77 results on '"Alexander V. Rudnev"'
Search Results
2. Improving the lifetime of hybrid CoPc@MWCNT catalysts for selective electrochemical CO2-to-CO conversion
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Changzhe Sun, Yuhui Hou, Nicola Lüdi, Huifang Hu, María de Jesús Gálvez-Vázquez, Mike Liechti, Ying Kong, Menglong Liu, Rolf Erni, Alexander V. Rudnev, and Peter Broekmann
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Physical and Theoretical Chemistry ,Catalysis - Published
- 2022
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3. Effective perspiration is essential to uphold the stability of zero-gap MEA-based cathodes used in CO2 electrolysers
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Huifang Hu, Ying Kong, Menglong Liu, Viliam Kolivoška, Alexander V. Rudnev, Yuhui Hou, Rolf Erni, Soma Vesztergom, and Peter Broekmann
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Renewable Energy, Sustainability and the Environment ,540 Chemistry ,570 Life sciences ,biology ,General Materials Science ,General Chemistry - Abstract
The application of gas diffusion electrodes (GDEs) for the electrochemical reduction of CO2 to value-added products creates the possibility of achieving current densities of a few hundred mA cm-2. To achieve stable operation at such high reaction rates remains, however, a challenging task, due to the flooding of the GDE. In order to mitigate flooding in a zero-gap membrane-electrode assembly (MEA) configuration, paths for effective electrolyte perspiration inside the GDE structure have to be kept open during the electrolysis process. Here we demonstrate that apart from the operational parameters of the electrolysis and the structural properties of the supporting gas diffusion layers, also the chemical composition of the applied catalyst inks can play a decisive role in the electrolyte management of GDEs used for CO2 electroreduction. In particular, the presence of excess amounts of polymeric capping agents (used to stabilize the catalyst nanoparticles) can lead to a blockage of micropores, which hinders perspiration and initiates the flooding of the microporous layer. Here we use a novel ICP-MS analysis-based approach to quantitatively monitor the amount of perspired electrolyte that exits a GDE-based CO2 electrolyser, and we show a direct correlation between the break-down of effective perspiration and the appearance of flooding-the latter ultimately leading to a loss of electrolyser stability. We recommend the use of an ultracentrifugation-based approach by which catalyst inks containing no excess amount of polymeric capping agents can be formulated. Using these inks, the stability of electrolyses can be ensured for much longer times.
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- 2023
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4. Size‐Dependent Structural Alterations in Ag Nanoparticles during CO 2 Electrolysis in a Gas‐Fed Zero‐Gap Electrolyzer
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Huifang Hu, Menglong Liu, Ying Kong, Iván Zelocualtecatl Montiel, Yuhui Hou, Alexander V. Rudnev, and Peter Broekmann
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Electrochemistry ,Catalysis - Published
- 2022
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5. Electrodeposition of lanthanides from ionic liquids and deep eutectic solvents
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Alexander V. Rudnev
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Lanthanide ,chemistry.chemical_compound ,chemistry ,Inorganic chemistry ,Ionic liquid ,General Chemistry ,Eutectic system - Abstract
Lanthanides belong to the most important raw materials and are highly demanded in high-tech industry. Low-temperature electrochemical deposition of lanthanides and lanthanide-based alloys for recycling and obtaining functional materials can provide a real alternative to the currently used high-temperature electrolysis of molten salts. The review summarizes the advancements in the field of electrodeposition of lanthanides from organic ionic systems, such as ionic liquids and deep eutectic solvents. The growing interest in these ionic systems is due to their excellent physicochemical properties, in particular non-volatility, thermal and electrochemical stability. The review also discusses further prospects and potential of the electrochemical approach for obtaining lanthanide-containing advanced materials. The bibliography includes 219 references.
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- 2020
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6. Environment Matters: CO2RR Electrocatalyst Performance Testing in a Gas-Fed Zero-Gap Electrolyzer
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Peter Broekmann, Alexander V. Rudnev, Pavel Moreno-García, Yuhui Hou, María de Jesús Gálvez-Vázquez, Matthias Arenz, Heng Xu, Ivan Zelocualtecatl Montiel, Huifang Hu, Benjamin J. Wiley, Vitali Grozovski, and Shima Alinejad
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Electrolysis ,Materials science ,010405 organic chemistry ,General Chemistry ,010402 general chemistry ,Electrocatalyst ,01 natural sciences ,Catalysis ,Cathode ,0104 chemical sciences ,law.invention ,Reaction rate ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Electrode ,Gaseous diffusion ,Carbon monoxide - Abstract
Among the electrolyzers under development for CO2 electroreduction at practical reaction rates, gas-fed approaches that use gas diffusion electrodes (GDEs) as cathodes are the most promising. Howev...
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- 2020
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7. Structural Changes of Au(111) Single‐Crystal Electrode Surface in Ionic Liquids
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Matthias Arenz, Timo Jacob, Peter Broekmann, Areeg Abdelrahman, Elena B. Molodkina, Alexander V. Rudnev, and M. R. Ehrenburg
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Surface (mathematics) ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,law ,Electrode ,Ionic liquid ,Electrochemistry ,Scanning tunneling microscope ,Single crystal ,Catalysis ,Surface etching ,law.invention - Published
- 2020
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8. Redox-transitions in NO/NH3 adlayers on a Pt(111) electrode in an acidic solution
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Elena B. Molodkina, Inna G. Botryakova, Alexander V. Rudnev, and Maria R. Ehrenburg
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General Chemical Engineering ,Electrochemistry - Published
- 2023
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9. Over- and underpotential deposition of copper from a deep eutectic solvent: Pt(1 1 1) single crystal versus polycrystalline Pt substrates
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Oleg I. Zaytsev, Maria R. Ehrenburg, Elena B. Molodkina, Peter Broekmann, and Alexander V. Rudnev
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General Chemical Engineering ,Electrochemistry ,Analytical Chemistry - Published
- 2022
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10. Accelerating effect of water on electroreduction of lanthanide ions in a dicyanamide ionic liquid: A generic phenomenon
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Elena B. Molodkina, Maria R. Ehrenburg, and Alexander V. Rudnev
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General Chemical Engineering ,Electrochemistry ,Analytical Chemistry - Published
- 2022
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11. A General and Facile Approach for the Electrochemical Reduction of Carbon Dioxide Inspired by Deep Eutectic Solvents
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Peter Broekmann, Dmitry V. Vasilyev, Alexander V. Rudnev, and Paul J. Dyson
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Materials science ,General Chemical Engineering ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Chloride ,0104 chemical sciences ,chemistry.chemical_compound ,General Energy ,chemistry ,Chemical engineering ,Ionic liquid ,medicine ,Environmental Chemistry ,General Materials Science ,0210 nano-technology ,Ethylene glycol ,Choline chloride ,Eutectic system ,Electrochemical reduction of carbon dioxide ,medicine.drug - Abstract
Deep eutectic solvents (DESs) were applied to the electrochemical CO2 reduction reaction (CO2 RR). Choline-based DESs represent a non-toxic and inexpensive alternative to room-temperature ionic liquids (RTILs) as additives to the system or as electrolyte. Following the study on choline-based DESs this approach was generalized and simple and organic-soluble systems were devised based on the combination of organic chloride salts with ethylene glycol (EG), allowing the chlorides to be readily used as cocatalysts in the CO2 RR. This approach negates the need for anion exchange and, because the chloride salt is usually the least expensive one, substantially reduces the cost of the electrolyte and opens the way for high-throughput experimentation.
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- 2019
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12. Initial stages of silver electrodeposition on single crystal electrodes from ionic liquids
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Peter Broekmann, Alexander V. Rudnev, M. R. Ehrenburg, and Elena B. Molodkina
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Materials science ,General Chemical Engineering ,Nucleation ,02 engineering and technology ,Chronoamperometry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Monolayer ,Electrochemistry ,Physical chemistry ,Crystallite ,Scanning tunneling microscope ,0210 nano-technology ,Single crystal ,Dicyanamide ,Voltammetry - Abstract
We present a comprehensive study on the initial stages of silver electrodeposition on Pt (111), Au (111), and Au (100) single crystal surfaces in low-viscosity ionic liquids (ILs) containing dicyanamide anions: 1-butyl-1-methylpyrrolidinium dicyanamide [BMP][DCA] and 1-butyl-3-methylimidazolium dicyanamide [BMIm][DCA]. Electrochemical methods in combination with in situ scanning tunneling microscopy (STM) and ex situ atomic force microscopy (AFM) are employed to explore the Ag underpotential (upd) and overpotential (opd) deposition processes as well as the stability of the single crystal electrode surfaces in the absence of Ag+ ions. The substrate material is shown to significantly affect the mechanism of Ag deposit nucleation and growth in the ILs. While no Ag upd is detected on Pt (111), the formation of a Ag upd monolayer on a Au (111) electrode in both ILs is clearly visualized by in situ STM. The Ag adlayer formation on the Au electrodes in the underpotential regime facilitates Ag opd, which starts on Au (111) and Au (100) at much less negative potentials than on Pt (111). There is an excellent agreement between the electrochemical (voltammetry and chronoamperometry), AFM and STM data, demonstrating the nucleation and growth of individual Ag crystallites on Pt (111) according to the Volmer–Weber mechanism and the layer–by–layer growth of Ag deposit on Au (111) and Au (100). Only at high overpotentials, the Ag growth on the gold electrodes switches to the Stranski-Krastanov mode involving the appearance of 3D crystallites.
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- 2019
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13. Oxo-functionalised mesoionic NHC nickel complexes for selective electrocatalytic reduction of CO
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Simone, Bertini, Motiar, Rahaman, Abhijit, Dutta, Philippe, Schollhammer, Alexander V, Rudnev, Fredric, Gloaguen, Peter, Broekmann, and Martin, Albrecht
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Chemistry - Abstract
Strategies for the conversion of CO2 to valuable products are paramount for reducing the environmental risks associated with high levels of this greenhouse gas and offer unique opportunities for transforming waste into useful products. While catalysts based on nickel as an Earth-abundant metal for the sustainable reduction of CO2 are known, the vast majority produce predominantly CO as a product. Here, efficient and selective CO2 reduction to formate as a synthetically valuable product has been accomplished with novel nickel complexes containing a tailored C,O-bidentate chelating mesoionic carbene ligand. These nickel(ii) complexes are easily accessible and show excellent catalytic activity for electrochemical H+ reduction to H2 (from HOAc in MeCN), and CO2 reduction (from CO2-saturated MeOH/MeCN solution) with high faradaic efficiency to yield formate exclusively as an industrially and synthetically valuable product from CO2. The most active catalyst precursor features the 4,6-di-tert-butyl substituted phenolate triazolylidene ligand, tolerates different proton donors including water, and reaches an unprecedented faradaic efficiency of 83% for formate production, constituting the most active and selective Ni-based system known to date for converting CO2 into formate as an important commodity chemical., Adding value to CO2: Tunable carbene complexes of Earth-abundant nickel catalyze the electrochemical reduction of CO2 to formate with high efficiency and selectivity and without formation of any byproducts such as CO.
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- 2021
14. The promoting effect of water on the electrodeposition of Eu in a dicyanamide ionic liquid
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M. R. Ehrenburg, Alexander V. Rudnev, Elena B. Molodkina, and Artem Mishchenko
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Electrolysis ,Materials science ,General Chemical Engineering ,Inorganic chemistry ,02 engineering and technology ,Glassy carbon ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Ionic liquid ,Molten salt ,0210 nano-technology ,Polarization (electrochemistry) ,Dicyanamide - Abstract
Rare-earth elements (REEs) are one of the most important raw materials and are of vast significance for the modern hi-tech industry. Electrochemical deposition of REE-containing materials can provide a real alternative to currently used high-temperature processes of molten salt electrolysis. Here we study the process of Eu electrodeposition from 1‑butyl‑1-methylpyrrolidinium dicyanamide IL, [BMP][DCA], containing controlled amount of water. The Eu deposition is performed on Pt(111) single crystal as well as on Au(111) and glassy carbon electrodes. We show that addition of water (up to 3.092 M) to a [BMP][DCA] solution promotes the electroreduction of Eu ions to Eu(0) shifting the potential of Eu deposition in the positive direction. The potential shift is already pronounced after addition of a moderate water amount and is equal to ~0.28 V upon increase in cH2O from 0.012 to 0.167 M. Microscopic and X-ray spectroscopic analyses of the electrodes after potentiostatic polarization confirm the formation of Eu deposit, however Eu in the deposit is mainly in the oxidized form. The oxidation of electrochemically deposited Eu(0) can occur simultaneously with the electrodeposition process in the chemical reaction with residual or added water. Furthermore, the electrode material is found to affect the overpotential of Eu deposition, and the deposition accelerates in the order of GC
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- 2021
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15. Oxo-functionalised mesoionic NHC nickel complexes for selective electrocatalytic reduction of CO 2 to formate
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Martin Albrecht, Peter Broekmann, Frédéric Gloaguen, Motiar Rahaman, Philippe Schollhammer, Alexander V. Rudnev, Abhijit Dutta, Simone Bertini, Universität Bern [Bern], Chimie, Electrochimie Moléculaires et Chimie Analytique (CEMCA), Institut Brestois Santé Agro Matière (IBSAM), Université de Brest (UBO)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, and Russian Academy of Sciences [Moscow] (RAS)
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chemistry.chemical_element ,[CHIM.INOR]Chemical Sciences/Inorganic chemistry ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,12. Responsible consumption ,Catalysis ,chemistry.chemical_compound ,540 Chemistry ,Environmental Chemistry ,Chelation ,Formate ,Oxo-functionalised mesoionic NHC nickel complexes ,Ni ,010405 organic chemistry ,Ligand ,Mesoionic ,Pollution ,Combinatorial chemistry ,3. Good health ,0104 chemical sciences ,Nickel ,chemistry ,Yield (chemistry) ,CO 2 ,H2 ,570 Life sciences ,biology ,Carbene - Abstract
International audience; Strategies for the conversion of CO2 to valuable products are paramount for reducing the environmental risks associated with high levels of this greenhouse gas and offer unique opportunities for transforming waste into useful products. While catalysts based on nickel as an Earth-abundant metal for the sustainable reduction of CO2 are known, the vast majority produce predominantly CO as a product. Here, efficient and selective CO2 reduction to formate as a synthetically valuable product has been accomplished with novel nickel complexes containing a tailored C,O-bidentate chelating mesoionic carbene ligand. These nickel(II) complexes are easily accessible and show excellent catalytic activity for electrochemical H+ reduction to H2 (from HOAc in MeCN), and CO2 reduction (from CO2-saturated MeOH/MeCN solution) with high faradaic efficiency to yield formate exclusively as an industrially and synthetically valuable product from CO2. The most active catalyst precursor features the 4,6-di-tert-butyl substituted phenolate triazolylidene ligand, tolerates different proton donors including water, and reaches an unprecedented faradaic efficiency of 83% for formate production, constituting the most active and selective Ni-based system known to date for converting CO2 into formate as an important commodity chemical.
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- 2021
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16. Municipal services and peculiarities of regulating the process of their provision
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Alexander V. Rudnev
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education.field_of_study ,Government ,Municipal entity ,lcsh:LC8-6691 ,Jurisdiction ,lcsh:Special aspects of education ,Process (engineering) ,Population ,Legislature ,Legislation ,ComputingMilieux_LEGALASPECTSOFCOMPUTING ,Public administration ,Local community ,Management ,Quality of services ,Municipal services ,Income ,Business ,education ,lcsh:L ,lcsh:Education - Abstract
Despite the great social importance of providing services to the population, solving this problem is complicated at present by difficulties associated with the lack of a unified methodology for managing services at the level of municipal entities, state social minimum standards, and also not fully resolved issues of delimiting powers and subjects of jurisdiction between the levels of government. It is necessary to understand that the provision of services to the local population, among other things, is the basis for the multiplicative development of the economy of a municipal entity. In modern conditions, there is a need to make some clarifications in the conceptual apparatus, highlighting the services provided to the population on the territory of a municipal entity ensuring the life of the local community. Currently, the legislation of the Russian Federation does not contain a clear definition of municipal functions, services, and works. The legislative acts regulating the basis for the provision of municipal services do not cover the entire range of actually provided services and are not coordinated with each other.
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- 2021
17. Underpotential Deposition of Silver on Au(111) from an Air‐ and Water‐Stable Ionic Liquid Visualized by In‐Situ STM
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M. R. Ehrenburg, Alexander V. Rudnev, Peter Broekmann, and Elena B. Molodkina
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In situ ,Materials science ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Underpotential deposition ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Ionic liquid ,Electrochemistry ,0210 nano-technology - Published
- 2018
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18. Solvent effect on electron transfer through alkanethiols
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Renat R. Nazmutdinov, Victoria A. Nikitina, Alexander V. Rudnev, Galina A. Tsirlina, and Thomas Wandlowski
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Aqueous solution ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Ruthenium ,chemistry.chemical_compound ,Electron transfer ,Reaction rate constant ,Ferrocene ,chemistry ,Ionic liquid ,Electrochemistry ,Physical chemistry ,Crystallite ,Solvent effects ,0210 nano-technology - Abstract
The data on the rate constants for ferrocene/ferrocenium (Fc/Fc + ) electron transfer in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate ([bmim][BF 4 ]) are reported for a series of -S-(CH 2 ) n -Fc adlayers (n = 8…16) on polycrystalline gold. The values and trends are compared to the previously published data for similar series in aqueous medium, as well as to the results for ‘free’ Fc at -S-(CH 2 ) n − 1 -CH 3 modified gold in the same ionic liquid. For the latter case, the trend is opposite as compared to that in the available aqueous series (attached and ‘free’ ruthenium ammine complex): the ratio of rate constants for attached and ‘free’ reactants decreases with electrode-reactant distance in the former case, and increases in the latter. The presented comparison discovers the role of reactant and product work terms, which are essential for attached reactants as well because of conformational diversity. Corresponding contributions are estimated from molecular modeling and considered in terms of reaction volume.
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- 2018
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19. Surface Structure Sensitivity of CO2 Electroreduction on Low-Index Gold Single Crystal Electrodes in Ionic Liquids
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M. R. Ehrenburg, Yongchun Fu, Alexander V. Rudnev, and Peter Broekmann
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Materials science ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Catalysis ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Electrode ,Ionic liquid ,Electrochemistry ,Surface structure ,Sensitivity (control systems) ,Scanning tunneling microscope ,0210 nano-technology ,Single crystal ,Surface reconstruction - Published
- 2018
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20. Interfacial effects in the electro(co)deposition of Nd, Fe, and Nd-Fe from an ionic liquid with controlled amount of water
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Alexander V. Rudnev, I. A. Arkhipushkin, M. R. Ehrenburg, and Elena B. Molodkina
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Lanthanide ,Aqueous solution ,Materials science ,General Chemical Engineering ,Oxide ,chemistry.chemical_element ,Ionic bonding ,Neodymium ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Ionic liquid ,Electrochemistry ,Hydroxide ,Electrowinning - Abstract
Neodymium is one of the most important rare earth elements due to its various applications, above all, in permanent magnets in consumer electronics and renewable power sources. Production of primary Nd is a rather complex and expensive process characterized by significant import dependency, which brings to the forefront Nd recovery from secondary sources. Electrowinning as one of the cheapest and processible solutions is not applicable for electropositive rare earths in aqueous systems but is a good option in the case of solutions based on ionic organic solvents. Nd electrodeposition and its induced codeposition with Fe are studied at room temperature in a fluorine-free dicyanamide ionic liquid (IL) using a complex set of electrochemical and physical (spectroscopic and microscopic) methods in dry solutions and in the presence of water. We show that the addition of water significantly promotes electrodeposition of individual metals in the respective single-component solutions but produces a hindering effect on the induced codeposition of Nd with Fe. We suggest an explanation for the acceleration of individual Nd and Fe in the presence of water based on the effects at the IL/electrode interface and for the inhibition of Nd-Fe deposition in the presence of water owing to the decelerating effect of formation of Nd oxide/hydroxide film. This is the first systematic study of the effect of water on the rare earth–transition metal codeposition in ILs providing information that can be essential for production of secondary rare earths and fabrication of novel lanthanide-based materials.
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- 2021
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21. Electroreduction of nitrate anions on cubic and polyoriented platinum nanoparticles modified by copper adatoms
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I.G. Botryakova, M. R. Ehrenburg, Elena B. Molodkina, A. I. Danilov, and Alexander V. Rudnev
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General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,Glassy carbon ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Platinum nanoparticles ,01 natural sciences ,Copper ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Transmission electron microscopy ,Specific surface area ,Electrochemistry ,Perchloric acid ,Cyclic voltammetry ,0210 nano-technology ,Single crystal - Abstract
In this work, electroreduction of nitrate anions on bare and copper-modified platinum nanoparticles (Pt NPs) supported on glassy carbon is studied using cyclic voltammetry. Two types of Pt NPs are chosen for this purpose: unshaped (polyoriented) NPs and cubic NPs displaying the preferential (100) orientation of faces. The modification of cubic and polyoriented Pt NPs by copper adatoms with submonolayer coverages is performed in a controlled way in solutions containing small concentrations of Cu 2 + ions, 10 − 5 M. Nitrate reduction is studied first in copper-free solutions and then in the presence of 10 − 5 M Cu 2 + . The transmission electron microscopy and voltammetric measurements of the cubic NPs indicate the presence of a significant amount of Pt(100) terraces on the surface of these NPs. In perchloric acid solutions containing 0.02 M NaNO 3 and 10 − 5 M Cu 2 + , accumulation of copper adatoms on the NPs results in a fast increase in the currents of nitrate electroreduction. These reduction currents on the cubic NPs are up to three times higher than on the polyoriented NPs at Cu coverages of 0.20–0.35. The comparison of the data on Pt NPs with the data for single crystal electrodes with (100) terraces of different width (Pt(610), Pt(210)) shows that the behavior of NPs can be simulated on the basis of the data for single crystal faces with wide (cubic NPs) and narrow (unshaped NPs) (100) terraces. Thus, cubic NPs manifest rather a high electrocatalytic activity in the studied reaction of nitrate anion electroreduction, which is typical for single crystal surfaces with relatively wide Pt(100) terraces. At the same time, in comparison with macro single crystalline electrodes, these NPs are characterized by sufficiently higher stability, larger specific surface area, and flexibility in application.
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- 2017
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22. Single Graphene Layer on Pt(111) Creates Confined Electrochemical Environment via Selective Ion Transport
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Yongchun Fu, Alexander V. Rudnev, Gustav K. H. Wiberg, and Matthias Arenz
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540 Chemistry ,570 Life sciences ,biology ,General Medicine - Abstract
Graphene is a promising candidate for an ideal membrane material. Its ultralow (one‐atomic) thickness potentially provides high permeation and at the same time high selectivity. Here, it is shown that these properties can be used to create a confined, two‐dimensional electrochemical environment between a graphene layer and a single‐crystal Pt(111) surface. The well‐defined fingerprint voltammetric characteristics of Pt(111) provide an immediate information about the penetration and intercalation of ions into the confined space. These processes are shown to be highly selective.
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- 2017
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23. Transport Matters: Boosting CO2 Electroreduction in Mixtures of [BMIm][BF4 ]/Water by Enhanced Diffusion
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Alexander V. Rudnev, Soma Vesztergom, Yongchun Fu, Florian Stricker, Ilche Gjuroski, Peter Broekmann, Julien Furrer, and Noémi Kovács
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Aqueous solution ,Tetrafluoroborate ,Chemistry ,Diffusion ,Inorganic chemistry ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,6. Clean water ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Viscosity ,chemistry.chemical_compound ,13. Climate action ,Ionic liquid ,Physical and Theoretical Chemistry ,0210 nano-technology ,Electrochemical reduction of carbon dioxide - Abstract
Room-temperature ionic liquids (RTILs) are promising new electrolytes for efficient carbon dioxide reduction. However, due to their high viscosity, the mass transport of CO2 in RTILs is typically slow, at least one order of magnitude slower than in aqueous systems. One possibility to improve mass transport in RTILs is to decrease their viscosity through dilution with water. Herein, defined amounts of water are added to 1-butyl-3methylimidazolium tetrafluoroborate ([BMIm][BF4 ]), which is a hydrophilic RTIL. Electrochemical measurements on quiescent and hydrodynamic systems both indicate enhanced CO2 electroreduction. This enhancement has its origin in thermodynamic/kinetic effects (the addition of water increases the availability of H+ , which is a reaction partner of CO2 electroreduction) and in an increased rate of transport due to lower viscosity. Electrochemically determined diffusion coefficients for CO2 in [BMIm][BF4 ]/water systems agree well with values determined by NMR spectroscopy.
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- 2017
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24. Scanning probe microscopy of an electrode/ionic liquid interface
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Alexander V. Rudnev and Yongchun Fu
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Materials science ,Interface (computing) ,Nanotechnology ,02 engineering and technology ,Electrolyte ,Scanning capacitance microscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,Scanning probe microscopy ,chemistry ,Electrode ,Ionic liquid ,Electrochemistry ,Scanning ion-conductance microscopy ,Energy transformation ,0210 nano-technology - Abstract
The full understanding of an electrode/ionic liquid (IL) interface is crucial for the use of ILs as electrolytes in applications for energy conversion and storage. Scanning probe microscopy (SPM) has proved to be a very powerful method to probe the local structure of this interface and obtain real-time and real-space images with an atomic resolution. Herein we present the recent advances in SPM studies on the electrode/IL interface and emphasize the aspects that are most important in our opinion. We finish with some thoughts on future research directions in the field.
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- 2017
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25. The promoting effect of water on the electroreduction of CO 2 in acetonitrile
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Thomas Wandlowski, Alexander V. Rudnev, Ulmas E. Zhumaev, Julien Furrer, Soma Vesztergom, Peter Broekmann, and Akiyoshi Kuzume
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Aqueous solution ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,Overpotential ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Solubility ,Cyclic voltammetry ,0210 nano-technology ,Platinum ,Acetonitrile ,Electrochemical reduction of carbon dioxide - Abstract
The promoting effect of water on the electrochemical reduction of carbon dioxide (CO2) from non-aqueous solvents has been studied by means of cyclic voltammetry and in-situ surface-enhanced infrared absorption spectroscopy (SEIRAS). CO2 electroreduction on gold is known to be highly selective towards CO formation in aqueous and in non-aqueous media. The use of non-aqueous solvents is advantageous due to the significantly increased solubility of CO2 compared to aqueous systems. However, in the absence of any proton source, extremely high overpotentials are required for the CO2 electroreduction. In this work, we demonstrate for the first time a tremendous accelerating effect of water additives on the electroreduction of CO2 taking place at gold/acetonitrile interfaces. Already moderate amounts of water, in the concentration range of 0.5 to 0.7 M, are sufficient to decrease significantly the overpotential of CO2 reduction while keeping the CO2 concentration as high as in the pure acetonitrile. The effect of water additives on the mechanism of CO2 electroreduction on gold is discussed on the basis of electrochemical and IR spectroscopic data. The results obtained from gold are compared to analogue experiments carried out on platinum.
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- 2016
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26. Electrodeposition of chromium on single-crystal electrodes from solutions of Cr(II) and Cr(III) salts in ionic liquids
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Peter Broekmann, M. R. Ehrenburg, Alexander V. Rudnev, and Elena B. Molodkina
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Chemistry ,General Chemical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,law.invention ,chemistry.chemical_compound ,Chromium ,Scanning probe microscopy ,X-ray photoelectron spectroscopy ,law ,Ionic liquid ,Electrochemistry ,Scanning tunneling microscope ,0210 nano-technology ,Platinum ,Dissolution ,Single crystal - Abstract
Herein, we present a study on the initial stages of chromium electrodeposition on platinum and gold single-crystal surfaces from an ionic liquid containing dicyanamide anions. We employed conventional electrochemical techniques in combination with in situ and ex situ scanning probe microscopy (in situ scanning tunneling microscopy (STM), ex situ atomic force microscopy (AFM)) and ex situ X-ray photoemission spectroscopy (XPS). Cr electrodeposition was carried out from Cr(II) and Cr(III) solutions of low (10 mM) and high (250 mM) Cr concentrations. The microscopic and spectroscopic approaches clearly demonstrate the formation of a Cr deposit, although the voltammetric responses are difficult to interpret. The absence of a pronounced Cr dissolution peak in the backward scan of the cyclic voltammograms and a relatively low amount of Cr deposit (as confirmed by AFM) suggest the passivation of Cr and the substrate during deposition, thus hindering both further deposition of Cr and its anodic dissolution.
- Published
- 2020
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27. Pyrazolium Ionic Liquid Co-catalysts for the Electroreduction of CO2
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Paul J. Dyson, Alexander V. Rudnev, Erfan Shirzadi, Peter Broekmann, and Dmitry V. Vasilyev
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chemistry.chemical_classification ,Electrolysis ,Chemistry ,Inorganic chemistry ,Energy Engineering and Power Technology ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,law ,Ionic liquid ,Materials Chemistry ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering ,Cyclic voltammetry ,0210 nano-technology ,Acetonitrile ,Alkyl ,Electrochemical reduction of carbon dioxide - Abstract
Pyrazolium ionic liquids (Pz ILs) were employed as co-catalysts for electrochemical conversion of CO2 to CO on a silver disk electrode, leading to a significant decrease in the onset potential for the reduction (ca. 500 mV). The electrochemical conversion of CO2 to CO proceeds in acetonitrile-based electrolytes containing Pz IL co-catalysts with Faradaic efficiencies (FEs) of nearly 100% over a range of at least 0.5 V, and the Pz cations remain intact over prolonged CO2 electrolysis. The impact of alkyl substituents on the Pz ring and the influence of water on the process are also discussed.
- Published
- 2018
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28. Robust Organic Radical Molecular Junctions Using Acetylene Terminated Groups for C−Au Bond Formation
- Author
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Enrique Burzurí, Ignacio Jose Olavarria-Contreras, Diego Gutiérrez, Francesc Bejarano, Marta Mas-Torrent, Herre S. J. van der Zant, Jaume Veciana, Concepció Rovira, Alexander V. Rudnev, Ivan Rungger, Andrea Droghetti, Núria Crivillers, European Commission, Centro de Investigación Biomédica en Red Bioingeniería, Biomateriales y Nanomedicina (España), Dirección General de Investigación Científica y Técnica, DGICT (España), Generalitat de Catalunya, Ministerio de Economía y Competitividad (España), and Netherlands Organization for Scientific Research
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Mass-spectrometry ,FOS: Physical sciences ,Alkyne ,Self-assembled monolayers ,02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Covalent bonds ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Monolayer ,Molecule ,Gold nanoparticles ,Au(111) ,chemistry.chemical_classification ,Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Conductance ,General Chemistry ,021001 nanoscience & nanotechnology ,Electron transport chain ,0104 chemical sciences ,Acetylene ,chemistry ,Covalent bond ,Tunneling spectroscopy ,Density functional theory ,0210 nano-technology - Abstract
Bejarano, Francesc et al., Organic paramagnetic and electroactive molecules are attracting interest as core components of molecular electronic and spintronic devices. Currently, further progress is hindered by the modest stability and reproducibility of the molecule/electrode contact. We report the synthesis of a persistent organic radical bearing one and two terminal alkyne groups to form Au-C σ bonds. The formation and stability of self-assembled monolayers and the electron transport through single-molecule junctions at room temperature have been studied. The combined analysis of both systems demonstrates that this linker forms a robust covalent bond with gold and a better-defined contact when compared to traditional sulfur-based linkers. Density functional theory and quantum transport calculations support the experimental observation highlighting a reduced variability of conductance values for the C-Au based junction. Our findings advance the quest for robustness and reproducibility of devices based on electroactive molecules., We acknowledge Dr. G. Sauthier from the ICN2 for the XPS measurements, Prof. Carlos Gomez from IcMOL for the SQUID measurements, A. Bernabé and Dr. V. Lloveras from ICMAB for the LDI-ToF and EPR measurements, respectively. This work was supported by FET ACMOL project (GA no. 618082), CIBER-BBN, the DGI (Spain) project FANCY CTQ2016-80030-R, the Generalitat de Catalunya (2014-SGR-17) and the MINECO, through the “Severo Ochoa” Programme for Centers of Excel-lence in R&D (SEV-2015-0496). F.B he is enrolled in the Materi-als Science Ph.D. program of UAB. We thank the Dutch science foundation NWO/FOM for financial support.
- Published
- 2018
29. Break junction under electrochemical gating: testbed for single-molecule electronics
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Wenjing Hong, Thomas Wandlowski, Cancan Huang, and Alexander V. Rudnev
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Materials science ,Molecular junction ,Testbed ,Molecular scale electronics ,Molecular electronics ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Gating ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,0210 nano-technology ,Break junction - Abstract
Molecular electronics aims to construct functional molecular devices at the single-molecule scale. One of the major challenges is to construct a single-molecule junction and to further manipulate the charge transport through the molecular junction. Break junction techniques, including STM break junctions and mechanically controllable break junctions are considered as testbed to investigate and control the charge transport on a single-molecule scale. Moreover, additional electrochemical gating provides a unique opportunity to manipulate the energy alignment and molecular redox processes for a single-molecule junction. In this review, we start from the technical aspects of the break junction technique, then discuss the molecular structure-conductance correlation derived from break junction studies, and, finally, emphasize electrochemical gating as a promising method for the functional molecular devices.
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- 2015
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30. Electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy: correlating structural information and adsorption processes of pyridine at the Au(hkl) single crystal/solution interface
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Thomas Wandlowski, Panneerselvam Rajapandiyan, Yue-Jiao Zhang, Jason R. Anema, Alexander V. Rudnev, Jacek Lipkowski, Song-Bo Li, Jian-Feng Li, Zhong-Qun Tian, and Wenjing Hong
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Nanoparticle ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,symbols.namesake ,chemistry.chemical_compound ,Crystallography ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Pyridine ,Electrode ,symbols ,0210 nano-technology ,Raman spectroscopy ,Single crystal - Abstract
Electrochemical methods are combined with shell-isolated nanoparticle-enhanced Raman spectroscopy (EC-SHINERS) for a comprehensive study of pyridine adsorption on Au(111), Au(100) and Au(110) single crystal electrode surfaces. The effects of crystallographic orientation, pyridine concentration, and applied potential are elucidated, and the formation of a second pyridine adlayer on Au(111) is observed spectroscopically for the first time. Electrochemical and SHINERS results correlate extremely well throughout this study, and we demonstrate the potential of EC-SHINERS for thorough characterization of processes occurring on single crystal surfaces. Our method is expected to open up many new possibilities in surface science, electrochemistry and catalysis. Analytical figures of merit are discussed.
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- 2015
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31. DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers
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Yuliia Vyborna, Mykhailo Vybornyi, Alexander V. Rudnev, and Robert Häner
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Models, Molecular ,Polymers ,Supramolecular chemistry ,macromolecular substances ,010402 general chemistry ,01 natural sciences ,Catalysis ,Polymerization ,Supramolecular assembly ,chemistry.chemical_compound ,Ribbon ,Polymer chemistry ,Nanotechnology ,chemistry.chemical_classification ,Pyrenes ,Base Sequence ,010405 organic chemistry ,technology, industry, and agriculture ,DNA ,General Medicine ,General Chemistry ,Polymer ,0104 chemical sciences ,Supramolecular polymers ,chemistry ,Nucleic Acid Conformation ,Self-assembly - Abstract
The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5'-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.
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- 2015
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32. Assembly of Extra-Large Nanosheets by Supramolecular Polymerization of Amphiphilic Pyrene Oligomers in Aqueous Solution
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Alexander V. Rudnev, Robert Häner, and Mykhailo Vybornyi
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Materials science ,Aqueous solution ,General Chemical Engineering ,Supramolecular chemistry ,Trimer ,Nanotechnology ,General Chemistry ,Oligomer ,Fluorescence spectroscopy ,chemistry.chemical_compound ,chemistry ,Polymerization ,Chemical engineering ,Amphiphile ,Materials Chemistry ,Pyrene - Abstract
The precise arraying of functional entities in a reproducible and predictable way in morphologically well-defined shapes is a key challenge in materials science. In this work, we describe the importance of kinetic effects in the two-dimensional (2D) self-assembly of a negatively charged pyrene trimer (Py3) in aqueous media. Under optimized experimental conditions the chain-folded oligomers assemble into exceptionally thin planar assemblies (∼2 nm thick) with a very high aspect ratio (area/thickness ratio ≈ 107 nm). The morphology of the nanosheets was characterized by different microscopic techniques (AFM, TEM, and optical microscopy), while UV-vis and fluorescence spectroscopy revealed details on the intramolecular folding of the oligomer strands. Temperature control was shown to be crucial for preventing the formation of kinetically trapped states, thus allowing the development of extra-large 2D assemblies.
- Published
- 2015
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33. Single Graphene Layer on Pt(111) Creates Confined Electrochemical Environment via Selective Ion Transport
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Matthias Arenz, Yongchun Fu, Alexander V. Rudnev, and Gustav K. H. Wiberg
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Graphene ,Intercalation (chemistry) ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Permeation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Ion ,law.invention ,Membrane ,law ,0210 nano-technology ,Confined space ,Ion transporter - Abstract
Graphene is a promising candidate for an ideal membrane material. Its ultralow (one-atomic) thickness potentially provides high permeation and at the same time high selectivity. Here, it is shown that these properties can be used to create a confined, two-dimensional electrochemical environment between a graphene layer and a single-crystal Pt(111) surface. The well-defined fingerprint voltammetric characteristics of Pt(111) provide an immediate information about the penetration and intercalation of ions into the confined space. These processes are shown to be highly selective.
- Published
- 2017
34. CO2 Electroreduction on Cu-Modified Platinum Single Crystal Electrodes in Aprotic Media
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Inna G. Botriakova, A. I. Danilov, M. R. Ehrenburg, Alexander V. Rudnev, Thomas Wandlowski, and Elena B. Molodkina
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chemistry.chemical_compound ,Chemistry ,Propylene carbonate ,Electrode ,Inorganic chemistry ,Electrochemistry ,chemistry.chemical_element ,Crystallite ,Platinum ,Acetonitrile ,Copper ,Single crystal - Abstract
Techniques of electrode modification by copper deposits are developed that allow obtaining compact bulk quasi-epitaxial deposits on basal Pt(hkl) single crystal faces. The issues of the deposit roughness and characterization are discussed. Problems of drying and transferring electrodes with copper deposits into other solutions are considered. The obtained deposits are used for CO2 electroreduction in propylene carbonate and acetonitrile solutions of 0.1 M TBAPF6, and the relationship between the electrode surface structure and its electrocatalytic activity in CO2 electroreduction is discussed. We also demonstrate that the restructuring of Cu deposits occurs upon CO2 electroreduction. Complementary reactivity studies are presented for bare Pt(hkl) and Cu(hkl) single crystal electrodes. Cu-modified Pt(hkl) electrodes display the highest activity as compared to bare Pt(hkl) and Cu(hkl). Particularly, the Cu/Pt(110) electrode shows the highest activity among the electrodes under study. Such high activity of Cu/Pt(hkl) electrodes can be explained not only by the increasing actual surface area but also by structural effects, namely by the presence of a large amount of specific defect sites (steps, kinks) on Cu crystallites.
- Published
- 2014
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35. Long Distance Electron Transfer at the Metal/Alkanethiol/Ionic Liquid Interface
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Thomas Wandlowski, Alexander V. Rudnev, Galina A. Tsirlina, and Victoria A. Nikitina
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Range (particle radiation) ,Chemistry ,Analytical chemistry ,Diabatic ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,Electron transfer ,General Energy ,Reaction rate constant ,Chemical physics ,law ,Monolayer ,Ionic liquid ,Physical and Theoretical Chemistry ,Scanning tunneling microscope ,Adiabatic process - Abstract
The rate constants of simple electron transfer (ET) reactions in room temperature ionic liquids (ILs) available now are rather high, typically at the edge of experimental accuracy. To consider ET phenomena in these media in view of theory developed earlier for molecular solvents, it is crucial to provide quantitative comparison of experimental kinetic data for certain reactions. We report this comparison for ferrocene/ferrocenium reaction. The ET distance is fixed by Au surface modification by alkanethiol self-assembled monolayers, which were characterized by in situ scanning tunneling microscopy. The dependence of ln kapp on barrier thickness in the range of ca. 6–20 A is linear, with a slope typical for the same plots in aqueous media. This result confirms diabatic mode of Fc oxidation at long distance. The data for shorter ET distances point to the adiabatic regime of ET at a bare gold surface, although more detailed computational studies are required to justify this conclusion.
- Published
- 2014
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36. CO Oxidation on Pt(100): New Insights based on Combined Voltammetric, Microscopic and Spectroscopic Experiments
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Thomas Wandlowski, Alexander V. Rudnev, Yongchun Fu, and Akiyoshi Kuzume
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Chemistry ,General Chemical Engineering ,Kinetics ,Analytical chemistry ,Nanoparticle ,Substrate (electronics) ,Electrochemistry ,law.invention ,symbols.namesake ,law ,Electrode ,symbols ,Scanning tunneling microscope ,Raman spectroscopy ,Electrode potential - Abstract
We present an experimental study of the CO electro-oxidation on Pt(100)-(1 × 1) electrodes employing electrochemical methods in combination with in situ scanning tunneling microscopy (STM) and shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). We discussed the nature and stability of the active sites in the preignition region in the presence of dissolved CO (COb) and monitored substrate structure changes during the COb electro-oxidation process. We corroborated that the electro-oxidation kinetics is determined decisively by the history of CO adlayer formation. A new mechanism was proposed for Pt(100) electrode deactivation in the preignition region after excursion of electrode potential to COb ignition region. We believe that this mechanism takes place on Pt surfaces independently on their crystallographic orientation.
- Published
- 2014
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37. Promising anchoring groups for single-molecule conductance measurements
- Author
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Thomas Wandlowski, Alexander V. Rudnev, Pavel Moreno-García, Wenjing Hong, Cancan Huang, Veerabhadrarao Kaliginedi, and Masoud Baghernejad
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Stereochemistry ,General Physics and Astronomy ,Anchoring ,Conductance ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electron transport chain ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Crystallography ,chemistry ,law ,Covalent bond ,Thiophene ,Molecule ,Physical and Theoretical Chemistry ,Scanning tunneling microscope ,0210 nano-technology ,Break junction - Abstract
The understanding of the charge transport through single molecule junctions is a prerequisite for the design and building of electronic circuits based on single molecule junctions. However, reliable and robust formation of such junctions is a challenging task to achieve. In this topical review, we present a systematic investigation of the anchoring group effect on single molecule junction conductance by employing two complementary techniques, namely scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques, based on the studies published in the literature and important results from our own work. We compared conductance studies for conventional anchoring groups described earlier with the molecular junctions formed through π-interactions with the electrode surface (Au, Pt, Ag) and we also summarized recent developments in the formation of highly conducting covalent Au-C σ-bonds using oligophenyleneethynylene (OPE) and an alkane molecular backbone. Specifically, we focus on the electron transport properties of diaryloligoyne, oligophenyleneethynylene (OPE) and/or alkane molecular junctions composed of several traditional anchoring groups, (dihydrobenzo[b]thiophene (BT), 5-benzothienyl analogue (BTh), thiol (SH), pyridyl (PY), amine (NH2), cyano (CN), methyl sulphide (SMe), nitro (NO2)) and other anchoring groups at the solid/liquid interface. The qualitative and quantitative comparison of the results obtained with different anchoring groups reveals structural and mechanistic details of the different types of single molecular junctions. The results reported in this prospective may serve as a guideline for the design and synthesis of molecular systems to be used in molecule-based electronic devices.
- Published
- 2014
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38. Quantifying perchlorate adsorption on Au(111) electrodes
- Author
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Alexander V. Rudnev, Ulmas E. Zhumaev, Adelene Lai, Akiyoshi Kuzume, Ilya Pobelov, and Thomas Wandlowski
- Subjects
General Chemical Engineering ,Inorganic chemistry ,Valency ,Infrared spectroscopy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,7. Clean energy ,01 natural sciences ,0104 chemical sciences ,Perchlorate ,chemistry.chemical_compound ,Adsorption ,Adsorption kinetics ,chemistry ,Electrode ,Electrochemistry ,Cyclic voltammetry ,0210 nano-technology ,Spectroscopy - Abstract
Perchlorate adsorption on Au(1 1 1) was investigated by cyclic voltammetry and surface-enhanced infrared absorption spectroscopy. We found that the electrosorption valency of ClO4− on Au(1 1 1) is ∼ 0.6 and the total coverage of ClO4− on Au(1 1 1) is higher (∼ 0.15) than previously estimated (∼ 0.04). Based on the experimental adsorption isotherms obtained from infrared spectra and the reconstruction-free cyclic voltammograms, we proposed a mechanism for the ClO4− adsorption on Au(1 1 1).
- Published
- 2014
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39. Tubes or sheets: divergent aggregation pathways of an amphiphilic 2,7-substituted pyrene trimer
- Author
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Alexander V. Rudnev, Robert Häner, Mykhailo Vybornyi, Yamileidi Bur-Cecilio Hechevarria, and Marlene Glauser
- Subjects
Aqueous solution ,Chemistry ,Metals and Alloys ,Supramolecular chemistry ,Trimer ,Nanotechnology ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Polymerization ,540 Chemistry ,Polymer chemistry ,Amphiphile ,Materials Chemistry ,Ceramics and Composites ,570 Life sciences ,biology ,Pyrene - Abstract
The self-assembly of an amphiphilic 2,7-linked pyrene trimer in an aqueous environment into two morphologically related forms is described. Supramolecular polymerization leads to the simultaneous formation of nanosheets and nanotubes.
- Published
- 2015
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40. Electro-oxidation of Au(111) in contact with aqueous electrolytes: New insight from in situ vibration spectroscopy
- Author
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Thomas Wandlowski, Akiyoshi Kuzume, Thu-Hien Vu, Ulmas E. Zhumaev, Jian-Feng Li, and Alexander V. Rudnev
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Chemistry ,General Chemical Engineering ,Analytical chemistry ,Oxide ,Infrared spectroscopy ,law.invention ,symbols.namesake ,chemistry.chemical_compound ,Adsorption ,law ,Electrochemistry ,symbols ,Scanning tunneling microscope ,Cyclic voltammetry ,Raman spectroscopy ,Spectroscopy ,Single crystal - Abstract
We carried out a comprehensive study of Au(1 1 1) oxidation–reduction in the presence of (hydrogen-) sulfate ions on ideally smooth and stepped Au(S)[n(1 1 1)-(1 1 1)] single crystal electrodes using cyclic voltammetry, in situ scanning tunneling microscopy (STM) and vibration spectroscopy, such as surface-enhanced infrared absorption spectroscopy (SEIRAS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). Surface structure changes and the role of surface defects in the potential regions of double layer charging and gold oxidation/reduction are discussed based on cyclic voltammetry and in situ STM data. SEIRAS and SHINERS provide complementary information on the chemical nature of adsorbates. In particular, the potential-dependent formation and stability ranges of adsorbed sulfate, hydroxide-species and of gold surface oxide could be resolved in detail. Based on our experimental observations, we proposed new and extended mechanisms of gold surface oxidation and reduction in 1.0 M H2SO4 and 1.0 M Na2SO4.
- Published
- 2013
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- View/download PDF
41. In Situ SHINERS at Electrochemical Single-Crystal Electrode/Electrolyte Interfaces: Tuning Preparation Strategies and Selected Applications
- Author
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Alexander V. Rudnev, Yongchun Fu, Jian-Feng Li, Thomas Wandlowski, and Nataraju Bodappa
- Subjects
Chemistry ,Inorganic chemistry ,General Engineering ,General Physics and Astronomy ,Nanoparticle ,chemistry.chemical_element ,Electrolyte ,Electrochemistry ,symbols.namesake ,Electrode ,symbols ,General Materials Science ,Cyclic voltammetry ,Platinum ,Raman spectroscopy ,Single crystal - Abstract
We have studied Au(55 nm)@SiO2 nanoparticles (NPs) on two low-index phases of gold and platinum single crystal electrodes in ClO4(-) and SO4(2-) ion-containing electrolytes by both electrochemical methods and in-situ shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS). We showed the blocking of the electrode with surfactants originating from the synthesis of as-prepared SHINERS NPs. We introduce an efficient procedure to overcome this problem, which provides a fundamental platform for the application of SHINERS in surface electrochemistry and beyond. Our method is based on a hydrogen evolution treatment of the SHINERS-NP-modified single-crystal surfaces. The reliability of our preparation strategy is demonstrated in electrochemical SHINERS experiments on the potential-controlled adsorption and phase formation of pyridine on Au(hkl) and Pt(hkl). We obtained high-quality Raman spectra on these well-defined and structurally carefully characterized single-crystal surfaces. The analysis of the characteristic A1 vibrational modes revealed perfect agreement with the interpretation of single-crystal voltammetric and chronoamperometric experiments. Our study demonstrates that the SHINERS protocol developed in this work qualifies this Raman method as a pioneering approach with unique opportunities for in situ structure and reactivity studies at well-defined electrochemical solid/liquid interfaces.
- Published
- 2013
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42. Ferrocene-terminated alkanethiol self-assembled monolayers: An electrochemical and in situ surface-enhanced infra-red absorption spectroscopy study
- Author
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Alexander V. Rudnev, Yasuyuki Yokota, Thomas Wandlowski, Ulmas E. Zhumaev, Chunjie Fan, Kenichi Fukui, and Toru Utsunomiya
- Subjects
chemistry.chemical_compound ,Aqueous solution ,Ferrocene ,chemistry ,Absorption spectroscopy ,General Chemical Engineering ,Monolayer ,Inorganic chemistry ,Electrochemistry ,Self-assembled monolayer ,Electrolyte ,Cyclic voltammetry - Abstract
The effect of anions on the redox behavior and structure of 11-ferrocenyl-1-undecanethiol (FcC11) monolayers (SAM) on Au(1 1 1) single crystal and Au(1 1 1-25 nm) thin film electrodes was investigated in 0.1 M solutions of HPF6, HClO4, HBF4, HNO3, and H2SO4 by cyclic voltammetry (CV) and in situ surface-enhanced infrared reflection-absorption spectroscopy (SEIRAS). We demonstrate that the FcC11 redox peaks shift toward positive potentials and broaden with increasing hydrophilicity of the anions. In situ surface-enhanced IR-spectroscopy (SEIRAS) provided direct access for the incorporation of anions into the oxidized adlayer. The coadsorption of anions is accompanied by the penetration of water molecules. The latter effect is particularly pronounced in aqueous HNO3 and H2SO4 electrolytes. The adlayer permeability increases with increasing hydrophilicity of the anions. We also found that even the neutral (reduced) FcC11 SAM is permeable for water molecules. Based on the property of interfacial water to reorient upon charge inversion, we propose a spectroscopic approach for estimating the potential of zero total charge of the FcC11-modified Au(1 1 1) electrodes in aqueous electrolytes.
- Published
- 2013
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43. A new approach to the studies of submicron particle suspensions based on the effect of pressure in capillary zone electrophoresis
- Author
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Boris Ya. Spivakov, N. G. Vanifatova, and Alexander V. Rudnev
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Capillary action ,Chemistry ,Clinical Biochemistry ,Analytical chemistry ,Electrophoresis, Capillary ,Thermal diffusivity ,Biochemistry ,Charged particle ,Analytical Chemistry ,Electrophoresis ,Capillary electrophoresis ,Suspensions ,Hydrodynamics ,Pressure ,Nanoparticles ,Particle ,Particle size ,Particle velocity ,Particle Size - Abstract
A new approach based on the effect of pressure in CZE is suggested for acceleration of particle migration in electrophoretic runs resulting in reduction of the analysis time. It provides conditions for studying fast processes in suspensions. The effect of pressure on the migration of silica spheres with average diameters of 100, 150, and 390 nm was studied by CZE at an applied voltage of 25 kV. The particle hydrodynamic behavior was also investigated under the same capillary dimensions and BGE composition. The total particle mobility (excluding the average flow rate) was found to increase with increasing the pressure applied and particle size. The particle migration mechanism explaining the effect of pressure on particle velocity was shown to be almost the same as in wide-bore hydrodynamic chromatography. It is based on changing radial distribution of particle concentration along the capillary cross section depending on particle diffusivity. On the basis of this mechanism appearance of a zone of negatively charged particles in electropherograms ahead of the marker peak can be explained.
- Published
- 2013
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44. Electrochemical characterization of self-assembled ferrocene-terminated alkanethiol monolayers on low-index gold single crystal electrodes
- Author
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Alexander V. Rudnev, Koji Yoshida, and Thomas Wandlowski
- Subjects
Materials science ,General Chemical Engineering ,Self-assembled monolayer ,Electrochemistry ,Crystallography ,chemistry.chemical_compound ,Ferrocene ,chemistry ,Electrode ,Monolayer ,Crystallite ,Cyclic voltammetry ,Single crystal - Abstract
We present a voltammetric and in situ STM study of 11-ferrocenyl-1-undecanethiol (FcC11) assembled on low-index single crystal and polycrystalline gold electrodes. The influence of electrode surface structure as well as of structure defects in the self-assembled FcC11 monolayers on the electrochemical response during the oxidation and reduction of the terminal ferrocene group is explored. The nature of the redox peaks is discussed in detail. We identified the coexistence of disordered FcC11 regions with 2D patches of “locally ordered” FcC11 species. We demonstrate that close-packed domains are preferentially formed at atomically flat terraces. Increasing the defect density of the substrate surface leads to a decreasing amount of locally ordered FcC11 molecules.
- Published
- 2013
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45. Formation of Two-Dimensional Supramolecular Polymers by Amphiphilic Pyrene Oligomers
- Author
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Gion Calzaferri, Thomas Wandlowski, Simon Matthias Langenegger, Robert Häner, Alexander V. Rudnev, and Mykhailo Vybornyi
- Subjects
chemistry.chemical_classification ,Aqueous medium ,010405 organic chemistry ,Atomic force microscopy ,technology, industry, and agriculture ,General Medicine ,macromolecular substances ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Fluorescence ,Catalysis ,0104 chemical sciences ,Folding (chemistry) ,Supramolecular polymers ,chemistry.chemical_compound ,chemistry ,Amphiphile ,Polymer chemistry ,Pyrene ,J-aggregate - Abstract
Reading the bands: Amphiphilic pyrene trimers self-assemble into two-dimensional, supramolecular polymers in aqueous medium. Folding and aggregation processes are accompanied by simultaneous development of J- and H-bands and significant changes in the fluorescence properties. The formation of sheet-like nano-structures is confirmed by AFM.
- Published
- 2013
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46. Covalent Modification of Highly Ordered Pyrolytic Graphite with a Stable Organic Free Radical by Using Diazonium Chemistry
- Author
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Alexander V. Rudnev, Marta Mas-Torrent, Gonca Seber, Núria Crivillers, Jaume Veciana, Concepció Rovira, Ivan Rungger, Andrea Droghetti, European Commission, Swiss National Science Foundation, European Research Council, Centro de Investigación Biomédica en Red Bioingeniería, Biomateriales y Nanomedicina (España), Dirección General de Investigación Científica y Técnica, DGICT (España), Generalitat de Catalunya, and Ministerio de Economía y Competitividad (España)
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02 engineering and technology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Redox ,Catalysis ,law.invention ,symbols.namesake ,Diazonium compounds ,law ,Electrochemistry ,Organic chemistry ,Molecule ,Pyrolytic carbon ,Redox chemistry ,Chemistry ,Organic Chemistry ,Radicals ,General Chemistry ,021001 nanoscience & nanotechnology ,Surface chemistry ,0104 chemical sciences ,Covalent bond ,symbols ,Density functional theory ,Cyclic voltammetry ,Scanning tunneling microscope ,0210 nano-technology ,Raman spectroscopy - Abstract
A novel, persistent, electrochemically active perchlorinated triphenylmethyl (PTM) radical with a diazonium functionality has been covalently attached to highly ordered pyrolytic graphite (HOPG) by electrografting in a single-step process. Electrochemical scanning tunneling microscopy (EC-STM) and Raman spectroscopy measurements revealed that PTM molecules had a higher tendency to covalently react at the HOPG step edges. The cross-section profiles from EC-STM images showed that there was current enhancement at the functionalized areas, which could be explained by redox-mediated electron tunneling through surface-confined redox-active molecules. Cyclic voltammetry clearly demonstrated that the intrinsic properties of the organic radical were preserved upon grafting and DFT calculations also revealed that the magnetic character of the PTM radical was preserved., We acknowledgeGuillaume Sauthier from the Ca talan Ins tituteof Nanoscience and Nanotechnology (ICN2) for XPS measure-ments.This work was supported by ACMOL (GA no. 618082),the Swiss National Science Foundation (grant no. 200020-144471), ERC StG 2012-306826 e-GAMES,ITN iSwitch (642196)project, the Networking Research Center of Bioengineering,Biomaterials and Nanomedicine(CIBER-BBN), the DGI (Spain)with project BE-WELL CTQ2013-40480-R, and the Generalitatde Catalunya with project 2014-SGR-17. N.C acknowledges theRyC program. We also acknowledge financial suppo rt from theSpanishMinistry of Economyand Competitiveness, throughthe “Severo Ochoa” Programme for Centres of Excellence inR&D (SEV-2015-0496).
- Published
- 2016
47. Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique
- Author
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Anders Borges, Stine T. Olsen, Joseph M. Hamill, Alexander V. Rudnev, Gemma C. Solomon, Kurt V. Mikkelsen, Jueting Zheng, Peter Broekmann, Mogens Brøndsted Nielsen, Yang Yang, Anne Ugleholdt Petersen, Thomas Wandlowski, Wenjing Hong, Masoud Baghernejad, Cancan Huang, and Martyn Jevric
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Multidisciplinary ,Materials science ,Science ,General Physics and Astronomy ,Conductance ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Chemical reaction ,General Biochemistry, Genetics and Molecular Biology ,Article ,0104 chemical sciences ,Chemical kinetics ,Photochromism ,Chemical physics ,Molecule ,0210 nano-technology ,Break junction ,Isomerization ,Quantum tunnelling - Abstract
Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting that the junction environment was perturbing the process significantly. This study opens the possibility of using nano-structured environments like molecular junctions to tailor product ratios in chemical reactions., The conductance across single-molecule junctions is highly dependent on the electronic properties of the molecule in question. Here the authors use this fact to monitor a photo-thermal reaction by analysing break junction data, and observe significant differences compared to solution state behaviour.
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- 2016
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48. A redox-active radical as an effective nanoelectronic component: stability and electrochemical tunnelling spectroscopy in ionic liquids
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Ivan Rungger, Andrea Droghetti, Jaume Veciana, Marta Mas-Torrent, Concepció Rovira, Alexander V. Rudnev, Ilya Pobelov, Gonca Seber, Carlos Franco, Núria Crivillers, European Commission, Swiss National Science Foundation, Centro de Investigación Biomédica en Red Bioingeniería, Biomateriales y Nanomedicina (España), Ministerio de Economía y Competitividad (España), Generalitat de Catalunya, European Cooperation in Science and Technology, and CSIC - Unidad de Recursos de Información Científica para la Investigación (URICI)
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endocrine system ,General Physics and Astronomy ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,Electrochemistry ,Photochemistry ,Single-molecule electronics ,01 natural sciences ,single-molecule electronics ,chemistry.chemical_compound ,Break junction ,540 Chemistry ,Physical and Theoretical Chemistry ,Voltammetry ,voltammetry ,complexes ,Component (thermodynamics) ,behavior ,Transistor ,ferrocene ,Conductance ,Molecular scale electronics ,500 Science ,021001 nanoscience & nanotechnology ,3. Good health ,0104 chemical sciences ,Ferrocene ,chemistry ,Ionic liquid ,transport ,570 Life sciences ,biology ,transistor ,break junction ,0210 nano-technology ,devices ,conductance - Abstract
A redox-active persistent perchlorotriphenylmethyl (PTM) radical chemically linked to gold exhibits stable electrochemical activity in ionic liquids. Electrochemical tunnelling spectroscopy in this medium demonstrates that the PTM radical shows a highly effective redox-mediated current enhancement, demonstrating its applicability as an active nanometer-scale electronic component., We acknowledge the financial support from the EU projects ACMOL (FET Young Explorers, GA no. 618082), ERC StG 2012- 306826 e-GAMES, ITN iSwitch (GA no. 642196), COST Action TD1002, the Swiss National Science Foundation (Grant No. 200020- 144471), the Networking Research Center of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), the DGI (Spain) with project BE-WELL CTQ2013-40480-R, the Generalitat de Catalunya with project 2014-SGR-17, and the Severo Ochoa program. N. C acknowledges the RyC program. C. F. is enrolled in the Materials Science PhD program of UAB., We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).
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- 2016
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49. Cooperative and Noncooperative Assembly of Oligopyrenotides Resolved by Atomic Force Microscopy
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Artem Mishchenko, Vladimir L. Malinovskii, Thomas Wandlowski, Alina L. Nussbaumer, Alexander V. Rudnev, and Robert Häner
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chemistry.chemical_classification ,Isodesmic reaction ,genetic structures ,Polymers and Plastics ,Organic Chemistry ,technology, industry, and agriculture ,Supramolecular chemistry ,macromolecular substances ,Oligomer ,Supramolecular assembly ,Inorganic Chemistry ,Supramolecular polymers ,chemistry.chemical_compound ,Crystallography ,chemistry ,Ionic strength ,Materials Chemistry ,Non-covalent interactions ,Spectroscopy - Abstract
The supramolecular assembly of amphiphilic oligopyrenotide building blocks (covalently linked heptapyrene, Py7) is studied by atomic force microscopy (AFM) in combination with optical spectroscopy. The assembly process is triggered in a controlled manner by increasing the ionic strength of the aqueous oligomer solution. Cooperative noncovalent interactions between individual oligomeric units lead to the formation of DNA-like supramolecular polymers. We also show that the terminal attachment of a single cytidine nucleotide to the heptapyrenotide (Py7-C) changes the association process from a cooperative (nucleation–elongation) to a noncooperative (isodesmic) regime, suggesting a structure misfit between the cytidine and the pyrene units. We also demonstrate that AFM enables the identification and characterization of minute concentrations of the supramolecular products, which was not accessible by conventional optical spectroscopy.
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- 2012
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50. Structural aspects of redox-mediated electron tunneling
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Alexander V. Rudnev, Ilya Pobelov, and Thomas Wandlowski
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chemistry.chemical_classification ,Chemistry ,General Chemical Engineering ,Analytical chemistry ,Molecular electronics ,Self-assembled monolayer ,Electron transport chain ,Analytical Chemistry ,Crystallography ,Electron transfer ,chemistry.chemical_compound ,Ferrocene ,Electrochemistry ,Vibrational energy relaxation ,Molecule ,Alkyl - Abstract
We investigated structural aspects of electron transfer (ET) in tunneling junctions (Au(1 1 1)vertical bar FcN vertical bar solution gap vertical bar Au STM tip) with four different redox-active N-thioalk(ano)ylferrocenes (FcN) embedded. The investigated molecules consist of a redox-active ferrocene (Fc) moiety connected via alkyl spacers with N = 4, 6, 8 and 11 carbon atoms to a thiol anchoring group. We found that for short FcNs (N = 4, 6,8) the redox-mediated ET response increases with the increase of the alkyl chain length, while no enhancement of the ET was observed for Fc1 1. The model of two-step ET with partial vibrational relaxation by Kuznetsov and Ulstrup was used to rationalize these results. The theoretical ET steps were assigned to two processes: (1) electron tunneling from the Fc group to the Au tip through the electrolyte layer and (2) electron transport from the Au(1 1 1) substrate to the Fc group through the organic adlayer. We argue that for the three short FcNs, the first process represents the rate-limiting step. The increase of the length of the alkyl chain leads to an approach of the Fc group to the STM tip, and consequently accelerates the first El' step. In case of the Fcl 1 junctions the rather high thickness of the organic layer leads to a decrease of the rate of the second ET step. In consequence, the contribution of the redox-mediated current enhancement to the total tunneling current appears to be insignificant. Our work demonstrates the importance of combined structural and transport approaches for the understanding of Er processes in electrochemical nanosystems. (C) 2010 Elsevier B.V. All rights reserved.
- Published
- 2011
- Full Text
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