Homogeneous Reaction Research Articles

Role of Ammonia in Aerosol Liquid Water, pH, and Secondary Inorganic Aerosols Formation at an Ammonia-rich City in Changzhou

Ammonia （NH3） is an important alkaline reactive nitrogen, which, as a precursor of fine particulate matter, raises public health issues. In this study, online NH3, SO2, NO2, PM2.5, and its water-soluble inorganic ions were detected to deduce the influence of NH3 on aerosol liquid water content （AWC） and aerosol pH, including the formation of water-soluble secondary ions in PM2.5 in winter in Changzhou, an ammonia-rich city in the Yangtze River Delta area in winter. The results showed that NH4+ mainly existed in the form of NH4NO3 and （NH4）2SO4, and the remaining NH4+ existed as NH4Cl. Owing to the NH3-NH4+ buffer system, the aerosol pH values were found at 4.2 ± 0.4, which was positively correlated with the NH3 content. The aerosol pH value variation narrowed with the increase in PM2.5 concentration and tended to be between 4 to 5. AWC increased exponentially with the increase in humidity and SNA content, among which NH4NO3, （NH4）2SO4, and NH4Cl contributed 58.5%, 18.4%, and 8.3%, respectively, due to their hygroscopicity. Aerosol pH, AWC, and NH3-NH4+ conversion promoted the gas-to-particle conversion of SO2 and NO2. In Changzhou, rich NH3-NH4+ were found to maintain relatively high pH values, push up AWC, and promote the heterogeneous reaction of SO2, whereas NO3- generation was dominated by a homogeneous reaction, which was accelerated by NH3. According to the simulation results, relatively noticeable changes in aerosol pH and AWC could be found by the reduction of up to 30% of NH3.

Correlation between photoluminescence and radiative defects in silicon oxycarbide films due to the growth temperature effect

In this work, the effect of growth temperature (678–988 °C) on silicon oxycarbide (SiCxOy) samples obtained by hot filament chemical vapor deposition (HFCVD) is reported. The samples were deposited on silicon (Si) n-type (100) and quartz substrates for optical and structural studies. At a lower temperature (678 °C), silicon oxycarbide powders were formed on Si substrates due to the homogeneous reaction occurring in the gas phase. However, for temperatures between 804 and 988 °C, silicon oxycarbide films were formed on Si substrates. By changing the temperature from 678 to 988 °C, both carbon (C) concentration (21.2–17.7 wt.%) and the relative percentage of Si–C bond density (%RtSi-C = 11.34–3.47 %) decreased, as demonstrated by EDS and FTIR measurements, respectively. On the other hand, the content of relative Si–O–Si bonds located around 1060 cm−1 remained dominant in all cases, resulting in SiCxOy films with an amorphous SiOx-type structure. These films exhibited strong photoluminescence (PL) centered in the blue region (∼3 eV), where Si–NOVS radiative centers were preferentially responsible for PL emission. At a lower temperature (678 °C), the PL intensity decreased. The determination of optical bandgap energy (Eopt) using Tauc Plots coincided with the emission due to luminescent centers (∼3 and ∼2.7 eV) observed in PL, indicating that the radiative transitions were due to defects. The AFM measurements showed an increase in roughness from 5.01 to 16.20 nm as the growth temperature decreased, as expected according to SEM measurements.

Micron-sized aluminum particle combustion under elevated gas condition: Equivalence ratio effect

Micron-sized aluminum (Al) particle combustion under elevated gas condition is critical for improving energetic material performance, impacting propulsion and explosives technology. This study utilizes Eulerian-Lagrangian method to investigate Al particle combustion dynamics, encompassing both heterogeneous reaction (HTR) and homogeneous reaction (HMR). It focuses on the critical role of the equivalence ratio in single Al particle combustion, highlighting the interplay between HTR and HMR, aiming to optimize energy release and emission control. Our study identifies four stages in the combustion of a single Al particle, where the highest heat release is attributed to HTR, succeeded by HMR, and the minimal from unburned Al vapor. We observe a decline in the total heat release rate with an increasing equivalence ratio, primarily due to the differential impacts of heterogeneous and homogeneous reactions. The thermal-runaway stage in HTR is governed by the particle temperature, while the subsequent decaying stage is influenced by either the diminishing effective Al droplet diameter or the availability of oxygen, contingent upon the fuel conditions. Utilizing Cantera software to analyze HMR allows us to elucidate the thermal effects of elementary reactions and the key reaction pathways. These findings underscore the complex interactions between Al particles and the surrounding gas, providing insights into optimizing the conditions for Al-containing reaction systems.

Three-Dimensional Radiative Rotating MHD Nanofluid Flow of Over a Stretched Sheet with Homogeneous-Heterogeneous Chemical Reactions

CNTs are employed in energy storage, device modelling, automobile parts, water filters, thin-film electronics, coating, and more. The continuous three-dimensional (3D) magnetohydrodynamics (MHD) rotational flow of water-based nanofluid comprising SWCNT and MWCNT past a stretching/shrinking sheet under magnetic field and homogeneous-heterogeneous chemical processes is examined in this study. Heat transport is also examined with thermal radiation and heat source/sink. The governing partial differential equations (PDEs) are transformed to non-linear ODEs using proper similarity transformations and solved numerically using MATLAB's bvp4c package. Graphs and tables show how magnetic field, rotational, suction/injection, thermal radiation, heat source/sink parameters, nanoparticle (NP) volume fraction, and homogeneous and heterogeneous reactions affect velocity, temperature, concentration, skin friction coefficient, and Nusselt number. For larger rotational parameters, the main velocity declines and the second velocity increases, and MWCNTs flow more than SWCNTs.

Computational study of homogeneous–heterogeneous reactions in bioconvective third-grade material flow

The flow of third-grade nanofluid over a stretched surface is analyzed with a particular focus on the transport of heat due to melting by taking into account both homogeneous and heterogeneous reactions. To account for various effects, the energy equation incorporating viscous dissipation, Joule heating and radiation is considered, as well as the influence of thermophoresis and Brownian motion. A similarity transformation is used to simplify the expressions such that the model is analyzable. Utilizing the homotopic technique, series solutions are obtained, and a convergence result is established. Our investigation based on this series solution explores the impact of different factors on the flow model, and demonstrates that increasing the melting parameter leads to a decrease in temperature, entropy rate and concentration, while to an increase in velocity.

Myxodiaspory in Adenostemma brasilianum (Asteraceae): morphological and histochemical strategies for diaspore dispersion

Abstract Myxodiaspory, the extrusion of sticky substances by the diaspores (seeds, fruits, anthocarps, and parts of infrutescences), has several selective advantages, one of which is aiding the adherence of diaspores between feathers/fur of animals that transport them over short or long distances. The diaspores of Asteraceae have three structures that can contain sticky substances: exocarp epidermal cells, exocarp trichomes, and viscid pappus. The South American species Adenostemma brasilianum (Asteraceae) has all three features. We examined the anatomy, secreted substances, and mode of adhesion of the diaspores of A. brasilianum to understand its strategies for dispersion. The fruit comprises an exocarp with glandular trichomes arranged spirally and scarce nonglandular trichomes, two layers of mesocarp separated by phytomelanin, and an endocarp. The pappus has a basal ring, a stalk, and a head with glandular trichomes. The mucilage, secreted by the glandular trichomes of fruit and pappus, reacted positively to tests for pectins, essential oils, lipophilic substances, and gums. The test for tannins gave a homogeneous positive reaction in the phytomelanin area, and as droplets, in the outer mesocarp layer and in the exocarp. The whole capitulum of A. brasilianum is adapted for successful transportation of its diaspores via diaspore release, secretion, and positioning. We discuss the idea that the dispersal adaptive traits found here evolved as phylogenetic parallelisms in the family.

Chemically reactive flow of mircopolar Eyring–Powell Ferrofluid passes through stretching surface

In this investigation, the behavior of a chemically reactive flow of micropolar Eyring–Powell ferrofluids over stretchable surface was examined. The study also considers heterogeneous and homogeneous chemical reactions, as well as thermal radiation and magnetic dipole impacts. By applying suitable similarity variables, the nonlinear partial differential governing equations, which describe the flow and energy dynamics of the micropolar fluid, were transformed into ordinary differential equations. The resultant equations were then numerically solved by using the shooting method with a Runge–Kutta update. The model equations are presented and discussed in dimensionless form through numerical approximations. A variety of numerical tests were performed for the dimensionless parameters to provide a comprehensive understanding. The MATLAB version 2023 was used for the numerical computations as well as graphical illustrations. It was concluded that the velocity field decreases with greater values of the ferro-magnetic parameter ß as well as for other fluid material parameters H, and ß. Whereas the temperature field increases by increasing the thermal radiation R while decreases with a higher dissipation parameter λ1 and Prandtl number Pr. The numerical simulation for these parameters were shown graphically, and the values were tabulated for clear illustration. Moreover, the current work was also compared with the findings of existing studies from recent literature to validate and contextualize the findings.

Fabrication of Ca-alginate microspheres by diffusion-induced gelation in double emulsion droplets for oral insulin

Sodium alginate has good biocompatibility and is widely used in the study of drug carriers. In this paper, a method to prepare calcium alginate microspheres with high sphericity based on double emulsion droplets was proposed, in which sodium alginate is used as the innermost phase. By adjusting the density of the system, the double-emulsion droplets could be suspended in the collecting solution, leading to the homogeneous reaction between the sodium alginate droplets and the calcium ions. By changing the flow rate, the size of the droplets could be changed, and by changing the concentration of calcium ions in the collecting solution, the sphericity of the calcium alginate microspheres could be changed. Then the swelling properties and drug release properties of calcium alginate microspheres were determined. The drug delivery study revealed that the insulin-loaded Ca-Alginate microspheres were able to decrease blood glucose by 41.4 % after oral administration to mice. Thus, the Ca-Alginate microsphere is a suitable candidate for controlled pH-sensitive drug delivery.

Analysis of Darcy–Forchheimer flow of magnetized hybrid nanofluid (MoS 2+ZnO/E) with non-linear heat source and quartic autocatalytic chemical reaction

In this article, an effort is made to analyze the 3 − D flow of hybrid nanofluid over a rotating stretching sheet. The hybrid nanofluid contains engine oil as a base fluid amalgamated with nano-particles Mo S 2 and ZnO . The flow is assumed to pass through a Darcy–Forchheimer medium subjected to the influence of an inclined magnetic field. In addition, heat radiation, Joule heating, viscous dissipation, nonlinear heat source, and quartic autocatalytic chemical reaction are applied to discourse heat and mass transfer features. The PDEs representing the physical problem are converted to ODEs with the introduction of similarity transformations. The solution of the problem is determined numerically by using MATLAB built-in bvp4c method. The proposed mathematical model’s validation is ascertained by comparing it with an earlier study in limiting case. In this regard, an excellent consensus is accomplished. The current investigation reveals that the flow along axial direction gets retarded by enhancing the values of rotational parameter, inertial parameter, and magnetic parameter, whereas the flow along radial direction gets accelerated. The increasing value of angle of inclination admirably resists the motion of nanofluid and hybrid nanofluid. The concentration profile gets decreased under the increasing influence of inclination angle and Schmidt number while it enhances for homogeneous reaction parameter. The enhancing values of rotational parameter, solid volume fraction and temperature, and exponential dependent heat generation parameters enhance the value of Nusselt number.

Carbon-Boosted and Nitrogen-Stabilized Isolated Single-Atom Sites for Direct Dehydrogenation of Lower Alkanes.

Lower olefins are widely used in the chemical industry as basic carbon-based feedstocks. Here, we report the catalytic system featuring isolated single-atom sites of iridium (Ir1) that can function within the entire temperature range of 300-600 °C and transform alkanes with conversions close to thermodynamics-dictated levels. The high turnover frequency values of the Ir1 system are comparable to those of homogeneous catalytic reactions. Experimental data and theoretical calculations both indicate that Ir1 is the primary catalytic site, while the coordinating C and N atoms help to enhance the activity and stability, respectively; all three kinds of elements cooperatively contribute to the high performance of this novel active site. We have further immobilized this catalyst on particulate Al2O3, and we found that the resulting composite system under mimicked industrial conditions could still give high catalytic performances; in addition, we have also developed and established a new scheme of periodical in situ regeneration specifically for this composite particulate catalyst.

Effects of electrochemical active surface area of Cu on electrochemical CO2 reduction in acidic electrolyte using Cu nanoparticles on surfactant-treated carbon

Electrochemical carbon dioxide reduction reaction (CO2RR) presents a viable approach for transforming CO2 into valuable products. Traditional employment of neutral or alkaline electrolytes in CO2RR aims to avoid the hydrogen evolution reaction (HER). However, the usage of such electrolytes has intrinsic limitations on the availability of CO2 due to homogeneous equilibrium reactions, resulting in high energy costs for electrolyte regeneration. Lowering the pH of electrolytes can mitigate this concern and facilitate industrially relevant efficiencies. While recent studies show promising results for CO2RR in acidic environments using flow cells, the translation of conventional electrocatalysts from neutral or alkaline conditions to acidic conditions remains unclear. Hence, our investigation focuses on assessing the impact of surfactant-modified synthesis methods on CO2RR performance in acidic electrolytes.We first synthesized Cu nanoparticles on surfactant-treated carbon black by employing various surfactants: hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate, and Triton X-100, representing cationic, anionic, and nonionic surfactants, respectively. The objective of this synthesis was to investigate how surfactants influence the size and distribution of Cu nanoparticles (Cu NPs), the electrochemical active surface area (ECSA) of Cu, and, consequently, the performance of CO2RR in acidic electrolytes. The findings reveal that Cu NPs on carbon black show a different profile of size and distribution depending on the surfactant used for synthesis, resulting in varied ECSA. In addition, ECSA plays a crucial role in the production of C2H4 in an acidic medium, determining the onset potential and production rate of C2H4 while maintaining original Cu activity. In summary, surfactant treatment not only controls the size but also enables the uniform distribution of Cu NPs on carbon black. Consequently, Cu NPs exhibiting larger ECSA demonstrate enhanced efficiency in the production of C2H4 compared to counterparts with smaller ECSA under acidic environment.

Experimental constraints on iron and sulfur redox equilibria and kinetics in basaltic melt inclusions

The oxidation states of dissolved iron (Fe) and sulfur (S) in silicate melts were studied experimentally by heating Hawaiian olivines containing S-bearing melt inclusions (MIs) in a 1 atm gas-mixing furnace. The MIs are closed with respect to S and C, but equilibrate with the oxygen fugacity (ƒO2) and water fugacity (ƒH2O) of the furnace. We also conducted experiments using a S-free synthetic Hawaiian MI composition held on Pt-loops. Experiments were run at 1225 °C for 8–96 hr in H2-CO2 gas mixtures corresponding to ƒO2 values that varied over seven orders of magnitude and then drop-quenched into water. Time-series experiments show that MI Fe3+/Fe2+ and S6+/S2− ratios reached constant values within ∼24 hr. The H2O contents of the Pt-loop glasses and the dehydrated MIs overlap and are proportional to the fH2O in the furnace gas. The slope of log10(Fe3+/Fe2+) vs. log10ƒO2 is 0.25±0.02(2σ) for the Pt-loop glasses and 0.23±0.01(2σ) for the quenched MIs; the slopes of the two sets of experiments are consistent with equilibrium having been reached via the reaction FeO + ¼ O2 = FeO1.5. S-bearing quenched MI glasses have Fe3+/Fe2+ ratios that are systematically low compared to ratios measured in the S-free Pt-loop glasses run at the same T and ƒO2; this may reflect an effect of S on Fe3+/Fe2+, although further experiments are needed to explore this possibility. S6+/S2− ratios in the experimental melt inclusions vary systematically as a function of ƒO2, and the measured ratios agree with independent calculations of S oxidation state in basaltic melts.After being held at 1225 °C for 24 or 48 hr, a subset of olivine-hosted MIs were cooled at rates of 1700–40,000 °C/hr and quenched at temperatures between 900 °C and 1150 °C to explore whether Fe and S speciation are modified during cooling. Fe and S speciation in isothermal and cooled MIs held initially at the same ƒO2 overlap within uncertainty, suggesting that the T dependence of the homogeneous reaction 8Fe3+ + S2− = 8Fe2+ + S6+ is small and/or its kinetics are sluggish relative to cooling rates required to quench basaltic liquids to glasses. The centers of unheated, naturally quenched MIs from Papakōlea, Hawaii with syneruptive cooling rates ranging from ∼50 to 12,000 °C/hr were also measured for Fe and S speciation. MIs that experienced the lowest cooling rates have higher Fe3+/Fe2+ and S6+/S2− ratios relative to rapidly cooled inclusions of comparable size. The increase in Fe3+/Fe2+ is due to olivine crystallization on the inclusion walls during cooling and diffusion of the resulting oxidized boundary layer into MI interiors. Diffusive modification is minimized in MIs that have been rapidly cooled and/or are sufficiently large such that the oxidized boundary layer is restricted to a narrow region adjacent to the inclusion walls. Our experiments and their comparison to naturally quenched MIs show that measurements of Fe3+/Fe2+ and S6+/S2− ratios in quenched basaltic glasses and in the centers of rapidly cooled and/or large MIs are likely to be representative of the redox state in the melt at magmatic temperatures prior to quenching to glass.

Studying the effect of various types of chemical reactions on hydrodynamic properties of dispersion and peristaltic flow of couple-stress fluid: Comprehensive examination

A mathematical model has been constructed to examine the creeping sinusoidal flowing and diffusion of a solute material of an incompressible couple-stress fluid across a porous medium with wall features in the existence of heterogeneous-homogeneous chemical reaction. The mean effective diffusion factor is calculated using the long wavelength hypothesis, Taylor’s limit criteria, and dynamic periphery restrictions. The graphs have been used to study the effects of important constraints on the mean effective diffusion coefficient. The mean effective diffusion factor is found to rise with wall characteristics and amplitude ratio, indicating that peristalsis causes an increase in scattering. Additionally, scattering increased with the permeability constraint but decreased with the couple-stress constraint, homogeneous reaction rates, and heterogeneous reaction rates.

Syngas production through CO2-assisted catalytic pyrolysis of ethylene vinyl acetate (EVA) with a cobalt-based catalyst

Ethylene vinyl acetate (EVA) is a representative copolymer widely adopted across various sectors owing to its superior physiochemical properties; however, an environmentally benign protocol for the disposal of EVA waste has not yet been established owing to the various ratios of acetate to polyethylene. Therefore, in this study, we proposed an innovative thermochemical technique for converting EVA waste into energy resources, specifically syngas. CO2 was used to enhance the environmental sustainability of pyrolysis. Thermogravimetric analysis revealed that most of the EVA (approximately 99 wt%) was converted into pyrolytic oil and gases. However, the mechanistic features of CO2 in the pyrolysis of EVA could not be fully elucidated through single- or double-stage pyrolysis owing to the slow kinetics of the homogeneous reaction between CO2 and volatiles. To expedite the reaction kinetics, we used a cobalt (Co)-based catalyst (Co/SiO2). In the presence of Co/SiO2, the concentration of CO produced under CO2 was approximately 30-fold higher than that under N2. Furthermore, the homogeneous reactions resulted in fewer benzene derivatives and polycyclic aromatic hydrocarbons (PAHs) in the pyrolytic oil under CO2 conditions. These experimental findings suggest that CO2 and EVA could serve as valuable feedstocks for the production of energy.

Characterization and Application of Cyrene as a Biomass-Based Solvent for Homogeneous Heck-Coupling Reaction.

Cyrene, a renewable, non-toxic substance having negligible vapor pressure, even at high temperatures, was proposed as a reaction medium for homogeneous Pd-catalyzed Heck-coupling reactions. It was first characterized by its temperature-dependent physicochemical properties, i.e., vapor pressure, density, surface tension, heat capacity, and viscosity, the key parameters of its reaction and process chemistry. Its refractive indices in the function of temperature were also determined. Hereafter, the effect of reaction parameters (Pd source, nature of the base, the water content of the reaction mixture, leaving group (-I, -Br, -Cl, and -OTf of aromatic substrates) on Pd-catalyzed Heck-coupling reaction was investigated using iodobenzene and styrene as model substrates. Subsequently, 4-substituted iodobenzene and styrene derivatives were applied to investigate the effect of electronic parameters on the reaction efficiency and functional group tolerance. To demonstrate the applicability of the system, thirteen stilbene derivatives were isolated with good to high yields and purity (> 95%) using 0.2 mol% of Pd, 1.5 eq. of Et3N as a base, in 1 mL of Cyrene for 2 h at 100 °C.

Production of combustible gas via incorporating CO2 to pyrolysis of medicinal herbal waste

With the recent increase in the utilization of medicinal herbs, the generation of medicinal herbal waste has increased. However, conventional protocols for solid waste management (landfill and incineration) present environmental threats considering the complex chemical composition of medicinal herbal waste. Thus, this study introduces a thermochemical approach for managing medicinal herbal waste, focusing on conversion of red ginseng marc (RGM) into energy resource. This study explores an innovative strategy to maximize the production of pyrogenic gases using CO2 form improved syngas generation. The experimental results revealed an enhancement in CO from the pyrolysis of RGM under the CO2 condition in reference with the N2 condition, which was ascribed to gas-phased homogeneous reaction of CO2 with volatile matters liberated from RGM. Moreover, gas-phase reactions have proven to be effective in decreasing the benzene analogs, especially polycyclic aromatic hydrocarbons (PAHs), in pyrogenic liquids. To accelerate the gas-phase reaction rate, a nickel (Ni)-based catalyst was employed for the RGM pyrolysis. The introduction of Ni catalyst to the gas-phase reaction led to an CO enhancement (272 %) from the RGM pyrolysis in the presence of CO2. All experimental observations highlight the potential of incorporating CO2 in thermochemical conversion of RGM as an innovative way to enhance energy recovery.

Recovery of gaseous fuels through CO2-mediated pyrolysis of thermosetting polymer waste

Thermosetting polymers are used in a wide range of applications due to their robust mechanical strength and superior flame retardancy. Despite these technical benefits, recycling of thermosetting polymers has been challenging because of their crosslinking nature. Moreover, their disposal through conventional methods (landfill and combustion) poses environmental concerns, such as microplastics and air pollutants. To address these issues, this study introduces a thermo-chemical disposal platform for thermosetting polymer wastes that employs carbon dioxide (CO2) as a reactive medium. In this work, melamine-formaldehyde was used as model compound of thermosetting polymers. In single-stage pyrolysis, it was revealed that CO2 plays a crucial role in controlling in the compositional matrices of pyrolytic gases, liquid products, and wax. These compositional changes were attributed to the homogeneous reactions between CO2 and the volatile compounds released from the thermolysis of MF. To enhance the thermal cracking of the MF, a double-stage pyrolysis process was tested, which increased the production of pyrolytic gases and eliminated wax formation. However, the slow kinetics governing the reactivity of CO2 limits the occurrence of homogeneous reactions. A nickel-based catalyst was used to accelerate reaction kinetics. The catalytic pyrolysis under CO2 conditions led to substantial increases in syngas (H2 and CO) production of 880% and 460%, respectively, compared with double-stage pyrolysis. These findings demonstrate that thermosetting polymer wastes can be valorized into gaseous fuels through thermo-chemical process, and CO2 enhances the recovery of energy and chemicals. Therefore, this study presents an innovative technical platform to convert thermosetting polymer wastes and CO2 into syngas.

Electrochemical activation of peroxymonosulfate facilitated by a stainless-steel scrubber cathode: Transition from non-radical to radical pathway mediated by iron leaching

This study investigated the feasibility and underlying mechanisms of peroxymonosulfate (PMS) activation by a stainless-steel scrubber (SSS) cathode. Experimental findings revealed that the system could achieve 100 % degradation of sulfamethoxazole (SMX) in 30 min at initial pH value ranging from 3 to 9. The activation mechanism was observed to occur in two distinct stages. The first stage was characterized by a non-radical 1O2 dominance (0–6 min), where the activation of PMS and O2 was primarily facilitated through direct electron transfer at the cathode surface. Subsequently, the second stage transitioned to a radical dominance (6–18 min), with SO4− playing a pivotal role. This was attributed to the release of Fe2+ ions resulting from cathodic corrosion, which induced both homogeneous and heterogeneous Fenton-like reactions. The PMS/SSS cathode system exhibited anti-interference against most water matrices, except for HCO3−. Notably, the system demonstrated exceptional performance in the degradation of pollutants within phosphate wastewater samples, suggesting its potential for application in such contexts. In addition, the electrical energy was calculated to be 0.025 kWh·m−3 at a current of 0.01 A and a voltage of approximately 2.0 V, providing significant economic benefits.

Highly sensitive turn-on electrochemical sensing of organophosphorus pesticides by integration of homogeneous reaction and heterogeneous catalytic signal amplification

Enzyme-inhibited electrochemical sensor is a promising strategy for detecting organophosphorus pesticides (OPs). However, the poor stability of enzymes and the high oxidation potential of thiocholine signal probe limit their potential applications. To address this issue, an indirect strategy was proposed for highly sensitive and reliable detection of chlorpyrifos by integrating homogeneous reaction and heterogeneous catalysis. In the homogeneous reaction, Hg2+ with low oxidation potential was employed as signal probe for chlorpyrifos detection since its electroactivity can be inhibited by thiocholine, which was the hydrolysate of acetylthiocholine catalyzed by acetylcholinesterase. Additionally, Co,N-doped hollow porous carbon nanocage@carbon nanotubes (Co,N-HPNC@CNT) derived from ZIF-8@ZIF-67 was utilized as high-performance electrode material to amplify the stripping voltammetry signal of Hg2+. Thanks to their synergistic effect, the sensor exhibited outstanding sensing performance, excellent stability and good anti-interference ability. This strategy paves the way for the development of high-performance OP sensors and their application in food safety.

Thermodynamics of Growth in Open Chemical Reaction Networks.

We identify the thermodynamic conditions necessary to observe indefinite growth in homogeneous open chemical reaction networks (CRNs) satisfying mass action kinetics. We also characterize the thermodynamic efficiency of growth by considering the fraction of the chemical work supplied from the surroundings that is converted into CRN free energy. We find that indefinite growth cannot arise in CRNs chemostatted by fixing the concentration of some species at constant values, or in continuous-flow stirred tank reactors. Indefinite growth requires a constant net influx from the surroundings of at least one species. In this case, unimolecular CRNs always generate equilibrium linear growth, i.e., a continuous linear accumulation of species with equilibrium concentrations and efficiency one. Multimolecular CRNs are necessary to generate nonequilibrium growth, i.e., the continuous accumulation of species with nonequilibrium concentrations. Pseudounimolecular CRNs-a subclass of multimolecular CRNs-always generate asymptotic linear growth with zero efficiency. Our findings demonstrate the importance of the CRN topology and the chemostatting procedure in determining the dynamics and thermodynamics of growth.