Room-Temperature Nitrophenol Reduction over Ag–CeO2 Catalysts: The Role of Catalyst Preparation Method

Ag–CeO2 catalysts (20 mol % Ag) were synthesized using different techniques (co-precipitation, impregnation, and impregnation of pre-reduced ceria), characterized by XRD, N2 sorption, TEM, H2-TPR methods, and probed in room-temperature p-nitrophenol reduction into p-aminophenol in aqueous solution at atmospheric pressure. The catalyst preparation method was found to determine the textural characteristics, the oxidation state and distribution of silver and, hence, the catalytic activity in the p-nitrophenol reduction. The impregnation technique was the most favorable for the formation over the ceria surface of highly dispersed silver species that are active in the p-nitrophenol reduction (the first-order rate constant k = 0.656 min−1).

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A highly-efficient La–MnOx catalyst for propane combustion: the promotional role of La and the effect of the preparation method

Catalysis Science & Technology ◽

10.1039/c6cy01663d ◽

2016 ◽

Vol 6 (23) ◽

pp. 8222-8233 ◽

Cited By ~ 19

Author(s):

Yujie Xie ◽

Yun Guo ◽

Yanglong Guo ◽

Li Wang ◽

Wangcheng Zhan ◽

...

Keyword(s):

Thermal Stability ◽

Preparation Method ◽

Deep Oxidation ◽

Precipitation Method ◽

Propane Combustion ◽

Highly Efficient ◽

Excellent Activity ◽

Co Precipitation

The La0.4–MnOx catalyst prepared by using the co-precipitation method exhibited excellent activity and thermal stability for propane deep oxidation.

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Kinetic Studies on Oxidation of Veratryl Alcohol by Laccase-Mediator System. Part 1. Effects of Mediator Concentration

Holzforschung ◽

10.1515/hf.2000.028 ◽

2000 ◽

Vol 54 (2) ◽

pp. 165-170 ◽

Cited By ~ 9

Author(s):

Mikhail Yu. Balakshin ◽

Chen-Loung Chen ◽

Josef S. Gratzl ◽

Adrianna G. Kirkman ◽

Harald Jakob

Keyword(s):

Kinetic Studies ◽

Veratryl Alcohol ◽

Alcohol Oxidation ◽

Order Rate Constant ◽

Molar Ratio ◽

Active Centers ◽

First Order ◽

System Part ◽

Kinetics Of

Summary Kinetics of the laccase-catalyzed oxidation of veratryl alcohol with dioxygen in the presence of 2,2′-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diamonium salt (ABTS), the mediator, were studied to elucidate the possible reaction mechanism and the role of the mediator in this reaction. The reaction follows a pseudo-first order reaction law. The first order rate constant (κ) is dependent on the Mediator/Substrate (M/S) ratio and has a maximum at M/S molar ratio of 0.15. The kinetic studies show that the mechanism of veratryl alcohol oxidation with dioxygen-laccase-ABTS is rather complex and includes different reaction pathways. The mediator is involved in competitive reactions. It has been suggested that at low mediator concentration, the veratryl alcohol is oxidized via the laccase redox cycle. The mediator acts mostly as a laccase activator at a M/S ratio lower than 0.15. With increasing ABTS concentration with respect to the substrate concentration, ABTS acts increasingly as a cosubstrate competing with the original substrate for active centers of the laccase. This results in inhibition of veratryl alcohol oxidation in the enzyme cycle and increases the role of substrate oxidation by an oxidized mediator.

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Magneto-Transport Properties of Co–Cu Thin Films Obtained by Co-Sputtering and Sputter Gas Aggregation

Nanomaterials ◽

10.3390/nano11010134 ◽

2021 ◽

Vol 11 (1) ◽

pp. 134

Author(s):

Ricardo López Antón ◽

Juan Pedro Andrés ◽

Mihail Ipatov ◽

Juan Antonio González ◽

Julián González ◽

...

Keyword(s):

Thin Films ◽

Room Temperature ◽

Preparation Method ◽

Magnetic Measurements ◽

Hysteresis Loops ◽

Ferromagnetic Behavior ◽

Fabrication Method ◽

Different Shapes ◽

The Magnetic Field

Cu100−xCox thin films have been obtained by sputtering (x = 3, 9) and sputter gas aggregation (x = 2.5, 7.5) and subsequent annealing at 400 °C for 1 h. We have studied their structural, magnetic, and magnetotransport properties, both for the as-deposited and annealed samples, confirming the important role of the fabrication method in the properties. The magnetic measurements and the fitting of the hysteresis loops evidence that as-deposited samples consist of superparamagnetic (SPM) and/or ferromagnetic clusters, but in the samples obtained by gas aggregation the clusters are greater (with ferromagnetic behavior at room temperature) whereas in the samples obtained by sputtering, the clusters are smaller and there are also diluted Co atoms in the Cu matrix. The annealing affects negligibly the samples obtained by gas aggregation, but the ones obtained by sputtering are more affected, appearing greater clusters. This behavior is also reflected in the magnetoresistance (MR) measurements of the samples, with different shapes of the MR curves depending on the preparation method: more lineal in the whole range for sputtering, saturation at low fields (about 10 kOe) for gas aggregation. Finally, a Kondo-like minimum in the resistance versus temperature is found in the samples obtained by sputtering, affected by the magnetic field and the annealing. The observed Kondo-like behavior and the influence of annealing on a Kondo-like minimum in sputtered thin films have been attributed to the presence of diluted Co atoms in the Cu matrix and the Co precipitations from the Co–Cu solid solution upon annealing respectively.

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Cutting in-line with iron: ribosomal function and non-oxidative RNA cleavage

10.1101/851097 ◽

2019 ◽

Cited By ~ 2

Author(s):

Rebecca Guth-Metzler ◽

Marcus S. Bray ◽

Moran Frenkel-Pinter ◽

Suttipong Suttapitugsakul ◽

Claudia Montllor-Albalate ◽

...

Keyword(s):

Divalent Cations ◽

Order Rate Constant ◽

Structure And Function ◽

List Type ◽

First Order ◽

Key Points ◽

Ribosomal Function ◽

Continued Use ◽

And Function

AbstractDivalent metal cations are essential to the structure and function of the ribosome. Previous characterizations of the ribosome performed under standard laboratory conditions have implicated Mg2+ as a primary mediator of ribosomal structure and function. Possible contributions of Fe2+ as a ribosomal cofactor have been largely overlooked, despite the ribosome’s early evolution in a high Fe2+ environment, and its continued use by obligate anaerobes inhabiting high Fe2+ niches. Here we show that (i) Fe2+ cleaves RNA by in-line cleavage, a non-oxidative mechanism that has not previously been shown experimentally for this metal, (ii) the first-order rate constant with respect to divalent cations is more than 200 times greater with Fe2+ than with Mg2+, (iii) functional ribosomes are associated with Fe2+ after purification from cells grown under low O2 and high Fe2+, and (iv) a small fraction of Fe2+ that is associated with the ribosome is not exchangeable with surrounding divalent cations, presumably because it is tightly coordinated by rRNA and buried in the ribosome. In total, these results expand the ancient role of iron in biochemistry and highlight a possible new mechanism of iron toxicity.Key PointsFe2+ cleaves rRNA by a non-oxidative in-line cleavage mechanism that is more than 200 times faster than in-line cleavage with Mg2+;ribosomes purified from cells grown under low O2 and high Fe2+ retain ~10 Fe2+ ions per ribosome and produce as much protein as low O2, high Mg2+-grown ribosomes;a small fraction (~2%) of Fe2+ that is associated with the ribosome is not exchangeable.

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The reaction of isocyanates with bisulphite salts

Australian Journal of Chemistry ◽

10.1071/ch9722583 ◽

1972 ◽

Vol 25 (12) ◽

pp. 2583 ◽

Cited By ~ 22

Author(s):

GB Guise ◽

MB Jackson ◽

JA Maclaren

Keyword(s):

Room Temperature ◽

Order Rate Constant ◽

Phenyl Isocyanate ◽

Water Soluble ◽

First Order ◽

Rate Of Reaction ◽

Solids Content ◽

Ph Range ◽

Increasing Temperature ◽

Insoluble Polymers

Aliphatic isocyanates react rapidly and quantitatively with aqueous bi- sulphite solutions to form stable water-soluble adducts which are salts of N-alkyl-carbamyl sulphonio acids. Phenyl isocyanate gives lower yields of the corresponding adduct which is less stable in water. The rate of reaction of n-butyl isocyanate with bisulphite increases with increasing pH and is proportional to [OH-]over the pH range from 5 to 8. The rate of decomposition of the butyl isocyanate-bisulphite adduct increases with increasing temperature and pH. A plot of the logarithm of the initial first-order rate constant for the decomposition of the adduct against pH is linear over the pH range from 2 to 7 and has a slope of 0.57 � 0.05. Water-insoluble polymers with aliphatic isocyanate groups do not form bisulphite adducts under the conditions which are suitable for simple isocyanates. However, the addition of water-soluble organic solvents such as dioxan and the lower alcohols enables the preparation of water-soluble bisulphite adducts which are indefinitely stable at room temperature and low pH. The relative quantity of the organic solvent must be kept within specific limits which depend on the nature of the prepolymer, the solids content of the final product, and the nature of the organic co-solvent.

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Kinetic Analysis of Catalytic Reductive Dechlorination of Chlorobenzene in Aqueous Solutions

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.777.65 ◽

2013 ◽

Vol 777 ◽

pp. 65-70 ◽

Cited By ~ 1

Author(s):

Hong Yi Zhou ◽

Si Liang ◽

Si Si Zeng ◽

Shuang Jian Lei

Keyword(s):

Rate Constant ◽

Organic Contaminants ◽

Room Temperature ◽

Solution Ph ◽

First Order ◽

Effective Removal ◽

Chlorinated Organic ◽

Ph Range ◽

Increasing Temperature

Deposition of Pd on the surface of zero-valent iron (Pd/Fe) further enhances the ability of the metal to reductively dechlorinate organic contaminants. This work determined the dechlorination of chlorobenzene in water by Pd/Fe and evaluated the effects of Pd loading in Fe, Pd/Fe dosage, solution pH and temperature on the reaction. Pseudo-first-order rate constants were obtained to analyze the reaction kinetics. Chlorobenzene was nearly completely dechlorinated within 60 min by Pd/Fe at room temperature. Benzene was the end product of the reaction, along with the release of chloride into water. The rate constant of chlorobenzene dechlorination increased with increasing Pd loading in Fe and Pd/Fe dosage within the tested ranges of 0.005 - 0.020% and 2.0 - 6.0 g/75 mL, respectively. The rate constant increased with decreasing solution pH over the tested pH range of 4.5 - 6.5, indicating the role of protons in dechlorination. The reaction was considered to occur primarily on the surface of Pd where protons were reduced to hydrogen species and chlorobenzene was subsequently dechlorinated by the hydrogen species. The rate of chlorobenzene dechlorination increased with increasing temperature. The estimated activation energy of the reaction was 47.94 kJ/mol within the temperature range of 15 - 40°C, indicating that the dechlorination of chlorobenzene by Pd/Fe readily occurs at room temperature. Pd/Fe may be a potential reductant for effective removal of chlorinated organic contaminants from water.

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Iron oxidation and transferrin formation by phosvitin

Biochemical Journal ◽

10.1042/bj1510519 ◽

1975 ◽

Vol 151 (3) ◽

pp. 519-525 ◽

Cited By ~ 13

Author(s):

S Osaki ◽

R C Sexton ◽

E Pascual ◽

E Frieden

Keyword(s):

Catalytic Activity ◽

Rate Constant ◽

Phosphate Buffer ◽

Iron Oxidation ◽

Order Rate Constant ◽

Half Time ◽

First Order ◽

Order Rate ◽

O2 Concentration

The catalytic activity of phosvitin in Fe(II) oxidation and the addition of iron to transferrin were studied under various conditions. It was concluded that the Fe(II) oxidized by phosvitin would bind to apotransferrin, although an appreciable fraction of Fe(III) remained bound to phosvitin. Fe(III) also migrated from phosvitin to apotransferrin. This reaction was first-order with respect to Fe(III)-phosvitin concentration with a half-time (t1/2) of 10 min, and a first-order rate constant, k=0.069min−1, in 700 μM-phosphate buffer, pH 7.2, at 30 degrees C. The catalysis of the oxidation of Fe(III) by phosvitin was proportional to O2 concentration, and is quite different from the relative O2 independence of Fe(II) oxidation as catalysed by ferroxidase. A scheme for the mobilization and transfer of iron in the chicken, including the role of ferroxidase, phosyitin and transferrin, is presented.

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Exploring Baryon Rich Matter with Heavy-Ion Collisions

Ukrainian Journal of Physics ◽

10.15407/ujpe64.7.583 ◽

2019 ◽

Vol 64 (7) ◽

pp. 583 ◽

Cited By ~ 1

Author(s):

S. Harabasz

Keyword(s):

Center Of Mass ◽

Heavy Ion ◽

State Density ◽

Heavy Nuclei ◽

First Order ◽

Center Of Mass Energy ◽

Ion Collisions ◽

Deconfinement Phase Transition ◽

Ground State Density

Collisions of heavy nuclei at (ultra-)relativistic energies provide a fascinating opportunity to re-create various forms of matter in the laboratory. For a short extent of time (10-22 s), matter under extreme conditions of temperature and density can exist. In dedicated experiments, one explores the microscopic structure of strongly interacting matter and its phase diagram. In heavy-ion reactions at SIS18 collision energies, matter is substantially compressed (2–3 times ground-state density), while moderate temperatures are reached (T < 70 MeV). The conditions closely resemble those that prevail, e.g., in neutron star mergers. Matter under such conditions is currently being studied at the High Acceptance DiElecton Spectrometer (HADES). Important topics of the research program are the mechanisms of strangeness production, the emissivity of matter, and the role of baryonic resonances herein. In this contribution, we will focus on the important experimental results obtained by HADES in Au+Au collisions at 2.4 GeV center-of-mass energy. We will also present perspectives for future experiments with HADES and CBM at SIS100, where higher beam energies and intensities will allow for the studies of the first-order deconfinement phase transition and its critical endpoint.

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Clustering-Triggered Efficient Room Temperature Phosphorescence from Nonconventional Luminophores

10.26434/chemrxiv.9959132 ◽

2019 ◽

Author(s):

Shuyuan Zheng ◽

Taiping Hu ◽

Xin Bin ◽

Yunzhong Wang ◽

Yuanping Yi ◽

...

Keyword(s):

Room Temperature ◽

High Efficiency ◽

Spin Orbit Coupling ◽

Design Rationale ◽

Emission Mechanism ◽

Room Temperature Phosphorescence ◽

Electronic Interactions ◽

Energy Gaps ◽

Theoretical Results

Pure organic room temperature phosphorescence (RTP) and luminescence from nonconventional luminophores have gained increasing attention. However, it remains challenging to achieve efficient RTP from unorthodox luminophores, on account of the unsophisticated understanding of the emission mechanism. Here we propose a strategy to realize efficient RTP in nonconventional luminophores through incorporation of lone pairs together with clustering and effective electronic interactions. The former promotes spin-orbit coupling and boost the consequent intersystem crossing, whereas the latter narrows energy gaps and stabilizes the triplets, thus synergistically affording remarkable RTP. Experimental and theoretical results of urea and its derivatives verify the design rationale. Remarkably, RTP from thiourea solids with unprecedentedly high efficiency of up to 24.5% is obtained. Further control experiments testify the crucial role of through-space delocalization on the emission. These results would spur the future fabrication of nonconventional phosphors, and moreover should advance understanding of the underlying emission mechanism.<br>

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Development of Sustained Release Multi-Component Microparticulate System of Diclofenac Sodium and Tizanidine Hydrochloride

International Journal of Pharmaceutical Sciences and Nanotechnology ◽

10.37285/10.37285/ijpsn.2008.1.1.9 ◽

1970 ◽

Vol 1 (1) ◽

pp. 97-105

Author(s):

Kamlesh Dashora ◽

Shailendra Saraf ◽

Swarnalata Saraf

Keyword(s):

Particle Size ◽

Sustained Release ◽

Cellulose Acetate ◽

Rate Constant ◽

Diclofenac Sodium ◽

Order Rate Constant ◽

Anomalous Transport ◽

First Order ◽

Sem Study ◽

Transport Type

Sustained released tablets of diclofenac sodium (DIC) and tizanidine hydrochloride (TIZ) were prepared by using different proportions of cellulose acetate (CA) as the retardant material. Nine formulations of tablets having different proportion of microparticles developed by varied proportions of polymer: drug ratio ‘’i.e.’’; 1:9 -1:3 for DIC and 1:1 – 3:1 for TIZ. Each tablet contained equivalent to 100 mg of DIC and 6mg of TIZ. The prepared microparticles were white, free flowing and spherical in shape (SEM study), with the particle size varying from 78.8±1.94 to 103.33±1.28 µm and 175.92± 9.82 to 194.94±14.28µm for DIC and TIZ, respectively. The first order rate constant K1 of formulations were found to be in the range of K1 = 0.117-0.272 and 0.083- 0.189 %hr-1for DIC and TIZ, respectively. The value of exponent coefficient (n) was found to be in the range of 0.6328-0.9412 and 0.8589-1.1954 for DIC and TIZ respectively indicates anomalous to non anomalous transport type of diffusions among different formulations

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