The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Krishna Nand Singh - One of the best experts on this subject based on the ideXlab platform.
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Superoxide induced oxidative aromatization of Hantzsch 1,4-dihydropyridines
Indian Journal of Chemistry Section B-organic Chemistry Including Medicinal Chemistry, 2008Co-Authors: Raghvendra Singh Raghuvanshi, Krishna Nand SinghAbstract:Tetraethylammonium Superoxide, obtained in situ by the phase transfer reaction of Potassium Superoxide and tetraethylammonium bromide, accomplishes an easy and efficient oxidative aromatization of llantzsch 1,4-dihydropyridines to their corresponding pyridines under mild reaction conditions, at room temperature.
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An efficient C-C bond cleavage of 1,2-diols using tetraethylammonium Superoxide
Indian Journal of Chemistry Section B-organic Chemistry Including Medicinal Chemistry, 2007Co-Authors: Krishna Nand Singh, Rajesh Kumar, Ajay Kumar ShuklaAbstract:Tetraethylammonium Superoxide, generated in situ by the phase-transfer reaction of Potassium Superoxide and tetraethylammonium bromide in DMF, brings about an easy cleavage of vicinal diols and related dihydroxy arenes under mild reaction conditions, at room temperature.
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Superoxide catalyzed oxidation of 4-alkylsubstituted pyrazol-5-ones to 4-alkyl-4-hydroxysubstituted pyrazol-5-ones
Journal of the Indian Chemical Society, 2007Co-Authors: Sundaram Singh, Satish Kumar Singh, Krishna Nand SinghAbstract:Superoxide ion, generated in situ by the phase transfer reaction of Potassium Superoxide and tetraethylammonium bromide, brings about an easy oxidation of different 4-alkylsubstituted pyrazol-5-ones to yield 4-alkyl-4-hydroxy pyrazol-5-ones in reasonably good yields.
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studies on the reactivity pattern of in situ generated tetraethylammonium Superoxide with 2 oxazolin 5 ones
Indian Journal of Chemistry Section B-organic Chemistry Including Medicinal Chemistry, 2005Co-Authors: Krishna Nand Singh, Rajesh KumarAbstract:A variety of 2-oxazolin-5-ones have been allowed to react under the mild reaction conditions of Potassium Superoxide and tetraethylammonium bromide in dry dimethylformamide at room temperature. Different products are obtained depending on the substituents attached to the C-4 position.
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Phase transfer reaction of Potassium Superoxide with benzylic methyl and methylene compounds in aprotic medium
Indian Journal of Chemical Technology, 2004Co-Authors: Ajay Kumar Shukla, Krishna Nand SinghAbstract:(0.003 mol) was finally introduced and the stirring was continued at room temperature for 8-12 h till the complete loss of starting material was indicated by TLC. After completion of the reaction, the mixture was treated with saturated sodium chloride solution (20 mL) to decompose the unreacted Potassium Superoxide. Saturated aq. NaHCO
Hyun Jae Kim - One of the best experts on this subject based on the ideXlab platform.
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Dual-Functional Superoxide Precursor To Improve the Electrical Characteristics of Oxide Thin Film Transistors
ACS applied materials & interfaces, 2018Co-Authors: Tae Soo Jung, Heesoo Lee, Hee Jun Kim, Jin Hyeok Lee, Hyun Jae KimAbstract:We investigated a method to simultaneously improve the mobility and reliability of solution-processed zinc tin oxide thin film transistors (ZTO TFTs) using a dual-functional Potassium Superoxide precursor. Potassium cations in the Potassium Superoxide (KO2) precursor act as carrier suppliers in the ZTO thin film to improve the carrier (electron) concentration, which allows the Potassium-doped ZTO TFT to exhibit high mobility. The anions in the precursor exist as Superoxide radicals that reduce oxygen vacancies during the formation of thin oxide film. Consequently, the KO2-treated ZTO TFTs exhibited improved mobility and reliability compared with pristine ZTO TFTs, with an increase in field effect mobility from 5.57 to 8.74 cm2/V s and a decrease in the threshold voltage shift from 7.18 to 3.85 V, after a positive bias temperature stress test conducted over 5000 s.
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Dual-Functional Superoxide Precursor To Improve the Electrical Characteristics of Oxide Thin Film Transistors
2018Co-Authors: Tae Soo Jung, Heesoo Lee, Hee Jun Kim, Jin Hyeok Lee, Hyun Jae KimAbstract:We investigated a method to simultaneously improve the mobility and reliability of solution-processed zinc tin oxide thin film transistors (ZTO TFTs) using a dual-functional Potassium Superoxide precursor. Potassium cations in the Potassium Superoxide (KO2) precursor act as carrier suppliers in the ZTO thin film to improve the carrier (electron) concentration, which allows the Potassium-doped ZTO TFT to exhibit high mobility. The anions in the precursor exist as Superoxide radicals that reduce oxygen vacancies during the formation of thin oxide film. Consequently, the KO2-treated ZTO TFTs exhibited improved mobility and reliability compared with pristine ZTO TFTs, with an increase in field effect mobility from 5.57 to 8.74 cm2/V s and a decrease in the threshold voltage shift from 7.18 to 3.85 V, after a positive bias temperature stress test conducted over 5000 s
Zhihua Sui - One of the best experts on this subject based on the ideXlab platform.
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Potassium Superoxide as an Alternative Reagent for Winterfeldt Oxidation of β-Carbolines
Organic letters, 2003Co-Authors: Weiqin Jiang, Xuqing Zhang, Zhihua SuiAbstract:Potassium Superoxide was examined as an alternative oxidation reagent for the Winterfeldt reaction. KO2 was found to be superior to the original Winterfeldt protocol for base-sensitive substrates.
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Potassium Superoxide as an alternative reagent for winterfeldt oxidation of beta carbolines
Organic Letters, 2003Co-Authors: Weiqin Jiang, Xuqing Zhang, Zhihua SuiAbstract:Potassium Superoxide was examined as an alternative oxidation reagent for the Winterfeldt reaction. KO(2) was found to be superior to the original Winterfeldt protocol for base-sensitive substrates. [reaction--see text]
Xiaodi Ren - One of the best experts on this subject based on the ideXlab platform.
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Potassium Superoxide: A Unique Alternative for Metal–Air Batteries
Accounts of chemical research, 2018Co-Authors: Neng Xiao, Xiaodi Ren, William D. Mcculloch, Gerald GourdinAbstract:ConspectusLithium–oxygen (Li–O2) batteries have been envisaged and pursued as the long-term successor to Li-ion batteries, due to the highest theoretical energy density among all known battery chemistries. However, their practical application is hindered by low energy efficiency, sluggish kinetics, and a reliance on catalysts for the oxygen reduction and evolution reactions (ORR/OER). In a Superoxide battery, oxygen is also used as the cathodic active medium but is reduced only to Superoxide (O2•–), the anion formed by adding an electron to a diatomic oxygen molecule. Therefore, O2/O2•– is a unique single-electron ORR/OER process. Since the introduction of K–O2 batteries by our group in 2013, Superoxide batteries based on Potassium Superoxide (KO2) have attracted increasing interest as promising energy storage devices due to their significantly lower overpotentials and costs.We have selected Potassium for building the Superoxide battery because it is the lightest alkali metal cation to form the thermodyna...
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Potassium Superoxide a unique alternative for metal air batteries
Accounts of Chemical Research, 2018Co-Authors: Neng Xiao, Xiaodi Ren, William D. Mcculloch, Gerald GourdinAbstract:ConspectusLithium–oxygen (Li–O2) batteries have been envisaged and pursued as the long-term successor to Li-ion batteries, due to the highest theoretical energy density among all known battery chemistries. However, their practical application is hindered by low energy efficiency, sluggish kinetics, and a reliance on catalysts for the oxygen reduction and evolution reactions (ORR/OER). In a Superoxide battery, oxygen is also used as the cathodic active medium but is reduced only to Superoxide (O2•–), the anion formed by adding an electron to a diatomic oxygen molecule. Therefore, O2/O2•– is a unique single-electron ORR/OER process. Since the introduction of K–O2 batteries by our group in 2013, Superoxide batteries based on Potassium Superoxide (KO2) have attracted increasing interest as promising energy storage devices due to their significantly lower overpotentials and costs.We have selected Potassium for building the Superoxide battery because it is the lightest alkali metal cation to form the thermodyna...
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Probing Mechanisms for Inverse Correlation between Rate Performance and Capacity in K–O2 Batteries
ACS applied materials & interfaces, 2016Co-Authors: Neng Xiao, Xiaodi Ren, William D. MccullochAbstract:Owing to the formation of Potassium Superoxide (K+ + O2 + e– = KO2), K–O2 batteries exhibit superior round-trip efficiency and considerable energy density in the absence of any electrocatalysts. For further improving the practical performance of K–O2 batteries, it is important to carry out a systematic study on parameters that control rate performance and capacity to comprehensively understand the limiting factors in Superoxide-based metal–oxygen batteries. Herein, we investigate the influence of current density and oxygen diffusion on the nucleation, growth, and distribution of Potassium Superoxide (KO2) during the discharge process. It is observed that higher current results in smaller average sizes of KO2 crystals but a larger surface coverage on the carbon fiber electrode. As KO2 grows and covers the cathode surface, the discharge will eventually end due to depletion of the oxygen-approachable electrode surface. Additionally, higher current also induces a greater gradient of oxygen concentration in th...
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a low overpotential Potassium oxygen battery based on Potassium Superoxide
Journal of the American Chemical Society, 2013Co-Authors: Xiaodi RenAbstract:Li–O2 battery is regarded as one of the most promising energy storage systems for future applications. However, its energy efficiency is greatly undermined by the large overpotentials of the discharge (formation of Li2O2) and charge (oxidation of Li2O2) reactions. The parasitic reactions of electrolyte and carbon electrode induced by the high charging potential cause the decay of capacity and limit the battery life. Here, a K–O2 battery is report that uses K+ ions to capture O2– to form the thermodynamically stable KO2 product. This allows for the battery to operate through the one-electron redox process of O2/O2–. Our studies confirm the formation and removal of KO2 in the battery cycle test. Furthermore, without the use of catalysts, the battery shows a low discharge/charge potential gap of less than 50 mV at a modest current density, which is the lowest one that has ever been reported in metal–oxygen batteries.
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A Low-Overpotential Potassium–Oxygen Battery Based on Potassium Superoxide
Journal of the American Chemical Society, 2013Co-Authors: Xiaodi RenAbstract:Li–O2 battery is regarded as one of the most promising energy storage systems for future applications. However, its energy efficiency is greatly undermined by the large overpotentials of the discharge (formation of Li2O2) and charge (oxidation of Li2O2) reactions. The parasitic reactions of electrolyte and carbon electrode induced by the high charging potential cause the decay of capacity and limit the battery life. Here, a K–O2 battery is report that uses K+ ions to capture O2– to form the thermodynamically stable KO2 product. This allows for the battery to operate through the one-electron redox process of O2/O2–. Our studies confirm the formation and removal of KO2 in the battery cycle test. Furthermore, without the use of catalysts, the battery shows a low discharge/charge potential gap of less than 50 mV at a modest current density, which is the lowest one that has ever been reported in metal–oxygen batteries.
Elodie Anxolabéhère-mallart - One of the best experts on this subject based on the ideXlab platform.
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Reactivity of MnII with Superoxide. Evidence for a [MnIIIOO]+ unit by low-temperature spectroscopies.
Inorganic chemistry, 2007Co-Authors: Sihem Groni, Guillaume Blain, Régis Guillot, Clotilde Policar, Elodie Anxolabéhère-mallartAbstract:Manganese Superoxide dismutase cycles between the MnIII and MnII states to produce oxygen and hydrogen peroxide from Superoxide. The formation of an adduct has been suggested, but its nature remains questionable because both [MnIIOO-] and [MnIIIOO2-] redox states have been proposed. Study of the reactivity of Superoxide with manganese complexes is of current interest. The reaction of [(L)MnII]2+ [L = N-methyl-N,N‘,N‘-tris(2-pyridylmethyl)ethane-1,2-diamine] with Potassium Superoxide has been investigated at low temperature in an anhydrous solvent using various techniques. Upon the addition of ca. 2 equiv of Potassium Superoxide, the [(L)MnII]2+ colorless solution turned blue and the UV−vis spectrum displayed a band at 590 nm (165 M-1 cm-1) and a shoulder at 430 nm (100 M-1 cm-1). Electrospray ionization mass spectrometry showed a peak (m/z = 434.1) assigned to [(L)MnO2]+. The X-band electron paramagnetic resonance spectrum parallel mode displayed a six-line signal separated by 6.6 mT and centered at 86 mT...
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Reactivity of MnII with Superoxide. Evidence for a [MnIIIOO]+ Unit by Low-Temperature Spectroscopies
Inorganic Chemistry, 2007Co-Authors: Sihem Groni, Guillaume Blain, Régis Guillot, Clotilde Policar, Elodie Anxolabéhère-mallartAbstract:Manganese Superoxide dismutase cycles between the MnIII and MnII states to produce oxygen and hydrogen peroxide from Superoxide. The formation of an adduct has been suggested, but its nature remains questionable because both [MnIIOO-] and [MnIIIOO2-] redox states have been proposed. Study of the reactivity of Superoxide with manganese complexes is of current interest. The reaction of [(L)MnII]2+ [L = N-methyl-N,N`,N`-tris(2-pyridylmethyl)ethane-1,2-diamine] with Potassium Superoxide has been investigated at low temperature in an anhydrous solvent using various techniques. Upon the addition of ca. 2 equiv of Potassium Superoxide, the [(L)MnII]2+ colorless solution turned blue and the UV-vis spectrum displayed a band at 590 nm (165 M-1 cm-1) and a shoulder at 430 nm (100 M-1 cm-1). Electrospray ionization mass spectrometry showed a peak (m/z = 434.1) assigned to [(L)MnO2]+. The X-band electron paramagnetic resonance spectrum parallel mode displayed a six-line signal separated by 6.6 mT and centered at 86 mT (g = 8.1). These results support the formation of an [MnIIIOO]+ adduct.