Mol-1 Min-1 Research Articles

Enhancement of the Piezocatalytic Response of La-Doped BiFeO3 Nanoparticles by Defects Synergy.

Because of their intrinsic polarization and related properties, ferroelectrics attract significant attention to address energy transformation and environmental protection. Here, by using trivalent-ion-lanthanum doping of BiFeO3 nanoparticles (NPs), it is shown that defects and piezoelectric potential are synergized to achieve a high piezocatalytic effect for decomposing the model Rhodamine B (RhB) pollutant, reaching a record-high piezocatalytic rate of 21360 L mol-1 min-1 (i.e., 100% RhB degradation within 20min) that exceeds most state-of-the art ferroelectrics. The piezocatalytic Bi0.99La0.01FeO3 NPs are also demonstrated to be versatile toward various pharmaceutical pollutants with over 90% removal efficiency, making them extremely efficient piezocatalysts for water purification. It is also shown that 1% La-doping introduces oxygen vacancies and Fe2+ defects. It is thus suggested that oxygen vacancies act as both active sites and charge providers, permitting more surface adsorption sites for the piezocatalysis process, and additional charges and better energy transfer between the NPs and surrounding molecules. Furthermore, the oxygen vacancies are proposed to couple to Fe2+ to form defect dipoles, which in turn introduces an internal field, resulting in more efficient charge de-trapping and separation when added to the piezopotential. This synergistic mechanism is believed to provide a new perspective for designing future piezocatalysts with high performance.

Understanding Nucleophilicity of Pyridine-N-oxides Towards 2,4,6-Trinitrophenylbenzoate Through Simple Absorption Spectroscopic Studies

Aims: Understanding nucleophilicity of poor nucleophiles like pyridine-N-oxides. Background: Nucleophilicity plays a vital role in substitution reactions. It helps to determine the possibility and extent of the substitution reactions. The study of the nucleophilicity of poor nucleophiles is challenging, and it has limited substrate scope. Understanding the strength of nucleophilicity of such poor nucleophiles in a quantitative way is important. Objective: Understanding the strength of nucleophilicity of such poor nucleophiles in a quantitative way. Selection of appropriate electrophile for the reactions with the poor nucleophiles-pyridine-N-oxides. Development of suitable methodology for kinetic studies of the reaction. Methods: UV-Vis spectroscopic methods for monitoring the reactions. Results: The kinetic studies revealed that the second-order rate constants of the nucleophilic reactions are 1.67× 102 L mol-1 min-1, 29.8 L mol-1 min-1, 29.51 L mol-1 min-1, where the nucleophiles are p-methylpyridine-N-oxide, pyridine-N-oxide, and p-nitropyridine-N-oxide, respectively. The UV-Vis spectroscopic analysis revealed the nucleophilicity of p-methylpyridine-N-oxide > pyri-dine-N-oxide > p-nitropyridine-N-oxide. Conclusion: This comparative study suggests that the strength of nucleophilicity of the p-methylpyridine-N-oxide is 5.6 times and 66.53 times more than that of pyridine-N-oxide and p-nitropyridine-N-oxide, respectively, whereas the strength of nucleophilicity of the pyridine-N-oxide is 11.87 times more than that of p-nitropyridine-N-oxide.

Exploiting Ru-Induced Lattice Strain in CoRu Nanoalloys for Robust Bifunctional Hydrogen Production.

Designing bifunctional catalysts capable of driving the electrochemical hydrogen evolution reaction (HER) and also H2 evolution via the hydrolysis of hydrogen storage materials such as ammonia borane (AB) is of considerable practical importance for future hydrogen economies. Herein, we systematically examined the effect of tensile lattice strain in CoRu nanoalloys supported on carbon quantum dots (CoRu/CQDs) on hydrogen generation by HER and AB hydrolysis. By varying the Ru content, the lattice parameters and Ru-induced lattice strain in the CoRu nanoalloys could be tuned. The CoRu0.5 /CQDs catalyst with an ultra-low Ru content (1.33 wt.%) exhibited excellent catalytic activity for HER (η=18 mV at 10 mA cm-2 in 1 M KOH) and extraordinary activity for the hydrolysis of AB with a turnover frequency of 3255.4 mol mol-1 (Ru) min-1 or 814.7 mol mol-1 (cat) min-1 at 298 K, respectively, representing one of the best activities yet reported for AB hydrolysis over a ruthenium alloy catalyst. Moreover, the CoRu0.5 /CQDs catalyst displayed excellent stability during each reaction, including seven alternating cycles of HER and AB hydrolysis. Theoretical calculations revealed that the remarkable catalytic performance of CoRu0.5 /CQDs resulted from the optimal alloy electronic structure realized by incorporating small amounts of Ru, which enabled fast interfacial electron transfer to intermediates, thus benefitting H2 evolution kinetics. Results support the development of new and improved catalysts HER and AB hydrolysis.

Boosted Reactivity of Ammonia Borane Dehydrogenation over Ni/Ni2P Heterostructure

Ammonia borane (AB) is regarded as a highly promising candidate for chemical hydrogen-storage materials. Developing low-cost yet efficient catalysts for the dehydrogenation of AB is central to achieving hydrogen conversion. Here a heterostructure of Ni/Ni2P nanoparticles deposited on a defective carbon framework for the hydrolysis of AB is developed by elaborately controlling phosphorization conditions. The electronic structure and interfacial interaction of the ternary components are probed by synchrotron-based X-ray absorption fine structure and further simulated via density functional theory. By adjusting the content of Ni and Ni2P in the hetrostructure, the optimized hybrid exhibits catalytic performance of H2 generation from the hydrolysis of AB under ambient conditions with a turnover frequency of 68.3 mol (H2) mol-1 (Cat) min-1 and an activation energy ( Ea) of 44.99 kJ mol-1, implying its high potential as an efficient supplement for noble-metal-based catalysts in hydrogen energy applications.

PROPİYONİK ASİTİN İZOBUTİL ALKOL İLE AMBERLYST 36 VE AMBERLYST 70 KATALİZÖRLERİ VARLIĞINDA ESTERLEŞME KİNETİĞİ

The esterification of propionic acid with isobutyl alcohol has been studied in a batch reactor in the presence of Amberlyst 36 and Amberlyst 70 catalysts. Reaction parameters applied in this study are speed of agitation (500-1000 rpm), particle size of catalyst (400-600 µm, 600+ µm), temperature (318-348 K) and catalyst loading (4-12 g-dry resin/L). A pseudo-homogeneous kinetic model was derived and all thermodynamic and kinetic parameters were calculated. Forward reaction rate constant for Amberlyst 36 and Amberlyst 70 determined as follows: k_1=160171 exp⁡((-56689)/RT) (L mol-1 min-1) k_1=293314 exp⁡((-57292)/RT) (L mol-1 min-1) In a comparison of the two catalysts used in this study, experimental results showed that Amberlyst 70 is more effective than Amberlyst 36.

Polymerization of Isoprene Promoted by Aminophosphine(ory)-Fused Bipyridine Cobalt Complexes: Precise Control of Molecular Weight and cis-1,4- alt-3,4 Sequence.

Ligands N-(dialkyl or arylphosphino)-(2,2'-bipyridin)-6-amine (L1, aryl = Ph; L2, alkyl = tBu; L3, alkyl = adamantyl (Ad)) as well as the corresponding oxidized N-(2,2'-bipyridin-6-yl)- P, P-dialkyl or aryl phosphinic amide (L4, aryl = Ph; L5, alkyl = tBu; L6, alkyl = Ad) congeners were designed and coordinated to cobalt dichloride. The structures of formed complexes were characterized by IR and elemental analyses, as well as characterizations of the X-ray diffractions for complexes Co4 and Co6, which revealed the cobalt center is expectedly pentacoordinated in a distorted trigonal bipyramidal configuration with a prolonged Co-O(═P) bond . In combination with MMAO, complex Co2 was highly active in cis-1,4- alt-3,4 enchained polymerization. The hemilabile nature of O═P is possible for the alternating η4- cis-1,4 and η2-3,4 coordination, and insertion at the metal-carbon bond ensued. In combination with AlEt2Cl, each of complexes Co4, Co5, and Co6 was capable of converting isoprene to polyisoprene in a control mode with observed polymerization rate constants ( kobs = 0.1531 L mol-1 min-1 (Co4), 0.1382 L mol-1 min-1 (Co5), and 0.0902 L mol-1 min-1 (Co6)). The activation energy of the polymerization by Co4 falls in the range of 27-31 kJ/mol by determining kobs values at 0, 30, and 50 °C. The 13C NMR analyses of the obtained polyisoprene revealed that complexes Co4, Co5, and Co6 have a cis-1,4 selectivity of 86.6-93.4% with a 3,4 selectivity of 6.6-13.4%. This catalyst system can also be applied to block copolymerization of isoprene and myrcene in a living cis-1,4 fashion; therefore, a new biosourced monomer-based elastomer has been achieved.

Homogeneous Catalysts for Hydrogen Generation Reactions Based on Nickel (II), Manganese (II), Cobalt (II), and Iron (II) Ions

The transportation industry has seen an increase in demand for green chemistry techniques that produce energy efficiently within hydrogen fuel cells, further eliminating the use of conventional combustion engines that require the use of fossil fuels. The hydrogen from these batteries must be readily produced through a catalyst that is efficient, economical, and safe within the process. These experiments compare the potential viability of using four metal-salt substrates: cobalt (II) chloride, nickel (II) chloride, manganese (II) chloride and iron (II) chloride as efficient and inexpensive catalysts in the presence of sodium borohydride and water. The reactions of each metal salt with NaBH4 were evaluated at different conditions that varied in terms of temperature, pH of solution, and different concentrations of NaBH4. The evolution of hydrogen was measured using a previously described water displacement system [1,2]. The NiCl2 and CoCl2 performed best in pH 7 trials at 22 °C with a rate constant of 3.393 L mol-1 min-1 and 5.02 L mol-1 min-1 respectively. Manganese had the best rate of 3.061 L mol-1 min-1 with an increase to pH 8 of solution, while iron (II) chloride had its best trial during increased concentrations of the sodium borohydride with a rate constant of 0.89 L mol-1 min-1. Thermodynamic parameters from combined rate constants were determined to show spontaneity of reaction. Nickel, manganese and cobalt were spontaneous reactions at each temperature condition with the exception being iron during the 0°C temperature trial. References T. Dushatinski, C. Huff, and T. Abdel-Fattah, Applied Surface Science, 385, 282 (2016). 2. C. Huff, T. Dushatinski, A. Barzanji, N. Abdel-Fattah, K. Barzanji, and T. Abdel-Fattah, ECS J Solid State, 6, M69-M71 (2017).

Kinetics Behavior and Sulfur Transformations of Iron Sulfide during Supercritical Water Oxiation

Oxidation of iron sulfide in supercritical water was investigated in the batch reactor. Iron sulfide was converted in two parallel processes: gasification by water and oxidation by oxygen. Assuming that the reaction order of H2O was 0, the activation energy and pre-exponential factor of the gasification process were determined to be 43kJ mol-1 and 22.4 min-1, correspondingly. It is found that above 773K the oxidation process was limited by the mass transfer of O2 to particles surface. Below 773K, with an assumption of zero order in H2O concentration and first-order reaction in oxygen concentration, the activation energy and pre-exponential factor for the rate of oxidation were estimated as154kJ mol-1 and 1.7×106m3 mol-1 min-1, respectively. With supercritical water oxidation under the experimental conditions, the sulfur-containing components in the product were sulfide, sulfite and sulfate, in which sulfide and sulfate were predominant. It is likely to completely convert the sulfur to the sulfate by supercritical water oxidation using high temperature and long reaction time. The reaction pathway of iron sulfide could be expressed as: iron sulfide → sulfide → sulfite → sulfate.

Comparison of Metal Alkoxide Initiators in the Ring-Opening Polymerization of Caprolactone

Four metal tert-butoxides, namely: aluminum (III) tert-butoxide, Al (Ot-C4H9)3, tin (II) tert-butoxide, Sn (Ot-C4H9)2, titanium (IV) tert-butoxide, Ti (Ot-C4H9)4, and lithium tert-butoxide, Li (Ot-C4H9), were used as initiators in the bulk ring-opening polymerization (ROP) of ε-caprolactone (CL). The polymerizations were carried out at 120 °C for 72 hrs. It was found that the Al (Ot-C4H9)3 only partially dissolved in the CL monomer and gave a low % conversion. The Li (Ot-C4H9) initiator did not dissolve and gave no polymerization. In contrast, the Sn (Ot-C4H9)2 initiator dissolved completely, albeit very slowly, and gave a high % conversion. The Ti (Ot-C4H9)4 initiator was by far the easiest and quickest to dissolve and also gave a high % conversion. Consequently, Ti (Ot-C4H9)4-initiated polymerization was studied further by dilatometry at 120°C. From the kinetic results, a first-order rate constant, kp, of 0.120 l mol-1 min-1 was obtained.

Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study

The kinetic behavior of esterification of lactic acid with isopropanol over an acidic cation exchange resin, Amberlyst 15, was studied under isothermal condition. Isopropyl lactate synthesized in this reaction is an important pharmaceutical intermediate. The experiments were carried out in a stirred batch reactor in the temperature range of 323.15 to 353.15 K. The effect of various parameters such as temperature, molar ratio and catalyst loading was studied. Variation in parameters on rate of reaction demonstrated that the reaction was intrinsically controlled. Kinetic modeling was performed using Eley-Rideal model which acceptably fits the experimental data. The activation energy was found to be 22.007 kJ/mol and frequency factor was 0.036809 l2 g-1 mol-1 min-1 for forward reaction. The value of entropy for the forward reaction was found to be 182.317 J K-1 mol-1. © 2011 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Evaluation of Oxime K203 as Antidote in Tabun Poisoning

We studied bispyridinium oxime K203 [(E)-1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide] with tabun-inhibited human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro, and its antidotal effect on tabun-poisoned mice and rats in vivo. We compared it with oximes K048 and TMB-4, which have proven the most efficient oxime antidotes in tabun poisoning by now. Tabun-inhibited AChE was completely reactivated by K203, with the overall reactivation rate constant of 1806 L mol(-1) min(-1). This means that K203 is a very potent reactivator of tabun-inhibited AChE. In addition, K203 reversibly inhibited AChE (Ki = 0.090 mmol L(-1)) and BChE (K(i) = 0.91 mmol L(-1)), and exhibited its protective effect against phosphorylation of AChE by tabun in vitro. In vivo, a quarter of the LD50 K203 dose insured survival of all mice after the application of as many as 8 LD50 doses of tabun, which is the highest dosage obtained compared to K048 and TMB-4. Moreover, K203 showed high therapeutic potency in tabun-poisoned rats, preserving cholinesterase activity in rat plasma up to 60 min after poisoning. This therapeutic improvement obtained by K203 in tabun-poisoning places this oxime in the spotlight for further development.

The Elbs and Boyland—Sims Peroxydisulfate Oxidations

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The Elbs and Boyland-Sims peroxydisulfate oxidations.

This paper reviews the recent literature on the title reactions and updates a 1988 review.

Features of Electrolysis of Nitric Acid Solutions of Silver: I. Behavior of Ag(II) in HNO3 Solutions

The current efficiency of Ag(II) formation in the course of electrochemical oxidative dissolution of PuO2 was determined. It approaches 72% at the anodic potentials from 1.9 to 2.1 V (vs. SHE) and the anodic current densities of 0.006-0.013 A cm-2. The behavior of Ag(II) in 4 M HNO3 at 8, 25, and 40°C was studied. The reaction of Ag(II) with water can be described by the equation d[Ag(II)]/dt = kapp[Ag(II)]n, where n ∼ 2 at 8-25°C and 2-1.5 at 39-41°C. The apparent rate constants of the reaction are 1.5 and 3.8 l mol-1 min-1 at 8.5°C and 25°C, respectively. At 39-41°C, the reaction order with respect to Ag(II) ranges from 2 to 1.5, and the rate constant is about 1.2 l1/2 mol-1/2 min-1.

Redox Reactions of Platinum Elements: XV. Kinetics of Rhodium(III) Oxidation with Xenon Difluoride in Nitric Acid Solutions

The rate of the reaction 2Rh(H2O)63+ + XeF2 = 2Rh(OH)3+ + Xe + 2HF + 4H+ + 6H2O is described by the second-order equation -d[Rh(III)]/dt = k1[Rh(III)][XeF2], where k1 = 15.4±0.8 l mol-1 min-1 at 17.8°C and the solution ionic strength μ = 2. The activation energy of the reaction is E1 = 60.6±1.0 kJ mol-1. This reaction is complicated by the parallel hydrolysis reaction 2XeF2 + 2H2O = 2Xe + O2 + 4HF. The reaction mechanism includes a slow stage of H atom transfer from Rh(H2O)63+ to XeF2 molecule with formation of XeF. radical as an intermediate. The subsequent stages of Rh(H2O)5(OH)3+ hydrolysis and reduction of XeF· radical to Xe proceed rapidly.

Bipolar/Monopolar Conformational Transitions of Selected Hydroxyoctadecanoic Acids and Esters: A Fluorescence Microscopy Study

The bipolar/monopolar conformational transitions of the hydroxyoctadecanoic acids (HOAs) [6-hydroxy-9-hydroxy- and 12-hydroxyoctadecanoic acid (6HOA, 9HOA, and 12HOA)] plus those of the methyl and ethyl esters of 12HOA have been studied using classical surface pressure (Π)/area per molecule (A) isotherms and fluorescence microscopy techniques. Most studies were carried out using identical compressional rates (5 A2 mol-1 min-1) and identical amounts of a fluid-phase soluble fluorescent probe 1-palmitoyl-2-[6-(7-nitro-2-1-3-benzoxadiazol-4-yl)amino] caproyl phosphatidylcholine (NBD-PC); however, the effect of both compressional rate and probe concentration was investigated. For 6HOA, condensed-phase domains are roughly diamond-shaped with both nucleation and apparent crystal growth being observed. Larger, essentially hexagonal, crystals were observed for 9HOA. For 12HOA the extent of nucleation was much greater, producing elongated needlelike crystals quite different from either 6- or 9HOA. This difference ...

Inhibition of acetylcholinesterase by three new pyridinium compounds and their effect on phosphonylation of the enzyme.

Three new mono-pyridinium compounds were prepared: 1-phenacyl-2-methylpyridinium chloride (1), 1-benzoylethylpyridinium chloride (2) and 1-benzoylethylpyridinium-4-aldoxime chloride (3) and assayed in vitro for their inhibitory effect on human blood acetylcholinesterase (EC 3.1.1.7, AChE). All the three compounds inhibited AChE reversibly; their binding affinity for the enzyme was compared with their protective effect (PI) on AChE phosphonylation by soman and VX. Compound 1 was found to bind to both the catalytic and the allosteric (substrate inhibition) sites of the enzyme with estimated dissociation constants of 6.9 microM (Kcat) and 27 microM (Kall), respectively. Compound 2 bound to the catalytic site with Kcat = 59 microM and compound 3 only to the allosteric site with Kall = 328 microM. PI was evaluated from phosphonylation measured in the absence and in presence of the compounds applied in a concentration corresponding to their Kcat or Kall value, and was also calculated from theoretical equations deduced from the reversible inhibition of the enzyme. Compounds 1 and 3 protected the enzyme from phosphonylation by soman and VX, whereas no protection was observed in the presence of compound 2 under the same conditions. Irrespective of the binding sites to AChE, PI for compounds 1 and 3 evaluated from phosphonylation agreed with PI calculated from reversible inhibition. Compound 3 was found to be a weak reactivator of methylphosphonylated AChE with Kr = 1.1 x 10(2) L mol-1 min-1.

Fate of a Highly Strained Hydrocarbon in Aqueous Soil Environment

Quadricyclane, a highly strained hydrocarbon, is currently being evaluated by the U.S. Air Force as a possible high-performance aviation fuel. It is therefore important to discover how it would interact with the environment in the event of a spill. The reactions of quadricyclane were investigated in water, 50/50 wt % water/2-propanol and pure 2-propanol, and in abiotic aqueous soil environments consisting of four different naturally occurring soils. The reaction products were exo-5-norbornen-2-ol and nortricyclyl alcohol. The reactions in the three solvent systems were pseudo-first-order in quadricyclane. Second-order rate constants were determined from plots of the pseudo-first-order rate constants versus [H+] and were found to be 26.0 L mol-1 min-1 in water, 0.195 L mol-1min-1 in 50/50 water/2-propanol, and 0.099 L mol-1min-1 in 2-propanol, all at 25 °C. The soil experiments were run for periods of up to 9 months. The most important factor affecting the reactivity of quadricyclane in the soils was pH, w...

Characterization of a Ryanodine Receptor in Periplaneta Americana

Specific binding sites for the alkaloid ryanodine were characterized in membrane preparations from sarcoplasmatic reticulum of Periplaneta americana skeletal muscle. Binding of [3H]ryanodine was optimal at pH 8 and at CaCl2 concentration of about 300 μmol l-1. The Ca-chelating agents EGTA (100 μmol l-1) and EDTA (100 μmol l-1) abolished 95 % and 90 % of the [3H]ryanodine binding respectively. Preincubation with Ca2+ (100 μmol l-1) restored the ryanodine binding in presence of up to 300 μmol l-1 EGTA. Radioligand binding experiments showed one class of high affinity binding sites for ryanodine. Determination of rate constants revealed 7.05 × 106 l mol-1 min-1 for associating and 3.77 × 10-3 min-1 for the dissociating [3H]ryandine ryanodine receptor complex. Solubility of the ryanodine receptor was examined with different anionic, non-ionic and zwitterionic detergents. Best solubilization results of “calcium release channel” of cockroach muscle membrane preparations were obtained with the detergent CHAPS in a concentration of 5 mg ml-1.

Novel acrylamido monomers with higher hydrophilicity and improved hydrolytic stability: II. Properties of N-acryloylaminopropanol.

The physico-chemical properties and the electrophoretic behavior of the novel set of monomers reported by (Simò-Alfonso et al., Electrophoresis 1996, 17, 723-731) have been evaluated. Of utmost importance was the combination of high hydrophilicity and extreme hydrolytic stability, most desired properties for, any electrophoretic matrix, especially for protein fractionation. One of these monomers (N-acryloylaminopropanol, AAP) was found indeed to be extremely hydrophilic (with a partition coefficient P of only 0.10, vs. P = 0.13 for N-acryloylaminoethoxyethanol and P = 0.20 for acrylamide) and to possess excellent stability to alkaline hydrolysis. Its hydrolysis constant (0.008 L mol-1 min-1), as a free monomer, in an alkaline milieu, was found to be about one order of magnitude lower than conventional acrylamide (0.05 L mol-1 min-1). In the polymer state, the resistance to hydrolysis of poly(AAP) was assessed as 500 times greater than a conventional poly(acrylamide) matrix.