its concentration depends on the seasonal features of the development of diatoms.

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Ellgaard, L. "Catalysis of disulphide bond formation in the endoplasmic reticulum". Biochemical Society Transactions 32, nr 5 (26.10.2004): 663–67. http://dx.doi.org/10.1042/bst0320663.

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Disulphide bonds are critical for the maturation and stability of secretory and cell-surface proteins. In eukaryotic cells, disulphide bonds are introduced in the ER (endoplasmic reticulum), where the redox conditions are optimal to support their formation. Yet, the correct pairing of cysteine residues is not simple and often requires the assistance of redox-active proteins. The enzymes of the thiol-disulphide oxidoreductase family catalyse oxidation, reduction and isomerization, and thereby play important roles for the folding of many proteins. To allow all three redox reactions to take place concurrently in the same compartment, specific protein–protein interactions regulate the function of individual enzymes, while a careful balance of the ER redox environment is maintained. At the same time, the system must be capable of responding to changes in the cellular conditions, caused, for instance, by oxidative stress and protein misfolding. This review presents recent progress in understanding how ER redox conditions are regulated and how protein disulphides are formed in the ER of mammalian cells.

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