scholarly journals Kinetic Monte Carlo simulation of the growth of CdSe nanocrystals

2021 ◽  
Vol 134 (1) ◽  
pp. 7-23
Author(s):  
S.M. Asadov ◽  
Keyword(s):  
Monte Carlo ◽  
Rate Constants ◽  
Reaction Rate ◽  
Kinetic Monte Carlo ◽  
Cdse Nanocrystals ◽  
Modified Model ◽  
Early Maturation ◽  
Reaction Rate Constants ◽  
Colloidal Crystallization ◽  
Kinetics Of

This article is devoted to modeling the kinetics of colloidal crystallization of cadmium selenide (CdSe) nanoparticles (NPs). The kinetic equation is modified, considering the contributions of the reaction rate constants of individual stages. It includes the reaction rate constants, thermodynamic and calculated parameters, and physical properties. There is used modified kinetic model based on the crystallization equation. There are considered the contributions of adsorption, desorption, and migration of nucleated particles at different times. Modified model assumes that, upon crystallization of NPs CdSe, monomer units depend on the frequency of attachment and detachment transitions of the monomer–CdSe complex. In this case, the transformation of the precursor into a monomer, the formation of an effective monomer and nucleation pass into the growth stage of (NC CdSe) nanocrystals with a seeded mass. In the process, the resulting nanocluster will continue to grow due to early maturation, aging, and subsequent growth into larger NC CdSe. The Kinetic Monte Carlo method (KMC) is used to approximate the model of the nucleation–growth of NC considering different contributions to the reaction rate constants. The modified model with the use of KMC allows to describe the dependences of the kinetic rate constants on the average radius of nanoparticles as a function of time, concentration, and distribution of NC CdSe at a given time. There are described conditions for the formation of NPs CdSe with an evolutionary distribution function of NC CdSe in size space. The results of modeling the kinetics of colloidal crystallization of CdSe can be used to control nucleation rate and growth of NPs CdSe, as well as similar systems in the formation of high-quality NC.

Kinetics of the Ozonation of Tetrabromobisphenol-A in Wastewater

2011 ◽  
Vol 383-390 ◽  
pp. 2945-2950 ◽  
Author(s):  
Jie Zhang ◽  
Shi Long He ◽  
Mei Feng Hou ◽  
Li Ping Wang ◽  
Li Jiang Tian
Keyword(s):  
Rate Constants ◽  
Apparent Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Kinetic Studies ◽  
Tetrabromobisphenol A ◽  
First Order ◽  
Reaction Rate Constants ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of TBBPA degradation by ozonation in semi-batch reactor was studied. The reaction rate constants of TBBPA with O3 and •OH were measured by means of direct ozone attack and competition kinetics, and the values of which were 6.10 l/(mol•s), 4.8×109 l/(mol•s), respectively. Results of kinetic studies showed that TBBPA degradation by ozonation under the different conditions tested followed the pseudo-first-order. The values of apparent rate constant of TBBPA degradation increased with the increase of ozone dosage and pH, but decreased with the increase of initial TBBPA concentration.

Carbohydrates in alkaline systems. II. Kinetics of the transformation and degradation reactions of cellobiose, cellobiulose, and 4-O-β-D-glucopyranosyl-D-mannose in 1 M sodium hydroxide at 22 °C

1969 ◽  
Vol 47 (21) ◽  
pp. 3957-3964 ◽  
Author(s):  
Donald J. MacLaurin ◽  
John W. Green
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Column Chromatography ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction System ◽  
Reaction Rate Constants ◽  
Degradation Reactions ◽  
Fructose 2 ◽  
Kinetics Of

Rates of isomerization, epimerization, and degradation reactions were measured for cellobiose (7), cellobiulose (8), and 4-O-β-D-glucopyranosyl-D-mannose (9) at 0.001 M in 1 M NaOH under N2 in the dark at 22 °C. Reaction system resolution was by column chromatography on anion resins in the borate form. Assay for D-glucose (1), D-fructose (2), D-mannose (3), and 7,8, and 9 was by continuous automated colorimetry of column effluent with orcinol–sulfuric acid as reagent. Reaction rate constants (h−1) found: k78 0.078, k79 0.0005, k7,10 0.002, k87 0.022, k89 0.003 k81 0.065, k8,12 0.023, k97 0.002, k98 0.013, k9,11 0.006 where 10,11, and 12 are other products than 1,2,3,7,8, and 9. Details for preparation of 8 and 9 are given.

Effects of Carrageenan and Chitosan as Coating Materials on the Thermal Degradation of Microencapsulated Phycocyanin from Spirulina sp.

2019 ◽  
Vol 15 (5-6) ◽  
Author(s):  
H. Hadiyanto ◽  
Marcelinus Christwardana ◽  
Meiny Suzery ◽  
Heri Sutanto ◽  
Ayu Munti Nilamsari ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Thermal Degradation ◽  
Rate Constants ◽  
Reaction Rate ◽  
Order Reaction ◽  
Coating Materials ◽  
First Order ◽  
Reaction Rate Constants ◽  
Kinetics Of

AbstractPhycocyanin is a natural substance that can be used as an antioxidant and food colorant. The quality of phycocyanin deteriorates when it is exposed to heat, and such deterioration is evidenced by decreases in its antioxidant activity and color. Encapsulation, which introduces a coating material over a substance of interest, has been applied to prevent changes in substance quality. The objective of the present research is to evaluate the kinetics of thermal degradation of phycocyanin coated with carrageenan or chitosan. Encapsulated phycocyanin samples were exposed to temperatures of 40, 50, or 60 °C for 90 min, and kinetics of the resulting degradation was evaluated to determine changes in sample quality. The results showed that the thermal degradation of encapsulated phycocyanin at 40–60 °C follows first-order reaction kinetics with reaction rate constants (k) of 4.67–9.17 × 10–5 s-1 and 3.83–7.67 × 10–5 s-1 for carrageenan and chitosan, respectively, and that the k of encapsulated phycocyanin is slower than that obtained from samples without the coating materials (control). Encapsulation efficiencies (EE) of 68.66 % and 76.45 %, as well as loading capacities of 45.28 % and 49.16 %, were, respectively, obtained for carrageenan and chitosan.

Carbohydrates in alkaline systems. I. Kinetics of the transformation and degradation of D-glucose, D-fructose, and D-mannose in 1 M sodium hydroxide at 22 °C

1969 ◽  
Vol 47 (21) ◽  
pp. 3947-3955 ◽  
Author(s):  
Donald J. MacLaurin ◽  
John W. Green
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Column Chromatography ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction System ◽  
Reaction Rate Constants ◽  
Degradation Reactions ◽  
Fructose 2 ◽  
Kinetics Of

Rates of isomerization, epimerization, and degradation reactions were measured for D-glucose (1), D-fructose (2), and D-mannose (3) at 0.002 M in 1 M NaOH under N2 in the dark at 22 °C. Reaction system resolution was by column chromatography on anion resins in the borate form. Assay for 1, 2, and 3 was by continuous automated colorimetry of column effluent using orcinol/sulfuric acid as a reagent. D-Allose and D-altrose were not detected. Reaction rate constants (h−1) found: k12 0.038, k13 0.0005, k15 0.002, k21 0.036, k23 0.006, k24 0.072, k31 0.0005, k32 0.011, k36 0.002, where 4, 5, and 6 are products formed from 1, 2, or 3, respectively.

scholarly journals Kinetics of the catalytic cracking of naphtha over ZSM-5 zeolite: effect of reduced crystal size on the reaction of naphthenes

2014 ◽  
Vol 4 (12) ◽  
pp. 4265-4273 ◽  
Author(s):  
Hiroki Konno ◽  
Ryota Ohnaka ◽  
Jun-ichi Nishimura ◽  
Teruoki Tago ◽  
Yuta Nakasaka ◽  
...  
Keyword(s):  
Rate Constants ◽  
Atmospheric Pressure ◽  
Catalytic Cracking ◽  
Reaction Rate ◽  
Crystal Size ◽  
Activation Energies ◽  
Reaction Rate Constants ◽  
Kinetics Of

The catalytic cracking of model naphthenes over ZSM-5 zeolites of different crystal sizes was examined at reaction temperatures ranging from 748 to 923 K under atmospheric pressure, focusing on the associated reaction rate constants and activation energies.

Dissolution kinetics of sepiolite from Eskisehir (Turkey) in hydrochloric and nitric acids

Clay Minerals ◽  
1990 ◽  
Vol 25 (2) ◽  
pp. 207-215 ◽  
Author(s):  
H. Cetisli ◽  
T. Gedikbey
Keyword(s):  
Activation Energy ◽  
Acid Concentration ◽  
Rate Constants ◽  
Reaction Rate ◽  
Dissolution Kinetics ◽  
Particle Sizes ◽  
Initial Particle ◽  
Reaction Rate Constants ◽  
Apparent Activation Energies ◽  
Kinetics Of

AbstractDissolution kinetics of sepiolite from Eskisehir (Turkey) have been investigated at various temperatures and particle sizes using dilute hydrochloric and nitric acids. Dissolution reaction rate constants were calculated and apparent activation energies were dependent on acid concentration. For both acids, apparent activation energy values reached a minimum of ∼11 kcal/mol at an acid concentration of 0·75 M. For the second-order reaction which is independent of the acid concentration, the activation energy was 14·5 kcal/mol for both acids. The reaction rate constants were proportional to the acid concentrations, and inversely proportional to the square-root of the initial particle radii of the sepiolite.

scholarly journals Aquation reaction of iminodiacetate complex of oxidovanadium(IV) with 2,2’-bipyridine induced by Fe(III) ions: Kinetic studies

2019 ◽  
Vol 44 (4) ◽  
pp. 300-306
Author(s):  
Joanna Drzeżdżon ◽  
Agnieszka Piotrowska-Kirschling ◽  
Lech Chmurzyński ◽  
Dagmara Jacewicz
Keyword(s):  
Aqueous Solutions ◽  
Computer Program ◽  
Rate Constants ◽  
Reaction Rate ◽  
Kinetic Studies ◽  
Reaction Rate Constants ◽  
Different Temperatures ◽  
Kinetics Of

The kinetics of the aquation reaction of the [VO(ida)(bipy)]·2H2O (VO(ida)(bipy)) complex (where ida = iminodiacetate anion and bipy = 2,2’-bipyridine) promoted by [Fe(H2O)6]3+ ions were investigated in aqueous solutions. Spectrophotometric studies were carried out at different temperatures in the range of 293.15–313.15 K. The concentration of the [Fe(H2O)6]3+ (Fe3+) ions was kept within the range of 2 × 10–4 to 8 × 10–4 mol L–1, and the concentration of VO(ida)(bipy) was 1 × 10–3 mol L–1. The values of the observable reaction rate constants were calculated based on the Glint computer program. Furthermore, the mechanism for the aquation of VO(ida)(bipy), induced by Fe(III) ions, has been proposed.

scholarly journals Bulk Polymerization Kinetics of Hydroxy Terminated Polybutadiene and Toluene Diisocyanate with Infrared Spectroscopy

2018 ◽  
Vol 18 (3) ◽  
pp. 552 ◽  
Author(s):  
Heri Budi Wibowo ◽  
Widhi Cahyo ◽  
Ratih Sanggra
Keyword(s):  
Reaction Temperature ◽  
Rate Constants ◽  
Reaction Rate ◽  
Bulk Polymerization ◽  
Isocyanate Group ◽  
Toluene Diisocyanate ◽  
Hydroxyl Group ◽  
Molar Ratio ◽  
Reaction Rate Constants ◽  
Kinetics Of

A study on bulk polymerization kinetics of HTPB (Hydroxy Terminated Polybutadiene) and TDI (Toluene Diisocyanate) with infrared (IR) spectroscopy has been conducted. The investigations included the molar ratio of 2,4-TDI to 2,6-TDI isomers, the initial molar ratio of isocyanate group to a hydroxyl group, and the reaction temperature. The polymerization rate constant was calculated based on the decrease rate of TDI. Kinetics model had been evaluated through the following reaction steps: (1) 2,4-urethane production, (2) 2,6-urethane production, (3) the reaction between 2,4-urethane and the isocyanate group of 2,4-TDI, (4) the reaction between 2,4-urethane and the isocyanate group of 2,4-TDI, (5) the reaction between 2,6-urethane and isocyanate group of 2,4-TDI, and (6) the reaction between 2,6-urethane and the isocyanate group of 2,6-TDI. Those reaction steps were assumed to be the first order reaction with the reaction rate constants k1, k2, k3, k4, k5, and k6, respectively. The reaction rate constants obtained at molar ratio of 2,4-TDI to 2,6-TDI of 80:20, isocyanate group to hydroxyl group (RNCO/OH) initial molar ratio of 1:1, and reaction temperature of 40 °C were 6.2 × 10-5, 5.8 × 10-5, 3.1 × 10-5, 2.8 × 10-5, and 2.5 × 10-5 L.mole-1.min-1 for k1, k2, k3, k4, k5, and k6, respectively, with the activation energy of 1152, 952, 1001, 656, and 1001 kJ/mole for reaction (1)–(6), respectively. The results show that the polymerization reaction rate-determining step was the reaction of 2,6-urethane and isocyanate group of 2,6-TDI (reaction (6)).

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