Reaction Rate Constant Research Articles

Quantum Chemistry Study on Cl-Initiated Reactions of 2-Chloropropane and 2-Methylpropanoyl Halogen (Cl, Br, F): Mechanism, Kinetics, and Atmospheric Implications.

Halogenated volatile organic compounds (HVOCs) pose significant bioaccumulative and toxicological risks, necessitating effective strategies for their removal. Here, we show, through a computational study employing density functional theory and coupled cluster methods, the detailed mechanism and kinetic properties of Cl-initiated degradation reactions of 2-chloropropane (2-CP, (CH3)2CHCl) and 2-methylpropanoyl halide ((CH3)2CHCOX, X = Cl, Br, F). The reaction rate constants of all the channels were calculated by the canonical variational transition state theory (CVT) with the correction of the small curvature tunneling effect (SCT) at 200-1000 K. The subsequent transformation pathways of the major radical products of (CH3)2CHCl and (CH3)2CHCOCl in the presence of O2, NO, and HO2 radical were investigated. The results elucidate the reaction pathways and rate constants, which are in excellent agreement with the experimental data at 296 K. We further explore the atmospheric implications of these reactions by assessing the atmospheric lifetime (τ) and ozone depletion potential (ODP). Additionally, we delve into the aquatic toxicity and bioaccumulation potential of the reactants and their transformation products. This study not only advances our knowledge of the atmospheric fate of halogenated hydrocarbons but also underscores the importance of considering the environmental and toxicological impacts in the development of HVOC mitigation strategies.

Quenching Rate Constants of Lewis Base-Boryl Radical by Substrates: a Laser Flash Photolysis Study.

The advanced strategy using Lewis base-boryl radicals (LBRs) has recently been proposed for the addition of alkyl substituents to the full-carbon quaternary center of an organic molecule. However, as the rate-determining step in the whole route, reaction rate constants of LBRs with substrates are extremely lacking. In this paper, 4-dimethylaminopyridine (DMAP)-BH2• was selected as a representative of LBRs, and its reactions with six monochloro-substituted substrates, including three methyl chlorobenzoates and three chlorinated acetanilides were studied in experiments and theoretical calculations. The bimolecular reaction rate constants, kq, were determined using laser flash photolysis approach. By comparing activation energies along the two addition pathways, we have clarified the rate-determining step as the attacking to carbonyl oxygen instead of chlorine atom. Furthermore, noncovalent interaction (NCI) analyses on these substrates indicate that weak interactions, such as hydrogen-bonding and van der Waals interactions, have significant influence on the reactivity of these substrates. Our study provides concrete clues to extend this synthetic strategy.

Synthesis of the cis‐ and trans‐3‐Fluoro Analogues of Febrifugine and Halofuginone

AbstractThe novel synthesis of racemic cis‐ and trans‐3‐fluorofebrifugine and halofuginone is described. This straight‐forward seven‐step process relies on an electrophilic fluorination‐allylation sequence that generates a mixture of N‐Cbz protected, diastereomeric 2‐allyl‐3‐fluoropiperidines. On separation, a Wacker oxidation‐methyl functionalisation sequence enabled introduction of the required quinazolinone portion. Finally, removal of the N‐Cbz protecting group lead to isolation of the 3‐fluorofebrifugine dihydrobromide analogues that are of potentially pharmacological use. Analysis of the NMR spectra for each stereoisomer provides information concerning the preferred conformers of the different diastereomers. Evidence indicates that the cis‐diastereomer favours a conformation where the F‐atom occupies an axial orientation. In contrast, for its trans‐stereoisomeric counterpart, the 2‐substituent overrides any F‐atom effect and it preferentially occupies a conformer where both substituents occupy equatorial positions. Finally, interconversion between the cis‐ and trans‐diastereomers was studied. In DMSO‐d6 and as their free‐bases, isomerisation of each diastereomer gave a common 65 : 35 ratio of trans‐ to cis‐3‐fluorofebrifugine. Determination of the reaction rate constants for the isomerisation process at different temperatures enabled calculation of the activation energy barriers, for each process, using an Arrhenius plot. The activation energy barrier for the isomerisation of the trans‐isomer was 94.3±4.9 kJ mol−1, whereas for the cis‐isomer it was 84.5±3.9 kJ mol−1.

Rapid oxidation of phenolic compounds by O3 and HO●: effects of the air–water interface and mineral dust in tropospheric chemical processes

Abstract. Environmental media affect the atmospheric oxidation processes of phenolic compounds (PhCs) released from biomass burning in the troposphere. To address the gaps in experimental research, phenol (Ph), 4-hydroxybenzaldehyde (4-HBA), and vanillin (VL) are chosen as model compounds to investigate their reaction mechanism and kinetics at the air–water (A–W) interface, on TiO2 mineral aerosols, in the gas phase, and in bulk water using a combination of molecular dynamics simulation and quantum chemical calculations. Of the compounds, Ph was the most reactive one. The occurrence percentages of Ph, 4-HBA, and VL staying at the A–W interface are ∼ 72 %, ∼ 68 %, and ∼ 73 %, respectively. As the size of (TiO2)n clusters increases, the adsorption capacity decreases until n > 4, and beyond this, the capacity remains stable. A–W interface and TiO2 clusters facilitate Ph and VL reactions initiated by the O3 and HO⚫, respectively. However, oxidation reactions of 4-HBA are little affected by environmental media because of its electron-withdrawing group. The O3- and HO⚫-initiated reaction rate constant (k) values follow the order of A–WPh > TiO2 VL > A–WVL > A–W4-HBA > TiO2 4-HBA > TiO2 Ph and TiO2 VL > A–WPh > A–WVL > TiO2 4-HBA > TiO2 Ph > A–W4-HBA, respectively. Some byproducts are more harmful than their parent compounds, so they should be given special attention. This work provides key evidence for the rapid oxidation observed in the O3/HO⚫ + PhC experiments at the A–W interface. More importantly, differences in the oxidation of PhCs by different environmental media due to the impact of substituent groups were also identified.

Empirically exploring the space of monostationarity in dual phosphorylation

AbstractThe dual phosphorylation network provides an essential component of intracellular signaling, affecting the expression of phenotypes and cell metabolism. For particular choices of kinetic parameters, this system exhibits multistationarity, a property that is relevant in the decision-making of cells. Determining which reaction rate constants correspond to monostationarity and which produce multistationarity is an open problem. The system’s monostationarity is linked to the nonnegativity of a specific polynomial. A previous study by Feliu et al. provides a sufficient condition for monostationarity via a decomposition of this polynomial into nonnegative circuit polynomials. However, this decomposition is not unique. We extend their work by a systematic approach to classifying such decompositions in the dual phosphorylation network. Using this classification, we provide a qualitative comparison of the decompositions into nonnegative circuit polynomials via empirical experiments and improve on previous conditions for the region of monostationarity.

Comparison of The Effects of Epidural Analgesia and Conventional Analgesia on Survival in Patients Undergoing Gynecological Oncological Surgery: A retrospective analysis

Purpose: We aimed to determine whether mortality due to gynecologic cancer differs in patients who received epidural analgesia versus conventional analgesia. Additionally, we aimed to investigate which analgesia approach results in a better prognosis for gynecologic cancer. Materials and Methods: Patients who underwent surgery for a gynecologic malignancy were divided into two study groups based on the type of analgesia used: the Epidural Analgesia Group (n=120) and the Conventional Analgesia Group (n=88). All data were retrospectively collected from patient case charts. Variables recorded included patients’ age, body mass index (BMI), presence of comorbid diseases, duration of anesthesia, amount of blood transfusion. During surgery, duration of hospital stay, duration of intensive care unit stay, presence of postoperative infection, and type of postoperative treatment. Results: Survival after surgery tended to be higher in patients who received conventional analgesia (81 out of 88 patients) compared to those who received epidural analgesia (102 out of 120 patients), although this difference was not statistically significant (p=0.123). After controlling for all other factors, the coefficient for blood transfusion was -0.192 with a p- value of 0.007, indicating that a lower amount of blood transfusion was associated with increased survival. Similarly, the coefficient for the presence of comorbid diseases was -0.163 with a p-value of 0.022, suggesting that fewer comorbidities contributed to better survival post-surgery. Conventional analgesia showed higher survival rates (coefficient=0.163,p=0.022) compared to epidural analgesia. None of the other variables showed a significant correlation with survival. Conclusion: This study is among the pioneering research efforts to explore the impact of analgesia methods on the prognosis of patients with non-metastatic gynecologic cancer. A lower amount of blood transfusion during surgery and fewer comorbid diseases contribute to improved survival rates.

Possible formation of long-lived photo-oxidants by photolysis of organic matter phenols in sunlit waters

AbstractPhotodegradation in sunlit waters is a major process of contaminant abatement, yet underlying chemical processes in the presence of dissolved organic matter are poorly known. Long-lived photo-oxidants are reactive species formed when the chromophoric dissolved organic matter absorbs sunlight, and they are involved in the degradation of contaminants. Previous works identified long-lived photo-oxidants with phenoxy radicals, which could be formed upon oxidation of natural phenols by the excited triplet states of chromophoric dissolved organic matter. Here, we generated reactive phenoxy radicals by direct ultraviolet-A photolysis of 2-nitrophenol and 4-nitrophenol. We measured the second-order rate constants for reaction of these phenoxy radicals with 2,4,6-trimethylphenol, a model electron-rich phenol. Results show rate constants of 9.39 × 108(M−1s−1) for the 2-nitrophenoxyl radical, and 1.56 × 108(M−1s−1) for the 4-nitrophenoxyl radical. These values are slightly lower than the typical rate constant of the reaction between 2,4,6-trimethylphenol and the excited triplet states of chromophoric dissolved organic matter, of 3 × 109(M−1s−1). This means that 2,4,6-trimethylphenol would not be degraded to comparable extents by the excited triplet states of chromophoric dissolved organic matter and by long-lived photo-oxidants, if long-lived photo-oxidants were generated solely by the triplet states of chromophoric dissolved organic matter. Overall, findings suggest the occurrence of new pathway involving the direct photolysis of organic matter phenols that generates long-lived photo-oxidants.

Transferable and Interpretable Prediction of Site-Specific Dehydrogenation Reaction Rate Constants with NMR Spectra.

Accurate and efficient determination of site-specific reaction rate constants over a wide temperature range remains challenging, both experimentally and theoretically. Taking the dehydrogenation reaction as an example, our study addresses this issue by an innovative combination of machine learning techniques and cost-effective NMR spectra. Through descriptor screening, we identified a minimal set of NMR chemical shifts that can effectively determine reaction rate constants. The constructed model performs exceptionally well on theoretical data sets and demonstrates impressive generalization capabilities, extending from small molecules to larger ones. Furthermore, this model shows outstanding performance when applied to limited experimental data sets, highlighting its robust applicability and transferability. Utilizing the Sure Independence Screening and Sparsifying Operator (SISSO) algorithm, we also present an interpretable rate constant-temperature-NMR (k-T-NMR) relationship with a mathematical formula. This study reveals the great potential of combining machine learning with easily accessible spectroscopic descriptors in the study of reaction kinetics, enabling the rapid determination of reaction rate constants and promoting our understanding of reactivity.

Overcoming clay structure challenges in lithium recovery from boron waste using high‐temperature pressure acid leaching

AbstractBoron mines contain significant amounts of lithium along with boron. After boron is extracted, lithium remains in the waste, which has a carbonate‐hosted clay‐type structure, along with other impurities. The scarcity of lithium resources and the increasing need for lithium worldwide make such resources economically important. Although the best hydrometallurgical method for the recovery of lithium trapped within the clay‐structured mineral resources is roasting with chemicals to disrupt the clay structure and acid leaching, the process is quite difficult and costly due to the high energy and chemical addition requirements. To overcome this challenge, this study proposed a high‐temperature–pressure sulphuric acid leaching process to recover lithium from the boron waste. Under the optimized conditions (liquid/solid ratio: 10, acid concentration: 1 M, temperature: 150°C, and contact time: 120 min), 100% of lithium was leached. The leaching mechanism was determined through mineral characterization (X‐ray diffractometry [XRD], X‐ray fluorescence spectrophotometer [XRF], scanning electron microscopy–energy‐dispersive X‐ray spectroscopy [SEM–EDX], Mastersizer), and a shrinking core heterogeneous kinetics model. It was found that high‐temperature–pressure sulphuric acid leaching disrupted clay structure and promoted the leaching of lithium, the leaching kinetics fit the shrinking core heterogeneous kinetics model, and was controlled by a dual mechanism with ash diffusion and chemical reactions on the particle surface. The reaction rate constants increased with increasing temperature, and the activation energy was found to be 32.17 kJ/mol.

Significance of heat transfer in a reversible esterification of Arrhenius activation energy with partial slip

The significance of heat transfer during a reversible esterification process in a magnetohydrodynamic boundary layer Casson fluid flow along a vertical stretching plate is examined. The multi-slip conditions are considered in a porous medium. The presence of chemical process requiring an activation energy is considered in the analysis. The study also investigates the hydromagnetic boundary layer Casson fluid flow alongwith partial slip conditions across a vertical stretching plate. The incorporation of multi-slip constraints in a porous medium, alongside magnetic fields and other parameters, highlights its relevance in diverse engineering fields such as thermal engineering, polymerization, and biodiesel industries. Understanding the characteristics of such fluids under complex conditions is vital for optimizing heat and mass transfer in industrial applications, making this investigation timely and valuable. The nonlinear differential set of equations are solved numerically involving Runge Kutta based shooting approach of fourth order and the results are verified with the bvp4c tool and the findings are explored using graphical plots. The predominance of significant factors on flow configurations are analyzed and presented in graphs and tables. A comprehensive analysis is provided on the effects on velocity, concentration, and temperature of diverse parameters such as reaction rate constant, magnetic parameter, suction parameter, mass Grashof number, Prandtl number, Casson parameter, thermal radiation parameter and slip parameters. The tabular representation of the adverse effects of drag coefficient, rate of mass transfer and Nusselt number on flow configurations for various significant parameters is presented. It is inferred that for the case of reversible and irreversible flows, the shear stress rate escalates by 29% when the magnetic parameter elevates from 0.5 to 1.5 and about 35% when the Casson parameter elevates from 0.5 to 1.5. For the suction parameter, the coefficient of drag increased by 27% and 26% for irreversible and reversible flows respectively. When the reaction rate increases from 0.5 to 1.5, the rate of shear stress elevates by 0.5% and 0.02% for irreversible and reversible flows in order. The Nusselt number decreased about 7% and 8% when the magnetic parameter and Casson parameter rises from 0.5 to 1.5 respectively, for irreversible and reversible flows. It is noteworthy that the previous studies are in precise agreement with the present investigation.

Potential of homogeneous persulfate activation as a strategy for the oxidative treatment of tetramethylammonium hydroxide: Superiority of sulfate radical over hydroxyl radical in the oxidation of methylammoniums

Tetramethylammonium hydroxide (TMAH) as the etching and chelating agent exhibits the extreme recalcitrance to advanced oxidation processes utilizing hydroxyl radical (OH). This study showed that based on the relative position of PDS/heat and PDS/UV against H2O2/UV in terms of TMAH degradation efficiency, sulfate radical (SO4−) was superior to OH in oxidizing TMAH. PDS/heat (at 60 °C) and PDS/UV at the initial pH = 7 achieved TMAH degradation efficiency of ∼ 80–90 % within 1 h whereas H2O2/UV barely eliminated TMAH, which contrasted with H2O2/UV decomposing phenol faster than the activated PDS. The high susceptibility of TMAH (in which four methyl groups bonded to nitrogen removed the lone pair of electrons) to oxidation by SO4− aligned with the pH–dependent efficiency of PDS/heat for the treatment of methylamines. PDS/heat effectively degraded methylammoniums (lacking nitrogen lone pair available for electron transfer due to amine protonation) under non–alkaline conditions, whereas acidification caused the efficiency loss of ∼ 90 % for H2O2/UV. Methylammoniums as radical scavengers retarded benzoic acid degradation by PDS/heat to a more pronounced extent than counterparts with deuterated N–methyl groups, which implied that hydrogen–atom abstraction primarily contributed to the SO4−–induced oxidation of methylammoniums. Estimation of the bimolecular reaction rate constants using laser flash photolysis and electron paramagnetic resonance spectroscopic detection of TMAH–derived carbon–centered radical supported the superiority of SO4− over OH in TMAH oxidation. These findings suggested the potential of homogeneous persulfate activation in the pH-insensitive oxidative treatment of alkylamines and quaternary ammonium cations structurally analogous to TMAH.

Evaluation of Ferric Ion Adsorption On The Surface Imprinting Adsorbent

<span lang="EN-AU">Rapidity in technological aspects encourages industrial sector to utilize and apply the latest technology to accelerate and optimize production in its field. Thus, waste from industry polluting various aspects of environment, such as water, gives rise to environmental impacts. Heavy metals, including iron, are one of the most common and dangerous pollutants often found in water environments. Therefore, consideration of methods for heavy metal separation from water becomes important. The adsorption method has been used for separating heavy metals because of its simplicity, thus effectively cuts energy consumption and costs in process. However, heavy metal characteristics in water can vary depending on the element. Consequently, understanding the heavy metal characteristics in water is important, hence capable of formulate appropriate and effective adsorption systems. This study, Fe(III)-IIPs was applied to adsorb and separate iron from water through repeated adsorption with parameter improvements. The pH parameter plays an important role, with ion competition happens at pH <2 and the formation of iron hydroxide species at pH >4.5, which results in adsorption inhibition. The modeling of adsorption kinetic equation was found that the adsorption system carries chemisorption characteristics, with adsorption capacity of 11.15 mg/g and reaction rate constant of 19 min<sup>-1</sup>.</span>

Mechanism of unactivated peroxymonosulfate-induced degradation of amino-G acid: Kinetics and transformation pathway

Amino-G acid (7-amino-1,3-naphthalenedisulfonic acid), a pollutant produced during textile preparation and in dyeing industries, is discarded in wastewater and causes ecological problems. In this study, amino-G acid (50.0 μM) could be completely removed by unactivated peroxymonosulfate (PMS) (1.0 mM) within 240 min, and the reaction kinetics exhibited strong pH dependence. A species-specific parallel reaction describes this pH dependence well, and the species-specific reaction rate constants of [amino-G acid]2− and [amino-G acid]− with HSO5− were calculated to be 0.0826 ± 0.0019 and 000122 ± 0.0027 M−1 s−1. The reactivity of the six naphthalene sulfonic acids and unactivated PMS varied according to the structure, and the amino group in naphthalene sulfonic acid, a typical electron-donating group, was more vulnerable to attack by unactivated PMS, which was further confirmed by the density functional theory results. The high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) spectral analysis results indicated that naphthalene sulfonic acid was first oxidized to hydroxylamine products and then further oxidized to nitroso compounds, which exhibited more ecological toxicity. However, as the reaction processing, the toxicity of the product gradually decreased. Our results provide new insights into the in-situ oxidation of unactivated PMS.

Efficient enhancement of piezo-catalytic activity of BaTiO3-based piezoelectric ceramics via phase boundary engineering

Piezoelectric catalysis stemmed from lead-free piezoelectric ceramics is an emerging catalytic technology applied extensively in degradation of organic pollutants due to its low energy consumption and non-pollution. However, the dissatisfied catalytic efficiency of lead-free piezoelectric ceramics has constrained their further development and application. Herein, we employ ion doping to modulate the phase boundary construction of BaTiO3-based piezoelectric ceramics (BaTi(1-x)(Zr1/3Sn1/3Hf1/3)xO3, BTZSH-x), and the degradation performances of organic dyes are explored to illuminate the piezo-catalytic mechanism. The ion doping alters the phase boundary of BaTiO3 ceramics and a two-phase coexistence of rhombohedral-orthorhombic is achieved at room temperature in BTZSH-0.04 ceramic. Consequently, the BTZSH-0.04 ceramic exhibits an excellent degradation efficiency of rhodamine B with 97.27% in 60min and a high reaction rate constant of 0.056 min−1 under ultrasonication which is 7.4 times more than that of pristine BaTiO3. This work provides an advisable policy for constructing environmental-friendly piezoelectric materials with glorious piezo-catalytic activity.

Green solvents assisted de-novo synthesis and defect-engineered UiO-66 for improved CO2 adsorption and kinetics- experimental and DFT approach

The CO2 concentration in the atmosphere is increasing at an alarming rate, which is causing distress to human society and the natural environment. Adsorption is one of the most widely used methods of removing CO2 from flue gases, which reduces its adverse effects on our environment. For adsorption purposes, a facile green solvent-assisted de-novo synthesis approach was developed to construct a UiO-66′s structure to target CO2 at low pressure due to the partial pressure of CO2 in flue gases in the atmosphere (0.01⁓0.02 MPa). In the de-novo synthesis approach, a combination of various types of modulators and deep eutectic solvents (DES) are utilized to graft structural defects and induce quantitative and dispersive deep eutectic solvents onto the UiO-66 structure, respectively. The green solvent-assisted de-novo synthesis approach helped to tune all three structural parameters and preserve extra open metal sites (Lewis acid and Bronsted basis sites) with active NH2 and OH groups for improved CO2 adsorption and kinetics under flue gas conditions (CO2/N2=15/85 %). In comparison to the parent UiO-66, de-novo synthesized ChClPropx5@UiO-66 showed increased CO2 uptake (65.04 mg g-1) by 73 % at 0.15 bar and 25 °C, and the cyclic capacity remained almost similar over 10 consecutive cycles with an almost 94 % retention rate. After 3 times of regeneration at 105 °C under N2 atmosphere, the sample reserved almost similar adsorption capacity and could be recycled without dropping CO2 uptake. The strong and rapid interaction between guest CO2 and de-novo synthesized UiO-66 was confirmed by pseudo-first-order and second-order kinetics with reaction rate constants of 0.00026 and 0.00259, respectively. Furthermore, through periodic Density Functional Theory (DFT) calculations, a variety of linker defects are engineered onto the UiO-66 structure to preserve more open metal sites. For each of the engineering defects, free energies, adsorption energies, and the interaction of CO2 molecules on defect structures with bond length (Ɩ, Å) and bond angle (θ˚) are calculated for the most stable structures of UiO-66.

Analytical justification of the thermochemical interaction between blast reagents and carbon-containing products under the influence of magnetic fields

Purpose. To justify and develop a model that describes the effect of magnetic treatment of blast reagents and carbon-containing products on the gasification process for predicting the intensification of gas formation. Methodology. The study involves theoretical modeling based on experimental data to investigate the influence of magnetic fields on the underground coal gasification process and co-gasification of coal and carbon-containing products. The Arrhenius equation was used to estimate the rate constants of gasification reactions in the temperature range of 800–1,000 °C. The effect of the magnetic field was incorporated by adjusting the activation energy (Ea). The results of analytical and experimental studies were processed using methods of computer and mathematical modeling. Findings. The results show that the application of magnetic fields significantly intensifies the gasification process of carbon containing products. Increasing the reactivity of the blast reagents, particularly water and oxygen, leads to a higher overall yield of combustible gases. The use of magnetic fields in the gasification process substantially increases the reaction rate (k) due to the reduction in activation energy (Ea), improving the overall efficiency of gasification. Originality. For the first time, an analytical model has been developed to describe the effect of magnetic treatment of blast reagents and carbon-containing products on the gasification process in the temperature range of 800–1,000 °C. The obtained reaction rates follow an exponential trend. The established and correlation-validated pattern shows the relationship between changes in the approximation coefficient (F ) and the change in the carbon fraction (C, %) during the magnetic treatment of blast components within the specified temperature range. Practical value. The results of this study can be applied to enhance the efficiency of industrial gasification processes, particularly underground coal gasification and co-gasification of coal and carbon-containing productss.

In Situ Uranium Extraction through the Synthesis of the Uranyl Peroxide Studtite Using a Nonthermal Plasma.

Extraction of uranium from water is an essential step in in situ leach (ISL) mining and environmental decontamination. This is often done by precipitating uranium in solution as the uranyl peroxide studtite, [(UO2)(O2)(H2O)2](H2O)2, by adding hydrogen peroxide, which is energy-intensive to produce and hazardous to transport. Here, we present a method for synthesizing studtite, by generating reactive oxygen species in solution using a nonthermal plasma. Precipitation of studtite is observed within 5 min of the onset of plasma treatment as confirmed by X-ray diffraction and Raman spectral analysis. The faradaic efficiency of studtite formation is analyzed to estimate the values of hydrogen peroxide yield, 1.23 molecules per incident ion, and the rate constant of the studtite-forming reaction, 4.44 × 107 M-1 s-1. This work is a proof of concept and identifies significant parameters for the future development of a larger scale, higher throughput system.

A Rootless Duckweed-Inspired Flexible Artificial Leaf from Plasmonic Photocatalysts.

The naturally existing leaves are ubiquitous two-dimensional flexible solar-to-chemical conversion systems that can run continuously in a sustainable manner. However, the current artificial photocatalytic systems are unable to achieve this due to the grand challenge in integrating existing photocatalysts in a flexible layout with high conversion efficiency and the ability to function independently. Here, we report on a rootless duckweed-inspired artificial leaf based on a lightweight, flexible, Janus plasmonic nanosheet-integrated sponge. The Janus plasmonic catalytically active nanosheet was made from self-assembled gold nanocube nanoassemblies grown on the porous sponges, which were further coated with an ultrathin palladium layer on one side via a ligand symmetry-breaking method. This sponge-based photocatalytic system is lightweight yet able to float on a water surface and conducts the gas-liquid reaction without auxiliary pumping and mixing devices. In a model reaction of 4-nitrophenol reduction, this floating leaf could achieve 2.5-fold and 65-fold higher efficiency than the corresponding dispersion and precipitation systems, respectively. The film theory is used to explain the sponge-based lightweight solar-to-chemical conversion system in a detailed kinetic and thermodynamic analysis, including the reaction rate constant, activation energy, enthalpy, entropy, Gibbs energy, and equilibrium constant.

TiO2 Catalysts Co-Modified with Bi, F, SnO2, and SiO2 for Photocatalytic Degradation of Rhodamine B Under Simulated Sunlight

The organic pollutants discharged from industrial wastewater have caused serious harm to human health. The efficient photocatalytic degradation of organic pollutants under sunlight shows promise for industrial applications and energy utilization. In this study, a modified TiO2 photocatalyst doped with bismuth (Bi) and fluorine (F) and composited with SnO2 and SiO2 was prepared, and its performance for the degradation of Rhodamine B (RhB) under simulated sunlight was evaluated. Through the optimization of the doping levels of Bi and F, as well as the ratio of SnO2 and SiO2 to TiO2, the optimal catalyst reached degradation efficiency of 100% for RhB within 20 min under simulated sunlight, with a first-order reaction rate constant of 0.291 min−1. This value was 15, 41, 6.5, and 3.3 times higher than those of TiO2/SnO2, Bi/TiO2, Bi-TiO2/SnO2, and F/Bi-TiO2/SnO2, respectively. The active species detection showed that h+ was the most crucial active species in the process. The role of Bi and F addition and SnO2-SiO2 compositing was investigated by characterization. Bi formed a chemical bonding with TiO2 by doping into TiO2. The absorbance intensity in the UV and visible light regions was improved by SnO2 and F modification. Composite with SiO2 led to a larger surface area that allowed for more RhB adsorption sites. These beneficial modifications greatly enhanced the photocatalytic activity of the catalyst.

The unexpected and important role of alcohol stabilizer in thermal cis-trans isomerization of push-pull dyes in chloroform solution

The study demonstrates the influence of ethanol as a stabilizer in chloroform on the thermal cis-trans isomerization kinetics of photochromic compounds based on azobenzene and azopyridine derivatives. The significance of the addition of ethanol as a stabilizer in chloroform-based solutions on the isomerization reaction of the hydroxy- and the 6-hydroxylalkoxy-substituted azo compounds was investigated. The results have revealed that the presence of a polar stabilizer in a solvent can significantly reduce the reaction rate constant of the dark cis-trans isomerization due to the formation of hydrogen bonds at both ends of the azo-chromophore, thereby inhibiting the isomerization. Furthermore, a stabilizer can facilitate the reversion of azo-hydrazone tautomers of azophenols to their azobenzene form, resulting in a decrease in the reaction rate constant. The research presented in this paper can be essential for scientists who study the kinetics of the trans-cis and the cis-trans isomerization reactions of azo-chromophores. The results show that the use of solvents with polar stabilizers should be rather avoided, as their usage without information about stabilizers can lead to different experimental data. The authors should ensure that detailed information about stabilizers used in unstable solvents is included in the experimental section of their works (a detail currently often omitted in the literature).