Kinetic Constants Research Articles

Oxalic acid capped tungsten oxide nanozyme mimicking peroxidase activity, its synthesis characterization, and kinetic data validation via spectrophotometric studies

The need for parody enzymes has attracted the interest of researchers globally. Nanomaterials have provided promising results as mimic catalysts termed nanozymes (NZMs). This article briefs the peroxidase mimicking behavior of Oxalic acid-capped WO3 nanoparticles (Ox-WO3 NPs), which were hydrothermally synthesized. The peroxidase parodying behavior of the synthesized NZMs was studied for H2O2 as substrate and PPDD-NEDA and TMB as a chromogenic reagent in Phosphate buffer at pH 6.5. The coupled product of PPDD-NEDA showed λmax=480 nm, and the method was linear between 0.2413 and 1.93 mM. The oxidized product of TMB λmax=650 nm was linear in the range of 0.1938–1.9386 mM. Km values corresponding to TMB, and PPDD-NEDA were 0.5308 and 0.3957 mM. Kinetic constants with respect to PPDD-NEDA i.e., Vmax, Kcat, Keff, and Kpow were found to be 0.1913 mM/min, 3.3639 min−1, 8.4999 mM−1 min−1, and 0.4833 min−1. The precision study for intra-day (1.27–2.49 %) and inter-day (1.09–1.52 %) has been calculated. LOD and LOQ of the reaction was found to be 56.34 and 170.73 µM respectively. Characterization of synthesized NPs were carried out with respect to morphology, crystallinity, size, zeta potential and others. The XRD of the sample revealed the crystallite size to be 42.6 nm (Williamson-Hall equation) and 35 nm (Scherrer equation), Crystal structure was identified to be a mixture of monoclinic and orthorhombic as compared with the JCPDS file and the crystallinity of the sample was found to be 79.75 %. The SEM images provided the morphology to be spherical in nature with more aggregation due to lower zeta potential value as recorded by the DLS. The elemental composition by EDS recorded the formation of WO3 NPs. The broad peak of FT-IR spectra between 2900 and 3900 cm−1 confirms the capping of oxalic acid to WO3 NPs.

A novel design of the electrostatic storage ring using quadrupole deflector

A novel electrostatic storage ring (ESR) design was created using an electrostatic quadrupole deflector (EQD) and quadrupole doublet lens (QDL). EQD was used to turn the electron beam 90 degrees in order to create an innovative ESR design. The impact of EQD designs on ESR performance was investigated, and the results showed that the performance of ESR was directly affected by the EQD design. The calculations showed that increasing the EQD diameter by 20% led to an enhancement in the electron beam dimensions by 88% for ∆x and 44% for ∆y for the initial angle of the electron beam α = 0.2°. Also, the design achieved its goal of keeping kinetic energy constant, where for an initial kinetic energy of 1000 eV, the difference between the energy of the injected electron beam and the emerging electron beam from the ESR is approximately 1–5 eV, i.e., despite changing the diameter of the EQD, the dimensions of the electron beam improve and the kinetic energy remains constant.

Synergistic interaction of S-type heterojunction and sulfur vacancies in g-C3N5@Sv-ZnIn2S4 composites: Simultaneous promotion of complete 2,4-dichlorophenol mineralization and Cr(VI) reduction

Constructing efficient heterojunction photocatalysts is an effective measure for degrading pesticides and reducing heavy metals. In this study, g-C3N5@Sv-ZnIn2S4 (g-C3N5@Sv-ZIS) composite with large specific surface area has been successfully prepared by a simple low-temperature water bath method. The g-C3N5@Sv-ZIS composite showed complete mineralization of 2,4-dichlorophenol (2,4-DCP) and reduction of Cr(VI) within 60 min. The results of electron spin resonance spectroscopy, photoelectrochemical characterization, and energy band structure calculations indicated the formation of an S-type heterojunction at the interface of g-C3N5 and Sv-ZIS. In situ XPS analysis showed the transfer of photogenerated charges from g-C3N5 to Sv-ZIS. The molecular structure of 2,4-DCP was analyzed using frontier molecular orbital and electrostatic potential calculations. The possible degradation pathways of 2,4-DCP were proposed based on liquid chromatography– mass spectrometry results. Biotoxicity simulations of the intermediates revealed decreased toxicities. Furthermore, The kinetic rate constant of CZSv-200 for degrading 2,4-DCP and Cr(Ⅵ) in deionized water was approximately 2.20, 3.10 and 2.46, 4.03 times higher than that in lake and sewage plant water, respectively. The composites designed in this study provide reliable theoretical support for the removal of composite pollutants.

Assessing excimer far-UVC (222 nm) irradiation for advanced oxidation processes: Oxidants photochemistry and micropollutants degradation

The KrCl* excimer lamp (UV222) is a promising alternative of low-pressure mercury lamp (UV254) for UV-based advanced oxidation processes (UV-AOPs), because it is mercury-free and has high photon energy. But there lacks a comprehensive assessment of UV222-AOPs based on different radicals. Herein, the properties (e.g., oxidant decay and innate radical quantum yield), and micropollutant degradation, were comprehensively studied for representative oxidants (i.e., hydrogen peroxide, persulfate (PDS), monochloramine, and free active chlorine (FAC)) under UV222 irradiation. UV222 outperformed UV254 for the activation of oxidants with 2.6–14.4 times fluence-based kinetic constant (kF). The main reason of enhanced activation varied with oxidants: higher UV absorbance for H2O2, higher innate quantum yield for monochloramine and FAC, and both reasons for PDS. Overall, PDS was the optimum oxidant under UV222 for the degradation of 8 representative micropollutants because of effective promotion of radical formation, as confirmed by radical competitive kinetics and modeling simulations. In real water, UV222/PDS still show advantages than UV254/PDS in terms of micropollutant elimination efficacy (3.2–5.3 times) and energy consumption (33.9 %-57.6 % lower) though it was more inhibited by water constituents via competing for UV222 photons. This study fills gaps in photochemistry knowledge and will facilitate engineering practice of UV222-AOPs.

Cell-free expression and biochemical characterization of polysaccharide-synthesizing glycosyltransferases

Polysaccharides like cellulose and hyaluronan are synthesized by membrane-bound family-2 glycosyltransferases (GTs) that play critical structural, metabolic, or functional roles in cells. Though GT-2 family has the maximum number of deposited gene sequences, the biochemistry is poorly understood due to enzyme production challenges. Here, we developed a cell-free expression (CFE) protocol to produce two GT-2 family representative cellulose synthase (PttCesA8 from Populus tremula x tremuloides) and hyaluronan synthase (SeHAS from Streptococcus equisimilis). The CFE products were obtained as reconstituted proteoliposomes directly at high yields and short processing times compared to other approaches. Enzyme expression was confirmed using SDS-PAGE and immunoblotting, while integration of GTs into lipid layers was observed using cryogenic electron microscopy. Both GTs were catalytically active with Michalis-Menten kinetic constants, Km for PttCesA8, was 295.8 µM, and SeHAS was 321.51 µM (toward UDP N-Acetyl Glucosamine) and 207.88 µM (toward UDP Glucuronic Acid), respectively, and with UDP inhibiting both GTs. Mutation of conserved residues in SeHAS also confirmed the importance of lysine-139, glutamine-248, and threonine-283 residues in hyaluronan biosynthesis. In summary, CFE methods enable expression of polysaccharide-synthesizing enzymes as proteoliposomes at high yields with relative ease for rapid biochemical and structural characterization studies.

Hydrogen bond-induced supramolecular self-assembly strategy to fabricate ultra-dispersed Cu-loaded porous tubular graphitic carbon nitride with rich nitrogen vacancies and CuNx sites for efficient photo-Fenton catalysis

The low utilization of visible light and easy recombination of charge carriers of graphitic carbon nitride (CN) restrain its application as photo-electron donor and metal site support in photo-Fenton system. Herein, a hydrogen bond-induced supramolecular self-assembly strategy was created to fabricate an ultra-dispersed Cu-loaded porous tubular CN composite (CA-Cu/TCN) by the hydrothermal–pyrolysis method with citric acid (CA) as initiator and chelating agent. CA-Cu/TCN with rich nitrogen vacancies (NVs) and abundant ultra-dispersed CuNx sites exhibited narrow bandgap, favorable visible light absorption capability, and high separation and transfer efficiency of charge carriers. CA-Cu/TCN effectively catalyzed the activation of H2O2 for generating abundant reactive oxygen species under visible light irradiation, contributing to efficient degradation of ciprofloxacin (CIP) with removal rate of 95.9 % and kinetic rate constant of 0.0948 min−1. The superior catalytic activity of CA-Cu/TCN can be ascribed to the effective transport of photogenerated electrons, high specific surface area, atomically dispersed Cu species, and enriched surface NVs. The mechanism of photo-Fenton catalytic degradation of CIP and possible degradation pathways were proposed as the dominant role of 1O2. Toxicity evaluation of CIP and intermediates indicated that the degradation of CIP was a gradual detoxification process. This work offers a novel self-assembly strategy to design and synthesize highly active and sustainable visible light-driven photo-Fenton catalysts for effectively degrading organic pollutants.

Prototype Alarm Integrating Pulse-Driven Nitrogen Dioxide Sensor Based on Holey Graphene Oxide/In2O3.

NO2 seriously threatens human health and the ecological environment. However, the fabrication of highly sensitive NO2 sensors with rapid response/recovery rates, low detection limits, and ease of integration remains a challenge. Herein, benefiting from the fast carrier transfer and rich active sites, holey graphene oxide (HGO) was adopted to functionalize the In2O3 nanosheet to construct NO2 gas sensors. Characterization and theoretical calculations established the merits of HGO decoration in the NO2 sensing. The optimal sample, 0.5 wt % HGO/In2O3-sheet, exhibited superior sensing properties, resulting in a 1.37-fold improvement in response to 1 ppm of NO2 compared to the GO/In2O3 counterpart. Gas-sensing kinetics analysis revealed its lower activation energy and higher kinetic rate constants. Importantly, pulsed-temperature modulation was employed to decouple the gas adsorption from surface activation processes, achieving an ultrahigh response of 2776 to 1 ppm of NO2 for the 0.5 wt % HGO/In2O3-sheet sensor. Compared to the isothermal mode, this strategy enhanced the response value by 1.6 times, reduced the response/recovery time by 33%/70%, and enabled the detection of NO2 concentrations as low as 1 ppb. Finally, an NO2 monitoring alarm system based on the 0.5 wt % HGO/In2O3-sheet sensor with pulsed-temperature modulation was demonstrated for hazard warnings.

Sustainable synthesis of ZnO and FexOy nanoparticles and their nanocomposite ZnFe2O4: Comprehensive characterization and applications in antioxidant activity and antibiotics degradation efficiency

This study focuses on developing and evaluating eco-friendly nanoparticles, specifically FexOy NPs, ZnO NPs, and a ZnFe2O4 nanocomposite (NC), for potential applications in environmental remediation and biomedicine. The nanoparticles were synthesized and characterized using X-ray diffraction (XRD), which revealed their crystalline structures with sizes of 20.3 nm for FexOy NPs, 22.1 nm for ZnO NPs, and 10.9 nm for ZnFe2O4 NC. Fourier-transform infrared (FTIR) spectroscopy identified functional groups, while UV–visible spectroscopy determined band gap energies of 2.35 eV, 3.38 eV, and 2.68 eV for FexOy NPs, ZnO NPs, and ZnFe2O4 NC, respectively. Morphological analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that FexOy NPs have cubic, hexagonal, and tetragonal forms, ZnO NPs are hexagonal nanorods, and ZnFe2O4 NC has a hexagonal-faced cubic structure. Antioxidant activity, assessed through the DPPH assay, revealed that ZnFe2O4 NC had the highest potency. Additionally, under sunlight irradiation, ZnFe2O4 NC demonstrated superior degradation of the antibiotic cephalexin (96 % within 30 min) compared to FexOy NPs (58.2 %) and ZnO NPs (52 %), with respective kinetic rate constants of 0.109 min−1, 0.029 min−1, and 0.025 min−1. These results highlight the nanoparticles’ potential for environmental and biomedical applications.

Facile C[sbnd]H aryl and O[sbnd]H bonds activation at dirhenium site of [Re2(CO)8(THF)2] complex

The activation of small molecules is a topic of great interest and previously we reported on the easy activation of different types of EH bonds at the dinuclear complex [Re2(CO)8(THF)2] (1) where labile THF molecules coordinate to adjacent rhenium(0) atoms. Here we extend the reactivity of 1 reporting on the oxidative addition of benzene and toluene at room temperature to give [Re2(μ-H)(μ-κC-Ar)(CO)8], Ar = −C6H5 (2) and −C6H4Me (3). Compound 3 is a new example of μ-κC-Ar dinuclear rhenium complex and has been obtained as para and meta isomers (3a,b). It is known from the literature that 2 can activate arenes and heteroarenes via reductive elimination of benzene and oxidative addition of CH bonds to the dinuclear fragment. Here we have studied the reaction of 2 with C6D6 and H2CC(H)Ph and determined the kinetic constants by 1H NMR (1.4 × 10−5 s−1 at 308 K and 1.1 × 10−5 s−1 at 298 K, respectively). The results indicate that the rate-determining step of the reaction is the reductive elimination of benzene, while the oxidative addition is fast. Water and methanol react with 1 in toluene at room temperature to give the hydroxo and methoxo hydrido complexes [Re2(μ-H)(μ-OR)(CO)8], RH (5) and CH3 (6). On reacting 1 with water in deuterated toluene, and monitoring by 1H/2H NMR, a preferential deuteration of the hydride site to give [Re2(μ-D)(μ-OH)(CO)8] is evidenced. This finding excludes the oxidative addition of water on the dinuclear “Re2(CO)8” fragment while supporting a heterolytic addition of water via protonation at the µ-κC-tolyl group, elimination of toluene and addition of OH−. Single crystal X-ray diffraction analyses have been performed for complexes 3a, 5 and 6 and their solid state structures have been determined. In particular, the crystal structure of 5 results in a new polymorphic form (5b) and it is discussed in comparison with the already known one (5a).

Boosting photocatalytic efficiency and nonlinear optical response of graphitic carbon nitride by infusing carbon nanotubes

Nanostructured materials are widely studied for their light-driven physical and chemical processes, which are key to their potential in photophysical applications. We introduce a one-pot solid-state pyrolysis technique for the synthesis of graphitic carbon nitride/carbon nanotube (g-C3N4/CNT) composites. The formation of the composite was characterized through X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron spectroscopy. Notably, UV-vis diffuse reflectance spectroscopy indicated a reduction in the bandgap of pure g-C3N4 from 2.6 eV to 2.35 eV with the incorporation of 0.5 wt% CNT. The nonlinear optical transmission of the samples was analyzed at 532 nm using the open-aperture Z-scan technique employing 5 ns laser pulses, revealing a twelve-fold increase in the two-photon absorption coefficient (b) for g-C3N4/CNT0.5 compared to pristine g-C3N4. Remarkably, g-C3N4/CNT0.5 showed enhanced photocatalytic efficiency in degrading bisphenol A (BPA), with the kinetic constant (k) being ten times higher than that of pure g-C3N4. The improved photocatalytic performance of g-C3N4/CNT0.5 is attributed to the presence of CNTs, which act as effective electron acceptors and transfer channels, significantly enhancing the separation of photogenerated charge carriers in g-C3N4, as evidenced by the decreased intensity in the photoluminescence spectrum.

Phosphorus heteroatom doped BiOCl as efficient catalyst for photo-piezocatalytic degradation of organic pollutant and unveiling the mechanism: Experiment and DFT calculation

A novel phosphorus heteroatom doped bismuth oxychloride (P-BiOCl) catalyst was synthesized and the photo-piezocatalytic degradation of rhodamine B dye performances were explored under the ultrasound vibration and light illumination. The P-BiOCl exhibited excellent photo-piezocatalytic degradation activity, such as an ultra-high reaction kinetic rate constant of 0.3961 min−1, efficient degradation efficiency (94.7 % within 8 min) and excellent stability compared to solely piezocatalysis and photocatalysis. More impressively, these outstanding performances of P-BiOCl exceeded pure BiOCl and most other catalytic materials systems. The relevant experimental and density functional theory (DFT) calculation results were exhibited to clarify enhanced photo-piezocatalytic mechanism. The introduction of P heteroatom could reduce the bandgap of BiOCl, modulate electronic structure and charge redistribution, provide novel electron channel to promote electron transfer and restrain charge carriers recombination. Additionally, P-doped could also enhance the adsorption of oxygen and water molecules, promote intrinsic catalytic activity, leading to the increased production of active free radicals ·O2– and ·OH, thus significantly boosting the efficiency of organic pollutant degradation. This work provides a comprehensive understanding of heteroatom doping enhancing photo-piezocatalytic activity and presents a potential new strategy for designing highly efficient catalysts for wastewater treatment.

Heterogeneous toluene nitration with mixed acid in microreactors: Reaction regime, characteristics and kinetic models

It is critical for reactor design and process safety to determine the reaction kinetics for toluene nitration. Herein, a continuous-flow platform based on capillary microreactors was established. First, reaction regimes for toluene nitration and its consecutive side reaction (MNT (mononitrotoluene) nitration) were identified. On this basis, the influence of process parameters on conversion of toluene, selectivity of MNT and DNT (dinitrotoluene) and their isomer distribution were meticulously examined, including molar ratio of reactants, sulfuric acid strength, reaction temperature, and residence time. Subsequently, reaction kinetic models coupled with mass transfer were developed, allowing the simultaneous kinetic determination for toluene nitration and MNT nitration. It was found that the logarithm of the observed kinetic constant is proportional to the sulfuric acid strength. The kinetic parameters under 72.7 to 80.1 wt% sulfuric acid strengths were obtained. The outcomes provide a basis for process intensification and optimization of toluene nitration as well as other similar aromatics.

Persistent ultraviolet luminescence and photocatalytic properties of SiO2-Zn2SiO4:Ga,Pb nanoparticles

Persistent phosphors possess unique afterglow optical properties. In this paper, a class of ultra-violet (UV) persistent luminescence nanoparticles were developed for catalytic photodegradation applications. UV persistent luminescence nanoparticles of SiO2-Zn2SiO4:Ga and SiO2-Zn2SiO4:Ga,Pb were successfully synthesized by using a mesoporous template method. The UV persistent luminescence intensity of SiO2-Zn2SiO4:Ga at 405 nm was enhanced up to ca. 3.5 times by co-doping with Pb2+ (396 nm), along with longer persistent luminescence duration. The photodegradation results indicate that it is useful to introduce UV persistent luminescence property into SiO2-Zn2SiO4:Ga,Pb to obtain enhanced catalytic activity of SiO2-Zn2SiO4 with a bigger catalytic oxidation reaction kinetic constant (up to ∼4 times). This kind of UV persistent catalysis strategy may become a potential feasible method for better catalytic photodegradation activity. The UV persistent photocatalyst has potential applications in the photooxidation of organic molecules in high chroma and/or turbidity aqueous systems.

Enhanced Fenton-like process on Co9S8 catalyst with Mixed-Valence Cobalt(0)/Cobalt(Ⅱ)

Peroxymonosulfate (PMS)-based Fenton-like reactions have great potential to revolutionize wastewater treatment, but achieving highly efficient decontamination at low chemical input remains extremely challenging. In this study, a carbon carrier-supported Co9S8 catalyst with Mixed-Valence Cobalt(0)/Cobalt(Ⅱ) was prepared, which enables 70.72 % PMS decomposition-rate and complete, highly efficient tetracycline (TC) removal. Through the cyclic conversion pathways of polyvalent cobalt and the auto-decomposition of PMS, which produced SO4•-, 1O2, •OH, and high-valence metals, the material’s efficiency in degrading TC through PMS activation was effectively enhanced (99.92 %). S2-, as one of the active sites, not only promotes the participation of Co3+/Co2+/Co0 in the generation of reactive oxygen species but also significantly facilitates electron transfer to further increase the catalytic reaction rate. Through metal-chelating agents, it is illustrated that Co2+ directly activates PMS to produce reactive oxygen species (ROS), while Co3+ promotes cycling. The normalized kinetic constant of Co9S8/Co-C (105.6 min−1M−1) was even four times larger than that of Co9S8 (26.4 min−1M−1). Co9S8/Co-C exhibited rapid degradation over a wide pH range and extensive cycling experiments, demonstrating its versatility and stability in various environments. Possible degradation pathways were speculated using liquid chromatography-mass spectrometry (LC-MS). Toxicological evaluations and mung bean germination toxicity tests indicated that the Co9S8/Co-C+PMS system effectively reduced toxicity. It enables the complete degradation of TC while remarkably reducing the toxic intermediates, ensuring that the catalyst is suitable for wastewater treatment applications.

A crystallinity control strategy for controllable Heterogeneous-Homogeneous reaction and catalytic performance in wet-mechanochemical synthesized FeS2 Fenton system

In heterogeneous Fenton system, the Heterogeneous-Homogeneous reaction type induced by surface-bonded or dissolved catalytic center plays a vital role in determining Fenton performance. However, how to directionally control the reaction type with facile method still remains challenging. Herein, a novel crystallinity control strategy based on wet-mechanochemical synthesis combined with heat-treatment was applied to synthesize FeS2 nanoparticles with different crystallinity. The different crystalline FeS2 based Fenton system exhibited superior sulfamethoxazole removal performance at wide pH range (5.6–11) with •OH as dominating reactive oxygen species. The relative degradation contribution of homogeneous and heterogeneous Fenton reaction was semi-quantitatively evaluated, and the relationship between crystallinity indexes of FeS2 and degradation kinetic constants was established. It’s found that FeS2 crystallinity was directly correlated with its degradation efficiency, which first increased and then declined with crystallinity increasing. Crystallinity control strategy effectively determined dominating reaction type (homogeneous or heterogeneous) and further regulated catalytic performance in FeS2 Fenton system based on the interaction of specific surface area and Fe2+ dissolution ability. This work provides a novel crystallinity control strategy to build a correlative bridge among crystallinity, dominating reaction type and catalytic performance in FeS2 Fenton system.

Could Olympic Gels of Polystyrene be Produced by ARGET ATRP From Bifunctional Initiators?

The kinetics of gelation in the Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) of styrene, using a bifunctional initiator and no crosslinking agents are investigated. By applying the method of moments, we develop a system of differential equations that accounts for the formation of polymer rings. The kinetic rate constants of this model are optimized on the experimentally determined kinetics, varying the reaction temperature and ethanol fraction. Subsequently, we explore how variations in the amounts of catalyst, initiator, and reducing agents affect the simulated equilibria of ARGET ATRP, the emergence of gelation, and the swelling properties of the resulting networks. These findings suggest that favoring ring formation enhances the gelation phenomenon, supporting the hypothesis that the networks formed under the reported reaction conditions are olympic gels.

Constructing interfacial electric field with rich oxygen vacancy modulated heterojunction FeVO4-MgZnAl LDH for enhanced photocatalytic degradation of doxycycline

FeVO4 nanorods were synthesized and integrated with plate-like MgZnAl layered double hydroxide (MZA LDH) using a combination of sonochemical coprecipitation and hydrothermal methods. The resulting FeVO4-MgZnAl LDH nanocomposites (NCs) were engineered to enhance photocatalytic performance through an S-scheme charge transfer mechanism. These NCs exhibited exceptional photocatalytic activity, achieving 93.7 % degradation of doxycycline (DXY) which is significantly outperforming its counterparts, FeVO4 (29.8 %) and MgZnAl LDH (49.8 %). Detailed analysis using scavenging tests and electron spin resonance (ESR) analysis confirmed that the photoexcited charges follow the S-scheme pathway, leading to the generation of hydroxyl (•OH) and superoxide (O2•⁻) radicals. This mechanism remarkedly improves the catalytic efficiency of FeVO4-MZA NCs with a kinetic rate constant of 4–9 times higher than those of its individual components. The photocatalyst's were comprehensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–vis-DRS), photoluminescence (PL) spectroscopy, and electrochemical impedance spectroscopy (EIS). The FeVO₄-MZA NCs demonstrated remarkable stability and reusability, indicating their suitability for large-scale water treatment applications. Additionally, the non-toxic nature of FeVO4-MZA NCs, coupled with effective charge carrier separation and reduced recombination rates, establishes them as highly efficient photocatalysts for the removal of pharmaceutical contaminants from aquatic systems and paves a way for manufacturing innovation.

Influence of Rheological Modifications on Primary Network Chemical and Structural Cure Kinetics for an Interpenetrating Polymer Network Resin.

The development of non-contact in situ techniques for monitoring cure kinetics has the potential to greatly improve both resin formulation and processing. We have recently shown that low-frequency Raman spectroscopy is a viable method for assessing resin structural cure kinetics and complements the traditional chemical conversion determined from the fingerprint region of the spectrum. In this work, we further evaluate the relationship between structural and chemical conversion by investigating two chemically identical yet rheologically different interpenetrating polymer network resin formulations. Rheological analysis demonstrates a relationship between structural conversion and storage modulus, which is not observed in the chemical conversion data. We show that one can produce master cure kinetics curves with comparable kinetic constants using both the chemical and structural conversion methodologies. Parametric analysis of the structural conversion, chemical conversion, and photorheological conversion was combined with a semi-empirical model for the storage shear modulus as a function of the extent of cure.

Electro-, photo-, and photoelectrochemical degradation of chloramphenicol on self-doping Ti nanotubes.

In this work, the photo-, electro-, and photo-electro-oxidation of chloramphenicol was investigated. The photo-experiments were carried out with different irradiation sources (an ultraviolet and a simulated solar source) using self-doped titanium nanotubes (SDTNT), a very promising and innovative material that deserves further investigations in the degradation of different pollutants. The photo-electrooxidation (j = 15mAcm-2) under simulated solar irradiation presented the best efficiency, with ca. 100% degradation and kinetic constant of k = 0.04427min-1. The FTIR analysis demonstrated a structural modification of the standard molecule occurred for all conditions used, suggesting a modification in functional groups responsible for the biological activity. Furthermore, the TOC analysis showed a significant mineralization of the pollutant (66% from the initial concentration). In addition, both photo-electrooxidation approaches have demonstrated a positive value of S, where the simulated solar irradiation reached the highest value S = 0.6960. The experimental results pointed out evidence that the methodology employed herein for chloramphenicol degradation is greatly interesting and the photo-electrooxidation under simulated solar irradiation is a promising approach for this purpose.

Effect of Cr Additions on the Coarsening Resistance of β′ Precipitates in Ferritic Fe–Ni–Al Alloys

The effect of Cr additions ON the coarsening of β′(NiAl) precipitates in (Fe,Cr)‐α matrix is studied using Fe–10%Ni–15%Al–15%Cr (FAN15Cr) and Fe–10%Ni–15%Al–22%Cr (FAN22Cr) alloys. Specimens are homogenized and subsequently aged at 850, 900, and 950 °C for different periods of time. The characterization is carried out with conventional and high‐resolution scanning electron microscopy, transmission electron microscopy, and Vickers hardness tests. Results indicate that the addition of Cr leads to an increase in the activation energy and the coarsening kinetics at high temperatures. The precipitate morphology during aging evolves from spheres with a random distribution, followed by cuboids aligned in preferential orientations and the formation of clusters. As aging progresses further, the morphology changes to semirounded precipitates with a polyhedral surface as revealed by the etching process. Transmission electron microscopy results reveal the formation of a dislocation network indicating a state of semicoherency in the precipitate–matrix interface. The activation energy for the coarsening process is determined from the coarsening kinetic constants. While the activation energy for the coarsening in FANCr15 is close to similar alloys, the value for FAN22Cr is unusually high and probably related to the dislocation networks observed.