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Ricciarelli, Damiano, Daniele Meggiolaro, Paola Belanzoni, Asma A. Alothman, Edoardo Mosconi i Filippo De Angelis. "Energy vs Charge Transfer in Manganese-Doped Lead Halide Perovskites". ACS Energy Letters 6, nr 5 (23.04.2021): 1869–78. http://dx.doi.org/10.1021/acsenergylett.1c00553.
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K. R., Pradeep, i Ranjani Viswanatha. "Mechanism of Mn emission: Energy transfer vs charge transfer dynamics in Mn-doped quantum dots". APL Materials 8, nr 2 (1.02.2020): 020901. http://dx.doi.org/10.1063/1.5140888.
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Mostafa, Gamal A. E., Tarek A. Yousef, Samir T. Gaballah, Atef M. Homoda, Rashad Al-Salahi, Haya I. Aljohar i Haitham AlRabiah. "Quinine Charge Transfer Complexes with 2,3-Dichloro-5,6-Dicyano-Benzoquinone and 7,7,8,8-Tetracyanoquinodimethane: Spectroscopic Characterization and Theoretical Study". Applied Sciences 12, nr 3 (18.01.2022): 978. http://dx.doi.org/10.3390/app12030978.
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The molecular charge transfer reactions of quinine (Q) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as a π-acceptor to form charge transfer (CT) complexes have been studied. The CT complexes were characterized by infrared spectra, NMR, mass spectrometry, conductometry and spectrometry. The Q-DDQ and Q-TCNQ charge transfer complexes were monitored at 480 and 843 nm, respectively. The results confirm the formation of CT complexes. The molar ratio of Q:DDQ and Q: TCNQ assessed using Job’s method was 1:1, which agrees with the results obtained by the Benesi-Hildebrand equation. The stability of the formed CT complexes was assessed by measuring different spectroscopic parameters such as oscillator strength, transition dipole moment, ionization potential, the energy of CT complex, resonance energy, dissociation energy and standard free energy change. The DFT geometry optimization of quinine, DDQ and TCNQ, its charge transfer complex, and UV theoretical vs. experimental comparative study were carried out. The theoretical and experimental results agreed. DFT/B3LYP/6-311++G(d,p) level of theory was used for the investigation of charge transfer between quinine as electron donor and (DDQ and TNCQ) as electron acceptors. The geometric structures, orbital energies, HOMO, LUMO and energy gaps were determined. The transition energies of the charge transfer complexes were computed using the TD-DFT/B3LYP/6-311++G(d,p) level of theory. The computed parameters were comparable to the experimental parameters, and the computational results aided in the analysis of the data.
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Lacy, W. B., K. L. Rowlen i J. M. Harris. "Quantitative Investigation of Charge-Trapping Effects on Raman Spectra Acquired Using Charge-Coupled-Device (CCD) Detectors". Applied Spectroscopy 45, nr 10 (grudzień 1991): 1598–603. http://dx.doi.org/10.1366/0003702914335373.
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Changes in spectral band parameters (width, center frequency, intensity) which arise from charge-trapping artifacts in the Thomson TH 7882 charge-coupled-device (CCD) detector are reported. These parameters are measured for a Raman scattering band of carbon tetrachloride with respect to CCD geometry (parallel vs. serial binning), in the presence and absence of preflash, vs. changes in integration time (variation in detected light level). The dependence of the spectral parameters on detector temperature was also measured. The degree of charge trapping and the charge transfer efficiency were estimated from the change in peak width and intensity vs. integration time, respectively, and were found to vary with detector temperature according to an Arrhenius relationship for the serial-binning geometry; from these results, the energy barriers to charge trapping and loss in the serial register were estimated. Practical guidelines for acquisition of binned spectra with this detector are suggested.
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Myers, Alexis, i Jeff Blackburn. "Fundamental Charge Transfer Dynamics in 2D TMDCs for Use in Novel Heterostructures". ECS Meeting Abstracts MA2022-01, nr 12 (7.07.2022): 865. http://dx.doi.org/10.1149/ma2022-0112865mtgabs.
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Efficient transfer of charge carriers and/or excitons between small organic molecules and two-dimensional (2D) semiconductor interfaces is being explored for applications in photovoltaics and quantum information processing. Interfaces of small molecules and 2D semiconductors such as graphene, nanocrystals, quantum dots and transition metal dichalcogenides (TMDCs) are capable of charge, energy, and spin singlet transfer. The long excited state lifetimes of spin triplet excitons makes triplet exciton transfer across such interfaces advantageous for exciton harvesting and photon upconversion. However, to date, triplet energy transfer between physisorbed small molecules and monolayer TMDCs has only been reported in a single study. To our knowledge, the process where photoexcitation of a TMDC/organic interface yields triplet excitons in the TMDC layer has not been reported. In quantum dot (QD) systems, direct covalent attachment of organic molecules to QD surfaces has shown to facilitate triplet energy transfer across the QD/molecule interface, but this covalent approach has not been widely applied to TMDC/molecule interfaces. Here we present a systematic study of covalently functionalized TMDC/molecule interfaces employing synthetically tailored thiolated acenes. We create tunable amounts of sulfur vacancies, which allows for subsequent covalent acene functionalization. We study the impact of covalent bonding on the charge transfer (CT) dynamics of TMDC/organic interfaces with energy level offsets suitable for charge and energy transfer (ET) as well as triplet acceptance and sensitization. We characterize the interfaces with a variety of steady-state and time-resolved spectroscopic techniques and initial results show success in selective isolation of CT vs ET pathways. Figure 1
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Mandal, Arkalekha. "Tuning p-type to n-type semiconductor nature by charge transfer cocrystallization: effect of transfer integral vs. reorganization energy". CrystEngComm 24, nr 11 (2022): 2072–80. http://dx.doi.org/10.1039/d2ce00006g.
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Rodrı́guez-Fernández, Jonathan, Koen Lauwaet, David Écija, Roberto Otero, Rodolfo Miranda i José M. Gallego. "Metal-Coordination Network vs Charge Transfer Complex: The Importance of the Surface". Journal of Physical Chemistry C 124, nr 14 (16.03.2020): 7922–29. http://dx.doi.org/10.1021/acs.jpcc.0c02166.
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Luo, Peng, Paul-Ludovic Karsenti, Benoit Marsan i Pierre D. Harvey. "Triplet energy vs. electron transfers in porphyrin- and tetrabenzoporphyrin-carboxylates/Pd3(dppm)3(CO)2+ cluster assemblies; a question of negative charge". New Journal of Chemistry 42, nr 10 (2018): 8160–68. http://dx.doi.org/10.1039/c7nj03943c.
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Alkorta, Ibon, Jose Elguero i Josep M. Oliva-Enrich. "Hydrogen vs. Halogen Bonds in 1-Halo-Closo-Carboranes". Materials 13, nr 9 (7.05.2020): 2163. http://dx.doi.org/10.3390/ma13092163.
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A theoretical study of the hydrogen bond (HB) and halogen bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique intermolecular bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.
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Dong, Rui Zhi. "Comparative Studies on VS2 Bilayer and VS2/Graphene Heterostructure as the Anodes of Li Ion Battery". Key Engineering Materials 894 (27.07.2021): 61–66. http://dx.doi.org/10.4028/www.scientific.net/kem.894.61.
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Due to the development of various mobile electronic devices, such as electric vehicles, rechargeable ion batteries are becoming more and more important. However, the current commercial lithium-ion batteries have obvious defects, including poor safety from Li dendrite and flammable electrolyte, quick capacity loss and low charging and discharging rate. It is very important to find a better two-dimensional material as the anode of the battery to recover the disadvantages. In this paper, first principles calculations are used to explore the performances of VS2 bilayer and VS2 / graphene heterostructure as the anodes of Li ion batteries. Based on the calculation of the valences, binding energy, intercalation voltage, charge transfer and diffusion barrier of Li, it is found that the latter can be used as a better anode material from the perspective of insertion voltage and binding energy. At the same time, the former one is better in terms of diffusion barrier. Our study provides a comprehensive understanding on VS2 based 2D anodes.
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Tulsiram, Nicholas, Christopher Kerr i Jennifer I. L. Chen. "Photoinduced Charge Transfer in Poly(3-hexylthiophene)/TiO2 Hybrid Inverse Opals: Photonic vs Interfacial Effects". Journal of Physical Chemistry C 121, nr 48 (22.11.2017): 26987–96. http://dx.doi.org/10.1021/acs.jpcc.7b09113.
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Xie, Xuan, i Rudolf Holze. "Electrode Kinetic Data: Geometric vs. Real Surface Area". Batteries 8, nr 10 (27.09.2022): 146. http://dx.doi.org/10.3390/batteries8100146.
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Kinetic data reporting the rate of electron transfer across an electrified interface are of fundamental as well as practical importance. They report the electric current caused by coupling the flow of electrons inside the electronically conducting electrode and the flow of ions in the adjacent ionically conducting phase. At equilibrium or rest, potential currents in both directions at the established dynamic equilibrium have the same absolute value: the net current is zero. This current describes the electrocatalytic activity of an electrode and is called the exchange current; with respect to the surface area, it is called the exchange current density. This study inspected the actually used surface areas because the reported activities may depend critically on the selection of this area. Charge transfer resistances corresponding to exchange currents I0 were determined for a simple redox system using a platinum disc electrode with constant geometric surface area but variable roughness. At all studied degrees of roughness, changes in I0 were found. With an electrochemically active surface area, exchange current densities j0 could be calculated, but the obtained values showed a dependency on roughness that could not be accounted for by using this surface area instead of the geometric one. It is suggested that j0 may be reported with respect to geometric surface area, but at least roughness data of the studied electrode should be provided.
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Maevskaya, Maria V., Aida V. Rudakova, Alexandra V. Koroleva, Aleksandr S. Sakhatskii, Alexei V. Emeline i Detlef W. Bahnemann. "Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings". Catalysts 11, nr 12 (23.11.2021): 1424. http://dx.doi.org/10.3390/catal11121424.
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Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by XPS, SEM, and AFM methods. The electronic energy structure of the heterostructure components (band gap, top of the valence band, bottom of the conduction band, and Fermi level position) was determined on the basis of experimental results obtained by XPS, UV-V absorption spectroscopy and Kelvin probe methods. According to their electronic energy structure, the ZnO/BiVO4 and TiO2/BiVO4 heterostructures correspond to type I and type II heterostructures, respectively. The difference in the type of heterostructures causes the difference in the charge transfer behavior at heterojunctions: the type II TiO2/BiVO4 heterostructure favors and the type I ZnO/BiVO4 heterostructure prevents the photogenerated hole transfer from BiVO4 to the outer layer of the corresponding metal oxide. The results of the comparative studies show that the interaction of the photogenerated holes with surface hydroxy-hydrated multilayers is responsible for the superhydrophilic surface conversion accompanying the increase of the surface free energy and work function. The formation of the type II heterostructure leads to the spectral sensitization of the photostimulated surface superhydrophilic conversion.
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Berg, Clara, Robert Morasch, Maximilian Graf i Hubert A. Gasteiger. "Comparison of Silicon and Graphite Anodes: Temperature-Dependence of Impedance Characteristics and Rate Performance". Journal of The Electrochemical Society 170, nr 3 (1.03.2023): 030534. http://dx.doi.org/10.1149/1945-7111/acc09d.
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A meaningful benchmarking of battery active materials with inherently different properties requires knowledge of both their intrinsic electrochemical properties as well as of the differences in the resulting porous electrode structures for equal, practically relevant areal capacities. Here we compare graphite and microsilicon anodes with practical areal capacities of 2.8 mAh cm−2 for lithium-ion batteries with regard to their temperature-dependent kinetic charge-transfer resistances (R ct) and their ion transport resistances through the electrolyte phase within the pores of the electrodes (R ion), measured via impedance spectroscopy. We deconvolute the kinetic resistance from the impedance spectra by individually measuring the temperature-dependent pore resistance between −5 and +45 °C, showing that the charge-transfer resistance dominates at low temperatures, while at high temperatures the pore resistance dominates for both electrode types due to the significantly higher activation energy of R ct. An analysis of the potential profile of the electrodes at different lithiation rates shows how the thinner silicon electrode is significantly less affected by R ion-induced transport losses compared to a thicker graphite electrode, resulting in lower overpotentials when fast-charging at high temperatures, despite similar kinetic resistances. Overall the silicon electrodes could be charged up to two times faster than graphite before reaching 0 V vs Li+/Li.
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Binzoni, T., i P. Cerretelli. "Bioenergetic approach to transfer function of human skeletal muscle". Journal of Applied Physiology 77, nr 4 (1.10.1994): 1784–89. http://dx.doi.org/10.1152/jappl.1994.77.4.1784.
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A mathematical model analogous to Chance's “transfer function” was derived on the basis of the energy consumption principle, which is suitable to describe the energetics of human skeletal muscle during aerobic activity. The implications and the characteristics of this model are that 1) the half time of phosphocreatine (PCr) hydrolysis at the onset of a mechanical constant-load exercise is independent of the imposed charge, 2) the changes of O2 consumption in the muscle at steady state when changing workload are linearly related to PCr concentration, 3) the kinetics of the intracellular oxygen consumption during a rest-to-work transient are influenced by anaerobic glycolysis, 4) it may explain the PCr-time relationship of different muscles types (e.g., skeletal, heart, trained vs. untrained), 5) it allows one to interpret correctly the significance of the oxygen consumption kinetics in the rest-to-work transient at the lung level, and 6) it is conceived for in vivo applications.
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Harvey, Pierre D., Liangbing Gan i Christiane Aubry. "Charge transfer emissive singlet excited states and photoinduced electron transfer properties in the diarylideneacetone compounds (RCHCH)2CO; R = phenyl, 1- and 2-naphthyl, 3-(N-ethylcarbazoyl), and 4-(C5H5)Fe(C5H4C6H4CHCH(CO)CHCHC6H5)". Canadian Journal of Chemistry 68, nr 12 (1.12.1990): 2278–88. http://dx.doi.org/10.1139/v90-351.
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Four diarylideneacetone compounds ((RCHCH)2CO, where the aryl groups are phenyl (dba), 1-naphthyl (1-dNapha), 2-naphthyl (2-dNapha), and 3-(N-ethylcarbazoyl) (dNECa)), and 4-(C5H5)Fe(C5H4C6H4CHCH(CO)CHCH(C6H5) (dba-Fc) have been prepared and characterized. The compounds are found to be fluorescent and photochemically and reversibly electrochemically active. The lowest-energy absorption bands for the diarylideneacetones are assigned to a charge transfer (CT) electronic transition, except for dba-Fc, in which a ferrocenyl ligand field transition assignment is made. The 77 K CT absorption and fluorescence bands are vibrationally structured (vibrational spacings = 1260–1360 cm−1). While the fluorescence decay at 293 K is monoexponential, the excited state fluorescence lifetimes (τF) for the 77 K samples exhibit double exponential decays, the short component being 0.38–0.64 ns and the long one 3.5–10.9 ns. The photophysical results are interpreted in terms of excited state deactivation processes dominated by radiationless pathways that are associated with the presence of fluorescent species with different geometries. Only the dNECa compound is found to be fluorescent in solution at 298 K [Formula: see text]. Cyclic voltammetry and coulometry measurements suggest that a reversible one-electron reduction process and an irreversible higher potential one-electron reduction process take place in the −1 to −2 V vs. SSCE range. In addition, dba-Fc also exhibits an electrochemically reversible one-electron oxidation wave at 0.52 V vs. SSCE centered at the ferrocenyl group. These results together with the spectroscopic electronic data have permitted evaluation of the reduction potentials of the lowest singlet (CT excited states (E1−/*);they range from 1.4 to 2.2 V vs. SSCE, with dba being the strongest photooxidizing agent and dNECa the weakest. Photoinduced intermolecular electron transfer reactions have been investigated by steady state fluorescence techniques and picosecond flash photolysis spectroscopy for dNECa and dba, respectively. The bimolecular deactivation rate constants, kq, for the reductive photoinduced electron transfer reactions of dNECa with diphenylamine (DPA) (kq = (2.65 ± 0.25) × 107 M−1 s−1) and N, N, N′, N′-tetramethylphenylenediamine (TMPM) (kq = (1.38 ± 0.03) × 108 M−1 s−1) have been obtained in THF solutions at 293 K. No fluorescence quenching is observed when oxidative and energy transfer quenchers are used with dNECa. For the non-emissive dba compound at room temperature, picosecond flash photolysis experiments show that quenching of the broad dba transient band (~500 nm) does indeed occur between 5 and 10 ns. Keywords: dibenzylideneacetone, charge transfer, photoelectron transfer.
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Li, Sanxiu, Yufei Kang, Chenyang Mo, Yage Peng, Haijun Ma i Juan Peng. "Nitrogen-Doped Bismuth Nanosheet as an Efficient Electrocatalyst to CO2 Reduction for Production of Formate". International Journal of Molecular Sciences 23, nr 22 (21.11.2022): 14485. http://dx.doi.org/10.3390/ijms232214485.
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Electrochemical CO2 reduction (CO2RR) to produce high value-added chemicals or fuels is a promising technology to address the greenhouse effect and energy challenges. Formate is a desirable product of CO2RR with great economic value. Here, nitrogen-doped bismuth nanosheets (N-BiNSs) were prepared by a facile one-step method. The N-BiNSs were used as efficient electrocatalysts for CO2RR with selective formate production. The N-BiNSs exhibited a high formate Faradic efficiency (FEformate) of 95.25% at −0.95 V (vs. RHE) with a stable current density of 33.63 mA cm−2 in 0.5 M KHCO3. Moreover, the N-BiNSs for CO2RR yielded a large current density (300 mA cm−2) for formate production in a flow-cell measurement, achieving the commercial requirement. The FEformate of 90% can maintain stability for 14 h of electrolysis. Nitrogen doping could induce charge transfer from the N atom to the Bi atom, thus modulating the electronic structure of N-Bi nanosheets. DFT results demonstrated the N-BiNSs reduced the adsorption energy of the *OCHO intermediate and promoted the mass transfer of charges, thereby improving the CO2RR with high FEformate. This study provides a valuable strategy to enhance the catalytic performance of bismuth-based catalysts for CO2RR by using a nitrogen-doping strategy.
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Silva, Cassio P., Gustavo T. M. Silva, Tássia de Sousa Costa, Vânia M. T. Carneiro, Farhan Siddique, Adelia J. A. Aquino, Adilson A. Freitas i in. "Chromophores inspired by the colors of fruit, flowers and wine". Pure and Applied Chemistry 92, nr 2 (25.02.2020): 255–63. http://dx.doi.org/10.1515/pac-2019-0226.
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AbstractAnthocyanins, which are responsible for most of the red, blue and purple colors of fruits and flowers, are very efficient at absorbing and dissipating light energy via excited state proton transfer or charge-transfer mediated internal conversion without appreciable excited triplet state formation. During the maturation of red wines, grape anthocyanins are slowly transformed into pyranoanthocyanins, which have a much more chemically stable pyranoflavylium cation chromophore. Development of straightforward synthetic routes to mono- and disubstituted derivatives of the pyranoflavylium cation chromophore has stimulated theoretical and experimental studies that highlight the interesting absorption and emission properties and redox properties of pyranoflavylium cations. Thus, p-methoxyphenyl substitution enhances the fluorescence quantum yield, while a p-dimethylaminophenyl substituent results in fast decay via a twisted intramolecular charge-transfer (TICT) state. Unlike anthocyanins and their synthetic analogs (flavylium cations), a variety of pyranoflavylium cations form readily detectable excited triplet states that sensitize singlet oxygen formation in solution and exhibit appreciable two-photon absorption cross sections for near-infrared light, suggesting a potential for applications in photodynamic therapy. These excited triplet states have microsecond lifetimes in solution and excited state reduction potentials of at least 1.3 V vs. SCE, features that are clearly desirable in a triplet photoredox catalyst.
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DiFranco, Marino, Joana Capote, Marbella Quiñonez i Julio L. Vergara. "Voltage-dependent Dynamic FRET Signals from the Transverse Tubules in Mammalian Skeletal Muscle Fibers". Journal of General Physiology 130, nr 6 (26.11.2007): 581–600. http://dx.doi.org/10.1085/jgp.200709831.
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Two hybrid voltage-sensing systems based on fluorescence resonance energy transfer (FRET) were used to record membrane potential changes in the transverse tubular system (TTS) and surface membranes of adult mice skeletal muscle fibers. Farnesylated EGFP or ECFP (EGFP-F and ECFP-F) were used as immobile FRET donors, and either non-fluorescent (dipicrylamine [DPA]) or fluorescent (oxonol dye DiBAC4(5)) lipophilic anions were used as mobile energy acceptors. Flexor digitorum brevis (FDB) muscles were transfected by in vivo electroporation with pEGFP-F and pECFP-F. Farnesylated fluorescent proteins were efficiently expressed in the TTS and surface membranes. Voltage-dependent optical signals resulting from resonance energy transfer from fluorescent proteins to DPA were named QRET transients, to distinguish them from FRET transients recorded using DiBAC4(5). The peak ΔF/F of QRET transients elicited by action potential stimulation is twice larger in fibers expressing ECFP-F as those with EGFP-F (7.1% vs. 3.6%). These data provide a unique experimental demonstration of the importance of the spectral overlap in FRET. The voltage sensitivity of QRET and FRET signals was demonstrated to correspond to the voltage-dependent translocation of the charged acceptors, which manifest as nonlinear components in current records. For DPA, both electrical and QRET data were predicted by radial cable model simulations in which the maximal time constant of charge translocation was 0.6 ms. FRET signals recorded in response to action potentials in fibers stained with DiBAC4(5) exhibit ΔF/F amplitudes as large as 28%, but their rising phase was slower than those of QRET signals. Model simulations require a time constant for charge translocation of 1.6 ms in order to predict current and FRET data. Our results provide the basis for the potential use of lipophilic ions as tools to test for fast voltage-dependent conformational changes of membrane proteins in the TTS.
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Feng, Cheng, Xihong Mi, Dingwen Zhong, Weiming Zhang, Yongping Liu, Dayong Fan, Ming Li, Jiefeng Hai i Zhenhuan Lu. "Chemically Bonded N-PDI-P/WO3 Organic-Inorganic Heterojunction with Improved Photoelectrochemical Performance". Catalysts 10, nr 1 (15.01.2020): 122. http://dx.doi.org/10.3390/catal10010122.
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The chemical bonding of bandgap adjustable organic semiconductors with inorganic semiconducting materials is effective in constructing a high-performance heterogeneous photoanode. In this study, a new asymmetric perylene diimide derivative molecule (N-PDI-P) was synthesized by connecting tert-butoxycarbonyl on an N-site at one end of a PDI molecule through methylene and connecting naphthalene directly onto the other end. This molecule was bonded onto the WO3 film surface, thereby forming the photoanode of organic-inorganic heterojunction. Under light illumination, the photocurrent density of chemically bonded N-PDI-P/WO3 heterojunction was twofold higher than that of physically adhered heterojunction for photoelectrochemical water oxidation at 0.6 V (vs. Ag/AgCl). Energy band structure and charge transfer dynamic analyses revealed that photogenerated electron carriers on the highest occupied molecular orbital (HOMO) of an N-PDI-P molecule can be transferred to the conduction band of WO3. The charge transfer and separation rates were accelerated considerably after the chemical bond formed at the N-PDI-P/WO3 interface. The proposed method provides a new way for the design and construction of organic-inorganic composite heterojunction.
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Lucke, J. C., J. R. Elbeery, T. C. Koutlas, S. A. Gall, T. A. D'Amico, G. W. Maier, J. S. Rankin i D. D. Glower. "Effects of cardiac glycosides on myocardial function and energetics in conscious dogs". American Journal of Physiology-Heart and Circulatory Physiology 267, nr 5 (1.11.1994): H2042—H2049. http://dx.doi.org/10.1152/ajpheart.1994.267.5.h2042.
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The physiological effects of intravenous ouabain on left ventricular (LV) systolic function and metabolic-to-mechanical energy transfer were examined in eight conscious dogs. LV pressure and volume were measured using micromanometers and ultrasonic dimension transducers during transient vena caval occlusions under control conditions and after increasing doses of ouabain. Doppler coronary flow and coronary sinus O2 saturations were used to determine arterial-to-coronary sinus O2 content difference and thereby to calculate LV O2 consumption; total mechanical energy was computed as the sum of LV stroke work and the product of end-diastolic volume and LV mean ejection pressure, neglecting LV unstressed cavitary volume. The slope (10(4) erg/ml) of the stroke work vs. end-diastolic volume relationship increased progressively with rising doses of ouabain from 7.0 +/- 1.6 at control to 9.6 +/- 1.7 after ouabain 0.75 mg (P = 0.0002). Regression analysis of LV O2 consumption (mW/cm3) vs. total mechanical energy (mW/cm3) yielded a linear relationship that did not change with 0.75 mg of ouabain (P > 0.4). These data indicate that ouabain possesses a significant positive inotropic effect on the intact left ventricle without a change in energy transfer efficiency or O2 wasting.
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Cotty, Stephen Richard, i Xiao Su. "Electrochemical Recovery and Concentration of Noble Metals". ECS Meeting Abstracts MA2022-02, nr 27 (9.10.2022): 1042. http://dx.doi.org/10.1149/ma2022-02271042mtgabs.
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Noble metals are integral materials to chemical and electronics industries for their unmatched chemical inertness, electrical conductivity, and catalytic activity. However, the growing demand for noble metals such as Pt, Pd, and Au is outpacing the dwindling supply, and without new recycle strategies these critical noble metal resources will run out. Therefore, energy and resource efficient noble metal recycling technologies are critical to develop sustainable use of these scarce and valuable resources. Recently, electrification of chemical process units has been receiving justifiable attention as an easily scalable means of increasing energy and material sustainability in industry, particularly for chemical separations. In particular, the incorporation of redox-active materials has been met with great success for chemical energy storage and chemical separations due to enhanced charge transfer and easily tunable target ion interactions. Here, we introduce an electrochemically mediated platform for capture, release, and up-concentration of noble metal complexes from mining ore, electronic waste, and valuable elements in industrial manufacturing, where favorable charge transfer binding of noble metals to electrode bound redox sites enables selective capture of target noble metals over other common competitors – all with the flick of a switch. Highlights of our system are its high uptake (>200 mg/g), selectivity (>5 vs competing ions), energy efficiency (<5 kJ/g-PGM), cyclability (>5000 reuse cycles), and scalability to flow system. Technoeconomic analysis of our system compared to current industrial separation technologies indicates economically significant improvements in capital and operating costs with our electrochemical noble metal recycling platform. By lowering the economic barrier of noble metal recycling, these critical materials can be sustainably used and reused for years to come.
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Avraham, Hanan, Yanir Kadosh, Eli Korin i Armand Bettelheim. "Charge and Hydrogen Storage Capacities of Electrodeposited Graphene Derivatives". ECS Meeting Abstracts MA2022-01, nr 7 (7.07.2022): 668. http://dx.doi.org/10.1149/ma2022-017668mtgabs.
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Graphene’s theoretical capacitance and physical hydrogen storage abilitiesmark it as one of the best candidates for energy storage application. Graphene oxide (GO) is easy to manufacture in bulk synthesis and can be considered as a precursor for graphene synthesis. The application of graphene on the surface of electrodes can be achieved by different techniques as drop-coating and electrodeposition. It has been reported that the electrochemical hydrogen storage is favored in samples with a well-developed porosity and a low content in surface oxygen complexes. Both features indicate that the unsaturated carbon atoms in the carbon materials have an important role for the hydrogen uptake. It has also been suggested that the total capacity of hydrogen storage is proportional to the interlayer distance and not to the carbon specific surface area. The present work presents an investigation of electrodeposited GO coatings (ED), which have subsequently been electroreduced to various degrees of rGO, and relate their charge capacitance and hydrogen storage capacity to the preparation mode, morphological structure, and surface chemistry. These properties were compared to those of drop-cast (DC) coatings of GO. The ED coatings were characterized by more accumulated graphene sheets imperfections as observed by cross section TEM analysis. These coatings, when reduced at -1.6 V vs Hg/HgO showed more efficient removal of phenolic groups than DC ones treated at the same potential (remaining contents of 2.1 and 18.1 %, respectively). They also showed lower charge transfer resistance (5.2 and 28 Ω cm2, respectively), higher capacitance (73.2 and 42.6 F/g, respectively), and higher hydrogen storage capacity (119 and 57 mAh/g, respectively). Moreover, they showed higher stability towards H2 charge/discharge cycles (retained hydrogen capacities of 95 and 40 % after 15 and 6 cycles for ED and DC coatings reduced at -1.5 V, respectively). The removal during the electroreduction process of phenolic groups located at the graphene sheets edges of the ED coatings and their higher pseudo-capacitance can explain their lower charge transfer resistance and their higher pseudo-capacitance, respectively. Their superior stability towards hydrogen charge/discharge cycles is suggested to stem from evolving hydrogen escape routes created during the ED process. The superior performance properties of coatings obtained by ED and subsequently electro-reduced make them promising electrode materials for energy storage.
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Suneesh, Chettiyam Veettil, Manikkedath Viswanathan Vinayak i Karical R. Gopidas. "Photoinduced Charge Separation in Two Bis(phenylethynyl)anthracene-Based Triads: Inverted Region Effect vs Distance Effect on Back Electron Transfer". Journal of Physical Chemistry C 114, nr 43 (11.10.2010): 18735–44. http://dx.doi.org/10.1021/jp107607f.
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Sihem, Filalli, i Hamdad Noura. "Optimizing Configurations for Determining the Electromagnetic Properties of CsFeF3, NaFeF3, and RbFeF3 Fluorides: GGA vs GGA+U and TB-mBj Approaches". Annals of West University of Timisoara - Physics 62, nr 1 (1.12.2020): 71–94. http://dx.doi.org/10.2478/awutp-2020-0005.
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AbstractThe structural, electronic and magnetic properties of (Cubic Pm-3m, Hexagonal-4H, orthorhombic Pnma, and orthorhombic Pbnm) phases of AFeF3 Fluorides (A = Cs, Na, and Rb) are reported theoretically using full potential linearized augmented plane waves method within the density functional theory (DFT). Using different exchange–correlation approximations including the generalized gradient approximation (PBE-GGA, WC-GGA, and PBEsol-GGA), also (GGA) with Hubbard potential (GGA + U) and The modified Becke Johnson potential (mBJ), we carried to determine various physical properties. The Calculations revealing that the estimated structural parameters are reliable with the experimentally reported data. Magnetically all these intermetallics are Ferromagnetic (FM). The ground-state energy of different magnetic phases studied showed that the magnetic moments are evaluated per atom, and overestimated by (GGA+U). Transfer charge reveals a strong covalent interaction between Fe-Fe atoms. Their electronic band structure and density of states indicate insulator behavior.
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Rutkowska, Iwona A., Pawel J. Kulesza, Justyna Lubera, Claudia Janiszewska, Vito Di Noto, Enrico Negro i Keti Vezzu. "(Invited) Charge Propagation in Highly Concentrated Iodine/Iodide Solutions As Potential Electrolytes for Redox Flow Batteries". ECS Meeting Abstracts MA2022-01, nr 48 (7.07.2022): 2001. http://dx.doi.org/10.1149/ma2022-01482001mtgabs.
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The technology of Redox Flow Batteries is an important option to store energy from the operating irregularly renewable energy sources. The perspectives concern stationary energy storage, including grid-scale energy storage, thanks to their high power performance, flexible design, and ease of scaling-up. The flow-based electrochemical energy storage systems utilize the appropriate electroactive species dissolved in externally flowing electrolytes which are ready to accumulate all (or part) of the charge. Among important issues is the search for highly efficient (i.e., capable of fast electron transfers) electroactive systems that would yield high power and energy densities during the systems’ operation. In the present work, we concentrate on utilization of highly concentrated iodine/iodide redox systems and their possibility to exhibit high rates of charge propagation. In practical terms, it can be combined with ZnI2, or other zinc salt, containing electrolyte. Reactions in the zinc/iodine (polyiodide) redox flow battery are as follows: Zn → Zn2+ + 2e- (E = −0.76 V vs SHE) at the negative electrode (anode), and 3I- → I3 − + 2e− (E = 0.54 V vs SHE) at the positive electrode (cathode) thus yielding a total theoretical potential output as high as ∼1.3 V. The increase of current density could be achieved not only by reducing the viscosity of the electrolyte, thus accelerating charge-carrier transport, but also – by referencing to my experience with the iodine/iodide couple as charge relay for dye-sensitized solar cells – through improvement of the dynamics of charge propagation in highly concentrated iodine/iodide solution via the catalyzed enhancement of rates of electron self-exchange (hopping) between iodine/iodide (polyiodide) redox species as well as by accelerating the interfacial kinetics at electrodes. This can be realized by choosing appropriate electrode materials and through their activation or modification. The electrochemical activities of the redox couples are usually significantly increased through application of nanostructured functionalized carbons. While dispersed in solutions they can improve electron transfers to the redox sites. The proposed chemistry has been first tested using the microelectrode methodology to determine mass-transport (effectively diffusional) coefficients for charge propagation, heterogeneous and homogeneous (electron self-exchange) rates of electron transfers. Unless catalyzed, both interfacial and bulk (self-exchange) electron transfers involving the iodine/iodide redox system are somewhat complicated; there is a need to break the I-I bond in the I3 -or I2 molecule; it has also been well-established that platinum (e.g. when deposited on the counter electrode) induces electron transfers within the iodine/iodide redox system [1]. In the presentation, we are going to explore the respective interfacial (electrocatalytic) phenomena on nanostructured metal oxides (e.g. zirconia), in addition to traces of expensive platinum or palladium nanoparticles (provided that catalytic centers are three-dimensionally distributed in the electrolyte phase), and we will utilize them to enhance iodine/iodide electron transfers to develop a new generation of redox mediators or ultra-fast components of redox electrolytes. Our results show that the catalyzed iodine/iodide system can reach extremely high electron self-exchange rates, namely on the level of 109 – 1010 mol-1 dm3 s-1 . [1] I.A. Rutkowska I.A., M. Marszalek, J. Orlowska, W. Ozimek, S.M. Zakeeruddin, P.J. Kulesza, M. Grätzel, ChemSusChem 8 (2015) 2560-2568.
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Yu, Xiaoyun, i Kevin Sivula. "Tuning Morphology and Defect Density in Self-Assembled Thin-Films of Solvent-Exfoliated WSe2 for Photoelectrochemical Hydrogen Production". ECS Meeting Abstracts MA2018-01, nr 31 (13.04.2018): 1900. http://dx.doi.org/10.1149/ma2018-01/31/1900.
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The layered semiconducting transition metal dichalcogenides can be exfoliated into atomically-thin 2D sheets offering promising opto-electronic characteristics for application in solar energy conversion. However, the challenges to fabricate high-quality thin films of these 2D sheets using scalable and cost-effective methods limit their practical application. Here we present novel solution-based approaches for large-area semiconducting films of liquid exfoliated WSe2 with controllable flake alignment and defect density, which is leveraged to advance the understanding of the morphological and structural factors on the optoelectronic performance in devices. Specifically, we develop a thin film self-assembly method employing spatial confinement of WSe2 nanoflakes which affords overlapping-free morphology and superior charge transfer character over films with aggregations.[1, 2] The critical roles of the flake edge density, flake lateral size and thickness on the photogenerated charge transport and transfer are established by both experimental (by solution-based flake size sorting) and theoretical (by anisotropic charge transport simulation) routes.[3] In addition, we recently develop approaches to reduce charge recombination at internal crystal defects and surface dangling bonds by applying pre-annealing and surfactant treatments, respectively, which affords a considerable improvement that represents a new benchmark for the performance of solution-processed WSe2. Solar photocurrents for H2 evolution up to 4.0 mA cm–2 (at 0V vs RHE, AM 1.5G illumination), and internal quantum efficiency over 60% are reported for 10 nm thick WSe2 photoelectrodes. [1] Yu X.; Prevot, M. S.; Guijarro, N.; Sivula, K. Nat. Commun. 2015, 6, 7596. [2] Yu X.; Prévot, M. S.; Sivula, K. Chem. Mater. 2014, 26, 5892. [3] Yu, X.; Sivula, K. Chem. Mater. 2017, 29, 6863.
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Schirmer, Niels, Florian Winter, Samir F. Matar, Andrea Balducci i Rainer Pöttgen. "Electronic Structure, Chemical Bonding and Electrochemical Characterization of Li2CuSn2 and Li2AgSn2". Zeitschrift für Naturforschung B 69, nr 9-10 (1.10.2014): 1010–20. http://dx.doi.org/10.5560/znb.2014-4141.
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Abstract Polycrystalline samples of the stannides Li2CuSn2 and Li2AgSn2 were obtained by high-frequency melting of the elements in sealed niobium ampoules in a water-cooled sample chamber. Both stannides crystallize with the tetragonal Li2AuSn2 type, space group I41/amd. They are characterized by three-dimensional [CuSn2]δ-, respectively [AgSn2]δ- networks which leave large channels for the lithium ions. Electronic structure calculations show extensive filling of the transition metal d bands and residual DOS at the Fermi energy, compatible with metallic character. Calculated Bader charges and the course of the crystal orbital overlap population curves fully support the bonding picture of cationic lithium and a covalently bonded polyanionic network with considerable charge transfer to both, transition metal and tin atoms. Electrochemical investigations have indicated that a reversible insertion and extraction of lithium into the stannides is taking place in the voltage range between 0 and 2:5 V vs. Li=Li+. From CV measurements, the diffusion coefficents of Li2CuSn2 and Li2AgSn2 were estimated to be in the order of 10-14 cm2 s-1
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Li, Sanxiu, Xuelan Sha, Xiafei Gao i Juan Peng. "Al-Doped Octahedral Cu2O Nanocrystal for Electrocatalytic CO2 Reduction to Produce Ethylene". International Journal of Molecular Sciences 24, nr 16 (11.08.2023): 12680. http://dx.doi.org/10.3390/ijms241612680.
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Ethylene is an ideal CO2 product in an electrocatalytic CO2 reduction reaction (CO2RR) with high economic value. This paper synthesised Al-doped octahedral Cu2O (Al–Cu2O) nanocrystal by a simple wet chemical method. The selectivity of CO2RR products was improved by doping Al onto the surface of octahedral Cu2O. The Al–Cu2O was used as an efficient electrocatalyst for CO2RR with selective ethylene production. The Al–Cu2O exhibited a high % Faradic efficiency (FEC2H4) of 44.9% at −1.23 V (vs. RHE) in CO2 saturated 0.1 M KHCO3 electrolyte. Charge transfer from the Al atom to the Cu atom occurs after Al doping in Cu2O, optimizing the electronic structure and facilitating CO2RR to ethylene production. The DFT calculation showed that the Al–Cu2O catalyst could effectively reduce the adsorption energy of the *CHCOH intermediate and promote the mass transfer of charges, thus improving the FEC2H4. After Al doping into Cu2O, the center of d orbitals shift positively, which makes the d–band closer to the Fermi level. Furthermore, the density of electronic states increases due to the interaction between Cu atoms and intermediates, thus accelerating the electrochemical CO2 reduction process. This work proved that the metal doping strategy can effectively improve the catalytic properties of Cu2O, thus providing a useful way for CO2 cycling and green production of C2H4.
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Yu, Chong, Xiaohu Wang, Jiajun Wu i Yongan Ma. "Characteristics of Vibration Velocity Signal Using Liquid Carbon Dioxide Rock-Breaking Technology". Applied Sciences 13, nr 7 (28.03.2023): 4285. http://dx.doi.org/10.3390/app13074285.
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Liquid carbon dioxide rock-breaking (L-CDRB) is a new physical blasting technology. To study the characteristics of its vibration velocity, rock-breaking field tests were conducted using a new type of liquid CO2 fracturing tube. Comparisons were made between explosive blasting and L-CDRB in terms of the peak values, frequencies, and energy distributions of the generated vibration velocities. The results show that (1) for the same scaled charge, L-CDRB (vs. explosive blasting) produced a smaller peak, a lower dominant frequency, and simpler frequency components of vibration velocities than explosive blasting. (2) The dominant frequency and energy distribution were related to the total liquid CO2 filling quantity. Higher total filling quantities resulted in higher dominant frequencies, and the energy distribution shifted from a low to a high-frequency band.
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Karabelli, Duygu, i Kai Peter Birke. "Feasible Energy Density Pushes of Li-Metal vs. Li-Ion Cells". Applied Sciences 11, nr 16 (18.08.2021): 7592. http://dx.doi.org/10.3390/app11167592.
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Li-metal batteries are attracting a lot of attention nowadays. However, they are merely an attempt to enhance energy densities by employing a negative Li-metal electrode. Usually, when a Li-metal cell is charged, a certain amount of sacrificial lithium must be added, because irreversible losses per cycle add up much more unfavourably compared to conventional Li-ion cells. When liquid electrolytes instead of solid ones are used, additional electrolyte must also be added because both the lithium of the positive electrode and the liquid electrolyte are consumed during each cycle. Solid electrolytes may present a clever solution to the issue of saving sacrificial lithium and electrolyte, but their additional intrinsic weight and volume must be considered. This poses the important question of if and how much energy density can be gained in realistic scenarios if a switch from Li-ion to rechargeable Li-metal cells is anticipated. This paper calculates various scenarios assuming typical losses per cycle and reveals future e-mobility as a potential application of Li-metal cells. The paper discusses the trade-off if, considering only the push for energy density, liquid electrolytes can become a feasible option in large Li-metal batteries vs. the solid-state approach. This also includes the important aspect of cost.
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Rong, Yan, i Siping Huang. "Self-Templating Synthesis of N/P/Fe Co-Doped 3D Porous Carbon for Oxygen Reduction Reaction Electrocatalysts in Alkaline Media". Nanomaterials 12, nr 12 (19.06.2022): 2106. http://dx.doi.org/10.3390/nano12122106.
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The development of low-cost, highly active, and stable oxygen reduction reaction (ORR) catalysts is of great importance for practical applications in numerous energy conversion devices. Herein, iron/nitrogen/phosphorus co-doped carbon electrocatalysts (NPFe-C) with multistage porous structure were synthesized by the self-template method using melamine, phytic acid and ferric trichloride as precursors. In an alkaline system, the ORR half-wave potential is 0.867 V (vs. RHE), comparable to that of platinum-based catalysts. It is noteworthy that NPFe-C performs better than the commercial Pt/C catalyst in terms of power density and specific capacity. Its unique structure and the feature of heteroatom doping endow the catalyst with higher mass transfer ability and abundant available active sites, and the improved performance can be attributed to the following aspects: (1) Fe-, N-, and P triple doping created abundant active sites, contributing to the higher intrinsic activity of catalysts. (2) Phytic acid was crosslinked with melamine to form hydrogel, and its carbonized products have high specific surface area, which is beneficial for a large number of active sites to be exposed at the reaction interface. (3) The porous three-dimensional carbon network facilitates the transfer of reactants/intermediates/products and electric charge. Therefore, Fe/N/P Co-doped 3D porous carbon materials prepared by a facile and scalable pyrolysis route exhibit potential in the field of energy conversion/storage.
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Güler, Ali Can, Jan Antoš, Milan Masař, Michal Urbánek, Michal Machovský i Ivo Kuřitka. "Boosting the Photoelectrochemical Performance of Au/ZnO Nanorods by Co-Occurring Gradient Doping and Surface Plasmon Modification". International Journal of Molecular Sciences 24, nr 1 (27.12.2022): 443. http://dx.doi.org/10.3390/ijms24010443.
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Band bending modification of metal/semiconductor hybrid nanostructures requires low-cost and effective designs in photoelectrochemical (PEC) water splitting. To this end, it is evinced that gradient doping of Au nanoparticles (NPs) inwards the ZnO nanorods (NRs) through thermal treatment facilitated faster transport of the photo-induced charge carriers. Systematic PEC measurements show that the resulting gradient Au-doped ZnO NRs yielded a photocurrent density of 0.009 mA/cm2 at 1.1 V (vs. NHE), which is 2.5-fold and 8-fold improved compared to those of Au-sensitized ZnO and the as-prepared ZnO NRs, respectively. The IPCE and ABPE efficiency tests confirmed the boosted photoresponse of gradient Au-incorporated ZnO NRs, particularly in the visible spectrum due to the synergistic surface plasmonic effect of Au NPs. A gradient Au dopant profile promoted the separation and transfer of the photo-induced charge carriers at the electrolyte interface via more upward band bending according to the elaborated electrochemical impedance spectroscopy and Kelvin probe force microscopy analyses. Therefore, this research presents an economical and facile strategy for preparing gradient plasmonic noble NP-incorporated semiconductor NRs, which have excellent potential in energy conversion and storage technologies.
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Costentin, Cyrille, Jean-Michel Savéant i Cédric Tard. "Ligand “noninnocence” in coordination complexes vs. kinetic, mechanistic, and selectivity issues in electrochemical catalysis". Proceedings of the National Academy of Sciences 115, nr 37 (24.08.2018): 9104–9. http://dx.doi.org/10.1073/pnas.1810255115.
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The world of coordination complexes is currently stimulated by the quest for efficient catalysts for the electrochemical reactions underlying modern energy and environmental challenges. Even in the case of a multielectron−multistep process, catalysis starts with uptake or removal of one electron from the resting state of the catalyst. If this first step is an outer-sphere electron transfer (triggering a “redox catalysis” process), the electron distribution over the metal and the ligand is of minor importance. This is no longer the case with “chemical catalysis,” in which the active catalyst reacts with the substrate in an inner-sphere manner, often involving the transient formation of a catalyst−substrate adduct. The fact that, in most cases, the ligand is “noninnocent,” in the sense that the electron density and charge gained (or removed) from the resting state of the catalyst are shared between the metal and the ligand, has become common-place knowledge over the last half-century. Insistent focus on a large degree of noninnocence of the ligand in the resting state of the catalyst, even robustly validated by spectroscopic techniques, may lead to undermining the essential role of the metal when such essential issues as kinetics, mechanisms, and product selectivity are dealt with. These points are general in scope, but their discussion is eased by adequately documented examples. This is the case for reactions involving metalloporphyrins as well as vitamin B12 derivatives and similar cobalt complexes for which a wealth of experimental data is available.
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Alkoshab, Monther Q., Eleni Thomou, Ismail Abdulazeez, Munzir H. Suliman, Konstantinos Spyrou, Wissam Iali, Khalid Alhooshani i Turki N. Baroud. "Low Overpotential Electrochemical Reduction of CO2 to Ethanol Enabled by Cu/CuxO Nanoparticles Embedded in Nitrogen-Doped Carbon Cuboids". Nanomaterials 13, nr 2 (4.01.2023): 230. http://dx.doi.org/10.3390/nano13020230.
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The electrochemical conversion of CO2 into value-added chemicals is a promising approach for addressing environmental and energy supply problems. In this study, electrochemical CO2 catalysis to ethanol is achieved using incorporated Cu/CuxO nanoparticles into nitrogenous porous carbon cuboids. Pyrolysis of the coordinated Cu cations with nitrogen heterocycles allowed Cu nanoparticles to detach from the coordination complex but remain dispersed throughout the porous carbon cuboids. The heterogeneous composite Cu/CuxO-PCC-0h electrocatalyst reduced CO2 to ethanol at low overpotential in 0.5 M KHCO3, exhibiting maximum ethanol faradaic efficiency of 50% at −0.5 V vs. reversible hydrogen electrode. Such electrochemical performance can be ascribed to the synergy between pyridinic nitrogen species, Cu/CuxO nanoparticles, and porous carbon morphology, together providing efficient CO2 diffusion, activation, and intermediates stabilization. This was supported by the notably high electrochemically active surface area, rich porosity, and efficient charge transfer properties.
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Mariappan, Kadarkaraisamy, Anwar Hussain, Nathaniel Nisly, Tanner J. Henning, Kathryn A. Goerl, Madhubabu Alaparthi i Andrew G. Sykes. "Synthesis and X-ray Structures of Potential Light-Harvesting Ruthenium(II) Complexes". Molbank 2023, nr 2 (27.04.2023): M1635. http://dx.doi.org/10.3390/m1635.
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We synthesized the luminescent ruthenium(II) polypyridyl complexes of type [Ru(bpy)2(L1)][ClO4]2 (1) (where L1 = 4,4-dicarboxy-2,2-bipyridine); [Ru(bpy)2(L2)][ClO4]2 (2); and [Ru(L2)3][ClO4]2 (3) (where L2 = 4,4-dimethanol-2,2-bipyridine). Photo-physical and electrochemical properties of the Ru(II) complexes were investigated along with the emission vs. pH. This reveals that the carboxylic acids in the 2,2-bipyridine ligand had a more important influence on the photophysical and electrochemical properties of the Ru(II) complexes than alcohol. The crystal structure of the Ru(II) complexes 1–3 is also discussed in this paper. The cyclic voltammetry of 1–3 yields a reversible RuIII/II wave that shifts 1.4–1.2 V. UV/Visible absorbance spectroscopy reveals that Metal-to-Ligand Charge Transfer (MLCT) transitions shift to lower energy upon deprotonation of the complex.
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Wan, Xiaokang, Dashun Lu, Xianyun Wang, Gezhong Liu, Yanming Fu, Chao Hu, Nai Rong, Haitao Wang i Zude Cheng. "Enhanced Photoelectrochemical Water Oxidation on BiVO4 Photoanodes Functionalized by Bimetallic Dicyanamide Molecular Catalysts". Sustainability 15, nr 4 (8.02.2023): 3129. http://dx.doi.org/10.3390/su15043129.
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A novel hybrid structure of bimetallic dicyanamide decorated BiVO4 is developed via a simple method to accelerate interfacial water oxidation kinetics. Two types of bimetallic dicyanamides, CoNi(dca)2 and CoFe(dca)2, are coated on BiVO4 photoanodes and are found to exhibit far more enhanced PEC performance than Co(dca)2 or Ni(dca)2 as cocatalysts. The successful deposition of metal dicyanamides on BiVO4 photoanodes is confirmed by physical characterizations including X-ray photoelectron spectroscopy (XPS). The optimized Co0.9Ni0.1(dca)2/BiVO4 photoanode exhibits the highest photocurrent density of 2.58 mA/cm2 at 1.23 V vs. RHE under 100 mW/cm2 AM 1.5 G irradiation, which is 2.5 times that of bare BiVO4. The substantial enhancement of PEC performance can be ascribed to the advantageous interfacial charge transfer and improved charge injection efficiencies. This work presents a feasible strategy using different types of bimetallic dicyanamides to design a modified BiVO4-based photoanode system for enhanced water oxidation efficiency.
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Shihai, Luo, Gao Mei, Chen Jun, Xing Xianran, Li Zhong, Zhou Xingtai i Wen Wen. "BiFeO3 as Electrode Material for Lithium Batteries". Journal of New Materials for Electrochemical Systems 14, nr 3 (19.04.2011): 141–46. http://dx.doi.org/10.14447/jnmes.v14i3.101.
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BiFeO3 was studied as electrode material for lithium battery applications. The voltage profile of BiFeO3 vs Li battery displays three discharge plateaus around 1.3, 0.7 and 0.4 V (vs Li/Li+) and the first discharge capacity is about 1000 mAh/g, with a cutoff voltage of 0.05 V. If the cutoff voltage is limited to 0.7 V, much better capacity retention is achieved. The structural changes of BiFeO3 during electrochemical cycling process were investigated using synchrotron-based in situ XRD and XANES. Lithium ions were inserted into BiFeO3 during the discharge process. The whiteline of Bi LIII-edge XANES spectra gradually decreased during the discharge process with their LIII edge position concomitantly shifted towards lower energy position. However, the Fe K-edge XANES spectrum of the fully discharged product is similar to that of the pristine one and displays no shifts. This indicates that Bi ions are responsible for charge transfer during the electrochemical cycling process. The reduction of Bi3+ to Bi0 as the gradual insertion of Li ions, is a three-step reduction process. Li2Bi alloy formation was observed at the end of the discharge process, which is not fully reversible towards lithium intercalation/extraction and decomposes to metallic Bi.
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Velasco-Plascencia, Melina, Octavio Vázquez-Gómez, Luis Olmos, Francisco Reyes-Calderón, Héctor J. Vergara-Hernández i Julio C. Villalobos. "Determination of Activation Energy on Hydrogen Evolution Reaction for Nickel-Based Porous Electrodes during Alkaline Electrolysis". Catalysts 13, nr 3 (3.03.2023): 517. http://dx.doi.org/10.3390/catal13030517.
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The aim of the present work is to evaluate the activation energy (Ea) at different cathodic overpotentials (η) by potentiodynamic tests which were carried out at different temperatures of Ni-based, NiCr-m, and NiCr-p porous electrodes, during the alkaline electrolysis processes. On the other hand, the electrochemical stability of the electrodes was evaluated by cyclic voltammetry after 1000 cycles of operation and by potentiostatic tests after 10 h at −1.5 V vs. SCE. The electrodes were sintered with a heating rate of 25 °C/min up to a temperature of 1000 °C (Ni-based and NiCr-m) and 1200 °C (NiCr-p) for 60 min. The results showed that the Ea value was lower for the Ni-based system at equilibrium; however, the NiCr-p electrode had a better performance due to higher negative apparent Ea values as a function of η (dEa/dη). The cyclic voltammetry tests suggest that the NiCr-p electrode improves its activity by about 71% in its long-term operation in comparison with Ni-based and NiCr-m. A similar behavior was observed in the potentiostatic test which showed a higher cathodic current density associated with a charge transfer process after 10 h. The higher stability of the NiCr-p is attributed to a homogeneous Cr distribution in the nickel matrix.
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Wan, Zhongyu, i Ruiqin Zhang. "Metallization of hydrogen by intercalating ammonium ions in metal fcc lattices at lower pressure". Applied Physics Letters 121, nr 19 (7.11.2022): 192601. http://dx.doi.org/10.1063/5.0127365.
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Metallic hydrogen is capable of showing room temperature superconductivity, but its experimental syntheses are extremely hard. Therefore, it is desirable to reduce the synthesis pressure of metallic hydrogen by adding other chemical elements. However, for most hydrides, the metallization of hydrogen by “chemical precompression” to achieve high-temperature superconductivity still requires relatively high pressure, making experimental synthesis difficult. How to achieve high-temperature superconductivity in the lower-pressure range (≤50 GPa) is a key issue for realizing practical applications of superconducting materials. Toward this end, this work proposes a strategy for inserting ammonium ions in the fcc crystal of metals. High-throughput calculations of the periodic table reveal 12 elements that can form kinetically stable and superconducting hydrides at lower pressures, where the highest superconducting transition temperatures of AlN2H8, MgN2H8, and GaN2H8 can reach up to 118, 105, and 104 K. Pressure-induced bond length changes and charge transfer reveal the physical mechanism of high-temperature superconductivity, where the H atom continuously gains electrons leading to the transition of H+ ions to atomic H, facilitating metallization of hydrogen under less extreme high pressure. Our results also reveal two strong linear scalar relationships: one is the H-atom charge vs superconducting transition temperature, and the other is the first ionization energy vs the highest superconducting transition temperature. In addition, ZnN2H8, CdN2H8, and HgN2H8 were found to be superconductors at ambient pressure, and the presence of interstitial electrons suggests that they are also electrides, whose relatively low work functions (3.03, 2.78, and 3.05 eV) imply that they can be used as catalysts for nitrogen reduction reactions as well.
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Jeong, Hohyun, Myung Jong Kang, Hyeyeong Jung i Young Soo Kang. "Electrochemical CO2 reduction with low overpotential by a poly(4-vinylpyridine) electrode for application to artificial photosynthesis". Faraday Discussions 198 (2017): 409–18. http://dx.doi.org/10.1039/c6fd00225k.
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Pyridine molecules have been used as a catalyst to reduce the activation energy of the CO2 reduction reaction. It has been reported that CO2 is reduced by pyridine catalysts at low overpotential around −0.58 V vs. SCE. Poly(4-vinylpyridine), which has pyridine functional groups shows similar catalytic properties to reduce CO2 at low overpotential like pyridinium catalysts. Different thickness of P(4-VP) coated Pt electrodes were analyzed to determine the catalytic properties for CO2 reduction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods showed the catalytic CO2 reduction properties of a P(4-VP)/Pt electrode. Thin P(4-VP)/Pt film showed a low current density of −0.16 mA cm−2 under CO2 atmosphere and the current density reached −0.45 mA cm−2 with increase of the P(4-VP) thickness. The increase of current density was explained by an increased surface concentration of adsorbed pyridinium groups of the thick P(4-VP) layer. Nyquist plots also showed decrease of impedance with increase of the P(4-VP) layer indicating fast charge transfer between Pt and the P(4-VP) layer due to the increase of hybrid ionic complex formation on the Pt surface. However, charge transfer is restricted when the P(4-VP) layer becomes more thick because of slowed protonation of pyridine groups adjacent to the Pt surface due to the suppressed permeability of electrolyte solution into the PVP membrane. This electrochemical observation provides a new aspect of P(4-VP) polymer for CO2 reduction.
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Zhang, Henan, Qi Liu, Alena Novoselova, Jing Yu, Valeri Smolenski, Jingyuan Liu, Jiahui Zhu, Yongde Yan, Milin Zhang i Jun Wang. "Study of the Electrochemical Behavior and Thermodynamic Properties of Lanthanum Compounds on Inert Mo and Liquid Ga Electrodes in Fused NaCl-2CsCl Eutectic". Journal of The Electrochemical Society 169, nr 4 (1.04.2022): 043508. http://dx.doi.org/10.1149/1945-7111/ac6246.
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For extraction of metallic lanthanum from molten NaCl-CsCl-LaCl3 solutions, the electrochemical reduction of La(III) ions on inert Mo and liquid Ga electrodes were explored. Transient electrochemical techniques have been used to explore the reduction mechanism, transport parameters and thermodynamics properties. The obtained results indicate that the electrochemical reaction of La(III) + 3ē → La on inert electrode is a single-stage irreversible process, which controlled by the charge transfer rate. Simultaneously, the diffusion coefficient of [LaCl6]3− complex ions was obtained at different temperatures. The apparent standard potentials of La3+/La couple and La-Ga alloy vs the temperature were determined. The base thermodynamic properties of lanthanum compounds were calculated. Furthermore, the potentiostatic method of electrolysis was used for the synthesis of La-Ga alloys.
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Polizzi, Nicholas F., Ting Jiang, David N. Beratan i Michael J. Therien. "Engineering opposite electronic polarization of singlet and triplet states increases the yield of high-energy photoproducts". Proceedings of the National Academy of Sciences 116, nr 29 (10.06.2019): 14465–70. http://dx.doi.org/10.1073/pnas.1901752116.
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Efficient photosynthetic energy conversion requires quantitative, light-driven formation of high-energy, charge-separated states. However, energies of high-lying excited states are rarely extracted, in part because the congested density of states in the excited-state manifold leads to rapid deactivation. Conventional photosystem designs promote electron transfer (ET) by polarizing excited donor electron density toward the acceptor (“one-way” ET), a form of positive design. Curiously, negative design strategies that explicitly avoid unwanted side reactions have been underexplored. We report here that electronic polarization of a molecular chromophore can be used as both a positive and negative design element in a light-driven reaction. Intriguingly, prudent engineering of polarized excited states can steer a “U-turn” ET—where the excited electron density of the donor is initially pushed away from the acceptor—to outcompete a conventional one-way ET scheme. We directly compare one-way vs. U-turn ET strategies via a linked donor–acceptor (DA) assembly in which selective optical excitation produces donor excited states polarized either toward or away from the acceptor. Ultrafast spectroscopy of DA pinpoints the importance of realizing donor singlet and triplet excited states that have opposite electronic polarizations to shut down intersystem crossing. These results demonstrate that oppositely polarized electronically excited states can be employed to steer photoexcited states toward useful, high-energy products by routing these excited states away from states that are photosynthetic dead ends.
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Meng, Ming, Yamin Feng, Chunyang Li, Zhixing Gan, Honglei Yuan i Honghui Zhang. "Black 3D-TiO2 Nanotube Arrays on Ti Meshes for Boosted Photoelectrochemical Water Splitting". Nanomaterials 12, nr 9 (24.04.2022): 1447. http://dx.doi.org/10.3390/nano12091447.
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Black 3D-TiO2 nanotube arrays are successfully fabricated on the Ti meshes through a facile electrochemical reduction method. The optimized black 3D-TiO2 nanotubes arrays yield a maximal photocurrent density of 1.6 mA/cm2 at 0.22 V vs. Ag/AgCl with Faradic efficiency of 100%, which is about four times larger than that of the pristine 3D-TiO2 NTAs (0.4 mA/cm2). Such boosted PEC water splitting activity primarily originates from the introduction of the oxygen vacancies, which results in the bandgap shrinkage of the 3D-TiO2 NTAs, boosting the utilization efficiency of visible light including the incident, reflected and/or refracted visible light captured by the 3D configuration. Moreover, the oxygen vacancies (Ti3+) can work as electron donors, which leads to the enhanced electronic conductivity and upward shift of the Fermi energy level, and thereby facilitating the transfer and separation of the photogenerated charge carrier at the semiconductor-electrolyte interface. This work offers a new opportunity to promote the PEC water splitting activity of TiO2-based photoelectrodes.
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Crespo, Alicia, Gabriel Zsembinszki, David Vérez, Emiliano Borri, Cèsar Fernández, Luisa F. Cabeza i Alvaro de Gracia. "Optimization of Design Variables of a Phase Change Material Storage Tank and Comparison of a 2D Implicit vs. 2D Explicit Model". Energies 14, nr 9 (2.05.2021): 2605. http://dx.doi.org/10.3390/en14092605.
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In this study, a thermal energy storage tank filled with commercial phase change material flat slabs is investigated. The tank provides heat at around 15 °C to the evaporator of a seasonal thermal energy storage system developed under the EU-funded project SWS-Heating. A 2D numerical model of the phase changed material storage tank based on the finite control volume approach was developed and validated with experimental data. Based on the validated model, an optimization was performed to identify the number, type and configuration of slabs. The final goal of the phase change material tank model is to be implemented into the whole generic heating system model. A trade-off between results’ accuracy and computational time of the phase change material model is needed. Therefore, a comparison between a 2D implicit and 2D explicit scheme of the model was performed. The results showed that using an explicit scheme instead of an implicit scheme with a reasonable number of nodes (15 to 25) in the heat transfer fluid direction allowed a considerable decrease in the computational time (7 times for the best case) with only a slight reduction in the accuracy in terms on mean average percentage error (0.44%).
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Kovalev, Andrey A., Elza R. Mikheeva, Dmitriy A. Kovalev, Inna V. Katraeva, Svetlana Zueva, Valentina Innocenzi, Vladimir Panchenko, Elena A. Zhuravleva i Yuri V. Litti. "Feasibility Study of Anaerobic Codigestion of Municipal Organic Waste in Moderately Pressurized Digesters: A Case for the Russian Federation". Applied Sciences 12, nr 6 (13.03.2022): 2933. http://dx.doi.org/10.3390/app12062933.
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Anaerobic digestion (AD) is a promising option to obtain renewable energy in the form of biogas and reduce the anthropogenic impact on the environment. In recent years there has been increasing interest in using pressurized digesters to improve the quality of biogas. However, maintaining high overpressure increases the requirements for the explosion safety of digesters. Consequently, there are natural limitations in the available technologies and facilities suitable for full-scale operation. In this work, we aimed to evaluate the possibility of using overpressure in the digester to improve the efficiency of codigestion of common municipal organic waste–sewage sludge and the organic fraction of municipal solid waste. Three levels of moderate excess pressure (100, 150 and 200 kPa) were used to meet requirements of existing block-modular anaerobic bioreactors based on railway tanks, which are widely utilized for AD in the Russian Federation. There was no significant change in methane content in biogas (65% ± 3%) at different values of overpressure, hydraulic retention time (HRT) and organic loading rate (OLR). The maximum methane and energy production rates (2.365 L/(L·day) and 94.27 kJ/(L·day), respectively) were obtained at an overpressure of 200 kPa, HRT of 5 days and OLR of 14 kg VS/(m3·day). However, the maximum methane yield (202.44 mL/g VS), energy yield (8.07 kJ/g VS) and volatile solids (VS) removal (63.21%) were recorded at an overpressure of 150 kPa, HRT of 7 days and OLR of 10.4 kg VS/(m3·day). The pressured conditions showed better performance in terms of AD stability at high OLRs.
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Martinez, Jose F., Nathan T. La Porte, Catherine M. Mauck i Michael R. Wasielewski. "Photo-driven electron transfer from the highly reducing excited state of naphthalene diimide radical anion to a CO2 reduction catalyst within a molecular triad". Faraday Discussions 198 (2017): 235–49. http://dx.doi.org/10.1039/c6fd00219f.
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The naphthalene-1,4:5,8-bis(dicarboximide) radical anion (NDI−˙), which is easily produced by mild chemical or electrochemical reduction (−0.5 V vs. SCE), can be photoexcited at wavelengths as long as 785 nm, and has an excited state (NDI−˙*) oxidation potential of −2.1 V vs. SCE, making it a very attractive choice for artificial photosynthetic systems that require powerful photoreductants, such as CO2 reduction catalysts. However, once an electron is transferred from NDI−˙* to an acceptor directly bound to it, a combination of strong electronic coupling and favorable free energy change frequently make the back electron transfer rapid. To mitigate this effect, we have designed a molecular triad system comprising an NDI−˙ chromophoric donor, a 9,10-diphenylanthracene (DPA) intermediate acceptor, and a Re(dmb)(CO)3 carbon dioxide reduction catalyst, where dmb is 4,4′-dimethyl-2,2′-bipyridine, as the terminal acceptor. Photoexcitation of NDI−˙ to NDI−˙* is followed by ultrafast reduction of DPA to DPA−˙, which then rapidly reduces the metal complex. The overall time constant for the forward electron transfer to reduce the metal complex is τ = 20.8 ps, while the time constant for back-electron transfer is six orders of magnitude longer, τ = 43.4 μs. Achieving long-lived, highly reduced states of these metal complexes is a necessary condition for their use as catalysts. The extremely long lifetime of the reduced metal complex is attributed to careful tuning of the redox potentials of the chromophore and intermediate acceptor. The NDI−˙–DPA fragment presents many attractive features for incorporation into other photoinduced electron transfer assemblies directed at the long-lived photosensitization of difficult-to-reduce catalytic centers.
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Melamed, Yarden, Nabasmita Maity, Louisa Meshi i Noam Eliaz. "Electroplating of Pure Aluminum from [HMIm][TFSI]–AlCl3 Room-Temperature Ionic Liquid". Coatings 11, nr 11 (19.11.2021): 1414. http://dx.doi.org/10.3390/coatings11111414.
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Electrodeposition of aluminum and its alloys is of great interest in the aerospace, automobile, microelectronics, energy, recycle, and other industrial sectors, as well as for defense and, potentially, electrochemical printing applications. Here, for the first time, we report room-temperature electroplating of pure aluminum on copper and nickel substrates from an ionic liquid (IL) consisting of 1-Hexyl-3-methylimidazolium (HMIm) cation and bis(trifluoromethylsulfonyl)imide (TFSI) anion, with a high concentration of 8 mol/L AlCl3 aluminum precursor. The aluminum deposits are shown to have a homogeneous and dense nanocrystalline structure. A quasi-reversible reaction is monitored, where the current is affected by both charge transfer and mass transport. The electrocrystallization of Al on Ni is characterized by instantaneous nucleation. The deposited Al layers are dense, homogeneous, and of good surface coverage. They have a nanocrystalline, single-phase Al (FCC) structure, with a dislocation density typical of Al metal. An increase in the applied cathodic potential from −1.3 to −1.5 V vs. Pt resulted in more than one order of magnitude increase in the deposition rate (to ca. 44 μm per hour), as well as in ca. one order of magnitude finer grain size. The deposition rate is in accordance with typical industrial coating systems.
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Umar Daraz, Umar Daraz, Tariq Mahmood Ansari Tariq Mahmood Ansari, Shafique Ahmad Arain Shafique Ahmad Arain i Muhammad Adil Mansoor and Muhammad Mazhar Muhammad Adil Mansoor and Muhammad Mazhar. "Structural, Topographical and Optoelectronic Properties of ZnIn2S4 Thin Films Deposited from Dual Source Using Aerosol Assisted Chemical Vapour Deposition (AACVD) Technique". Journal of the chemical society of pakistan 42, nr 2 (2020): 155. http://dx.doi.org/10.52568/000624/jcsp/42.02.2020.
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The ZnIn2S4 (ZIS) thin films have been successfully developed from a homogeneous toluene solution of dithiocarbamate complexes of zinc and indium with formula [Zn(S2CNCy2)2(py)] (1) and [In(S2CNCy2)3].2py (2) via aerosol assisted chemical vapor deposition (AACVD) technique. Deposition experiments were carried out at 500oC in an inert atmosphere of argon gas on FTO substrate. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and Raman spectroscopy have been used for the determination of phase purity, surface topography of the uniformly distributed particles and oxidation states of the elements present in thin films. Further UV-visible spectrophotometry elucidates that the thin films absorbs in entire visible region and give estimated band gap energy of 2.37 eV. The photoelectrochemical (PEC) response in terms of linear scan voltammetry (LSV) provides a photocurrent density 2.27 mA.cm-2 at 0.7 V vs Ag/AgCl/3M KCl using 0.05 M sodium sulphide solution under AM 1.5 G illumination (100 mW.cm-2). The LSV results are further reinforced by electrochemical impedance spectroscopy (EIS) that gives charge transfer resistance (Rct) value of 5.7 x 104 Ω under dark conditions and reduces to 3.7 x 104 Ω under illumination.
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Tan, Chao, Haocheng Yin, Victoria Brooks, Prabhu U. Arumugam i Shabnam Siddiqui. "A Study of the Effect of Electrochemical Roughening of Platinum on the Sensitivity and Selectivity of Glutamate Biosensors". Journal of The Electrochemical Society 169, nr 3 (1.03.2022): 037510. http://dx.doi.org/10.1149/1945-7111/ac5ad5.
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A systematic study of electrochemically roughened (ECR) thin film platinum (Pt) microelectrodes for glutamate, GLU (a major excitatory neurotransmitter) detection is presented. Scanning electron microscopy, energy dispersive spectroscopy, surface profilometry, electrochemical impedance spectroscopy and amperometry techniques were applied to investigate the effect of high-frequency electrical pulses on Pt microelectrode roughness, electroactive area, charge transfer resistance, and sensitivity and selectivity to hydrogen peroxide, a by-product of enzymatic biosensors and GLU. An increase in the mean surface roughness from 9.0 ± 0.5 to 116.3 ± 7.4 nm (n = 3) was observed which resulted in a 55 ± 2% (n = 3) increase in the electroactive area. An ECR microelectrode treated at +1.4 V and coated with a selective coating produced a GLU selectivity value of 342 ± 34 (n = 3) vs ascorbic acid and the highest GLU sensitivity of 642 ± 45 nAμM−1cm−2 (n = 3) when compared to other surface-treated Pt microelectrodes reported in the literature. An impedance model was created to elucidate the microstructural and electrochemical property changes to the ECR microelectrodes. The ECR surface comprises of uniformly distributed homogenous pores with very low impedance, which is ∼6-times lower when compared to a methanol cleaned electrode. The model could lay a foundation for the rational designing of biosensors for enhanced neurotransmitter detection.