Solvent Research Articles

Dependency of fentanyl analogue protomer ratios on solvent conditions as measured by ion mobility-mass spectrometry.

Recently, our group has shown that fentanyl and many of its analogues form prototropic isomers ("protomers") during electrospray ionization. These different protomers can be resolved using ion mobility spectrometry and annotated using mobility-aligned tandem mass spectrometry fragmentation. However, their formation and the extent to which experimental variables contribute to their relative ratio remain poorly understood. In the present study, we systematically investigated the effects of mixtures of common chromatographic solvents (water, methanol, and acetonitrile) and pH on the ratio of previously observed protomers for 23 fentanyl analogues. Interestingly, these ratios (N-piperidine protonation vs. secondary amine/O = protonation) decreased significantly for many analogues (e.g., despropionyl ortho-, meta-, and para-methyl fentanyl), increased significantly for others (e.g., cis-isofentanyl), and remained relatively constant for the others as solvent conditions changed from 100% organic solvent (methanol or acetonitrile) to 100% water. Interestingly, pH also had significant effects on this ratio, causing the change in ratio to switch in many cases. Lastly, increasing conditions to pH ≥ 4.0 also prompted the appearance of new mobility peaks for ortho- and para-methyl acetyl fentanyl, where all previous studies had only showed one single distribution. Because these ratios have promise to be used qualitatively for identification of these (and emerging) fentanyl analogues, understanding how various conditions (i.e., mobile phase selection and/or chromatographic gradient) affect their ratios is critically important to the development of advanced ion mobility and mass spectrometry methodologies to identify fentanyl analogues.

Simultaneous determination of 10 quaternary ammonium salt bactericides in oral care products by high performance liquid chromatography-evaporative light-scattering detection

Quaternary ammonium salt bactericides are broad-spectrum bactericides often used in oral care products because of their high antibacterial efficacy, strong penetration, and low toxicity. However, the excessive use of quaternary ammonium salt bactericides may cause contact dermatitis, scalding poisoning, and even death. Existing methods to determine quaternary ammonium salt bactericides are unable to meet current requirements owing to the lack of determination components. Therefore, establishing a simple and accurate method for the simultaneous detection of more quaternary ammonium salt bactericides is necessary. In this study, a method that couples sample pretreatment with high performance liquid chromatography-evaporative light-scattering detection (HPLC-ELSD) was developed for the simultaneous determination of quaternary ammonium salt bactericides in oral care products, including dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, benzethonium chloride, tetradecyl trimethyl ammonium chloride, tetradecyldimethylbenzylammonium chloride, N-hexadecyltrimethylammonium chloride, benzyldimethylhexadecylammonium chloride, trimethylstearylammonium chloride, stearyldimethylbenzylammonium chloride, and docosyltrimethylammonium chloride. Some of these bactericides do not absorb ultraviolet light, so a universal evaporative light-scattering detector was used owing to testing cost and stability concerns. The paste samples contained thickening agents, which are highly soluble in water but insoluble in organic solvents; these agents can seriously affect the results of sample pretreatment and damage the chromatographic column. Hence, sample dehydration was necessary. In this study, four dehydration methods were compared. Anhydrous sodium sulfate (Na2SO4) was selected, and the amount of Na2SO4 was optimized. Based on the solubility of the 10 target compounds and extraction efficiency, three extraction solvents were compared, and ethanol was selected. Ultrasonic extraction was the primary extraction process used in this study. The effects of different ultrasonication times, temperatures, and powers on the extraction recoveries were also investigated. Ultimately, the optimized conditions were as follows: extraction of the dehydrated paste and powder samples using ethanol at room temperature (25 ℃) for 20 min under 100 W ultrasound power, and dilution of the liquid sample with ethanol. After extraction, the samples were separated on an Acclaim Surfactant column (150 mm×4.6 mm, 5 μm) with 50 mmol/L ammonium acetate aqueous solution (pH=5.5) (A) and acetonitrile (B) as mobile phases. The gradient elution program were as follows: 0-5.0 min, 75%A-35%A, 5.0-15.0 min, 35%A-20%A, 15.0-20.0 min, 20%A, 20.0-21.0 min, 20%A-75%A, 21.0-25.0 min, 75%A. An external standard method was used for quantitative determination. The 10 compounds were analyzed within 25 min. Linear equations, correlation coefficients, and linear ranges were obtained by analyzing a series of mixed standard working solutions. The limits of detection (LODs, S/N=3) and quantification (LOQs, S/N=10) of the 10 components were determined. Stearyldimethylbenzylammonium chloride and docosyltrimethylammonium chloride showed good linear relationships in the range of 10-200 mg/L, while the other compounds demonstrated good linear relationships in the range of 5-100 mg/L. In all cases, correlation coefficients (R2) of no less than 0.9992 were obtained. The LODs and LOQs were in the range of 1.42-3.31 mg/L and 4.25-9.94 mg/L, respectively. Ten analytes were spiked in blank matrices, such as toothpaste (paste), mouthwash (liquid), and dentifrice powder (powder) at three levels, and the recoveries and precisions were calculated. The average recoveries were 87.9%-103.1%, and the corresponding relative standard deviations (RSDs) did not exceed 5.5% (n=6). The developed method was used to detect 109 oral care products. Benzyldimethylhexadecylammonium chloride and stearyldimethylbenzylammonium chloride revealed high detection rates. Moreover, the amount of stearyldimethylbenzylammonium chloride in one toothpaste sample exceeded regulatory requirements. Given its advantages of good precision and accuracy, the developed method is suitable for the quantitative analysis of the 10 aforementioned compounds in typical oral care products. The study findings can serve as a reference for the quality and safety monitoring of oral care products.

Solid-Phase Synthesis of Well-Defined Multiblock Copolymers by Atom Transfer Radical Polymerization.

Solid-phase polymer synthesis, historically rooted in peptide synthesis, has evolved into a powerful method for achieving sequence-controlled macromolecules. This study explores solid-phase polymer synthesis by covalently immobilizing growing polymer chains onto a poly(ethylene glycol) (PEG)-based resin, known as ChemMatrix (CM) resin. In contrast to traditional hydrophobic supports, CM resin's amphiphilic properties enable swelling in both polar and nonpolar solvents, simplifying filtration, washing, and drying processes. Combining atom transfer radical polymerization (ATRP) with solid-phase techniques allowed for the grafting of well-defined block copolymers in high yields. This approach is attractive for sequence-controlled polymer synthesis, successfully synthesizing di-, tri-, tetra-, and penta-block copolymers with excellent control over the molecular weight and dispersity. The study also delves into the limitations of achieving high molecular weights due to confinement within resin pores. Moreover, the versatility of the method is demonstrated through its applicability to various monomers in organic and aqueous media. This straightforward approach offers a rapid route to developing tailored block copolymers with unique structures and functionalities.

Solvent Effect for the Structural Control of Molecular Architectures Consisting of Trinuclear Ruthenium Clusters and Ligands at the HOPG Surface.

The molecular architecture of a triruthenium complex and 1,4-di(4-pyridyl)benzene on highly oriented pyrolytic graphite was investigated by drop-casting mixed tetrahydrofuran and methanol solutions. Atomic force microscopy revealed the formation of one-dimensional molecular wires on highly oriented pyrolytic graphite after heating the mixed tetrahydrofuran solution, whereas large ring structures were formed in the methanolic solution. It was found that the molecular architectures composed of triruthenium complexes and 1,4-di(4-pyridyl)benzene strongly depend not only on the temperature of the solution but also on the organic solvents. The formation of the molecular architecture was supported by the ultraviolet-visible absorption spectra of the mixed solution and the electrochemical responses of the deposited film.

Intrinsic Permanent Shape Reconfigurable Semicrystalline Biopolyester Thermoset.

Catalyst-free, volatile organic solvent (VOC)-free synthesis of biobased cross-linked polymers is an important sustainable feature in polyesterification. To date, these polyesters have been extensively studied for their fundamental sustainability across various uses. The ultimate potential sustainability for these materials, however, is constrained to static structural parts due to their intractable rigid three-dimensional (3D) network. Here, we reveal intrinsic dynamic exchangeable bonds within this type of cross-linked semicrystalline network, poly(1,8-octanediol-co-1,12-docanedioate-co-citrate) (PODDC), enabling permanent shape reconfigurability. Annealing at slightly above melting-transition temperature (Tm) allows for shape reconfigurability up to nine times, comparable in performance to the existing bond-exchange systems. No reagents are involved from synthesis to shape reconfiguration, suggesting an exciting feature exhibited by this sustainable cross-linked material without the need for further chemical modification. We further extend this benefit of reconfigurability to enable flexible shape design in a smart shape-memory polymer (SMP), showing it as one of its potential applications. After its applications, it can undergo hydrolytic degradation. We envision that such multifaceted sustainability for the material will attract interest in environmentally friendly applications such as fabricating external part of soft robots and shape-morphing devices with reduced environmental impact.

Mining electronics waste: Experimental and computational mechanistic insights into organic aqua regia as an extraction method

In the previous decade, organic aqua regia (OAR) was discovered as a mixture of pyridine and thionyl chloride that has been observed to surprisingly yet notably selectively dissolve precious metals, dissolution‐resistant gold. Given the novel combination is two common organic solvents, it has immense potential to contribute to a circular economy of metal recycling, economically and environmentally. The underlying mechanisms behind its metal dissolution and interesting properties are not well‐understood. Using both the original mixture and derivatives, the role of each OAR reagent was analyzed in the dissolution of gold to begin probing and illuminating the novel mechanism. Three mechanisms were proposed: radical based, oxidant and ligand, and Lewis acid and base. Computational means were used to propose possible mechanisms. Experiments were used to explicate the possible mechanisms. Discoveries from the original publication were used to verify assessments and suggest future areas of study for further confirmation. Based on the finding that 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) does not significantly affect the amount of gold dissolved, the radical mechanism was dismissed. Findings from experiments replacing pyridine with its derivatives disproved the likelihood of the oxidant and ligand mechanism. Finally, with the support of proton nuclear magnetic resonance (1H NMR) and other characterization techniques, the Lewis acid and base mechanism was determined to be the most probable mechanism of OAR. The mechanistic findings reported herein will pave the way for continued understanding of the mechanism to be exploited and optimized for other metals and organometallic chemistry in the recycling of metals.

Influence of Solvent Polarity on the Conformer Ratio of Bicalutamide in Saturated Solutions: Insights from NOESY NMR Analysis and Quantum-Chemical Calculations

The study presents a thorough and detailed analysis of bicalutamide’s structural and conformational properties. Quantum chemical calculations were employed to explore the conformational properties of the molecule, identifying significant energy differences between conformers. Analysis revealed that hydrogen bonds stabilise the conformers, with notable variations in torsion angles. Conformers were classified into ‘closed’ and ‘open’ types based on the relative orientation of the cyclic fragments. NOE spectroscopy in different solvents (CDCl3 and DMSO-d6) was used to study the conformational preferences of the molecule. NOESY experiments provided the predominance of ‘closed’ conformers in non-polar solvents and a significant presence of ‘open’ conformers in polar solvents. The proportions of open conformers were 22.7 ± 3.7% in CDCl3 and 59.8 ± 6.2% in DMSO-d6, while closed conformers accounted for 77.3 ± 3.7% and 40.2 ± 6.2%, respectively. This comprehensive study underscores the solvent environment’s impact on its structural behaviour. The findings significantly contribute to a deeper understanding of conformational dynamics, stimulating further exploration in drug development.

Exploring the Growth Dynamics of Size-Selected Carbon Atomic Wires with In Situ UV Resonance Raman Spectroscopy.

Short carbon atomic wires, the prototypes of the lacking carbon allotrope carbyne, represent the fundamental 1D system and the first stage in carbon nanostructure growth, which still exhibits many open points regarding their growth and stability. An in situ UV resonance Raman approach is introduced for real-time monitoring of the growth of carbon atomic wires during pulsed laser ablation in liquid without perturbing the synthesis environment. Single-chain species' growth dynamics are tracked, achieving size selectivity by exploiting the peculiar optoelectronic properties of carbon wires and the tunability of synchrotron radiation. Diverse solvents are systematically explored, finding size- and solvent-dependent production rates linked to the solvent's C/H ratio and carbonization tendency. Carbon atomic wires' growth dynamics reveal a complex interplay between formation and degradation, leading to an equilibrium. Water, lacking in carbon atoms and reduced polyynes solubility, yields fewer wires with rapid saturation. Organic solvents exhibit enhanced productivity and near-linear growth, attributed to additional carbon from solvent dissociation and low relative polarity. Exploring the dynamics of the saturation regime provides new insights into advancing carbon atomic wires synthesis via PLAL. Understanding carbon atomic wires' growth dynamics can contribute to optimizing PLAL processes for nanomaterial synthesis.

Sustainable magnetic covalent organic framework materials for multi-residue analysis of pyrethroid pesticides in tobacco, fruits and vegetables

Magnetic covalent organic frameworks (MCOFs) materials were synthesized in deep eutectic solvents (DESs) instead of traditional toxic organic solvents under ambient conditions. The reaction time could be reduced to about 3 h, which was more than 12 h for the traditional synthesis method. Materials characterization indicated that the MCOFs materials with Tp and BD as monomer synthesized in ChCl-urea based DESs (i.e. Urea-MTpBD) showed good magnetic property and higher specific surface area. The Urea-MTpBD materials were used as a magnetic solid phase extraction (MSPE) sorbent for the enrichment and determination of 16 pyrethroid pesticides (PYs), coupled with GC-MS/MS technology. The effective enrichment of PYs with Urea-MTpBD materials was achieved, which was due to the synergistic effects of π-π stacking and hydrophobic interactions. The limits of detection (LODs) of 16 PYs with the developed method ranged from 2.15 to 5.67 ng/mL, while the recovery was between 70.99 % and 109.09 % with excellent intra-day and inter-day precisions (RSDintra ≤ 5.78 %, RSDinter ≤ 9.13 %). The developed method was applied successfully to determine 16 PYs in tobacco, fruits and vegetables. Furthermore, the Urea-MTpBD materials could be reused three times, which showed not only highly efficient, but also economical and sustainable.

Selection of suitable organic electrolyte for CO2 electro-reduction to CO in three-compartment electrolysis cell with NaOH and Cl2 yielded as byproducts

Developing high performance electrolyte is essential in improving the performance of CO2 electro-reduction. In this work, we have constructed a three-compartment electrolysis cell for CO2 reduction to CO in organic electrolyte, with NaOH and Cl2 produced as byproducts. The generated CO and Cl2 can be served as feedstock for the production of phosgene, which is a widely used acylating agent for producing valuable downstream products. In order to improve the performance of the electrolysis cell, various commonly used organic solvents and supporting electrolytes were investigated. Consequently, 0.72 M Bu4NCF3SO3 in propylene carbonate (PC) was selected due to its high CO2 solubility. This electrolyte enabled the achievement of a current density of 27 mA/cm2 at a potential of −2.0 V (vs. SHE), with a stable Faradaic efficiency of 93 % for CO production. Compared with an aqueous catholytes, the altered double electric layer in the organic electrolyte prevents cathode poisoning, which is crucial for practical applications.

Unravelling the effect of soxhlet extracted Pisolithus arhizus fungi in bio-sensitized solar cells in response to diverse polar solvents

The potential application of Pisolithus arhizus fungi as an effective sensitizer in bio-sensitized solar cells (BSSCs) is the first of its kind to investigate the photovoltaic performance of BSSCs in polar protic and aprotic solvents. The soxhlet extraction method was employed to extract dye molecules in organic solvents including chloroform, 2-propanol, acetone, ethanol, methanol and DMSO and named PA1, PA2, PA3, PA4, PA5, PA6 to fabricate BSSCs. TiO2 and Platinum were used as working and counter electrodes. The structural, optical, morphological properties of the extracted dyes and dye anchored TiO2 films were analyzed through FTIR, UV–Vis spectroscopy and FESEM analysis. The optical absorption analysis revealed the presence of pisoquinone pigments in the fungi, from flavonoid family. The current-voltage, electrochemical impedance and cyclic voltammetry analysis showed that the PA4 ethanolic-based BSSC demonstrated the highest power conversion efficiency of 1.31 % compared to other DSSCs, with a Jsc of 3.40 mA cm−2 and Voc of 514 mV and the bandgap energy of 1.8eV. The order of the conversion efficiency for DSSCs with different solvents was ethanol (PA4) > methanol (PA5) > acetone (PA3) > DMSO (PA6) > 2-propanol (PA2) > chloroform (PA1). This finding highlights that selecting optimal, novel sensitizers and extraction solvents is crucial to maximize solar cell efficiency.

Improving the efficiency of acidic eluents for elution of Scandium from Lewatit® VP OC 1026 and TP 272 solvent impregnated ion exchange resins

Scandium is a strategic element with exceptional applications however, its widespread application has been limited mainly due to its high price which itself originates from lack of enriched primary reserves. Mineralized waste materials and mine tailings collected from various mining activities often contain low amounts of Sc and rare earth elements (REE), along with much higher levels of contaminants such as Si, Fe and Al. Ion exchange resins, especially phosphorus containing solvent impregnated ones, show extremely high selectivity for quantitative adsorption of Sc from pregnant leach solutions. However, efficient and economical elution of Sc from these types of resins is still a challenge. In this study, a series of water miscible organic solvents including methanol, ethanol, 1-propanol, 2-propanol and acetone are explored with sulfuric acid in elution of Sc at room temperature (25 °C). With the proposed binary solvent system in this study, 98% of the adsorbed Sc was eluted from VP OC 1026 (impregnated with D2EHPA) with 4 M H2SO4 in 50 vol.% 1-propanol while negligible amount of Sc could be recovered with 2 M H2SO4 even at high temperatures. Also, exceeding 97% of the loaded Sc on TP 272 (impregnated with Cyanex 272) could be successfully eluted with 6 M H2SO4 containing 50 vol.% 2-Propanol. Nevertheless, the elution efficiency of Sc from TP 272 was notably constrained, falling below 20 %, when 2 M H2SO4 was employed as the eluent. The added organic solvents also significantly increased the performance of H2SO4 in elution of Sc from the resins in columns. The addition of just 10 vol.% 2-propanol to 2 M H2SO4 led to significant increase in the elution of Sc from TP 272. The maximum concentration of Sc in the eluted fractions increased by over threefold, going from 167.0 mg/L to 532.6 mg/L, when compared to using 2 M H2SO4 under similar elution conditions.

Aerodynamic thermal breakup droplet ionization combined with a β-irradiation source for mass-spectrometric analysis of samples in a nonpolar solvent

A method is proposed for increasing the number of ions during mass-spectrometric analysis of samples in a nonpolar solvent (benzene). For this purpose, aerodynamic thermal breakup droplet ionization (ATBDI) with the impact of β-radiation on the aerosol droplets used in ATBDI was evaluated. This modification of the method, which we named β-ATBDI, allows to shift a nonvolatile analyte (trinitrotoluene in the negative ionization region and cocaine in the positive ionization region, as an example) into a gas phase as an aerosol at room temperature (in contrast to atmospheric pressure chemical ionization). In addition, β-ATBDI enables a researcher to distinguish mass spectrometric peaks of the compounds located in an aerosol droplet from compounds located outside the droplet, i.e., to identify background peaks. Also briefly discussed the ionization of two antibiotics—azithromycin in methylene chloride and sulfadiazine in salt water with β-ATBDI, ATBDI and electrospray ionization source.

Papain-Mediated Conjugation of Peptide Nucleic Acids to Delivery Peptides: A Density Functional Theory/Molecular Mechanics Metadynamics Study in Aqueous and Organic Solvent.

Enzymatic peptide synthesis is a powerful alternative to solid-phase methods, as enzymes can have high regio- and stereoselectivity and high yield and require mild reaction conditions. This is beneficial in formulation research due to the rise of nucleic acid therapies. Peptide nucleic acids (PNAs) have a high affinity toward DNA and RNA, and their solubility and cellular delivery can be improved via conjugation to peptides. Here, we designed and assessed the viability of the papain enzyme to conjugate four PNA-peptide models in water and an organic solvent using QM/MM metadynamics. We found that the reactions in water yield better results, where three conjugates could potentially be synthesized by the enzyme, with the first transition state as the rate-limiting step, with an associated energy of 14.53 kcal mol-1, although with a slight endergonic profile. The results highlight the importance of considering the enzyme pockets and different substrate acceptivities and contribute to developing greener, direct, and precise synthetic routes for nucleic acid-based therapies. By exploring the enzyme's potential in conjunction with chemical synthesis, current protocols can be simplified for the synthesis of longer nucleic acids and peptide sequences (and, by extension, proteins) from smaller oligo or peptide blocks.

A Photoinduced Annulation Strategy Towards a Novel Polycyclic Heteroaromatic Chromophore: Scope, Mechanism, Properties and Applications.

This article reports a detailed mechanistic and kinetic study of an unusual photoreaction leading to the (diazonia)tetrabenzonaphthacene skeleton. The photo‐triggered double intramolecular nucleophilic aromatic substitution (SNAr∗) has been investigated by varying the leaving groups. Photoreaction quantum yields have been determined and mechanistic insights have been supported by theoretical calculations using DFT and TD‐DFT methods. Additionally, we show that this light‐triggered formed diazonia constitutes a potent photosentitizer with a singlet oxygen generation quantum yield of 55 %, both in organic solvents and in water, which is an extremely relevant value in view of PDT applications or use as an oxidation photocatalyst in aqueous media. Once again, the experimental observations were supported by TD‐DFT calculations showing a large density of triplet states below the S1 excited state along with large spin‐orbit couplings. The reaction is not restricted to solutions but can also occur in solid PDMS matrices thus allowing for photochemical encoding of information that will progressively vanish upon prolonged UV‐exposure.

Fabrication and Efficient Interfacial Assembly of Bright Red-Emitting Carbon Quantum Dots for Security-Warning Textiles.

Carbon quantum dots (CQDs) have attracted more attentions due to their multiple performances. However, the fabrication of long-wavelength emitting CQDs with aliphatic precursors still remains a challenge, mainly because it is difficult to generate large sp2 domains to reduce energy gap, which is not conducive to a redshift of the luminescence peak. Hereon, by regulating the pH of citric acid and thiourea mixture, a N, S co-doped CQD emitting bright red fluorescence at 635nm is successfully fabricated through the solvothermal reaction under acidic condition, achieving a high quantum yield of 32.66%. Solvatochromic effects of the CQDs are discussed through theoretical equations and models, which confirm that the hydrogen-bonding interaction dominates the fluorescence emission behavior of CQDs in polar solvents. Besides, a feasible strategy is proposed to prepare an anti-counterfeiting textile via the deposition of red-emitting CQDs onto cotton fibers, through rapidly evaporating the preferred organic solvent. As expected, the CQD-decorated textiles exhibit encouraging anti-counterfeiting and security-warning functions, along with underwater and long-distance detectability, washability, and sun resistance. It is worth noting that the present work is innovative in realizing the application of red-light-emitting CQDs in the fields of security-warning textiles.

Chiral metal-organic frameworks grown in situ for monolithic capillary electrochromatographic enantioseparation.

Chiral metal-organic frameworks (CMOFs) with chiral selectivity are one of the high-quality stationary phases for capillary electrochromatography (CEC). However, there is a problem of unsatisfactory enantioseparation performance of capillary columns due to insufficient loading. In this work, a lamellar CMOF (Cu-TC) was grown in situ on the surface of the monolith in a capillary monolithic column to obtain a Cu-TC@monolithic column. The CEC system constructed based on the Cu-TC@monolithic column shows a satisfactory chiral separation performance. Compared with the Cu-TC-based coated column (Cu-TC@coated column), the enantioseparation performance of the CEC system based on the Cu-TC@monolithic column was greatly improved, and the resolutions (Rs) of the model analytes were increased by 80-500%. In addition, the effects of experimental conditions such as the number of cycles of Cu-TC in situ growth, buffer concentration, buffer pH, organic solvent addition and applied voltage on the performance of CEC were also investigated. Finally, the chiral selection mechanism of the stationary phase was explored by selective adsorption experiments. The present work provides a new idea for the development of capillary stationary phases, which has great potential considering the diversity of CMOFs.

Li-Ion Batteries with a Binder-Free Cathode of Carbon Nanotubes-LiFePO4-Al Foam

With the increasing demand for Li resources worldwide, the easy recycling of Li-ion batteries materials becomes essential. We report a binder-free cathode consisting of carbon nanotubes (CNTs) and LiFePO4 (LFP) nanoparticles embedded in a 3D Al network. The electrode stability depends on the CNT ratio, where 3% CNT-wrapping LFPs provide a stable structure free of detachment from Al foam, as observed on Al foil. The binder-free cathode sheet exhibited excellent performance for high-rate discharge and long-term cycle life. Materials on the cathode can be easily detached with ultrasonic treatment when immersed in organic solvent, which is advantageous for a green and high-efficiency strategy of recycling all valuable materials compared to the binder-used electrode.

A Mechanistic Study on Iron-Based Styrene Aziridination: Understanding Epoxidation via Nitrene Hydrolysis

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([FeII(PBI)3](CF3SO3)2 (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k2 = 7.16 × 10−3 M−1 s−1 in MeCN, 2.58 × 10−3 M−1 s−1 in CF3CH2OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logkrel) and the total substituent effect (TE, 4R-PhCHCH2) parameters with slopes of 1.48 (MeCN) and 1.89 (CF3CH2OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [FeIII(N•Ts)] under experimental conditions.

Experimental study and analysis of CO2 and SO2 absorption in various water-based nanofluids by response surface methodology

The absorption of acidic gases in the oil and gas industries is important due to their toxicity and corrosive effects. Recently, the application of nanofluids based on aqueous or organic solvents as absorbents has been examined by a variety of researchers. In this study, a single bubble column was exploited to study the effect of water-based nanofluids on the absorption processes of SO2 and CO2 using response surface methodology (RSM) based on Box-Behnken three-level experiment design. With this in mind, CO2 and SO2 are separately injected at the bottom of a bubble column filled with one of the nanofluids: Al2O3-water, SiO2-water, or ZnO-water for each experiment. Then, the rate of SO2 or CO2 absorption in the nanofluids has been elucidated. The effect of important parameters including the weight fraction of the nanoparticles (NPs) (0.01, 0.055, and 0.1 wt.%), gas–liquid contact time (150, 300, and 450 s), and the diameter of nozzle for gas injection (0.46, 0.57, and 0.68 mm) have been studied. Results revealed that the maximum molar flux of both gases was observed in the ZnO-water nanofluid, followed by the SiO2-water nanofluid. In addition, increasing the nanoparticle mass fraction and the bubble size causes the molar flux to rise. However, increasing the gas–liquid contact time causes the molar flux of the mentioned gases to decrease. Finally, a set of the accurate equations has been proposed to predict the molar flux of SO2 and CO2 in the various nanofluids assessed in this work.