Reactive Study Research Articles

Interfacial interaction energies at the interface of graphene/conductive polymer nanocomposites: A reactive molecular dynamics study

Reactive molecular dynamics (RMD) simulation was employed to investigate the interaction in the polymer nanocomposites, including functionalized graphene nanosheet (FGN) and conductive polymers namely poly (3-phenylhydrazone thiophene) (PPHT), poly (3-(4-n-octyl)-phenylthiophene) (POPT). FGN structures were resulted from incorporation of aryl functional groups containing various substitutions, including hydroxyl, ether. The effect of alkyl chain attached to hydroxyl was also examined. Based on the obtained results, the highest level of interaction energy was achieved in the PPHT/graphene-phenethyl alcohol (G-PhCH2CH2OH) and POPT/G-phenol (G-PhOH). The cause of the increase or decrease interaction energy in certain interaction in polymer nanocomposites was investigate by examining radial distribution function (RDF) diagrams in the case of different reactive sites. In addition, the polymer's state in terms of expansion or contraction during its interaction with FGN was determined based on radius of gyration (Rg) of the polymer. The impact of temperature variations among other parameters, was also examined. For this purpose, the nanocomposite of polymers/graphene-phenyl methyl ether (G-PhOCH3) was investigated at elevated temperature above 300 K. Ultimately, the investigation based on obtained RMD simulation results demonstrated a strong agreement with other reported other papers.

Chemistry of the interaction between Imidazole derivatives as corrosion inhibitors molecules and copper/brass/zinc surfaces: A DFT, reactive and classical molecular force fields study

In the present research, we explored the corrosion inhibition mechanisms on metals and alloys by imidazole, methylimidazole, and benzimidazole applying density functional theory (DFT), reactive (ReaxFF), and classical force fields. Our investigation focused on the interaction of these molecules with different types of bare metal surfaces. The results of our studies have been compiled to compare the protection efficiency of the three organic molecules for copper, zinc, and copper-zinc alloys (Cu63%-Zn37%) exposed to the same corrosion conditions in an acid environment. The calculated interaction energy quantities are strongly correlated with the experimental corrosion inhibition efficiencies BIM > MIM > IM. The imidazole derivative studied, significantly better protect copper than zinc, which is attributed to the higher bond strength of Cu–N (formation of chemical bonds) than of Zn–N, confirms the increase in the protection effectiveness against corrosion of Zn < Cu63%-Zn37% < Cu. This present study demonstrates the enormous potential of ReaxFF calculations to accurately simulate the adsorption of inhibitor molecules onto metal surfaces at a fraction of the computational cost of DFT, as well as the performance of the umbrella sampling method to assess the adsorption free energies.

New insights into the hydrothermal carbonization process of sewage sludge: A reactive molecular dynamics study

In this work, reactive molecular dynamics simulations using the ReaxFF force field were performed to investigate the hydrothermal carbonization (HTC) process of sewage sludge. The focus was on the reaction mechanism, the effect of water content and temperature on the formation of different products. The results showed that temperature was the most important factor controlling the HTC process, with higher temperatures leading to more rapid carbonization reactions and lower H/C and O/C ratios in the hydrochar product. The estimated activation energy of the HTC process was in the range of 126–169 kJ/mol, depending on the water content. The H/C and O/C ratios of the hydochar product obtained from the simulation were in excellent agreement with experimental data. Overall, this work provides valuable new insights into the reaction mechanism and key factors influencing the HTC process of sewage sludge.

Microscopic mechanism for CO2-assisted co-gasification of polyethylene and softwood lignin: A reactive force field molecular dynamics study

Co-gasification of biomass and waste plastic to produce syngas and value-added products is an attractive technology for renewable energy utilization and waste disposal. CO2 as a gasifying agent has received much attention as it can act as carbon source and oxidant in the reaction. In this paper, the feasibility and characteristics of CO2-assisted co-gasification of polyethylene and softwood lignin were explored. Simulation results showed that the lignin macromolecule began to decompose through C–O–C bond breaking and the PE chain gradually decomposed through C–C bond breaking. CO2-assisted co-gasification showed a negative synergistic effect on gas yield at the early stage, which delayed the reaction, but showed a positive synergistic effect at the late stage. The reaction between CO2 and carbon-containing fragments greatly promoted CO production. The hydrogen and hydrocarbon radicals from PE were actively involved in H2 and hydrocarbon gas production. Compared with O2-assisted co-gasification, the CO2-assisted and CO2/O2-assisted co-gasification yielded more CO, hydrocarbon gases and combustible gases and increased the lower heating value of gas product. This work sheds light on the underlying mechanisms of CO2-assisted co-gasification of polyethylene and softwood, and would be helpful for the development of this technology.

Agglomeration inhibition mechanism of SiO2 in the Ca(OH)2/CaO thermochemical heat storage process: A reactive molecular dynamics study

As a promising thermochemical heat storage material, the Ca(OH)2/CaO can be agglomerated after repeated heat storage cycles, which will affect its performance severely. Experimental evidence indicated that the dopant of SiO2 particles alleviated the agglomeration phenomenon of Ca(OH)2/CaO. However, the mechanisms have not been clarified in theory, including the agglomeration of Ca(OH)2/CaO and the agglomeration inhibition of SiO2. Investigating these mechanisms is important for the broad application of Ca(OH)2/CaO thermochemical heat storage technology. In this paper, reactive molecular dynamics is employed to simulate and quantify the agglomeration of Ca(OH)2 and the inhibition by SiO2 during the heat storage process. Then, the agglomeration phenomena under the two processes are quantitatively described. The mechanisms are analyzed by using the parameters of kinetics and thermodynamics. From the phenomenological analysis, smaller size changes, larger mass center distances, and smaller atomic displacements indicate that SiO2 doping reduces the tendency of nanoparticles to agglomerate into a larger cluster. From the kinetic perspective, the diffusion of pure Ca(OH)2 clusters conforms to viscous flow, while the diffusion of the SiO2-doped clusters is close to surface diffusion. The dopant of SiO2 increases the activation energy of the diffusion process, which would increase the atomic mobility resistance and thus inhibit the agglomeration. From the thermodynamic perspective, cluster agglomeration is mainly caused by the work done by van der Waals forces, which leads to a decrease in potential energy, especially surface potential energy. By doping SiO2, the interatomic van der Waals forces are increased, which lowers the stable potential energy surface of the clusters, thereby obtaining a more stable structure to inhibit agglomeration.

Revealing Al–O/Al–F reaction dynamic effects on the combustion of aluminum nanoparticles in oxygen/fluorine containing environments: A reactive molecular dynamics study meshing together experimental validation

Improving the energy conversion efficiency in metallic fuel (e.g., Al) combustion is always desirable but challenging, which often involves redox reactions of aluminum (Al) with various mixed oxidizing environments. For instance, Al–O reaction is the most common pathway to release limited energy while Al–F reaction has received much attentions to enhance Al combustion efficiency. However, microscopic understanding of the Al–O/Al–F reaction dynamics remains unsolved, which is fundamentally necessary to further improve Al combustion efficiency. In this work, for the first time, Al–O/Al–F reaction dynamic effects on the combustion of aluminum nanoparticles (n-Al) in oxygen/fluorine containing environments have been revealed via reactive molecular dynamics (RMD) simulations meshing together combustion experiments. Three RMD simulation systems of Al core/O2/HF, n-Al/O2/HF, and n-Al/O2/CF4 with oxygen percentage ranging from 0% to 100% have been performed. The n-Al combustion in mixed O2/CF4 environments have been conducted by constant volume combustion experiments. RMD results show that Al–O reaction exhibits kinetic benefits while Al–F reaction owns thermodynamic benefits for n-Al combustion. In n-Al/O2/HF, Al–O reaction gives faster energy release rate than Al–F reaction (1.1 times). The optimal energy release efficiency can be achieved with suitable oxygen percentage of 10% and 50% for n-Al/O2/HF and n-Al/O2/CF4, respectively. In combustion experiments, 90% of oxygen percentage can optimally enhance the peak pressure, pressurization rate and combustion heat. Importantly, Al–O reaction prefers to occur on the surface regions while Al–F reaction prefers to proceed in the interior regions of n-Al, confirming the kinetic/thermodynamic benefits of Al–O/Al–F reactions. The synergistic effect of Al–O/Al–F reaction for greatly enhancing n-Al combustion efficiency is demonstrated at atomic-scale, which is beneficial for optimizing the combustion performance of metallic fuel.

A pore-scale reactive transport modeling study for quorum sensing-driven biofilm dispersal in heterogeneous porous media

Microorganisms regulate the expression of energetically expensive phenotypes via a collective decision-making mechanism known as quorum sensing (QS). This study investigates the intricate dynamics of biofilm growth and QS-controlled biofilm dispersal in heterogeneous porous media, employing a pore-scale reactive transport modeling approach. Model simulations carried out under various fluid flow conditions and biofilm growth scenarios reveal that QS processes are influenced not only by the biomass density of biofilm colonies but also by a complex interplay between pore architecture, flow velocity, and the rates of biofilm growth and dispersal. This study demonstrates that pore architecture controls the initiation of QS processes and advection gives rise to oscillatory growth of biofilms. Such oscillation is suppressed if biofilm dynamics are in favor of sustaining a sufficiently high signal concentration, such as fast growth or slow dispersal rates. By establishing a mathematical framework, this study contributes to the fundamental understanding of QS-controlled biofilm dynamics in complex environments.

Extended ICI treatment after first-line chemoimmunotherapy could predict the clinical benefit of ramucirumab plus docetaxel in advanced non-small lung cancer: Post hoc analysis from NEJ051 (REACTIVE study).

The factors that predict the clinical response to ramucirumab plus docetaxel (RD) after first-line chemoimmunotherapy are unresolved. We explored whether the therapeutic efficacy of prior chemoimmunotherapy could predict the outcome of RD as sequential therapy in patients with advanced non-small cell lung cancer (NSCLC). Our study comprised 288 patients with advanced NSCLC who received RD as the second-line treatment after first-line chemoimmunotherapy at 62 Japanese institutions. Chemoimmunotherapy consisted of a platinum-based regimen and immune checkpoint inhibitors (ICIs). The association between several variables and the therapeutic outcome of RD was determined via logistic regression analysis. Of the 288 patients, 225 (78.1%) received maintenance therapy and 108 (37.5%) received both ICI treatment for >180 days and maintenance therapy. All of 108 patients having ICIs for >180 days received maintenance therapy. Univariate analysis identified performance status, histology (adenocarcinoma), maintenance therapy, and ICI treatment >180 days as significant predictors of better progression-free survival (PFS) and overall survival (OS) after RD administration. Multivariate analysis confirmed that these factors independently predicted favorable PFS and OS. The therapeutic response and PD-L1 expression were not closely associated with outcome after RD treatment. In particular, maintenance therapy >4 cycles was more predictive of the better prognosis for RD treatment. Extended ICI treatment after chemoimmunotherapy and maintenance therapy enhanced the efficacy of second-line RD treatment in patients with advanced NSCLC.

Reactive molecular dynamics study on carbon steel corrosion induced by chloride: Effects of applied potential and temperature

The corrosion and oxidation mechanisms of steel in chloride-contaminated environment were studied through the utilization of reactive molecular dynamics simulations with self-developed force fields under various applied electric fields and temperatures. The impact of variations in the external electric field on the thickness of the oxide layer and the dissolution of iron during the corrosion reaction process was scrutinized. The results reveal that under an electric field strength of 10 MV/cm, marginal corrosion was observed within the iron matrix during the simulation period. The surface lattice of the iron matrix retained a relatively intact and regular arrangement. However, under alternative external electric field conditions, as the strength of the external electric field increased, the corrosion behavior of iron in chloride ion solutions became increasingly severe, leading to deeper oxidation levels. Additionally, localized pitting on the iron matrix surface gradually evolved into larger corroded spots. Simulation results within the temperature range studied (278 K, 298 K, 318 K) suggest that temperature elevation amplifies the thermodynamic energy of chemical reactions on the iron surface, consequently leading to a reduction in the bond strength of Fe-O and increase in the corrosion extent.

Atomic insights into hydrogen peroxide decomposition on the surface of pure and pre-treated silver: A reactive molecular dynamics simulation study

Based on ReaxFF molecular dynamics simulation, H2O2 decomposition on pure and pre-treated silver catalyst is studied at a microscopic level. The pretreatment undergoes a surface annealing with redundant H2O2 on top of catalyst. The simulation results indicate that H2O2 decomposition can be drastically accelerated by elevating temperature. The extent of decomposition is closely related to bond, hydrogen bond, and potential energy of simulation system. It is found that H2O2 decomposition follows a four-stage HOOH bond break mechanism while it needs three times longer for pre-treated silver catalyst than pure silver catalyst. The activation energy of pre-treated silver catalyst is about 50 % lower than pure silver catalyst. However, the overall reaction rate of pre-treated silver catalyst is about an order of magnitude slower than pure silver catalyst, which owes to the much smaller pre-factor. It is believed that although the pretreatment causes silver oxide to be formed on the surface, it leads to more hydrogen and oxygen atoms deposited so that most active sites for catalytic reaction are blocked for further decomposition. This may be helpful to understand the inherent mechanism of H2O2 decomposition on silver-based catalyst and provide instructional advice for further catalyst modification design.

Formulation of multicomponent inclusion complex of cyclodextrin-amino acid with Chrysin: Physicochemical characterization, cell viability and apoptosis assessment in human primary glioblastoma cell line

Chrysin (CR) is a water-insoluble drug reported for different therapeutic effects. The microwave irradiation method was used in this study to create a multicomponent inclusion complex (CR-MC) containing CR (drug) and carrier hydroxyl propyl beta cyclodextrin (HP β CD) and L-arginine (LA). The prepared inclusion complex (CR-MC) was evaluated for dissolution study and results were compared with chrysin physical mixture (CR-PM). Further, the samples were assessed for infra-red (IR), nuclear magnetic resonance (NMR), differential scanning calorimeter (DSC), scanning electron microscope (SEM) and molecular docking. Finally, the cell viability, reactive oxygen species and flow cytometer studies were also assessed to check the potential of the prepared inclusion complex on the human primary glioblastoma cell line (U87-MG cell). The phase solubility findings revealed a stability constant (773 mol L−1) as well as a complexation efficiency of 0.027. The dissolution study displayed a significant increase in CR release from CR-MC (99.03 ± 0.39%) > CR-PM (70.58 ± 1.16%) > pure CR (35.29 ± 1.55%). NMR and IR spectral data revealed no interaction between CR and carriers. SEM and DSC study results revealed the conversion into amorphous form. The molecular docking results illustrated a high docking score, which supports the findings of complex formation. The cell viability, reactive oxygen species, and flow cytometry studies results showed enhanced activity from CR-MC against the tested human primary glioblastoma cell line. From the results it has been observed that chrysin solubility significantly increased after complexation and there in vitro activity also enhanced against cancer cell line.

Alternative Local Melting‐Solidification of Suspended Nanoparticles for Heterostructure Formation Enabled by Pulsed Laser Irradiation

AbstractPhase formation by pulsed laser irradiation of suspended nanoparticles has recently been introduced as a promising synthesis technique for heterostructures. The main challenge still lingers regarding the exact mechanism of particle formation due to the non‐equilibrium kinetic by‐products resulting from the localized alternative, fast, high‐temperature nature of the process. Here, the authors analyze the bond breaking/formation of copper or copper (II) interfaces with ethanol during the absorption of pulses for Cu‐CuO‐Cu2O formation applicable as an electrocatalyst in ethanol oxidation fuel cells. This study includes but is not limited to, a comprehensive discussion of the interaction between nano‐laser pulses and suspension for practical control of the synthesis process. The observed exponential and logarithmic changes in the content of heterostructures for the CuO‐ethanol and Cu‐ethanol samples irradiated with different fluences are interpreted as the dominant role of physical and chemical reactions, respectively, during the pulsed laser irradiation of suspensions synthesis. It is also shown that the local interface between dissociated ethanol and the molten sphere is responsible for the oxidative/reductive interactions resulting in the formation of catalytic‐augmented Cu3+ by‐product, thanks to the reactive bond force field molecular dynamics studies confirmed by ab‐initio calculations and experimental observations.

Ethyl trifluoroacetate formation as a means to recover trifluoroacetic acid from dilute aqueous mixture: reaction, separation and purification

ABSTRACT Recovery of trifluoroacetic acid (TFA) by distillation is difficult due to the existence of a high boiling azeotrope. Esterification of TFA to ethyl trifluoroacetate was performed in this work in order to recover the acid from its dilute aqueous mixture. The reaction was carried out in a batch reactor. Parameter estimation was done to obtain a kinetic model by using the experimental data. Reactive distillation studies were performed to explore its feasibility and process intensification. Methodology to obtain almost pure ethyl trifluoroacetate from dilute aqueous reaction mixture was devised.

Effect of oil-based drilling fluid on the evolution of friction interface: A reactive molecular dynamics study at different temperatures

Oil-based drilling fluids (OBDF) have good lubricating properties and are indispensable in oil drilling engineering. Temperature significantly affects the lubricity performance of OBDF, but the effect's mechanism is unclear. In this paper, the tribological properties of OBDF were investigated under three different temperature environments. Its flow ability and interfacial wear were explored using reactive molecular dynamics. Studies have shown that the flow of OBDF becomes unstable with increasing temperature, leading to a higher degree of frictional fluctuation. The wear regions at the friction interface increase with increasing temperature, and OBDF inhibits the transformation of the body-centered cubic lattice to an amorphous structure, thereby reducing wear.

The Etching Mechanisms of Diamond, Graphite, and Amorphous Carbon by Hydrogen Plasma: A Reactive Molecular Dynamics Study

AbstractUnderstanding how hydrogen plasma etches various potential products during the diamond growth process can contribute to improving the knowledge of diamond growth. However, due to the absence of an in situ characterization technique during the etching process, the complex chemical reactions involved in the process obscure the atomic‐scale etching mechanisms. In this paper, the etching mechanisms of diamond (001), graphite (0001), and amorphous carbon substrates irradiated by hydrogen plasmas are investigated and compared using molecular dynamics simulations based on ReaxFF. When the incident energy of H atoms is 1 eV, the rate of carbon loss from graphite and amorphous carbon are far higher than that from diamond. As the incident energy of H atoms increases, the etching rate of diamond shows a slow increase, while the etching rates of amorphous carbon and graphite exhibit more significant increases. It can be concluded that the etching rate of diamond is significantly lower than that of graphite and amorphous carbon under H plasma. In the Chemical Vapor Deposition (CVD) process of diamond growth, the generated graphite and amorphous carbon are rapidly etched, leaving only diamond. This offers a plausible explanation for the growth mechanism of diamond through CVD.

Effect of water on mechano-chemical reactions of perfluoropolyether lubricant films in heat-assisted magnetic recording: A reactive molecular dynamics study

A comprehensive understanding of the decomposition of perfluoropolyether (PFPE) films is crucial for establishing effective lubrication of heat-assisted magnetic recording (HAMR) systems. In this study, to examine the combined influence of heat, mechanical stress, and water, we conducted nonequilibrium reactive molecular dynamics simulations using our ReaxFF force field for the PFPE D-4OH films mixed with water. We thoroughly analyzed the reaction rates, types, pathways, and products, and identified vulnerable bonds. The results demonstrate that water significantly accelerates the reactions of D-4OH, particularly at lower normal pressures. We found that water molecules form clusters and are surrounded by the D-4OH end groups. Consequently, water induces hydrolysis of D-4OH or catalyzes reactions between D-4OH by dissociating C–O bonds in the end groups.

CO2 electroreduction to multicarbon products from carbonate capture liquid

CO2 electroreduction to multicarbon products from carbonate capture liquid

Kinetics of reactive extraction of free fatty acids in jatropha oil with monoethanolamine in methanol: A key biodiesel pre-processing step

Unrefined vegetable oils and fats contain free fatty acids and they ought to be minimized for use in food and non-food applications. Traditional deacidification of vegetable oils and fats adopts alkali neutralization for the removal of free fatty acids. Here, a simple method for the removal of free fatty acids from jatropha oil by reactive extraction using monoethanolamine in methanol is proposed. Reactive extraction kinetic studies with initial free fatty acids concentration (0.1–0.5 kmol/m3) using monoethanolamine (0.4141–1.6568 kmol/m3) in methanol at 30 °C was performed and investigated. Parameters like distribution coefficient, equilibrium complexation constant for free fatty acids extraction were obtained to arrive at equilibrium and kinetic conclusions. Most importantly, the criteria for reaction regime was established through Hatta number. The study revealed that reactive extraction of free fatty acids using monoethanolamine in methanol falls under reaction regime 2. The study demonstrated that reactive extraction was highly successful in reduction of the free fatty acids in jatropha oil. Further biodiesel was prepared using the deacidified oil and the specifications obtained were well within the standard ASTM limits.

Reactive Force Field Molecular Dynamics Study of the Effects of Gaseous Species on the Composition and Crystallinity of Silicon–Germanium Thin Films

We simulated the growth of a silicon–germanium (SiGe) film using reactive force field molecular dynamics (ReaxFF MD) in combinations of SiH3, SiH2, GeH3, and GeH2 radicals to evaluate the effects of gaseous species on thin-film composition and crystallinity and to understand the growth mechanisms. The film compositions could be estimated in these combinations because of the linear increase in the Ge content of the films. The average crystallinity grown by SiH3 was higher than that by SiH2 radicals. The crystallinity of the film grown by SiH3 radicals tends to be drastically decreased by GeH2 radicals. The growth mechanisms for XH3 and XH2 (X = Si or Ge) radicals were compared. XH3 radicals abstracted surface H atoms, and then more XH3 radicals chemisorbed onto the formed dangling bonds, resulting in film growth through a two-step reaction known as the Eley–Rideal-type (ER-type) mechanism. The ER-type mechanism grows the film with a low hydrogen content and high crystallinity. In contrast, XH2 radicals displayed not only the ER-type mechanism but also a one-step reaction, the H-capturing mechanism, which incorporates surface H atoms into the gaseous species. The H-capturing mechanism results in film growth with high hydrogen content and low crystallinity. The growth mechanisms are influenced by high/low H-coverage. The surface H atoms thermally move around the bonded atoms and give their kinetic energy to the diffusing gaseous species. Excess surface H atoms promote desorption. Our results from the ReaxFF MD suggested experimental settings and conditions that would enable the growth of high-quality films. Our results also suggested that SiH3 and GeH3 radicals should be mainly generated in the gas phase for high-quality SiGe film growth.

First-principles and reactive molecular dynamics study of the elastic properties of pentahexoctite-based nanotubes

Pentahexoctite (PH) is a pure sp2 hybridized planar carbon allotrope whose structure consists of a symmetric combination of pentagons, hexagons, and octagons. The proposed PH structure was shown to be an intrinsically metallic material exhibiting good mechanical and thermal stability. PH nanotubes (PHNTs) have also been proposed, and their properties were obtained from first principles calculations. Here, we carried out fully-atomistic simulations, combining reactive (ReaxFF) molecular dynamics (MD) and density functional theory (DFT) methods, to study the PHNTs elastic properties and fracture patterns. We have investigated the mechanical properties behavior as a function of the tube diameter and temperature regimes. Our results showed that the PHNTs, when subjected to large tensile strains, undergo abrupt structural transitions exhibiting brittle fracture patterns without a plastic regime.