Effect Of Redox Reactions Research Articles

Combined experimental and theoretical approach to improve measurement accuracy of temperature-dependent reflectance of copper for near-infrared lasers

AbstractThe low process stability of laser welding of copper with near-infrared lasers requires precise input data for process control and meaningful simulations. But meanwhile, available datasets of temperature-dependent reflectance or absorptance for near-infrared lasers on copper do not show good agreement between the different sources and often do not include the fusion process, which is of crucial importance for realistic laser welding simulations. Additionally, most of the datasets are only calculated. Therefore, in a previous study, temperature-dependent reflectance measurements were performed on electro tough-pitch copper using a near-infrared laser. The measurements revealed a reflectance drift, which was induced by the setup behavior during heating, and the time-dependence of chemical reactions like the redox-reaction as possible error sources. In this study, experiments on laser melting as the fundamental process of laser welding were performed, together with corresponding simulations using the measured reflectance values for oxide-reduced and for untreated copper from the previous study. Then, the simulations were compared with the experiments to estimate the accuracy of the reflectance measurements. To provide context, the same simulations were also conducted using reflectance datasets from other authors. In a second step, the reflectance data were corrected with respect to the reflectance drift and the effects of redox reactions were adapted to the conditions of the laser melting experiments. Using the resulting reflectance curves, an improved agreement of simulation results and the experiments was achieved over a range of different test cases, without the necessity of correction factors in the simulation model.

Open-cage fullerenes as ligands for metals.

The remarkable structures of open-cage fullerenes with functionalization on the outer surface and an accessible inner void make them interesting ligands for reactions with metal complexes. The behaviors of open-cage fullerenes in reactions with various metal complexes are examined and compared to the corresponding reactions with intact fullerenes. The structural results from X-ray diffraction are emphasized. Open-cage fullerenes frequently undergo unanticipated structural changes such as carbon-carbon bond cleavage upon reactions with metal complexes. Much more remains to be learned about the possibility of inserting metal ions larger than Li+ into the interior void of these open-cage fullerenes and about the effects of redox reactions on metal complexes of open-cage fullerenes.

The Effect of Redox Reactions on the Stability of Perovskite Solar Cells

AbstractOrganic–inorganic hybrid perovskites have attracted tremendous attention in the photovoltaic industry because of their low cost, simple production process, and high efficiency. However, (photo)stability is still one of the main problems that limits their development and enormous efforts have been made in this area. In this Review, we focus on the ubiquitous redox reactions in perovskite solar cells (PSCs), reveal the reasons behind the occurrence of the reactions (both external and internal factors) and the resulting effects (favorable and unfavorable), and collect methods to mitigate or block the occurrence of the reaction. Then, we summarize the means of characterizing redox reactions to visualize their presence and mechanisms. Finally, we envision future research directions in this field and consider redox reactions a double‐edged sword. We hope that these insights will contribute to accelerating the commercialization of PSCs.

Operando magnetic resonance imaging for mapping of temperature and redox species in thermo-electrochemical cells

Low-grade waste heat is an abundant and underutilised energy source. In this context, thermo-electrochemical cells (i.e., systems able to harvest heat to generate electricity) are being intensively studied to deliver the promises of efficient and cost-effective energy harvesting and electricity generation. However, despite the advances in performance disclosed in recent years, understanding the internal processes occurring within these devices is challenging. In order to shed light on these mechanisms, here we report an operando magnetic resonance imaging approach that can provide quantitative spatial maps of the electrolyte temperature and redox ion concentrations in functioning thermo-electrochemical cells. Time-resolved images are obtained from liquid and gel electrolytes, allowing the observation of the effects of redox reactions and competing mass transfer processes such as thermophoresis and diffusion. We also correlate the physicochemical properties of the system with the device performance via simultaneous electrochemical measurements.

Switching characteristics of anthraquinone molecular devices based on graphene electrodes

With the development of microelectronics and the miniaturization of electronic devices, the use of molecular materials to construct various components in electronic circuits has become a most likely development trend. Compared with silicon-based semiconductor components, molecular electronic device has the advantages of small size, high integration, low energy consumption and fast response. In recent years, more and more molecules have been used to design molecular devices such as molecular diodes, molecular switches, molecular field effect transistors and molecular memories. In this paper, sandwich structure devices based on graphene nanoribbon electrodes are constructed. The first-principles calculation method combining density functional theory and non-equilibrium Green’s function is adopted to design the molecular devices with functional characteristics. The effects of redox reactions on the electrical transport properties of molecular devices are systematically discussed. The main research contents of this paper are as follows. The switching characteristics of an anthraquinone molecular device based on graphene electrode are studied. The zigzag-edge nanoribbons and armchair-edge graphene nanoribbons are selected as electrodes. Considering the two isomers of anthraquinone (HQ) and anthraquinone (AQ) molecules in the redox reaction, the double electrode molecular junction is constructed. The effects of redox reaction and electrode structure on the switching characteristics of anthraquinone molecular devices are discussed. It is found that the current in the HQ configuration is significantly greater than that in the AQ configuration, regardless of the zigzag-edge graphene electrode or the armchair-edge graphene electrode. That is, under the redox reaction, the anthraquinone molecules show significant switching characteristics. The switching ratio of zigzag-edge graphene electrode is selected to reach a maximum of 3125, and that of armchair-edge graphene electrode is selected to maximum of 1538. In addition, when the armchair-edge graphene is used as an electrode in the HQ configuration, the negative differential resistance is obviously between 0.7 and 0.9 V.

Relaciones de factores hidrogeológicas, condiciones de oxidación-reducción del agua subterránea, y distribuciones espacial y temporal de nitrato, Valle Centro-Oriental de San Joaquín, California, EEUU

In a 2,700-km2 area in the eastern San Joaquin Valley, California (USA), data from multiple sources were used to determine interrelations among hydrogeologic factors, reduction-oxidation (redox) conditions, and temporal and spatial distributions of nitrate (NO3), a widely detected groundwater contaminant. Groundwater is predominantly modern, or mixtures of modern water, with detectable NO3 and oxic redox conditions, but some zones have anoxic or mixed redox conditions. Anoxic conditions were associated with long residence times that occurred near the valley trough and in areas of historical groundwater discharge with shallow depth to water. Anoxic conditions also were associated with interactions of shallow, modern groundwater with soils. NO3 concentrations were significantly lower in anoxic than oxic or mixed redox groundwater, primarily because residence times of anoxic waters exceed the duration of increased pumping and fertilizer use associated with modern agriculture. Effects of redox reactions on NO3 concentrations were relatively minor. Dissolved N2 gas data indicated that denitrification has eliminated >5 mg/L NO3–N in about 10% of 39 wells. Increasing NO3 concentrations over time were slightly less prevalent in anoxic than oxic or mixed redox groundwater. Spatial and temporal trends of NO3 are primarily controlled by water and NO3 fluxes of modern land use.

Electrochemical Control of Solubilization by Redox-Active Surfactants

The solubilization of organic molecules in surfactant molecular assemblies may be controlled effectively by electrochemical reactions using redox-active surfactants. In this study, several aromatic compounds were solubilized in aqueous micellar solution of ferrocene-modified nonionic surfactant (11-ferrocenylundecyl polyoxyethylene ether : FPEG) and the effects of redox reactions on solubilization were examined. The solubilization equilibrium constant (K) of the solutes in FPEG micelles, which represents the distribution of solubilizates between micelles and bulk solution, was noted to decrease with the oxidation of ferrocenyl moieties of FPEG molecules, but increase with reduction of ferrocenyl moieties. Electrochemical control of vesicle formation and applications for solubilization control were investigated using aqueous mixtures of a ferrocene-modified cationic surfactant (FTMA) and anionic sodium dodecylbenzene sulfonate (SDBS).

Effect of redox reaction on the sintering behavior of cerium oxide

Hydrothermally synthesized nano-size CeO 2 powders, chemically precipitated CeO 2 powders and commercial micron-size CeO 2 powders were investigated by DTA TGA and TEM. The sintering behavior of these powders was studied by continuous monitoring of the shrinkage kinetics. The microstructural features of the sintered specimens were observed by SEM. The sinterability of the CeO 2 powder compact increased with decrease in particle size. During the high temperature sintering process a redox reaction occurred, i.e. CeO 2 was reduced to Ce 2O 3, and oxygen gas was released. The redox reaction influenced the sintering behavior of CeO 2, resulting in a decrease in density and microcracking for the hydrothermally synthesized nano-size CeO 2 powder compacts, and sagged points in the sintering curves for the chemically precipitated and commercial micron-size CeO 2 powder compacts. It was found that the redox reaction of ceria produced additional pores during the sintering process and thus a much higher temperature was needed to achieve a high density.

A study of leucoemeraldine and effect of redox reactions on molecular weight of chemically prepared polyaniline

We present the first study of the chemical interconversion between leucoemeraldine and emeraldine bases of polyaniline in relation to the molecular weight (MW) and molecular weight distribution (MWD). Electronic absorption spectroscopy and GPC were employed to monitor the changes in the oxidation state and MW of the polyaniline, soluble in NMP during the redox reactions. The MW and MWD of polyaniline were found to change drastically when the redox reactions were performed with the polymers in the solid phase while relatively little when the reactions were carried out with the polymers in the solution phase

Redox Behavior of Diazotized Amines in Aprotic Solvents

The redox behavior of diazotized aromatic and aliphatic amines is discussed. The half-wave potentials of their cathodic and/or anodic waves is correlated with their chemical reactivity. The effect of redox reactions on the stability of the nitrogen moiety of diazo compounds is elaborated. The lability of nitrogen in the resulting ion-radical species is suggested as a key to fixation of nitrogen via redox schemes.