Showing papers on "Anhydrous published in 2023"

Preparation and Analysis of Pueraria lobata Polysaccharides.

Abstract: Pueraria lobata polysaccharides (PLPs) were obtained by a hot water extraction method. Starting from the single factor experiment, the extraction was optimized by response surface methodology, and the following optimal extraction parameters were obtained: the extraction temperature was 84 °C, the liquid-solid ratio was 11 mL/g, the extraction time was 73 min, and the extraction rate of polysaccharides was 8.59%. The Sevag method was used to remove the protein soluble in water and H2O2 was used to remove the pigment; then PLPs were precipitated with three times of anhydrous ethanol, soluble salts and other small molecules were removed by dialysis, and finally refined PLPs were obtained by freeze-drying.

Fast and High-Yield Anhydrous Synthesis of Ti3 C2 Tx MXene with High Electrical Conductivity and Exceptional Mechanical Strength.

Abstract: 2D transition metal carbides or nitrides (MXenes) have attracted considerable attention from materials scientists and engineers owing to their physicochemical properties. Currently, MXenes are synthesized from MAX-phase precursors using aqueous HF. Here, in order to enhance the production of MXenes, an anhydrous etching solution is proposed, consisting of dimethylsulfoxide as solvent with its high boiling point, NH4 HF2 as an etchant, CH3 SO3 H as an acid, and NH4 PF6 as an intercalant. The reaction temperature can be increased up to 100 °C to accelerate the etching and delamination of Ti3 AlC2 MAX crystals; in addition, the destructive side reaction of the produced Ti3 C2 Tx MXene is suppressed in the etchant. Consequently, the etching reaction is completed in 4 h at 100 °C and produces high-quality monolayer Ti3 C2 Tx with an electrical conductivity of 8200 S cm-1 and yield of over 70%. The Ti3 C2 Tx MXene fabricated via this modified synthesis exhibits different surface structures and properties arising from more F-terminations than those of Ti3 C2 Tx synthesized in aqueous HF2 T. The atypical surface structure of Ti3 C2 Tx MXene results in an exceptionally high ultimate tensile strength (167 ± 8 MPa), which is five times larger than those of Ti3 C2 Tx MXenes synthesized in aqueous HF solution (31.7 ± 7.8 MPa).

Incorporation of Upconverting LiYF4:Yb3+, Tm3+ Nanoparticles with High Quantum Yield in TiO2 Metallogels for Near Infrared-Driven Photocatalytic Dye Degradation

Abstract: By using anhydrous conditions, we report here an optimized synthesis of small but highly emitting upconverting nanoparticles (UCNPs) of LiYF4:Yb3+, Tm3+ without any surface passivation layers of silica or undoped matrix. For this, anhydrous precursors [Li(TFA)(monoglyme)] and [Ln(TFA)3(monoglyme)] (Ln = Y, Gd, Tm, Yb; TFA = trifluoroacetate) were synthesized via a facile one-pot synthetic protocol, which showed excellent thermal decomposition compatibility to afford Ln3+-doped LiLnF4 NPs by simultaneous decomposition in the solution phase. A detailed study of the influence of many key parameters such as the ratio of dopant ions and solvents, concentration of precursors, reaction time, and temperature over crystalline phase, size, shape, morphology, and upconverting properties of the NPs produced followed by a mechanism for the formation of LiYF4-based NPs is presented. The high quality of these NPs is manifested by the fact that their upconversion efficiency is quite comparable to that of a bulk single crystal of the same composition (bulk materials are believed to have far better UC performance due to low surface area and less defects). Successful incorporation of these UCNPs in transparent TiO2 metallogels provided an alternative strategy of highly homogeneous UCNP-TiO2 composites of variable composition (1–10% of NPs) having very high specific surface area (435–580 m2/g).

Selective Removal of Sulfate from Water by Precipitation with a Rigid Bis-amidinium Compound.

Abstract: A simple, readily-prepared biphenyl bis-amidinium compound (1∙Cl2) is able to selectively precipitate sulfate from water. The precipitant is effective at concentrations as low as 1 mM and shows complete selectivity against monovalent anions, and high selectivity even against CO32- and HPO42-. It is highly effective (> 90% sulfate removed) in both seawater and highly acidic conditions relevant to mining waste-streams. X-ray crystallography reveals that 1∙SO4 forms a tightly packed, anhydrous, structure where each sulfate anion receives eight hydrogen bonds from amidinium N-H hydrogen bond donors.

Novel Hydrate and Anhydrate Cocrystals/Salts of Norfloxacin and Their Physicochemical Properties

Abstract: The low solubility and low permeability of Biopharmaceutics Classification System BCS class IV antibiotic drug norfloxacin (NORF) were studied for improvement of physicochemical properties in hydrated and anhydrous cocrystals/salts of NORF with methyl paraben (MBZ), ethyl paraben, methanesulfonic acid (MSA), benzenesulfonic acid (BSA), p-toluenesulfonic acid (PTSA), and tyramine (TYM). These crystalline forms were characterized by powder X-ray diffraction (PXRD), thermal [differential scanning calorimetry (DSC)], gravimetric [thermogravimetric analysis (TGA)], spectroscopic [infrared (IR)], and microscopy [scanning electron microscopy (SEM)] techniques. The crystal structures of NORF-MBZ-HYD, NORF-MSA-HYD, NORF-PTSA, and NORF-TYM-HYD were analyzed by single-crystal X-ray diffraction. Further, the hydrated and anhydrous forms were characterized by IR, DSC, and TGA to understand the hydration and dehydration events and by field emission SEM for crystal morphology and shape/size characteristics. Solubility, dissolution, and diffusion measurements showed that NORF anhydrous forms are more soluble and diffusible than their corresponding hydrated forms. Notably, NORF ionic crystal forms with MSA and BSA are highly soluble with good dissolution rates and high cumulative drug diffusion.

Solubility-consistent force field simulations for aqueous metal carbonate systems using graphical processing units

Abstract: Crystallization of alkaline earth metal carbonates from water is important for biomineralization and environmental geochemistry. Here, large-scale computer simulations are a useful approach to complement experimental studies by providing atomistic insights and even by quantitatively determining the thermodynamics of individual steps. However, this is dependent on the existence of force field models that are sufficiently accurate while being computationally efficient enough to sample complex systems. Here, we introduce a revised force field for aqueous alkaline earth metal carbonates that reproduces both the solubilities of the crystalline anhydrous minerals, as well as the hydration free energies of the ions. The model is also designed to run efficiently on graphical processing units thereby reducing the cost of such simulations. The performance of the revised force field is compared against previous results for important properties relevant to crystallization, including ion-pairing and mineral–water interfacial structure and dynamics. This article is part of a discussion meeting issue ‘Supercomputing simulations of advanced materials’.

Correlation of the presence of acrolein with higher alcohols, glycerol, and acidity in cachaças.

Abstract: Acrolein is a toxic aldehyde that can be present in various beverages, such as cachaça and other distilled spirits from sugarcane. The objective of this work was to detect and quantify acrolein in samples of cachaça produced by different processes in all regions of Brazil and to evaluate the possible routes of formation of this contaminant from the correlation with other secondary compounds present in the beverage using principal component analysis. Approximately 27.0% of the samples analyzed were outside the limit established by Brazilian legislation for this contaminant, with an average acrolein concentration of 14.01 mg 100 mL-1 anhydrous alcohol (aa). In the other samples, the average concentration was 0.97 mg 100 mL-1 aa. After selecting the variables that most closely correlated with the presence of acrolein in beverages, a positive correlation was found with the presence of butan-2-ol, propan-1-ol and volatile acids, and a slight correlation with the presence of phenolic compounds. Therefore, the presence of acrolein in cachaça can be associated with contamination of the fermentation must by bacteria of the genus Lactobacillus, as a result of the chemical degradation and enzymatic conversion of the glycerol produced during fermentation.

Experimental Investigation of Eco-Friendly Anhydrous Calcium Sulfate Whisker and Waste Cooking Oil Compound Modified Asphalt Mixture

Abstract: In recent years, waste material recycling and reuse have attracted great interest as environmentally friendly modifiers to improve asphalt pavement performance. In this study, anhydrous calcium sulfate whiskers (ACSW), synthesized using phosphogypsum waste, and waste cooking oil (WCO), one of the most prevalent waste oils, were used together as modifiers to create an environmentally friendly asphalt mixture. In particular, WCO was used to compensate for the negative effects of ACSW on asphalt mixture performance at low temperatures. A variety of ACSW and WCO compound-modified asphalt mixtures were fabricated. High-temperature stability, medium-temperature fatigue, low-temperature anti-cracking, moisture susceptibility, repeated freeze–thaw, and long-term aging tests were conducted to comprehensively evaluate the pavement performance. Compared to the base asphalt mixture, the compound-modified asphalt mixtures were demonstrated to have better high- and low-temperature, moisture susceptibility, fatigue, anti-freezing, and anti-aging properties, especially for the 6%ACSW and 2%WCO compound-modified asphalt mixture. Therefore, the 6%ACSW and 2%WCO compound-modified asphalt mixture was ultimately selected for use in construction, as this mixture can meet the requirements for regions with cold winters and hot summers.

Anhydrous Thermogalvanic Gel for Simultaneous Waste Heat Recovery and Thermal Management of Electronics

Abstract: Due to their distinctive characteristics of adequate flexibility, stability, and functional diversity, thermogalvanic gels have demonstrated tremendous promise in the area of renewable energy sources. However, their inability to adapt to low or high temperature environments greatly limits their practical applications. In this work, an anhydrous thermogalvanic gel prepared from dimethyl sulfoxide (DMSO)/ethylene glycol (EG) binary organic solvent is developed with Fe3+/2+ as a redox pair, which displays an exceptional temperature tolerance (−80 to 80 °C) and remarkable antidrying property (80% weight retention at 70 °C after 12 h), while maintaining stable mechanical flexibility and electrical conductivity over a wide temperature range. These merits result from the formation of numerous hydrogen bonds between DMSO and EG molecules, which prevent crystallization and hinder evaporation of the solvent simultaneously. As an applicative demonstration, by placing the thermogalvanic gel on the surface of a charging battery/charger/chip, it acts as a thermal-conductive network while performing the thermal-electric conversion, revealing a viable strategy for simultaneous waste heat recovery and thermal management. This research provides new insight into the creation of flexible thermoelectric materials for energy recovery and self-powered wearable electronics.

Anhydrous MgCO3: Controllable synthesis of various morphology based on hydrothermal carbonization

Abstract: A novel, simple and efficient anhydrous MgCO3 (AMC) synthesis method using ascorbic acid (ASA) has been developed based on the hydrothermal carbonization. In this process, ASA acts as both a CO2 source and a crystal modifier to regulate and control the crystallization of AMC. Furan derivatives, aldehydes and ketones from ascorbic acid play an unexpected role as a structure-directing agent. The effect of pH values of ASA, reaction time and the concentrations and types of Mg2+ were systematically investigated. Pure AMC with different morphology were successfully prepared.

Crystal growth and crystal structures of gold(V) compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4×HF

Abstract: Crystal growth from anhydrous hydrogen fluoride solutions of M2+ (M=Cu, Ag) and [AuF6]− gave M(AuF6)2 salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF6)2 consists of layers of Cu2+ cations connected by [AuF6]− anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF6)2 consists of a three-dimensional framework in which Ag+ cations are linked by [AuF6]− anions. Both structures are members of the MII(XVF6)2 family, in which seven different structure types have been observed to date. In the crystal structure of O2(CuF)3(AuF6)4 ⋅ HF, the bridging AuF6 units connect [−Cu−F−Cu−F−]∞ chains to form stacks between which O2+ cations and HF molecules are located.

Simultaneous Removal of As(III) and Fluoride Ions from Water Using Manganese Oxide Supported on Graphene Nanostructures (GO-MnO2)

Abstract: In the present research, the use of manganese oxides supported on graphene nanostructures (GO-MnO2), which support the synergistic action of adsorption and oxidation, in the combined removal of arsenic and fluoride from drinking water was studied. The simultaneous occurrence of fluoride and arsenic in groundwater is one of the major environmental problems, occurring mainly in anhydrous regions of Latin America and the world. These pollutants cause significant health problems and are difficult to remove simultaneously from drinking water. The structure of GO-MnO2 was characterized by the application of FTIR, EDS and SEM techniques. The effects of the adsorbent’s dosage, the pH value, the contact time and the initial concentrations of As(III) and F ions (F−) were examined with respect to the removal of As(III) and F ions. According to the results, the presence of arsenic enhances fluoride removal with increasing arsenic concentrations, and the presence of fluoride enhances arsenic removal with increasing fluoride concentrations, mainly at a neutral pH value. The co-presence removal efficiencies were 89% (a residual concentration of 1.04 mg/L) for fluoride and about 97% (a residual concentration of 2.89 μg/L) for arsenic.

Covalent Pyrimidine Frameworks via a Tandem Polycondensation Method for Photocatalytic Hydrogen Production and Proton Conduction.

Abstract: The development of heteroaromatic conjugated porous polymers (H-CPPs) have received enormous research interests, because of the important functional roles of the heteroatoms in photocatalysis and proton conduction. However, due to the synthetic challenges deriving from the stable structures, the structural diversity and synthetic methods of them are still limited. Herein, a new type of H-CPPs, covalent pyrimidine frameworks (CPFs), via an efficient tandem polycondensation reaction between aldehyde, acetyl, and amidine monomers is reported. The resulting CPFs are bridged by pyrimidine units, rich of nitrogen atoms and can be structurally regulated on demand. The CPFs are shown to be active photocatalysts for hydrogen evolution from methanol via a photo-thermo-catalysis process, achieving an excellent hydrogen evolution rate of 5282.8 µmol h-1 g-1 . The CPFs can be further processed into a mixed matrix membrane, displaying an excellent proton conductivity of 1.30 × 10-2 S cm-1 at 413 K under anhydrous condition.

NaGaSe2: A Water-Loving Multifunctional Non-van der Waals Layered Selenogallate.

Abstract: A missing member of well-known ternary chalcometallates, a sodium selenogallate, NaGaSe2, has been synthesized by employing a polyselenide flux and stoichiometric reaction. Crystal structure analysis using X-ray diffraction techniques reveals that it contains supertetrahedral adamantane-type Ga4Se10 secondary building units. These Ga4Se10 secondary building units are further connected via corners to form two-dimensional (2D) [GaSe2]∞- layers stacked along the c-axis of the unit cell, and the Na ions reside in the interlayer space. The compound has an unusual ability to absorb water molecules from the atmosphere or a nonanhydrous solvent to form distinct hydrated phases, NaGaSe2·xH2O (where x can be 1 and 2), with an expanded interlayer space, as verified by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), desorption, and Fourier transform infrared spectroscopy (FT-IR) studies. The in situ thermodiffractogram indicates the emergence of an anhydrous phase before 300 °C with the decrease of interlayer spacings and reverting to the hydrated phase within a minute of re-exposure to the environment, supporting the reversibility of such a process. Structural transformation induced through water absorption results in an increase of Na ionic conductivity by 2 orders of magnitude compared to that of the pristine anhydrous phase, as verified by impedance spectroscopy. Na ions from NaGaSe2 can be exchanged in the solid-state route with other alkali and alkaline earth metals in a topotactic or nontopotactic way, leading to 2D isostructural and three-dimensional networks, respectively. Optical band gap measurements show a band gap of ∼3 eV for the hydrated phase, NaGaSe2·xH2O, which is in good agreement with the calculated band gap using a density functional theory (DFT)-based method. Sorption studies further confirm the selective absorption of water over MeOH, EtOH, and CH3CN with a maximum water uptake of 6 molecules/formula unit at a relative pressure, P/P0, of 0.9.

Mechanisms of Mg carbonates precipitation and implications for CO2 capture and utilization/storage

Abstract: The mechanisms involved in the natural formations of dolomite (CaMg(CO3)2) and magnesite (MgCO3) have endured as challenging research questions over centuries, being yet a matter under investigation in multiple fields....

Solvent-Free Mechanochemical Dense Pore Filling Yields CPO-27/MOF-74 Metal–Organic Frameworks with High Anhydrous and Water-Assisted Proton Conductivity

Abstract: Proton-conducting solids operating in both anhydrous and humid conditions are of paramount importance for the development of fuel cells. We demonstrate that incorporating formamidinium or methylammonium ions in CPO-27/MOF-74 metal–organic frameworks renders them highly conductive under the two conditions. Highest proton conductivities reach 8 × 10–4 S/cm under anhydrous conditions, exceed 10–3 S/cm already at low relative humidity (30–50% RH) and low temperatures (25–60 °C), and reach 10–2 S/cm at 60 °C and 70% RH. The dense pore filling with the protic cations is enabled by solvent-free mechanochemistry and stoichiometric saturation of open metal sites (Mg, Ni) with thiocyanate ligands. DFT modeling reveals that high anhydrous proton conductivity is associated with the presence of water-free extended networks of hydrogen bonds along the [001] channel and together with electrochemical impedance measurements (EIS) shed light on the mechanism of proton transport.

Proton-Conducting Polymeric Membranes Based on 1,2,4-Triazole

Abstract: In this review, a comparative analysis of the literature and our own results obtained in the study of the physicochemical, dielectric, and proton-conducting properties of composite polymer materials based on 1H-1,2,4-triazole has been carried out. It has been established that 1H-1,2,4-triazole and homopolymers and copolymers of 1-vinyl-1,2,4-triazole are promising for the development of proton-conducting fuel cell membranes. They significantly improve the basic characteristics of electrolyte membranes, increase their film-forming ability, increase thermal stability up to 300–330 °C, increase the electrochemical stability region up to 3–4 V, promote high mechanical strength and morphological stability of membranes, and provide high ionic conductivity (up to 10−3–10−1 S/cm) under anhydrous conditions at temperatures above 100 °C. There is also an improvement in the solubility and a decrease in the glass transition temperature of polymers based on 1-vinyl-1,2,4-triazole, which facilitates the processing and formation of membrane films. The results obtained demonstrate the uniqueness of 1H-1,2,4-triazole and (co)polymers based on 1-vinyl-1,2,4-triazole and the promise of their use for the creation of heat-resistant plastic and electrochemically stable, mechanically strong proton-conducting membranes with high ionic conductivity under anhydrous conditions and at high temperatures.

Cu(II)-Catalyzed Cascade of N-Phenyl-o-phenylenediamine with Benzaldehyde: One-Step Direct Construction of 2-(1-Phenyl-1H-benzo[d]imidazol-2-yl)phenols.

Abstract: A practical protocol for the construction of hydroxylated 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenols (PBIs) from N-phenyl-o-phenylenediamine with benzaldehydes was developed. The cascade reaction was enabled by heating a mixture of the two substrates in the presence of air as an oxidant and anhydrous Cu(OAc)2 as a catalyst in dimethyl sulfoxide, and a diverse series of PBIs were synthesized in moderate to good yields (69-81%). Furthermore, the synthesis of the PBIs was enabled via a one-pot cascade reaction that proceeded through subsequent dehydration condensation, intramolecular cyclization, and aromatic C-H hydroxylation. This protocol can be used for the synthesis of hydroxylated PBI via a one-pot annulation C-H hydroxylation reaction rather than through a series of multistep reactions, which provides the possibility of further modification.

Limits in reaching the anhydrous state of wood and cellulose

Abstract: Abstract Water-sorption studies and certain organic chemistry reactions require water removal from cellulosic samples. This is hindered by the strong interaction of cellulosic materials with water, and it remains uncertain if a completely anhydrous state can be reached under common drying conditions. Here, different drying conditions were applied to wood and cellulose, and the residual moisture contents were quantified either gravimetrically or by coulometric Karl-Fischer titration. Vacuum-drying at 103 °C and ≤ 1 mbar for at least 360 min decreased the moisture content to ≤ 0.04%. However, in automated sorption balances, drying at atmospheric pressure under dry air or nitrogen flow left some samples with more than 1% moisture content. The residual moisture content obtained under dry gas flow was temperature dependent. Increasing the temperature up to 55 °C decreased the residual moisture content and cooling resulted in a moisture re-uptake, presumably due to small quantities of water vapor in the surrounding atmosphere. These effects must be considered in fundamental studies on water interactions of cellulosic materials.

The role of silanol groups on the reaction of SiO 2 and anhydrous hydrogen fluoride gas

Abstract: It is essential to etch SiO2 for producing silica glass components, semiconductor devices, and so on. Although wet-etching with hydrogen fluoride (HF) solutions is usually employed for this purpose, it faces a drawback that microstructures stick during the drying of the solution. To overcome this problem, we have developed a dry-etching technique with gaseous HF at high temperatures. In the present study, an interesting phenomenon was found that silicon thermal oxides were much less etched than vitreous silica by gaseous HF. Such difference had not been found in wet- or humid HF gas etching. Because their bulk chemical formulae are the same (SiO2), it was suggested that the surface species affected the reaction rate. In fact, preprocessing with water vapor plasma remarkably increased the etching rate on the thermal oxides layer, and vacuum heating almost completely suppressed the reaction on the vitreous silica and the plasma-treated thermal oxides. These results indicate that the surface silanol groups enhance the reaction between SiO2 and gaseous HF. Based on the results, a model of chain reaction for SiO2 and gaseous HF was proposed, where the surface silanol groups act as the reaction center.

Light-assisted drying (LAD) for anhydrous preservation of biologics: processing of samples inside glass lyophilization vials

Abstract: Protein-based therapeutics are used to treat or prevent a range of diseases, but a challenge for the expanded use of these products is the need for cold storage that makes distribution difficult in low-resource settings. Lyophilization is a common method used to stabilize protein-based products. However, this process remains expensive, and many freeze-dried proteins require cold-chain storage. Anhydrous preservation in an amorphous trehalose matrix has been successfully used as an alternative to lyophilization. A new processing technique called light assisted drying (LAD) has been used to successfully dry proteins in preparation for anhydrous storage. Water is selectively heated via near-infrared (1064 nm) illumination, rapidly removing water from a sample, and forming an amorphous matrix that can be stored at supra-zero temperatures. In previous work, large volume samples (0.25 ml) were successfully LAD processed on glass coverslips, but this substrate is not typically used in industry. In this study, large volume samples are LAD processed in vials that are commonly used to lyophilize vaccines. After LAD processing, the samples are stored at room temperature (20◦C) or refrigerated (4◦C) for one month. The end moisture content of samples was determined immediately after processing/storage to evaluate the effectiveness of water removal via LAD. The trehalose matrix was characterized using polarized light imaging to determine if crystallization occurred during storage, potentially damaging embedded proteins. These preliminary studies indicate that LAD can effectively stabilize large volume samples in glass lyophilization vials and demonstrates the potential use of LAD to stabilize products such as vaccines.