kJ Mol Research Articles

Study of thermal behavior and crystallization kinetics of glass microspheres in the Y3Al5O12-Al2O3 system

AbstractFive types of glass microspheres with alumina and 40–80 mol.% Y3Al5O12 were prepared using solgel Pechini and flame synthesis techniques. Glass thermal behavior was analyzed using DSC/TG, XRD and SEM, and the JMAK model was applied to study crystallization kinetics and determine prevailing mechanisms. All samples, except the one with 80 mol.% YAG, had two exothermic effects in their DSC curves. The first appeared between 937 and 950 °C, while the second was observed between 958 and 1102 °C. XRD analysis of crystallized microspheres confirmed the presence of YAG and various forms of alumina phases in the samples with lower YAG/higher Al2O3 content (40 and 50 mol.%). The sample with the highest YAG content showed the strongest tendency to crystallize in the kinetics study. The value of apparent activation energy (Eapp) of this sample was 987.3 ± 13.0 kJ mol−1. For the remaining samples, the values of Eapp were higher and ranged from 1215.1 ± 10.6 to 1847.5 ± 9.3 kJ mol−1, indicating the lowest ability of these compositions to crystallization. The growth of three-dimensional (3-D) YAG crystals was predominant in glasses with the highest (80 mol.%) YAG content. One-dimensional (1-D) growth of γ-Al2O3 crystals and 3-D growth of YAG crystals was predominant in glasses with the lowest (40 mol.%) YAG content.

Study of the Sodium Borohydride Hydrolysis Reaction's Performance via a Kaolin-Supported Co-Cr Bimetallic Catalyst

Hydrogen is an attractive source of energy because of its properties, which include superior quality, effectiveness, pureness, dependability, and sustainability. Technologies for producing and storing hydrogen are being developed in parallel with fuel cell development. Chemical storage of hydrogen in a metal hydride containing boron eliminates the problem of hydrogen transportation and storage. Through catalytic reactions, hydrogen stored in solid form in boron hydrides can be recovered. In this study, a nowel developed Co-Cr bimetallic catalyst supported by kaolin, a natural mineral, was synthesized to be used for hydrogen production by hydrolysis of sodium boron hydride. The structural characteristics of the produced Co-Cr@Kaolin catalyst were ascertained by EDX, FTIR, and SEM analyses. Next, the ideal conditions for the hydrolysis reaction of sodium borohydride (NaBH4) catalyzed by Co-Cr@Kaolin were examined. These included the concentration of the catalyst, the amount of support material (kaolin), the amount of catalyst, and the concentration of NaBH4. The optimal hydrolysis conditions were found to be 2.5% NaOH concentration, 40 mg of catalyst, and 2% NaBH4 concentration at 303 K. The maximum rate of hydrogen production was determined as 5007 ml g-1 min-1 under optimal conditions. After conducting hydrolysis operations at different temperatures to elucidate the reaction kinetics, it was found that the catalytic hydrolysis reaction was of the 0th order and that the reaction activation energy was 19.36 kJ mol-1. The hydrogen production rate obtained as a result of the hydrolysis reaction accompanied by a Co-Cr catalyst was determined as 3166 ml g-1 min-1. It is therefore established that supporting kaolin to Co-Cr catalyst enhances its efficacy.

Obtaining a fiber-rich ingredient from blueberry pomace through convective drying: Process modeling and its impact on techno-functional and bioactive properties

This study aimed to optimize the convective drying of blueberry pomace (BP) to enhance fiber functionality and bioactive compound retention. BP was dried at 50−90 °C with an airflow of 2.5 m s−1. Drying kinetics were modeled using five mathematical models, with the Page model showing the highest accuracy (R2 = 0.9965−0.9996). Higher temperatures increased drying rates (3.7 × 10−3 to 1.2 × 10−2 kg H2O kg−1 db min−1) and moisture diffusivity (4.00 × 10−8 to 2.17 × 10−7 m2 s−1), with an activation energy of 39.55 kJ mol−1. Total dietary fiber remained stable (20.85 ± 0.17 g 100 g−1 db), while soluble fiber increased (3.11–4.66 g 100 g−1 db) with temperature. Water- and oil-holding capacities decreased (10.86–8.61 mL g−1 db and 3.85 to 3.44 mL g−1 db, respectively). The highest total phenolic content (13.65 ± 0.12 mg GAE g−1 db) and antioxidant activity (6.65 mg AAE g−1 db for DPPH) were observed at 70 °C. Energy consumption decreased significantly (13.88–6.95 kW h−1), leading to reduced CO2 emissions. This study demonstrates the effective use of the Page model to optimize convective drying at 70 °C, reducing production costs by 47% and highlighting its potential to produce fiber-rich ingredients from BP with enhanced techno-functional and bioactive properties.

Machine learning based prediction and iso-conversional assessment of oxidatively torrefied spent coffee grounds pyrolysis

This research focused on developing a predictive model for mass loss during the pyrolysis of oxidatively torrefied spent coffee grounds (SCG) using machine learning techniques. Four algorithms were employed: artificial neural networks (ANN), k-nearest neighbors (k-NN), random forest (RF), and decision tree (DT), with the RF model demonstrating superior performance (R2 > 0.9981, RMSE <1.346) for both training and testing sets. The pyrolysis behavior, kinetics, and thermodynamics of SCG were also investigated using thermogravimetric analysis (TGA) under an inert atmosphere at different heating rates. Higher heating rates in TGA cause Tpeak values to shift to higher temperatures with increased DTGpeak values, while also resulting in lower Tonset and higher Toffset. Kinetic analysis, using the Flynn-Wall-Ozawa (FWO) method, was identified as the most suitable approach for determining activation energy (Ea), with values ranging from 192.66 to 288.13 kJ mol−1, indicating differences in energy requirements for pyrolysis across samples. Thermodynamic analysis further revealed that both raw SCG and oxidatively torrefied SCG pyrolysis were endothermic reactions. These findings contribute valuable insights into the optimization of biomass conversion technologies, highlighting the potential of machine learning in improving predictive accuracy and efficiency in thermal behavior modeling. This research advances sustainable bioenergy production by promoting the use of SCG, an abundant waste material, as a renewable feedstock in pyrolysis-based processes.

Redox reaction of a RuIII(pic)3 complex with cysteine: Spectral, kinetic and biological studies

The kinetics of the reduction of [RuIII(pic)3] (pic− = picolinate) with cysteine leading to the formation of the corresponding red coloured [RuII(pic)3]− complex (λmax = 466 nm, εmax = 12000 M−1 cm−1) was studied by using stopped-flow and rapid scan spectrophotometry. The time course of the reaction was followed at 466 nm as a function of cysteine concentration, pH and temperature. Kinetic data (k = 291 ± 4 M−1 s−1 at 25 °C and pH 8.4) and activation parameters (ΔH≠ = 36 ± 1 kJ mol−1 and ΔS≠ = −78 ± 3 J mol−1 deg−1) are interpreted in terms of a mechanism involving rate-determining outer-sphere electron transfer between Ru(III) and the cysteine. Inhibition of bacterial growth (Klebsiella pneumonia and Staphylococcus aureus) by the [RuIII(pic)3] complex both in absence and presence of cysteine has been examined, and the results show a positive effect of cysteine addition on the anti-bacterial activity of the complex for S.aureus.

Polymer tethering strategy modified ZIF67 derived cobalt-confined nanocage for norfloxacin degradation: Tailored reactive sites and beneficial local microenvironment

The refined state of reactive sites and their local microenvironment largely determined the reaction performance of catalyst. Herein, we constructed hollow cobalt-confined carbon nanocage (Co-NC@Co/C-x) with rich surface pyridinic N and more exposed tailored Co sites through cobalt-incorporated polymer tethering strategy modified ZIF67 and later thermal depolymerization. Such features facilitate rapid surface enrichment of contaminants, accelerated electron transfer and enhance the availability of unpaired electron oxygen of metallic cobalt, demonstrating exceptional efficiency in Norfloxacin degradation (NFX, 97.7 % within 20 min, kobs = 0.528 min−1) with a significantly lower activation energy of 6.39 KJ mol−1. Mechanistic investigations prove the promotive interplay of peroxymonosulfate with reactive sites and elucidate the dominant role of non-free radicals 1O2 for NFX degradation. The theoretical calculation showcases that unpaired-electron surface oxygen of metallic cobalt induces the impurity cleavage of the O-O bond, triggering the promotive generation of 1O2. Co-NC@Co/C-6 samples exhibit robust NFX degradation across different aqueous matrices, demonstrating cyclic stability and universal degradation performance against various pollutants, and flowing degradation experiments and immobilized recyclable monolith fiber-like bobbles experiments further underline the green recovery and practical potential in wastewater treatment.

Harvesting low-cost gold-based catalysts from e-waste by a cationic covalent triazine organic framework for 4-nitrophenol reduction

Gold (Au)-based catalysts are commonly used for the hydrogenation of 4-nitrophenol, however, the high cost of Au has limited their widespread application. Therefore, developing affordable Au-based catalysts is highly desirable yet challenging. Herein, we synthesized a cationic covalent triazine framework to recover Au from e-waste, leading to the creation of cost-effective Au NPs@iCTF-TPM catalysts. Adsorption experiments demonstrate that cationic iCTF-TPM exhibits exceptional Au adsorption capabilities, with a maximum capacity of 1919 mg g−1. Notably, the iCTF-TPM selectively recovers Au from the e-waste leaching solution, achieving 99 % removal of Au within just 5 min. Moreover, the adsorbed AuCl4− can be self-reduced to form fine Au nanoparticles, resulting in the formation of Au NPs@iCTF-TPM catalysts. Remarkably, Au NPs@iCTF-TPM could convert 4-nitrophenol to 4-nitroaniline with a low activation energy of 26.15kJ mol−1 and a high rate constant of 1.73 × 10−2 s−1. Electron paramagnetic resonance spectroscopy indicates that the high catalytic activity is primarily due to the generation of active hydrogen radicals facilitated by Au NPs@iCTF-TPM. This study opens new avenues for developing low-cost Au-based catalysts from e-waste leaching solutions.

High Temperature Oxidation Behavior of ODS Ferritic Stainless Steel Fe-16Cr-4Al-1Ni-0.4Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

This study investigates the isothermic oxidation behavior of the new ODS alloy Fe-16Cr-4Al-1Ni-0.4Y2O3 (% by weight) at 700, 800 and 900 °C, with exposure times of 5, 20, 50, and 100 h at each temperature. The purpose is to obtain new data on its high-temperature parabolic oxidation constant for assessing oxidation resistance. The methods used include isothermal oxidation testing, XRD, SEM-EDS characterization, and analysis of oxidation kinetics by monitoring changes in oxide thickness using microscopy and SEM-EDS. The oxide products formed on the sample surface are Fe2O3, Fe3O4, AlFe2O4, and (Fe,Cr)2O3. Al and Cr oxides are located under the dominant Fe oxide layer on the surface of the sample. The oxidation test results showed that the most protective sample was obtained at a temperature of 700 °C for 100 h with an oxide thickness of 263.99 μm. The kinetics analysis correlates strongly with the parabolic equation (R2 ≈ 1). The oxidation rate constants at temperatures of 700, 800, and 900 °C were 681.76, 2957.5, and 12300 μm2 h−1, respectively. The activation energy required by the oxidation reaction in this alloy is 136.5 kJ mol−1. This research enhances understanding and potential applications of the Fe-16Cr-4Al-1Ni-0.4Y2O3 alloy in high-temperature environments.

Eco‐Friendly Preparation of Pectin‐Stabilized Ruthenium Catalyst for Hydrogen Generation from Sodium Borohydride Hydrolysis

AbstractIn this study, we report that pectin‐supported ruthenium nanoparticles (pectin@Ru0) can be easily prepared at room temperature by a simple and effective method and that they exhibit outstanding catalytic activity in the hydrolysis of sodium borohydride (NaBH4). The structure, oxidation state, morphology, and thermal studies were analyzed using XRD, XPS, SEM, TEM and TGA analysis. The kinetic performance of pectin@Ru0 biocatalyst was evaluated depending on ruthenium loading, NaBH4 concentration, NaOH concentration, temperature, reusability and storage. The pectin@Ru0 biocatalyst containing 2 wt.% Ru0 metal catalyzed the hydrolysis of 50 mM NaBH4+1 wt.% NaOH with 100 % yield. The activation energy (Ea) and the TOF values of the reaction was estimated as 54.7 kJ mol−1 and 53.1 mol H2 (mol Ru0 min) −1 at 30 °C and this is consistent with other previously reported catalysts, making it a remarkable result in comparison. Reusability and catalytic life studies reported that pectin@Ru0 biocatalyst is also highly active and relatively long‐lived catalyst in the hydrolysis of NaBH4 in a slightly basic solution.

Magnetite Fe3O4 nanoparticles impregnated on Chlorella vulgaris microalgae: Its role in obtaining hydrogen from the sodium borohydride-hydrolysis

Recently, the single-celled green freshwater microalgae species “Chlorella vulgaris” has attracted the attention of researchers due to its different usage areas. In particular, research focuses on the technology of obtaining bio‑hydrogen with various techniques. This research involves, for the first time, the use of the microalga Chlorella vulgaris as a bio-supporting material for magnetite Fe3O4 nanoparticles (Fe3O4NPs@Chlorella vulgaris) and the production of hydrogen through catalytic hydrolysis of NaBH4 (sodium borohydride, SB) in the presence of the resulting magnetite nanoparticles. Here, detailed kinetic studies were carried out during the SB-hydrolysis by taking magnetite Fe3O4NPs@Chlorella vulgaris and SB in varying amounts and at varying temperatures, and the activation energy and lifetime of magnetite Fe3O4NPs@Chlorella vulgaris was found to be 23.49 kJ mol−1 and 93,280 mol H2 (mol Fe3O4)−1, respectively. No change in the chemical and physical structure of the biocatalyst was observed during the hydrolysis of SB, so only detailed characterization of microalgae and magnetite Fe3O4NPs@Chlorella vulgaris was performed, and the particle size of the catalyst was calculated as 10.19 ± 2.17 nm. The results showed that these Fe3O4NPs@Chlorella vulgaris, which can be easily separated magnetically and have high catalytic activity, are a “clean” and quite surprising catalyst in terms of hydrogen production.

Behaviour and mechanics of phenolic sorption by novel bio-based graphene derivatives as adsorbents

Phenolic compounds, notorious for their environmental and health hazards, demand efficient removal from wastewater. Our research leads in synthesizing bio-based graphene derivatives from biomass-derived lignin, such as graphene oxide (bGO) and reduced graphene oxide (brGO), and these materials show promise in effectively removing hydrophobic pollutants like phenol and tannic acid. Hence, this study investigated the mechanical and dynamical aspects of their sorptions by bGO and brGO. Both adsorbents demonstrated a comparable adsorption pattern, with enhanced efficiency observed at higher adsorbent dosage, prolonged contact time, neutralized pH solutions, and elevated temperatures. Of note, phenol is removed at a much greater rate (>94%) than tannic acid (>84%) by both adsorbents at a dosage of 180 mg L−1, pH 6.5, 900 min, and 25 °C. The Freundlich model provided the best fit for the isotherm data of both phenol (R2 = 0.99) and tannic acid (R2 = 0.98), while the pseudo-second-order model effectively described the adsorption kinetics of phenol (R2 = 0.99) and tannic acid (R2 = 0.99). The determined activation energy exceeds 5.88 kJ mol−1, affirming the prevalence of physisorption as the dominant mechanism in the adsorption process. Thermodynamic analysis confirmed that the adsorption process is endothermic (ΔH) and occurs spontaneously (ΔG), indicating a random (ΔS) nature. However, the percentage removal plunged considerably after five consecutive adsorption-desorption cycles, attributed to the alterations of active sites on bGO and brGO.

Estimation of Rheological Coefficients of Acacia nilotica Gum: A Versatile Biopolymer for Biomedical and Food Industries

Introduction: Polysaccharides are widely used in the biomedical and food industries as thickening, gelling, emulsifying, hydrating, and suspending agents. Polysaccharides have adequate viscoelastic properties and flow characteristics. The purpose of this study was to determine various rheological parameters of Acacia nilotica (Babool) gum. Methods: Understanding the influence of temperature on rheological properties is quite important for polymeric materials to be considered as pharmaceutical excipients. Thus, a polymeric solution of purified Babool gum was prepared, and the influence of temperature on its rheological behaviour (viscosity and surface tension) was investigated to develop a better understanding of the structural organization of the gum. Furthermore, viscosity, surface tension, temperature coefficient, activation energy, Gibbs free energy, Reynolds number, and entropy of fusion were calculated using the Arrhenius, Gibbs–Helmholtz, Frenkel–Eyring, and Eotvos equations, respectively. Results: The activation energy of the gum was 3.81 ± 0.18 kJ/mol. Changes in entropy and enthalpy were 0.56 ± 0.23 and 4.27 ± 0.81 kJ/mol, respectively. The calculated amount of entropy of fusion was found to be 0.014 ± 0.01 kJ mol−1 K−1. Conclusion: The study outcomes showed that the viscosity and surface tension increased as the temperature decreased. The good rheological properties of Babool gum make it a suitable excipient for its applications in the food and pharmaceutical industries.

Characterization of Monosubstituted Benzene Ices

Aromatic structures are fundamental for key biological molecules such as RNA and metabolites and the abundances of aromatic molecules on young planets are therefore of high interest. Recent detections of benzonitrile and other aromatic compounds in interstellar clouds and comets have revealed a rich aromatic astrochemistry. In the cold phases of star and planet formation, most of these aromatic molecules are likely to reside in icy grain mantles, where they could be observed through IR spectroscopy. We present laboratory IR spectra of benzene and four monosubstituted benzene molecules—toluene, phenol, benzonitrile, and benzaldehyde—to determine their IR ice absorbances in undiluted aromatic ices, and in mixtures with water and CO. We also characterize the aromatic ice desorption rates, and extract binding energies and respective pre-exponential factors using temperature-programmed desorption experiments. We use these to predict at which protostellar and protoplanetary disk temperatures these molecules sublimate into the gas phase. We find that benzene and monosubstituted benzene derivatives are low-volatility with binding energies in the 5220–8390 K (43–70 kJ mol−1) range, which suggests that most of the chemistry of benzene and of functionalized aromatic molecules is to be expected to occur in the ice phase during star and planet formation.

Kinetic modelling and mechanism elucidation of catalyst-free dimethyl terephthalate hydrolysis process intensification by reactive distillation

Polyethylene terephthalate (PET) is a widely used thermoplastic polymer in the packaging and materials industries, and is predicted to have continuous market growth in the future. Methods such as glycolysis and methanolysis of PET have been identified as promising approaches in sustainable chemical recycling of PET. The latter produces dimethyl terephthalate (DMT), which can be easily hydrolyzed to terephthalic acid (TPA) at elevated temperatures and pressures, and further reused for PET production. The aim of this study was to develop a kinetic model for the hydrolysis of dimethyl terephthalate, using the experimental data. Various reaction conditions (temperature, pressure, time) have been investigated and used to calculate the activation energies and reaction rate constants, while the variation in reactor setup with methanol (MeOH) removal was conducted to show its detrimental effect on the efficiency of the reaction and selectivity towards terephthalic acid. The first reaction step of DMT to monomethyl terephthalate (MMT) is relatively irreversible, while the second reaction step of MMT to TPA ceases, as soon as the equilibrium is reached. Highest yields of TPA (76.7 %) were obtained after 40 min at 265 °C, with MeOH removal, and the activation energy was calculated to be 95 and 64 kJ mol−1 for the first and second hydrolysis reaction step, respectively.

Lipophilic EDTA-based ligands in different diluents for the extraction of rare earths: Preliminary results with Nd(III), Dy(III) and Pr(III) in chloride and nitrate media

A separation method for the recovery of neodymium(III) from two different media, chloride and nitrate, by implementing solvent extraction technique with a novel lipophilic diamide derivative of ethylenediamine tetraacetic acid (EDTA), namely 2,2’-N,N′-didecyl-dioxo-N,N′,N″,N″’-tetraazatetratriacontane-N″,N″’-diyl diacetic acid (H2E4C10), has been investigated. Initial screening results demonstrated acceptable solubility (ca. 15 mM) of the diamide in 1,3-diisopropylbenzene (DiPB) and in a 93:7 v:v n-dodecane:n-octanol mixture (DOm) as non-polar diluents. Further investigations aiming at determining operational parameters associated with the befitted extractant systems were conducted at pH ranging from 2 to 4 in chloride and nitrate media. A pH-dependent performance of the proposed systems revealed loading capacity peaking at pH = 3 with the respective values of 1.7 and 2.0 g L−1 in nitrate and chloride media. The extraction efficiency, the distribution coefficients, and the separation factor (E%,D and SF, respectively) were determined for an equimolar mixture of neodymium and two other potential competitive lanthanides, namely dysprosium and praseodymium. The best selectivity was observed in the chloride medium at pH = 4 yielding SFNd/Pr = 1.48 and SFNd/Dy = 2.03. Neodymium-to-extractant stoichiometry was evidenced in chloroform to be 1:1 H2E:Nd at pH = 2. Thermodynamic constants related to the considered extraction equilibrium have been determined by using the Van't Hoff relation and the slope analysis method. It appeared within the selected pH-range that the mechanism of the Nd3+ transfer was strongly influenced by the nature of the diluent. This was illustrated by the enthalpy-driven transfer when Nd3+ was extracted with the H2E-4C10-Dom system (aliphatic diluent) while the transfer became entropy-driven when the extraction was performed with the H2E-4C10-DiPB system (aromatic diluent). The complexation of Nd3+ involved mainly the participation of both the amide and carboxylic functional groups. The transfer of the cation to the organic phase might occur through the formation of the Nd(HE)A2 complex (where A is either a nitrate or a chloride anion), allowing for the lowest associated standard Gibbs free energy of transfer (−28 < ΔG° < −24 kJ mol−1) regardless of the aqueous feed.

Deformation behaviour and microstructure evolution of Ti-2.3Al-2.6Zr alloy in the temperature range of 700–1000 °C

Ti-2.3Al-2.6Zr alloy was hot deformed at temperatures from 700 to 1000 °C and strain rates from 10−2 −30 s−1. The uniaxial compression tests were conducted in vacuum to a true strain of 1 for this alloy. Strain rate sensitivity was calculated from the true stress- true strain data and plotted as contour plots to generate the strain rate sensitivity map. The hot working condition of this model α-Ti alloy was optimized by using the strain rate sensitivity map. The optimized hot workability domains were identified for α-phase as (a) 780–900 °C at strain rate of 10−2 to 0.3 s−1 and (b) 825–900 °C at strain rate of 3–30 s−1. The domain of hot processing condition for β-phase was found at 930–1000 °C for all strain rates. In α-phase domain the strain rate sensitivity was about 0.3, the stress exponent was 4.3 and the activation energy for deformation was 285 kJ mol−1 whereas in β-phase domain the strain rate sensitivity was about 0.34, the stress exponent was 5.3 and the activation energy for deformation was 210 kJ mol−1. These deformation parameters suggest the deformation process to be a dislocation based mechanism. Samples deformed within the high strain rate sensitivity domains showed microstructural features of dynamic recrystallization. In α-phase fine equiaxed recrystallized grains with high angle boundaries were observed. Deformation at 900 °C and 0.01 s−1 resulted in fully recrystallized equiaxed grains in the α-phase, whereas the β-phase showed lamellar grain morphology with very fine recrystallized grains.

Kinetics of Colour, Clarity Changes and HMF Formation in Pear Juice Concentrate During Storage

In terms of providing delicious taste and excellent source of nutritional content, pears are highly consumed fruit all around the world. Pear juice concentrate (PJC) is one of the most frequently used products in the manufacturing processes of beverages, syrup base for canning fruits, vinegar, and wine. Colour, clarity, and the formation of hydroxy methyl furfural (HMF), a mark of Maillard browning reactions, were appraised as quality indices changes of PJC throughout storage. The samples were kept at 47°, 37°, and 27°C for 32 weeks and kinetic criteria were calculated for changes in color, clarity, and the generation of HMF. According to the model of zero-order reaction, the results demonstrated that the quantity of HMF rose linearly with temperature and storage period. The values of clarity and colour were both linearly reduced to align with the zero-order reaction kinetic. The dependence on temperature of the rate constant of the reactions examined and the activation energy values were calculated as 153.14, 93.81 and 61.48 kJ mol-1 for the generation of HMF, clarity, and colour changes with the help of Arrhenius equation.

Solvation structure and thermodynamics for Ln(III), (Ln = Pr, Nd, Tb, and Dy) complexes in phosphonium-based ionic liquids evaluated by Raman spectroscopy and DFT calculation

The coordination states of trivalent praseodymium, neodymium, terbium, and dysprosium complexes in triethyl-n-octylphosphonium bis(trifluoromethylsulfonyl)amide ([P2228][TFSA]) ionic liquid were examined using Raman spectroscopy. In [P2228][TFSA], the concentration dependence of lanthanide (Ln) ions on the Raman spectrum was investigated in the range of 0.24–0.48 mol kg−1 of Ln(III), (Ln = Pr, Nd, Tb, and Dy) in [P2228][TFSA]. Based on classical analysis, solvation numbers n of Ln(III) (Ln = Pr, Nd, Tb, and Dy) in [P2228][TFSA] were determined as 4.80 ± 0.04, 5.08 ± 0.03, 5.15 ± 0.04, and 4.92 ± 0.03, respectively, at 373 K.Based on the temperature dependence of the Raman spectrum measured at temperatures between 298 and 398 K, thermodynamic parameters with ΔisoG, ΔisoH, and ΔisoS for the isomerism of [TFSA]− from the trans- to the cis-coordinated isomer in the bulk and first solvation sphere of the centered Ln3+ (Ln = Pr, Nd, Tb, and Dy) cation in [P2228][TFSA] were evaluated in this study. As indicated by the positive value of ΔisoH(bulk) = 6.86 kJ mol−1, the trans-[TFSA]− was found to be the dominant contributor to enthalpy. In [P2228][TFSA], the value of TΔisoS(bulk) = 7.92 kJ mol−1 was slightly larger than that of ΔisoH(bulk), indicating that cis-[TFSA]− was entropy controlled. Conversely, in the first solvation sphere of the Ln3+ cation, ΔisoH(Ln) became significantly negative, indicating stabilization of cis-[TFSA]− isomers via enthalpic contributions. This result clearly indicates that the cis-[TFSA]− conformer bound to Ln3+ cation is the preferred coordination state of [Ln(III)(cis–TFSA)5]2− in [P2228][TFSA], because ΔisoH(Ln) contributes to a significant decrease in ΔisoG(Ln).Furthermore, DFT calculations using the Amsterdam Density Functional package were used to investigate the optimized geometries and binding energies of [Ln(III)(cis-TFSA)5]2−, (Ln = Pr, Nd, Tb, and Dy) clusters. The bonding energy, ΔEb, was calculated as ΔEb = Etot(cluster) − Etot(Ln3+) − nEtot([TFSA]−), and ΔEb ([Ln(III)(cis-TFSA)5]2−), (Ln = Pr, Nd, Tb, and Dy) were calculated as −4349.2 ± 7.2, −4354.6 ± 7.6, −4278.6 ± 7.2, and −4296.4 ± 7.8 kJ mol−1, respectively. The thermodynamic properties were consistent with the average atomic charges and bond distances of these clusters. Additionally, the highest occupied molecular orbital and lowest unoccupied molecular orbital estimated from DFT methods were consistent with the coordination states of [Ln(III)(cis-TFSA)5]2−, (Ln = Pr, Nd, Tb, and Dy) analyzed by Raman spectroscopy.

A novel and facile oxygen-activated time-temperature indicator with wide temperature monitoring range and good stability based on the laccase-like nanozyme

BackgroundTime-Temperature Indicator (TTI) is an indicator device for real-time monitoring of the thermal history of the product. Due to the enzymatic reactions are affected by both time and temperature, enzymatic TTIs have been extensively studied and developed in recent years. However, enzymatic TTIs contain biologically active molecules (enzymes), which require high storage and use conditions. Most of them are designed to mix the system species together and irreversible reaction is undertaken. Nanozymes are the synthetic nanomaterials with similar biocatalytic functions as natural enzymes, which have extensive applications in analytical chemistry, biosensing, and environmental protection due to their facile synthesis, low cost, high stability and durability. ResultsThis work proposed to replace the natural laccase to laccase-like nanozyme, designed a novel and facile O2-activated time-temperature indicator for the first time. Nanozyme had excellent thermal and storage stability, which could maintain fabulous catalytic activity in the wide temperature range of 10–80 °C and after a long-term storage. Based on the O2 was required to participate in the oxidation of laccase-catalyzed substrates, a squeeze-type O2-activated TTI was designed by controlling O2 in the TTI system. The TTI was activated through extruding the O2-coated airbag ruptured and producing an irreversible color reaction. Combined with a smartphone to extract the chromaticity for portable visual real-time monitoring. Five sets of TTIs were prepared based on the concentration of nanozyme, and the activation energies (Ea) ranging from 28.45 to 72.85 kJ mol−1, which were able to be fitted to products with Ea ranging from 3.45 to 97.8 kJ mol−1 and the monitoring-time of less than 7 days. SignificanceCompared to the traditional enzymatic TTI, the TTIs designed based on nanozyme has the advantages of controlled activation, wider temperature monitor range and good stability. Providing a new approach to the development of real-time monitoring of smart devices.

Adsorption and Catalytic Reduction of Nitrogen Oxides (NO, N2O) on Disulfide Cluster Complexes of Cobalt and Iron-A Density Functional Study.

The reactivity of nitrogen oxide, NO, as a ligand in complexes with [Fe2-S2] and [Co2-S2] non-planar rhombic cores is examined by density functional theory (DFT). The cobalt-containing nitrosyl complexes are less stable than the iron complexes because the Co-S bonds in the [Co2-S2] core are weakened upon NO coordination. Various positions of NO were examined, including its binding to sulfur centers. The release of NO molecules can be monitored photochemically. The ability of NO to form a (NO)2 dimer provides a favorable route of electrochemical reduction, as protonation significantly stabilizes the dimeric species over the monomers. The quasilinear dimer ONNO, with trans-orientation of oxygen atoms, gains higher stability under protonation and reduction via proton-electron transfer. The first two reduction steps lead to an N2O intermediate, whose reduction is more energy demanding: in the two latter reaction steps the highest energy barrier for Co2S2(CO)6 is 109 kJ mol-1, and for Fe2S2(CO)6, it is 133 kJ mol-1. Again, the presence of favorable light absorption bands allows for a photochemical route to overcome these energy barriers. All elementary steps are exothermic, and the final products are molecular nitrogen and water.