Subsequent Solvent Research Articles

Macroscopic Monograin Nano-Gyroid Thin Films in 4-inch Scale Through Shear-Rolling and Subsequent Solvent Annealing.

The gyroid structure from self-assembly is highly attractive for optical applications such as photonic crystals and metamaterials. However, due to the direction-dependent nature of these applications, achieving a monograin-level structure over a large area has remained challenging. In this study, the fabrication of unidirectionally oriented anisotropic nanocylinders of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is reported block copolymer thin films up to a 4-inch scale via a shear-rolling process, followed by solvent annealing to induce phase transition to nearly monograin gyroid structures. Grazing-incidence small-angle X-ray scattering (GISAXS) analysis and cross-sectional scanning electron microscope (SEM) images in the direction parallel to the shear-rolling direction reveal the preferential orientation with the (111) plane onto the YZ axis of the film, while only the (110) plane on the YZ axis of the film is observed in the perpendicular direction, with grain sizes approaching single-grain levels. For metamaterial applications, the PDMS domain is selectively removed, and gold is electroplated to produce monograin gold gyroid films.

Transparent and high-porosity aluminum alkoxide network-forming glasses

Metal-organic network-forming glasses are an emerging type of material capable of combining the modular design and high porosity of metal-organic frameworks and the high processability and optical transparency of glasses. However, a generalizable strategy for achieving both high porosity and high glass-forming ability in modularly designed metal-organic networks has yet to be developed. Herein, we develop a series of aluminum alkoxide glasses and monoliths by linking aluminum-oxo clusters with alcohol linkers. A bulky monodentate alcohol modulator is introduced during synthesis and act as both network plasticizer and pore template, which can be removed by the subsequent solvent exchange to give gas accessible pores. Glasses synthesized with the modulator template exhibit well-defined glass transitions in their as-synthesized form and high surface areas up to 500 m2/g after activation, making them among the most porous glassy materials. The aluminum alkoxide glasses also have optical transparency and fluorescent properties, and their structures are elucidated by pair-distribution functions, spectroscopic and compositional analysis. These findings could significantly expand the library of microporous metal-organic network-forming glasses and enable their future applications.

Solvent-Induced Structural Rearrangement in Ultrasound-Assisted Synthesis of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are crystalline extended structures featuring permanent porosity, assembled from metal ions and organic ligands, often synthesized by the solvothermal method (50-260°C, 12-72h). Here, an alternative synthetic approach-solvent-induced structural rearrangement in ultrasound-assisted synthesis is presented. Six representative Zn-based MOFs, each composed of distinct secondary building units, are synthesized within 2-180min consuming less solvent (>0.03m) at room temperature. It is observed that ultrasonication induces the construction of a coordination network, and subsequent solvent exchange triggers structural rearrangement to yield MOFs of high crystallinity and porosity. Furthermore, the scalability of this method is demonstrated through the bulk synthesis of MOF-5, MOF-74, ZIF-8, and MFU-4l within 90min. The initiation of nucleation through ultrasound and the subsequent transformation induced by solvent exchange offer an alternative method for efficiently synthesizing MOFs in bulk, potentially broadening their range of applications.

In-situ welding and thermal activation enabled robust nanofibers based triboelectric nanogenerator for sustainable energy harvesting

Nanofiber-based triboelectric nanogenerators (TENGs) show great promise in energy harvesting and sensing applications. However, the poor strength and the instability of the nanofiber structures lead to the constraints on the durability and the lack of stability in the output performance. In this study, BaTiO3@PVDF-HFP nanofibers were prepared by electrospinning, in which BaTiO3 nanoparticles enhanced the charge trapping ability of the nanofibers and provided nucleation sites for β-phase growth. Subsequent solvent and annealing treatment in-situ welded the nanofibers, which greatly improved the mechanical strength and stability of the nanofiber membranes. The annealing process further thermally activated the electroactive β-phase in the PVDF-HFP, which increased the surface charge density of the nanofibers. A flexible TENG based on BaTiO3@PVDF-HFP-p nanofiber was prepared to harvest mechanical energy, which could achieve a maximum output of 482.5 V and 1.9 W m−2, the voltage is more than 1.2–1.5 times higher compared to uncrosslinked nanofibers. The BaTiO3@PVDF-HFP-p-based TENG maintains ultra-stable Voc generation over 7000 cycles compared to the nanofibers without solvent and annealing treated. Finally, its practical application in harvesting ambient mechanical energy was demonstrated, which can harvest wind energy to power LEDs and small electronic devices such as temperature and humidity sensors.

Photochemistry of Ru(II) Triazole Complexes with 6-Membered Chelate Ligands: Detection and Reactivity of Ligand-Loss Intermediates.

Photochemical ligand release from metal complexes may be exploited in the development of novel photoactivated chemotherapy agents for the treatment of cancer and other diseases. Highly intriguing photochemical behavior is reported for two ruthenium(II) complexes bearing conformationally flexible 1,2,3-triazole-based ligands incorporating a methylene spacer to form 6-membered chelate rings. [Ru(bpy)2(pictz)]2+ (1) and [Ru(bpy)2(btzm)]2+ (2) (bpy = 2,2'-bipyridyl; pictz = 1-(picolyl)-4-phenyl-1,2,3-triazole; btzm = bis(4-phenyl-1,2,3-triazol-4-yl)methane) exhibit coordination by the triazole ring through the less basic N2 atom as a consequence of chelation and readily undergo photochemical release of the pictz and btzm ligands (ϕ = 0.079 and 0.091, respectively) in acetonitrile solution to form cis-[Ru(bpy)2(NCMe)2]2+ (3) in both cases. Ligand-loss intermediates of the form [Ru(bpy)2(κ1-pictz or κ1-btzm)(NCCD3)]2+ are detected by 1H NMR spectroscopy and mass spectrometry. Photolysis of 1 yields three ligand-loss intermediates with monodentate pictz ligands, two of which form through simple decoordination of either the pyridine or triazole donor with subsequent solvent coordination (4-tz(N2) and 4-py, respectively). The third intermediate, shown to be able to form photochemically directly from 1, arises through linkage isomerism in which the monodentate pictz ligand is coordinated by the triazole N3 atom (4-tz(N3)) with a comparable ligand-loss intermediate with an N3-bound κ1-btzm ligand also observed for 2.

Synergistic impact of heat and salicylic acid pretreatment on gluten films: Characterization and functional properties

This study investigates how wheat gluten (WG) films in the presence of salicylic acid are influenced by thermal pretreatment. Unlike previous methods conducted at low moisture content, our procedure involves pretreating WG at different temperatures (65 °C, 75 °C, and 85 °C), in a solution with salicylic acid. This pretreatment aims to enhance protein unfolding, thus providing more opportunities for protein-protein interactions during the subsequent solvent casting into films. A significant increase in β-sheet structures was observed in FTIR spectra of samples pretreated at 75 °C and 85 °C, showing a prominent peak in the range of 1630–1640 cm−1. The pretreatment at 85 °C was found to be effective in improving the water resistivity of the films by up to 247 %. Moreover, it led to a significant enhancement of 151 % in tensile strength and a 45 % increase in the elastic modulus. The reduced solubility observed in films derived from pretreated WG suggests the development of an intricate protein network arising from protein-protein interactions during the pretreatment and film formation. Thermal pretreatment at 85 °C significantly enhances the structural and mechanical properties of WG films, including improved water resistivity, tensile strength, and intricate protein network formation.

Wearable Sensor Based on a Tough Conductive Gel for Real-Time and Remote Human Motion Monitoring.

The usage of a conductive hydrogel in wearable sensors has been thoroughly researched recently. Nonetheless, hydrogel-based sensors cannot simultaneously have excellent mechanical property, high sensitivity, comfortable wearability, and rapid self-healing performance, which result in poor durability and reusability. Herein, a robust conductive hydrogel derived from one-pot polymerization and subsequent solvent replacement is developed as a wearable sensor. Owing to the reversible hydrogen bonds cross-linked between polymer chains and clay nanosheets, the resulting conductive hydrogel-based sensor exhibits outstanding flexibility, self-repairing, and fatigue resistance performances. The embedding of graphene oxide nanosheets offers an enhanced hydrogel network and easy release of wearable sensor from the target position through remote irradiation, while Li+ ions incorporated by solvent replacement endow the wearable sensor with low detection limit (sensing strain: 1%), high conductivity (4.3 S m-1) and sensitivity (gauge factor: 3.04), good freezing resistance, and water retention. Therefore, the fabricated wearable sensor is suitable to monitor small and large human motions on the site and remotely under subzero (-54 °C) or room temperature, indicating lots of promising applications in human-motion monitoring, information encryption and identification, and electronic skins.

Sustainable Manufacturing of Graphitic Carbon from Bio‐Waste Using Flash Heating for Anode Material of Lithium‐Ion Batteries with Optimal Performance

AbstractTo address the fundamental challenge of resource sustainability and to effectively deal with issues pertaining to supply chain resilience, cost efficiency, environmental impact, and the ability to meet specific local needs; there is an urgent need for high‐grade battery anode materials produced locally from readily available raw materials. In this work, synthesis of high‐quality graphitic carbon (GH) derived from human hair is demonstrated using an in‐house engineered reactor based on Joule's Flash heating method. The GH is characterized using various techniques to examine its chemical composition, particle morphology, crystallinity, and demonstrate its usability as an anode material for lithium‐ion batteries. Fabricated coin cell with active material exhibits a gravimetric capacity of 320 mAh g−1 at a current density of 30 mA g−1 (equivalent to a C rate of ≈0.1C) over the 100 cycles. The in situ and ex situ studies using XRD, Raman, XPS, and UPS techniques conclude that during the initial charge cycle for GH, lithium ions diffused into the electrode during the resting period are effectively removed. This not only improves the lithium inventory to start with but also mitigates subsequent solvent degradation during solid electrolyte interphase (SEI) formation. Thus, these improvements ultimately enhance the capacity of the anode to 500mAh g−1 at a current density of 20 mA g−1. The study offers the potential to initiate a new realm of research by redirecting the focus to a material once considered as mere waste.

Hydrometallurgical processing of molybdenum middlings from Shatyrkul-Zhaysan cluster ore

This research investigates the hydrometallurgical processing of molybdenum middlings extracted from copper-molybdenum ore in the Shatyrkul-Zhaysan cluster in Kazakhstan. A molybdenum intermediate obtained after selective flotation of the copper-molybdenum concentrate was used, with a recovery of 0.07%, a molybdenum content of 22.23% and an extraction of 74.91%. The mineralogical analysis shows molybdenite and chalcopyrite as the main minerals. In experiments, atmospheric leaching with nitric acid in single-stage and two-stage countercurrent processes was investigated to optimize molybdenum extraction and reduce acid consumption. The optimum conditions obtained were: 300 g/L nitric acid, 100 g/L sulfuric acid, 90?C temperature and 2 hours leaching time in the single-stage leaching, which extracted 98.8% molybdenum. The two-stage leaching under optimized conditions allows the extraction of 94.3% molybdenum in solutions with lower residual acidity (0.89 g-eq/L) and redox potential (550 mV) without reducing the extraction of valuable component. Molybdenum extraction reaches 94.3% in the subsequent solvent extraction stage from two-stage leaching solutions. The final product, calcium molybdate with a molybdenum content of 46.83%, meets commercial grade specifications. This research demonstrates an effective process for hydrometallurgical production of commercial grade calcium molybdenite from copper-molybdenum ore, with high molybdenum recovery, reduced acid consumption through two-stage leaching, and minimal hazardous discharges.

Inefficacy of dietary test substance administration in Amphibian Metamorphosis Assay (AMA) studies.

Traditionally, the Amphibian Metamorphosis Assay (AMA; OECD TG 231) is performed by exposing Xenopus laevis tadpoles to test substances dissolved in laboratory water. Recently, the use of dietary administration has been proposed to combat poorly soluble test substances in ecotoxicologically-based regulatory endocrine disruption (ED) studies, specifically the AMA warranting an investigation into the efficacy of dietary administration. An efficacy study comprised of two phases: 1) evaluation of the physical influence of the loading process via solvent and 10, 1, and 0.1 mg/l test substance or surrogate (sunflower oil, SFO) on the Sera® Micron Nature (SMN) diet, and 2) performance of a modified AMA in which Nieuwkoop and Faber (NF) stage 51 X. laevis larvae were exposed to dechlorinated tap water using one concentration of the SFO in the diet for 21 days, was performed. In phase 1, the addition of acetone or acetone with bis(2-propylheptyl) phthalate (DPHP) or SFO to SMN with subsequent solvent purge altered the diet reducing the density of the liquified diet and dietary pellet size following centrifugation indicative of alteration of the physical properties of the diet. Treatments used in the modified AMA were acetone alone and 0.1 mg/l SFO dissolved in acetone. These treatments were evaluated against an SMN benchmark using standard AMA endpoints. Both the acetone-treated SMN and 0.1 mg/l SFO-treated diets significantly reduced survival rates, 67 and 70% relative to the SMN benchmark (100%), decreased developmental stage distribution and snout-vent length-normalized hind limb length relative to the SMN benchmark, and slightly increased the prevalence and severity of thyroid follicular cell hypertrophy. Although the acetone-treated diets may have impacted the hypothalamo-pituitary-thyroid axis, clinical signs of gastrointestinal impaction and tail flexure were also observed in the acetone-treated diets, but not the SMN diet alone. Ultimately, test substance exposure via the diet in an AMA study can produce results that may confound data interpretation, which suggests that the traditional aqueous exposure route is generally more appropriate.

Reverse Iontophoresis: Noninvasive Assessment of Topical Drug Bioavailability.

Assessing drug disposition in the skin after the application of a topical formulation is difficult. It is hypothesized that reverse iontophoresis (RI), which can extract charged/polar molecules for monitoring purposes, may provide a noninvasive approach for the assessment of local drug bioavailability. The passive and RI extraction of salicylic acid (SA) and nicotine (NIC) from porcine skin in vitro was assessed after a simple solution of the former and a transdermal patch of the latter had been applied for 24 and 8 h, respectively. Immediately after this "passive skin loading", the amount of drug in the stratum corneum (SC) and "viable" tissue (VT) was measured either (a) after tape-stripping and subsequent solvent extraction of both skin layers or (b) following RI extraction over 4 h. Parallel experiments were then performed in vivo in healthy volunteers; in this case, the VT was not sampled and the skin loading period for NIC was only 4 h. RI extraction of both drugs was significantly higher (in vitro and in vivo) than that achieved passively, and the cumulative RI extraction profiles as a function of time were mathematically analyzed using a straightforward compartmental model. Best-fit estimates of drug amounts in the SC and VT (ASC,0 and AVT,0, respectively) at the end of "loading" and two first-order rate constants describing transfer between the model compartments were then determined. The in vitro predictions of ASC,0 and AVT,0 were in excellent agreement with the experimental results, as was the value of the former in vivo. The rate constants derived from the in vitro and in vivo results were also similar. In summary, the results provide proof-of-concept that the RI method has the potential to noninvasively assess relevant metrics of drug bioavailability in the skin.

The effects of holocellulose treatments on the yield and structure of dimethylsulfoxide-extracted birchwood xylans

Xylans with naturally occurring acetylation are vital to the plant cell wall functionalities and are also demonstrating excellent dispersing properties which can be applied in fine chemicals and advanced materials. The acetyl structure of xylan can be maintained by dimethyl sulfoxide (DMSO) extraction. A disadvantage of DMSO extraction is that its yield is much lower than that of alkali extraction, which is unfavorable to the research and application of xylans. In this study, sodium chlorite was used as the delignification method to produce holocellulose from birch wood. The effects of subsequent holocellulose solvent exchange, drying and ball-milling on xylan DMSO extraction were studied. The differences of three successive DMSO extractions from the same holocellulose sample and gradient xylan precipitation from DMSO were also evaluated. The majority of xylans are extracted in the first two extractions, while the xylans extracted in the third extraction usually had low yields and low molecular weights. Xylans extracted directly from aqueously wet holocellulose without drying had a very low yield of less than 1%, while xylans extracted from freeze or vacuum dried holocellulose have total yields of 4–9%. T-butanol or ether washed holocellulose shows slightly lower xylan yield than water washed holocellulose. Ball milled holocellulose has twice the xylan yield of holocellulose sample without ball milling. For gradient xylan precipitation, more than 95% of the xylans precipitate in 50% and 70% ethanol. Gradient ethanol precipitation fractionates xylans by molecular weight, but does not fractionate xylans by degree of acetylation. This study is significant for promoting the researches and applications of DMSO extraction of xylan.

Pollutant reduction and closed-loop process for recovering high value-added products from spent lithium-ion batteries

The conventional hydrometallurgical process for recycling spent ternary lithium-ion batteries has incomplete lithium recovery, excessive chemical consumption, and generation of wastewater and waste residues. Herein, an innovative route is employed to recover valuable metals from spent ternary cathode material. Firstly, LiNixCoyMnzO2 is dissociated and reduced into Li2CO3, elemental Ni and Co, and MnO via self-reduction roasting with graphite and precise control of phase transformation. Second, 92.8% of Li is selectively extracted via carbonation water leaching. Finally, ammonia leaching in the (NH4)2CO3–NH3–O2 system is used for the first time to selectively extract approximately 98% of Ni and Co from the leaching residue. The trace leaching leaching of Mn and impurity elements simplifies the subsequent solution purification and solvent extraction processes, and reduces the generation of waste residues. Because of the valence difference between Ni and Co in the ammonia leachate, they can be deeply separated via a two-stage solvent extraction, followed by ammonia evaporation to obtain cobalt products directly from the raffinate. Leaching agents and mother liquor can be reused, reducing recycling costs and avoiding the generation of high-salt wastewater. Economic and environmental evaluation results show that the proposed process has low energy consumption, low greenhouse gas emissions, and high recycling profit.

Molar masses and molar mass distributions of commercial regenerated cellulose materials and softwood dissolving pulp determined by SEC/MALLS

The molar masses and molar mass distributions of three commercial regenerated cellulose samples, viscose rayon, Tencel, and Bemliese (or cuprammonium nonwoven), have been determined by dissolution in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) and subsequent size-exclusion chromatography with multi-angle laser-light scattering detection (SEC/MALLS). Before dissolution in LiCl/DMAc, the regenerated cellulose samples were pretreated by the following three methods: (1) soaking in ethylene diamine (EDA) and subsequent solvent exchange to N,N-dimethylacetamide (DMAc) through methanol, (2) soaking in water and subsequent solvent exchange to DMAc through ethanol, and (3) soaking in water and subsequent solvent exchange to tert-butyl alcohol through ethanol and freeze dying. The pretreated samples were dissolved in 8% (w/w) LiCl/DMAc by stirring the cellulose/LiCl/DMAc mixtures for 1–3 weeks followed by dilution to 1% (w/v) LiCl/DMAc for SEC/MALLS analysis. The EDA- and water-pretreated samples gave almost the same SEC-elution pattens and molar mass plots, resulting in similar number- and mass-average molar masses. However, the freeze-dried samples gave 10%‒20% lower mass recovery ratios than those obtained for the EDA- or water-pretreated samples, probably because of incomplete dissolution of the freeze-dried samples in 8% (w/w) LiCl/DMAc. The average mass-average degree of polymerization values of viscose rayon, Tencel, and Bemliese were 340, 530, and 880, respectively. The slopes of the conformation plots were 0.58–0.62, showing that all of the molecules in the three regenerated cellulose samples were dissolved in 1% (w/v) LiCl/DMAc, forming linear random-coil conformations.Graphical abstract

Reversible Morphology Locking via Metal Infiltration in a Block Copolymer.

Metal infiltration from an acid solution of a metal precursor into the poly(2-vinylpyridine) (P2VP) microdomains of a polystyrene-b-P2VP block copolymer is shown to reduce the uptake of solvent vapor during a subsequent solvent annealing process, locking the morphology of the self-assembled microdomains. The amount of metal, here Pt, incorporated into the P2VP increases with both metal precursor [PtCl4]2- and hydrochloric acid concentrations, reaching 0.83 Pt atom per pyridine unit. The metal is then exfiltrated using a KOH + ethylenediaminetetraacetic acid disodium salt dihydrate (Na2EDTA) complexing solution, which restores solvent uptake and unlocks the morphology. The reversibility of the metal infiltration and morphology locking is demonstrated in a multistage annealing process and is confirmed for Fe as well as Pt. Reversible locking and unlocking of block copolymer microdomain morphologies expand their utility for nanofabrication processes by allowing the morphology to be fixed during subsequent process steps.

Post-processing of a lavender flowers solvent extract using supercritical CO2 fractionation

BackgroundSupercritical Fluid Extraction (SFE) was performed using an unconventional material, the solid extract of lavender flowers obtained by liquid solvent extraction and subsequent solvent elimination. MethodsSystematic extraction experiments were carried out at 8 MPa and 40 °C, and the extract was fractionated in semi-continuous mode in the SFE plant. To understand mass transfer phenomena driving the process, CO2 mass flow rates ranging between 0.60 and 1.50 kg/h were used, and yield vs. time curves were obtained. Significant findingsFractionation produced a cuticular waxes selective precipitation in the first separator and the floral fragrance in the second separator. The most abundant species in the extract were τ-cadinol (13%), lavandulol (10.5%), β-caryophyllene (10%), viridiflorene (8.5%), isocaryophyllene (6%), cedrenalol (4.5%), linalool (4%) and 1,8-cineol (4%). The fragrance contained no waxes, indicating that the fractionation was successful. At higher mass flow rates (from 0.90 to 1.50 kg/h), an asymptotic extraction yield of 5.2% w/w was obtained; whereas, at lower mass flow rates, the extraction yield was lower (2.3% w/w) since the vegetable bed was not completely wetted by the extraction fluid. The overall results indicated that an external mass transfer resistance controlled the process.

Bifunctional Hole-Transport Materials with Modification and Passivation Effect for High-Performance Inverted Perovskite Solar Cells.

Hole-transport materials (HTMs) play an important role in perovskite solar cells (PSCs) to enhance the power conversion efficiency (PCE). The innovation of HTMs can increase the hole extraction ability and reduce interfacial recombination. Three organic small molecule HTMs with 4H-cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) as the central unit was designed and synthesized, namely, CPDTE-MTP (with the 2-ethylhexyl substituent and diphenylamine derivative end-group), CPDT-MTP (with the hexyl substituent and diphenylamine derivative end-group), and CPDT-PMTP (with the hexyl substituent and triphenylamine derivative end-group), which can form bifunctional and robust hole transport layer (HTL) on ITO and is tolerable to subsequent solvent and thermal processing. The X-ray photoelectron spectroscopy (XPS) results proved that CPDT-based HTMs can both interact with ITO through the nitrogen element in them and the tin element in ITO and passivate the upper perovskite layer. It is worth noting that the champion efficiency of MAPbI3 PSCs based on CPDT-PMTP achieved 20.77%, with an open circuit voltage (VOC) of 1.10 V, a short-circuit current (JSC) of 23.39 mA cm-2, and a fill factor (FF) of 80.83%, as three new materials were introduced into p-i-n PSCs as dopant-free HTMs.

Investigating analyte breakthrough under non-linear isotherm conditions during solid phase extraction facilitated by non-targeted analysis with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

Solid phase extraction (SPE) sample preparation for the analysis of complex organic mixtures is often applied assuming all analytes of interest will preconcentrate on the stationary phase. This assumption ignores the reality that extraction is a dynamic interactive process and a diverse range of affinities for the stationary phase will result in equally diverse breakthrough volumes due to competitive sorption processes. To study this dynamic interactive process, and further to take advantage of it, we extracted a JP-8 jet fuel spiked with 40 ppm of a polar compound mix with silica and alumina SPE cartridges and analyzed sequential extracted fractions of the fuel to both assess the shifting chemical landscape present in the extraction and the impact of both SPE stationary phases on this process. Tile-based 1v1 comparative analysis (a recently reported extension of tile-based Fisher ratio analysis) was used to discover the (polar) compounds whose concentrations change between extracted fractions, discovering 21 compounds extracted with silica and 27 compounds extracted with alumina with at least a 2-fold change in concentration from the neat sample relative to the first 1 mL pass fraction sample. These compounds were quantified in each fraction to construct concentration ratio profiles, defined as the concentration ratio for a given SPE fraction per analyte compound relative to the analyte concentration in the neat fuel, for which the extraction behavior for each analyte could be assessed. These analyte compounds were found to breakthrough at different rates, with some analytes remaining on the column indefinitely (until extracted with a subsequent polar solvent) and other analytes eluting before the extraction is complete. Furthermore, in a comparison of the effect of selected stationary phase, alumina was found to retain oxygen-containing phenolic compounds to a greater extent than silica. Principal component analysis (PCA) was used to analyze the concentration ratio profiles of the various trace analytes in the JP8 fuel (phenols, indoles, etc.) in the context of their stationary phase affinity (silica or alumina) and competitive sorption behavior.

Understanding Precatalyst Activation and Speciation in Manganese-Catalyzed C-H Bond Functionalization Reactions.

An investigation into species formed following precatalyst activation in Mn-catalyzed C-H bond functionalization reactions is reported. Time-resolved infrared spectroscopy demonstrates that light-induced CO dissociation from precatalysts [Mn(C^N)(CO)4] (C^N = cyclometalated 2-phenylpyridine (1a), cyclometalated 1,1-bis(4-methoxyphenyl)methanimine (1b)) in a toluene solution of 2-phenylpyridine (2a) or 1,1-bis(4-methoxyphenyl)methanimine (2b) results in the initial formation of solvent complexes fac-[Mn(C^N)(CO)3(toluene)]. Subsequent solvent substitution on a nanosecond time scale then yields fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)], respectively. When the experiments are performed in the presence of phenylacetylene, the initial formation of fac-[Mn(C^N)(CO)3(toluene)] is followed by a competitive substitution reaction to give fac-[Mn(C^N)(CO)3(2)] and fac-[Mn(C^N)(CO)3(η2-PhC2H)]. The fate of the reaction mixture depends on the nature of the nitrogen-containing substrate used. In the case of 2-phenylpyridine, migratory insertion of the alkyne into the Mn-C bond occurs, and fac-[Mn(C^N)(CO)3(κ1-(N)-2a)] remains unchanged. In contrast, when 2b is used, substitution of the η2-bound phenylacetylene by 2b occurs on a microsecond time scale, and fac-[Mn(C^N)(CO)3(κ1-(N)-2b)] is the sole product from the reaction. Calculations with density functional theory indicate that this difference in behavior may be correlated with the different affinities of 2a and 2b for the manganese. This study therefore demonstrates that speciation immediately following precatalyst activation is a kinetically controlled event. The most dominant species in the reaction mixture (the solvent) initially binds to the metal. The subsequent substitution of the metal-bound solvent is also kinetically controlled (on a ns time scale) prior to the thermodynamic distribution of products being obtained.

Fast Expandable Chitosan‐Fibers Cryogel from Ambient Drying for Noncompressible Bleeding Control and In Situ Tissue Regeneration

AbstractHemorrhage control, especially noncompressible wound hemostasis, is a tremendous challenge in military injuries and other traumas worldwide. Here, a cryogelation strategy and subsequent solvent exchange are developed for the hydrogen bond‐induced self‐assembly of chitosan fibers and the production of fast expandable chitosan cryogel. Importantly, the ambient drying process facilitates the repeatable deformation performance of the shape‐memory cryogel with a response time of ≈1.7 s. Due to the capillary‐like structure of the cryogel and high hydrophilicity, rapid shape recovery is accompanied by 41 times water absorption ability. It is further demonstrated that chitosan cryogel is beneficial for in situ tissue regeneration by taking advantage of the biodegradability and biocompatibility of chitosan. Thus, chitosan cryogels prepared by this simple and benign method should have efficient hemostatic effect on noncompressible bleeding and severe fatal high‐pressure hemorrhage.