Presence Of KOH Research Articles

Quinoline-2-thione-based fluorescent probes for selective and sensitive detections of mustard gas and its analogues

Sulfur mustard (SM, also called as mustard gas (HD)) is a persistent and highly toxic gas used as chemical weapon in wars and military conflicts. Moreover, owing to its simple structure and easy synthesis, it is the most likely chemical agent used by terrorists. For this reason, it is vital important to develop a facile, rapid and reliable detection system for SM. In this paper, we have developed four quinoline-2-thiones as fluorescent probes, 2a-2d, for the detection of SM and its analogues, half sulfur mustard (CEES) and a nitrogen mustard NH1. In the presence of KOH, these quinoline-2-thiones deprotonated to quinoline-2-thiophenol anions, which react with SM and its analogues rapidly to form quinoline-2-thiethers with highly efficient fluorescence, giving turn-on fluorescence response. The sensing products with CEES were isolated and fully characterized, thereby, the sensing mechanism was firmly established. The fluorescent probes with 4-trifluoromethyl group, 2b and 2d, exhibit rapid response to SM, CEES and NH1 (within 1 min at 60 °C for CEES and NH1), high sensitivity (limit of detection, 50 nM for SM and 20 nM for NH1) and high selectivity. Furthermore, polymer film test strips were fabricated with probe-embedded poly(ethylene oxide) for the detection of CEES vapor. These test strips displayed a rapid response (<4 min) to gaseous CEES with high sensitivity (0.2 ppm) and high selectivity. These results show that fluorescent probes 2b and 2d have a good application prospect in the field detection of mustard gas.

PENGARUH RASIO METANOL / MINYAK TERHADAP PARAMETER KECEPATAN REAKSI METANOLISIS MINYAK JELANTAH DAN ANGKA SETANA BIODIESEL

Over the last few years, biodiesel derived from vegetable oil have good potential as alternative diesel fuel. It has assumed importance as research in process optimization and engine performance test. This aim of this research was developing equation between reaction rate parameters and catalyst concentration. Methyl esters (biodiesel) were produced by alcoholysis of waste edible oil with methanol in the presence of KOH as catalyst. The reaction was performed in a batch reactor with temperature controller to maintain it isothermally. The equivalent ratio of methanol-oil was varied at 1 to 4 times theoretically, and the catalyst concentration was fixed at 2.5 % wt oil based. The temperature was 323 K and the mixing intensities was held constant at 400 rpm. At various times, sample was drawn quickly and quenched for ester analyzed. At various equivalent ratio of methanol-oil, the relation was k = 383,26P exp. (-E/RT), with average error 1.13%. The cetane number was 55.02 to 64.6. The ratio of methanol / oil did not affected the cetane number significantly.

Composite Polymer Anion Exchange Membranes with Sandwich Structure and Improved Performance for Zn-Air Battery.

In this study, we fabricated a composite polymer anion exchange membrane (AEM) with a sandwich structure. This prepared AEM demonstrated high ionic conductivity (0.25 Scm−1), excellent alkali resistance (8 M KOH), and good mechanical properties (tensile strength of 0.455 MPa and elongation at break of 82.13%). Here, degrease cotton (DC) treated with LiOH/urea aqueous solution was used and immersed into a coagulation bath to form a film. This film was immersed in acrylic acid (AA) monomers, and in-suit polymerization was carried out in the presence of KOH and an initiator. Finally, a composite polymer membrane with sandwich structure was achieved, in which the upper and bottom layers were mainly composed of polymerized AA (PAA) while the central layer was mainly composed of DC derived film. The central layer acted as a skeleton to improve the mechanical properties and alkali resistance. The top and bottom layers (PAA-rich layers) acted as OH- ion transport carriers, making basic cations migrate along the main chain of PAA. This newly developed composite membrane showed increased tensile strength and an elongation at break of 2.7 and 1.5 times, respectively, when compared to a control PAA/KOH AEM film. Furthermore, an electrochemical stability window of 2.0 V was measured via the cyclic voltammetry curve test, showing a wide electrochemical window and promising application in Zn–Air batteries.

The catalytic activity of new iridium(I) N-heterocyclic carbene complexes for hydrogen transfer reaction of ketones

In this paper, the reaction of [Ir(COD)Cl]2 with in situ prepared Ag–N-heterocyclic carbene (NHC) complexes yields a series of [IrCl(COD)(NHC)] complexes. All compounds were fully characterized by 1H NMR, 13C NMR, and FT–IR spectroscopy. The manuscript focused on the preparation of new Ir–NHC complexes, characterization and catalytic behavior. A series of hydrogenation transfer reactions were performed to reveal the effects of the Ir–NHC complexes. The new Ir–NHC complexes of benzimidazole-2-ylidene are effective catalysts for the transfer of hydrogenation of different ketones, using i-PrOH as the source of hydrogen in the presence of KOH. The reactions were conducted at a substrate/catalyst/base (S/C/base) molar ratio of 1:0.001:2. Although all of the complexes are active catalysts for the transfer hydrogenation of ketones, moderate yields were obtained with acetylnaphthalene and conversion was not observed with very substituted ketones such as 2′,3′,4′,5′,6′-pentamethylacetophenone. It was observed that for transfer hydrogenation reactions Ir–NHC catalysts were more active, compared to Ru–NHC catalyzed studies performed by our team.

Alkynyl-Based sp 2 Carbon-Conjugated Covalent Organic Frameworks with Enhanced Uranium Extraction from Seawater by Photoinduced Multiple Effects

Biofouling is a major obstacle to the efficient extraction of uranium from seawater due to the numerous marine microorganisms in the ocean. Herein, we report a novel amidoxime (AO) crystalline cova...

Optimization of Sibipiruna activated carbon preparation by simplex-centroid mixture design for simultaneous adsorption of rhodamine B and metformin

The present paper reports the application of augmented simplex-centroid mixture design to obtain a high BET surface area activated carbon using as reactants KOH, K2CO3 and K2C2O4. The optimum mixture composition was 2.51 g of KOH, 0.49 g of K2CO3 and absence of K2C2O4, generating an optimized AC (ACop) with SBET value equals to 1984 m2 g−1. The results herein obtained show that low amounts of K2CO3 can catalyze the pore development in the presence of KOH, increasing the surface area. Furthermore, the fractal dimensions of ACop are greater than 2.72, indicating the material has a complex pore structure with irregularities self-similar upon variations of resolution, as seen by SEM images. The TPD curves showed that the ACop has different oxygenated molecular fragments, which agrees with the pHPZC value (5.05). The ACop was applied in the adsorption of rhodamine B (RhB) and metformin (Met) in both binary and monocomponent systems. The simultaneous adsorption at 30 °C reveals that the adsorption capacity of RhB is 630.94 mg g−1, while for Met the value is 103.83 mg g−1.

Experimental Investigation of Performance and Emissions of Spark Ignition Engine Fueled with Blends of HHO Gas with Gasoline and CNG

Fossil fuels are widely used all over the world to power the motor vehicles. Due to superfluous consumption of these fuels, their reservoirs are depleting continuously. The huge demand of crude oil has caused the unprecedented price rise, environmental pollution, and global warming which directly affects the living beings as well as the surroundings in which they are surviving. Alternative fuels can suffice the demand with less adverse effects on the environment through the means of different sustainable technologies. Hydroxy gas (HHO) can be effective source of energy to combat these prominent issues. This work covers the experimental analysis of different parameters related to advantages and disadvantages of using HHO as a blend with gasoline and CNG fuel mixture. The analysis is based on engine performance and emissions. The experiments were performed on engine model fueled with a mixture of fuel and HHO gas. HHO was used as a fuel supplement. A compact HHO gas kit was installed in the engine compartment. A 219cc, four stroke, single cylinder spark ignition engine was used. No modifications were required in the engine design as HHO was used as a fuel supplement. The production of HHO was accomplished by the electrolysis of double distilled water in the presence of KOH(aq.) as an electrolyte. Products of water electrolysis consisted of H2 and O2 in the ratio of 2:1 by volumetric basis. Performance enhancement in overall engine characteristics such as brake power, specific fuel consumption, and overall efficiency was observed. Furthermore, a significant reduction in the emissions of unburnt hydrocarbons, carbon monoxide, and carbon dioxide was noticed. However, due to lean air-fuel mixture and tremendous peak combustion temperature the amount of NOx was increased.

Uticaj sastava masnih kiselina na brzinu reakcije metanolize biljnih ulja

The base-catalyzed methanolysis of roadside pennycress, olive, melon, grapeseed, hempseed, sunflower, and plum kernel oils was performed in the presence of KOH (1% to the oil weight) at the temperature of 60° C and the methanol/oil molar ratio of 6:1. The aim of this work was to reveal the influence of the fatty acid composition of the oils on the kinetics of these methanolysis reactions. The irreversible pseudo-first-order reaction was used for modeling the kinetics of the methanolysis reactions, and the reaction rate constant was correlated with the content of unsaturated fatty acids in the oil. The value of the reaction rate constant increases linearly with increasing the unsaturated fatty acids content in the oil. The applicability and reliability of the model were confirmed by high values of the coefficient of determination and low values of the mean relative percentage deviation between the calculated and experimental triacylglycerols conversion degree.

Hierarchical porous carbon derived from Gardenia jasminoides Ellis flowers for high performance supercapacitor

Low cost and high performance electrode materials are essential for the development of sustainable energy conversion and storage systems. Herein, we report on the preparation of hierarchical porous carbon for high performance supercapacitor by using the flowers of Gardenia jasminoides Ellis (GE) as the biomass precursor. The GE flowers were firstly pre-carbonized at moderate conditions, and then hydrothermally treated in the presence of KOH. After the final simultaneous activation and carbonation at high temperature, hierarchical porous carbon with large specific surface area was obtained. Electrode based on the porous carbon offers a high specific capacitance (255 F g−1 at 0.5 A g−1), excellent rate capability and cycling stability (98.3% capacitance retention after 20,000 cycles) in 6 M KOH aqueous solution in a three-electrode system. Furthermore, symmetric supercapacitor with aqueous electrolyte provides a high specific capacitance of 153.7 F g−1 at 0.5 A g−1 and an energy density of 5.2 Wh kg−1 at power density of 246.9 W kg−1. The study demonstrated an efficient and sustainable approach for high performance supercapacitors by using biomass waste carbon.

Novel Pyrimidines with Extended π-Conjugated Chains

The reactions of benzamidine, 4-methyl-, 4-iso-butoxy-, and 4-butoxybenzamidine hydrochlorides with chalcone and substituted chalcones in alcohol in the presence of KOH yielded 2,4,6-triarylpyrimidines. 4-Phenyl-2,6-bis(4-methylphenyl)pyrimidine and 1,3-bis(4-phenyl-6-{4-[(E)-styryl]phenyl]pyrimidin-2-yl}benzene) were reacted with (2-chlorophenyl)[(1E)-phenylmethylene]amine in the system KOH/LiH/DMF to give, respectively, 4-phenyl-2,6-bis{4-[(E)-styryl]phenyl}pyrimidine and 1,3-bis(4-phenyl-6-{4-[(E)-styryl]phenyl}pyrimidin-2-yl)benzene.

Particle size effect in the mechanically assisted synthesis of β-cyclodextrin mesitylene sulfonate.

The mechanically assisted synthesis of organic compounds has recently focused considerable attention as it may be unique in features to selectively direct the reaction pathway. In the continuation of our work on the synthesis of modified cyclodextrins (CDs) via mechanochemical activation, we sought to discriminate the contribution of supramolecular effects and grinding during the course of a reaction in the solid state. As such, we recently investigated the influence of the particle size of β-CD in the synthesis of β-CD mesitylene sulfonate (β-CDMts) in the solid state using a vibrating ball-mill. We were particularly interested in the role of the particle size on the kinetics of the reaction. In this study, we show that grinding β-CD reduces the particles size over time down to a limit of 167 nm. The granulometric composition remains rather invariant for grinding times over 1 h. Each type of β-CD particles reacted with mesitylenesulfonyl chloride (MtsCl) to produce β-CDMts. Contrary to what could be intuitively anticipated, smaller particles did not lead to the highest conversions. The impact of grinding on the conversion was limited. Interestingly, the proportion of β-CDMts mono-substituted on the primary face significantly increased over time when the reaction was carried out in the presence of KOH as a base. The data series were confronted with kinetics models to get insight in the way the reactions proceeded. The diversity of possible models suggests that multiple mechanochemical processes can account for the formation of β-CDMts in the solid state. Throughout the study, we found that the reactivity depended more upon diffusion phenomena in the crystalline parts of the material than on the increase in the surface area of the CD particles resulting from grinding.

Elucidation of YBCO Growth Mechanism in KOH Flux Method

In this work, we present an extremely low-temperature (600 °C) liquid-phase synthesis method using KOH as flux to grow YBCO powder and epitaxial films. Oxides utilize solution medium KOH in which target materials are generated by cation’s physical and chemical transformations. Y123 and Y124 films could be synthesized by controlling configuration which is related to oxygen diffusion. Later, the process and mechanism of YBCO growth will be elucidated by DSC. In the presence of KOH, the decarboxylation of BaCO3 is kinetically favored with the formation of Ba (OH)2 at the first step, the same as Y2O3 and CuO. Above 350 °C, the formation of Y2Cu2O5 will take precedence over Ba2Cu3O5 due to the weak solubility of Y3+ and Cu2+ in molten KOH. With temperature increasing, liquid Ba(OH)2 begins to dehydrate, and Ba2+ subsequently reacts with Y3+ and Cu2+ to precipitate YBCO in the last step. Molten KOH provides a liquid chemical environment, which allows the synthesis of YBCO at low temperature. This low-temperature method is applicable to epitaxial superconductor and superconducting joint.

A novel grafting-template method to prepare three-dimensional hierarchical porous carbon with high surface area and electrical conductivity for superior-performance supercapacitors

A novel grafting-template method is proposed to prepare three-dimensional hierarchical porous carbons (MGSExKy) simultaneously possessing high surface area (~3000 m2 g−1) and electrical conductivity (~1200 S m−1). The ethylenediamine is chemically grafted into calcium lignosulfonate precursor with the presence of KOH under hydrothermal condition, subsequently being removed to generate abundant nanopores in MGSExKy. Meanwhile, increased C/O atom ratio and graphitization degree are achieved. The mesopore/micropore volume ratio of MGSExKy can be regulated by varying the dosages of ethylenediamine and KOH. Consequently, MGSE1K0.5 yields a large specific capacitance of 250 F g−1 at 0.25 A g−1 and excellent rate capability (198 F g−1 at 50 A g−1) in a two-electrode system using 3 M KOH as electrolyte. The symmetric supercapacitor based on MGSE1K0.5 electrodes delivers high energy densities of 48.3 W h kg−1 and 28.7 W h kg−1 at the power densities of 395.0 W kg−1 and 10.3 kW kg−1 in 1 M (C2H5)4NBF4/PC electrolyte, respectively. More importantly, a remarkable energy density of 101.4 W h kg−1 at 457.3 W kg−1 can be harvested for the symmetric supercapacitor based on MGSE1K0.5 electrodes in ion liquid electrolyte, retaining an impressive value of 38.4 W h kg−1 at an ultrahigh power density of 14.9 kW kg−1.

Substituent effects in the formation of a few acenaphthenone-2-ylidene ketones and their molecular docking studies and in silico ADME profile

We observed intriguing substituent effects in the reaction between 4-substituted acetophenones and acenaphthenequinone in the presence of KOH in methanol. In all cases, expected Claisen-Schimdt condensation was the first step. However, depending on the nature of 4-substituent on acetophenone, the initially formed condensation product remain unchanged or underwent Domino sequence of reactions to give three different 2:2 adducts arising through three distinct pathways. The interactions of acenaphthenone-2-ylidene ketones with the target proteins were performed by molecular docking studies. The prediction of in silico ADME belongings of the synthesized compounds revealed substantial drug-likeness characters based on Lipinski's rules.

Improved H2O2 photogeneration by KOH-doped g-C3N4 under visible light irradiation due to synergistic effect of N defects and K modification

KOH-doped graphitic carbon nitride (g-C3N4) prepared by thermal copolymerization in the presence of KOH was used for photogeneration of H2O2 under visible light irradiation. The H2O2 yield of the KOH-doped g-C3N4 photocatalyst with isopropanol (IPA) as a scavenger was 704 μM·g−1g-C3N4·h−1, twelve times that of unmodified g-C3N4. The total H2O2 output with IPA as a scavenger increased to 86.08 mM after 60 h. The photogeneration of H2O2 with g-C3N4 occurred as two single-electron reactions in which oxygen was reduced to the superoxide radical by one photogenerated electron and further reduced to H2O2 by reacting with another electron and two protons released by oxidization of IPA by holes. KOH doping had a synergistic effect owing to the strong electron-withdrawing ability of N defects caused by N vacancies and cyano groups, and enhanced electron transport due to K bridges between the C3N4 layers. These effects significantly enhanced the H2O2 photogeneration performance of g-C3N4 by improving the quantum efficiency, narrowing the band gap, strengthening IPA adsorption on g-C3N4, and lowering the energy barrier of the oxygen reduction reaction. This work provides an attractive and promising strategy for green H2O2 production.

Composite Ag/AgCl/KCl Screen-Printed Reference Electrode

The drive for automation in multiple industries has generated unmet demand for low-cost, disposable sensors with short response times for routine electrochemical sensing. Glass ion selective electrodes containing a liquid electrolyte have remained the standard for decades, despite their fragile, bulky nature and regular maintenance requirements restricting their suitability for long-term in-situ monitoring. Advances in printing technologies have enabled solid thick film electrodes to emerge as a possible solution to these challenges.Screen printing can be used to mass-produce units of simple, modifiable, and reproducible sensors using minimal materials, increasing portability and reducing fabrication costs. Traditional glass electrode materials are not suitable for printed fabrication, so new materials and designs are required to deliver reliable and robust printed sensors for a variety of industries. While electrochemical sensors can be used to monitor key aqueous environmental indicators, including pH, heavy metals, and oxidation-reduction potential, they often require a stable reference electrode to gain meaningful measurements. Many previous printed electrochemical sensors have relied on a pseudo-reference electrode containing no stabilising electrolyte, however any resultant potential variation can affect measurement accuracy in unknown solutions.In this study, a new screen-printed "true" reference electrode was developed based on Ag/AgCl and a solid composite KCl electrolyte. The electrode lifetime was tested in a 0.1 M K2SO4 solution, and open circuit potential (OCP) stability was tested in H2SO4, KOH, alkali cations (Li+, K+, Na+), halogen anions (F-, Cl-, Br-, I-), KMnO4, H2O2, ascorbic acid, KCl, and standard pH buffers (pH 4, 7, 10). The initial stabilisation and water permeation was monitored via electrochemical impedance spectroscopy (EIS).The observed electrode lifetime in 0.1 M K2SO4 was up to 39 days, with less than 5 mV deviation from the theoretical value (-45 mV vs SCE) and a shelf life of over 1 year. According to the EIS and OCP data, the electrode typically stabilised within 2 hours. In the stability tests, the electrode potential did not deviate more than 10 mV from the theoretical value in the presence of KOH, alkali cations, halogen anions, ascorbic acid, KCl, and standard pH buffers. The electrode was also stable in H2O2 at concentrations up to 0.1 M. On average, the electrode potential was 12 mV below the theoretical value in 10% H2SO4 and was significantly below the theoretical value in 0.1 M KMnO4.The results of this study suggest that this screen-printed reference electrode is suitable for use in electroanalytical systems in most tested chemical environments. The relatively long lifetime and stability of the electrode allows it to be used in a variety of applications, including environmental monitoring, laboratory measurements, and industrial process monitoring, as part of a printed sensor system.

Synthesis and Anticancer Activity of (E)-5-[(1-Aryl-1H-1,2,3-triazol-4-yl)methylene]thiazolidine-2,4-diones

A novel series of 1,2,3-triazolylthiazolidinedione analogs have been synthesized by the condensation of the corresponding 1-aryl-1H-1,2,3-triazole-4-carbaldehydes with thiazolidine-2,4-dione in the presence of KOH. The title compounds were evaluated for their in vitro anticancer activity using MTT assay against four cancer cell lines: A549 (lung), HT-29 (colon), MCF-7 (breast), and A375 (melanoma). Most compounds displayed good anticancer activity, but hydroxy- and nitro-substituted derivatives showed higher activity than the others.

Visible-light-driven H2O2 production from O2 reduction with nitrogen vacancy-rich and porous graphitic carbon nitride

Visible-light-driven H2O2 production from O2 reduction is an eco-friendly strategy and attracts increasing attentions. In this study, KOH modified graphitic carbon nitrides (CNKx) were constructed through the thermolysis of melamine-cyanuric acid supramolecular-complex in the presence of KOH. The BET specific surface area of CNK0.2 with porous structure was 92 m2 g−1. The photocatalyst was characterized by XPS, ESR and element analysis and the analysis suggested that nitrogen vacancy was created in the framework of g-C3N4. Photoluminescence (PL) spectra indicated that the recombination of photogenerated electrons and holes was efficiently suppressed. ζ-potential revealed that more negative charge on the surface of CNK0.2, which promoted the adsorption of O2 and accelerated the photocatalytic H2O2 production. ESR experimental and radical quenching results illustrated that superoxide radical (O2-) was the primary intermediate during the O2 reduction process, suggesting the O2 reduction pathway by CNK0.2 was the sequential two-step single-electron reduction.

Superbase‐Mediated Indirect Friedländer Reaction: A Transition Metal‐Free Oxidative Annulation toward Functionalized Quinolines

A superbase mediated indirect Friedländer reaction towards functionalized quinolines has been realized. The reaction was performed with o‐aminobenzyl alcohol and ketones having an active methylene moiety in the presence of KOH and in DMSO. The reaction proceeds predominantly via initial formation of an imine intermediate and subsequent oxidation of the benzyl alcohol functionality and condensation to afford substituted quinolines. We could also demonstrate that a minor fraction of the reaction proceeds via a chalcone intermediate. The transition metal‐free oxidative annulation was found to be general affording 2‐substituted, 2,3‐disubstituted/fused or multi‐substituted quinolines. The reaction was extended towards the functionalization of natural products and the applicability of the reaction for gram‐scale synthesis of quinolines was also demonstrated.

Spectral, structural, biological and molecular docking studies of a new mixed-valence V(IV)/V(V) ofloxacin complex

In this study, a biologically active mixed-valence V(IV)/V(V) complex [VO(Hofloz)2(H2O)][V4O12]0.5.6H2O (1) (Hofloz = zwitterionic isomer of ofloxacin) was synthesized by the reaction of VOSO4 with ofloxacin (Hofloz) in presence of KOH with 1:1:1 ratio. The complex was characterized through the usage of elemental analysis, FT-IR, molar conductivity and single-crystal X-ray diffraction and thermogravimetric analysis (TGA). The results of single crystal X-ray structure determination revealed an ionic structure consisting of [VO(Hofloz)2(H2O)]2+ and [V4O12]4− units with 1:0.5 stoichiometry. The V+4 ion in the cationic unit has octahedral geometry while each V+5 ion of the eight-member cyclic tetravanadate anion is tetrahedrally coordinated. In regards to the crystal structure of 1, the bidentate ofloxacin ligand is coordinated to the V+4 ion in its zwitterionic form (+HN–···–COO-) through the oxygen atoms of the pyridone and carboxylato groups. The thermodynamic stability of two isomeric forms of Hoflo and 1 along with their charge distribution patterns was studied by DFT and NBO analysis. Also, the ability of the ligand to interact with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) was investigated by docking calculations. These studies revealed that this ligand can bind to the proteins and DNA molecule and could be consider as biologically active compound. Finally, the antibacterial activities of the free Hoflo ligand and its vanadium complex have been evaluated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains through the utilization of broth microdilution and well diffusion methods. The complex showed antibacterial effect similar to the free Hoflo ligand on the selected bacterial strains and these compounds were more active against Gram-negative bacteria.