Aqueous Sodium Hydroxide Solution Research Articles

ISOLATION, STRUCTURE AND PHYSICO-CHEMICAL PROPERTIES OF CHITIN-GLUCAN COMPLEXES OF HIGHER FUNGI

The article is devoted to the study of isolation processes, chemical structure and rheological properties of chitin-glucan complexes from the biomass of Armillaria mellea. Because of the studies, it was found that the yield of chitin-glucan complexes ranged from 11.0 to 24.9% with a degree of deacetylation from 24 to 55%. The maximum yield was obtained by treating the fruiting bodies of fungi at the stage of deproteinization with a 3% aqueous solution of sodium hydroxide with mechanical stirring at 225 rpm for 60 min at 75±5°C. It is shown that the degree of deacetylation correlates with the values of the alkali concentration used. The IR spectra of the obtained samples of chitin-glucan complexes include absorption bands characteristic of stretching and bending vibrations of the bonds of chitin and glucan links and coincide with the spectra of chitin-glucan complexes of other fungi. It has been established that the viscosity characteristics of a 1% solution of a chitin-glucan complex in 2% hydrochloric acid are 14 and 190 times lower than 5% and 10% solutions, respectively. Increasing the shear rate makes it possible to detect a decrease in the viscosity of all studied solutions. Storage of a 1% solution of chitin-glucan complexes for 7 days at 25±2°C is accompanied by a decrease in viscosity; the viscosity of 5 and 10% solutions remains stable.

Solubility and thermodynamic properties of sodium theophylline salt in aqueous sodium hydroxide solution at different temperatures

The solubility data of sodium theophylline salt in the water and aqueous sodium hydroxide systems with molarities of 0.00, 0.01, 0.10, 0.20, 0.49, and 0.96 mol kg−1at temperatures ranging from 283.15 to 368.15 K are determined via the equilibrium method. The experimental results show that the solubility of sodium theophylline increases on increasing the temperature at the same concentration of NaOH solution and decreases with an increase in the NaOH concentration at the same temperature. These results correlate well with the polynomial empirical equation, the modified Apelblat equation, and the λh equation. At the same time, it is found that the modified Apelblat equation gives better correlation results than the polynomial empirical and the λh equations. The results show that the three models correlate well with the solubility data of sodium theophylline. The modified Van’t Hoff equation is used to estimate the thermodynamic properties including the dissolution enthalpy, the dissolution entropy, and the Gibbs free energy change of sodium theophylline when dissolved in aqueous NaOH solution at different concentrations. The solubility data and correlation results obtained from the experiments can provide basic data for the cooling crystallization, separation, and purification of sodium theophylline and are expected to be of great significance for the research and development of sodium theophylline and for caffeine production.

Стресс-тесты антраценпроизводных растительного происхождения

Objective: to study the stability of solutions of standard samples of sennoside B and glucofrangulin A by stress tests using high performance liquid chromatography (HPLC). Materials and methods. The objects of the study were solutions of standard samples of sennoside B, as well as glucofrangulin A. Stress agents were 0.5M aqueous solution of copper (II) chloride (CuCl2), 0.5M aqueous solution of iron (III) chloride (FeCl3), 0.1M aqueous solution of hydrochloric acid (HCl), as well as 0.1M aqueous solution of sodium hydroxide (NaOH) and a solution of hydrogen peroxide (H2O2) 3%. The study was carried out using an Agilent 1100 liquid chromatograph. For this purpose, a Zorbax SB-C18 reverse-phase column (4.6×250 mm, 5 µm) was used. Elution of the mobile phase (acetonitrile and highly purified water, which was adjusted to pH 2 with phosphoric acid) was carried out in a gradient mode. Detection was carried out at wavelengths of 360 nm and 435 nm. Results. It was found that a solution of a standard sample of glucofrangulin A is stable for 14 days under the influence of 0.1M aqueous solution of HCl and 0.1M aqueous solution of NaOH, as well as 0.5M aqueous solution of FeCl3 and 3% H2O2 solution. When a solution of a standard sample of glucofrangulin A interacts with a 0.5M aqueous solution of CuCl2, its destruction is observed. When a standard sample of sennoside B reacts with a 3% H2O2 solution and a 0.5M aqueous CuCl2 solution, it remains stable. When interacting with other stress agents, its destruction occurs. Conclusion. The results obtained on the stability of solutions of standard samples of anthracene derivatives determine the main physico-chemical factors that cause their destruction, which can be taken into account when validating analytical methods, justifying the conditions of storage, packaging and processing of medicinal plant materials that contain anthracene derivatives.

STUDY OF THE PRODUCTION PARAMETERS INFLUENCE OF HIGHLY POROUS CELLULOSIC MATERIALS ON THEIR STRUCTURAL CHARACTERISTICS

Highly porous materials based on natural polymers are present of particular interest in various applications. Among them, for example, biomedicine, water purification, thermal insulation. This paper describes the developed method for obtaining highly porous materials based on cellulose, which include: dissolving microcrystalline cellulose in an aqueous solution of sodium hydroxide with urea; cross-linking cellulose using epichlorohydrin; drying the resulting gels. The influence of the concentrations of cellulose and the crosslinking agent and the drying method – freeze-drying (obtaining cryogels) and supercritical drying (obtaining aerogels) – on the final structural characteristics of the obtained materials has been studied. Cryogels and aerogels based on cellulose have been characterized by helium pycnometry, nitrogen porosimetry, and scanning electron microscopy. It was found that with an increase in the concentration of cellulose and epichlorohydrin, the porosity of the samples significantly decreases (from 84% to 22% for aerogels). For samples with the highest concentration of the crosslinking agent, the porosity of cryogels is higher (63%) than that of aerogels (22%). The specific surface area and mesopore volume were determined by nitrogen porosimetry, and nitrogen adsorption-desorption isotherms were obtained. Despite the fact that aerogels have a lower porosity, they are characterized by a higher specific surface area than cryogels (162 m2/g for aerogel and 65 m2/g for cryogel containing 6 wt.% cellulose and 4 wt.% epichlorohydrin). Scanning electron microscopy images were obtained, from which it can be seen that aerogels have a porous fibrous structure, while cryogels are characterized by a layered macroporous structure. The use of supercritical drying using CO2 avoids the destruction of the mesoporous structure of the material. For citation: Fedotova O.V., Trofimova K.V., Tsygankov P.Y., Safarov R.R. Study of the production parameters influence of highly porous cellulosic materials on their structural characteristics. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 107-113. DOI: 10.6060/ivkkt.20236602.6736.

Pulping of Mitsumata by using Twin Screw Extruder

he bast fiber of Mitsumata （Edgeworthia papyrifera Sieb. et Zucc.） has traditionally been used as a raw material of paper. Mitsumata belongs to Thymelaeaceae family, and the paper made from its bark is known to have hue of egg yolk color and unique texture. Mitsumata pulp for paper making is manufactured as follows. Mitsumata branches are steamed and barks are taken off, from which its epidermis and cuticle are removed. Then, the residual white bark is cooked with an aqueous alkaline solution in the digester. Compared to the chemical composition of wood, the white bark contains more amount of pectin and less amount of lignin. So, pulping of Mitsumata primarily aims to remove pectin that works as a binder among cells, and pectin in the white bark can be removed by alkaline solution under heated.In this research, we used twin screw extruder to produce Mitsumata pulp from its white bark. Twin screw extruder consists of two co-rotating screws in a cylinder barrel, and it is widely used in the manufacturing industry for material processing such as shearing, kneading, heating and mixing. The white bark is impregnated with an aqueous solution of sodium hydroxide before defiberizing by twin screw extruder. The process of twin screw extruder is continuous and its processing time is short compared to normal cooking process.The effect of processing temperature and addition rate of sodium hydroxide on defiberizing of Mitsumata fiber was investigated. We found that Mitsumata fibers could be defiberized by twin screw extruder at lower temperature than cooking process.Handsheets were made from the pulp produced by twin screw extruder, and their optical and physical properties were studied. The ISO brightness of the handsheet produced by twin screw extruder was high compared to the handsheet produced by normal cooking process. The pulp yield produced by twin screw extruder was also higher than the yield by cooking process. The side chemical reaction is considered to be suppressed during the extrusion process because of the low processing temperature and the short processing time.

High performance nano hydroxyapatite coating on zinc for biomedical applications

Zinc and its alloys have been given promising consideration as a new biodegradable implant for use in the human body. Compact and uniform nano hydroxyapatite coatings containing chitosan were successfully deposited onto zinc substrate in an aqueous solution utilizing microwave-assisted process in about 10 min. The quick composite coatings are derived by microwave heating compared with the coatings derived by electrodeposition. The as-deposited coatings formed by electrodeposition synthesis were known as brushite, which was converted to hydroxyapatite after 1 h of immersion (post treated) in 1 M aqueous sodium hydroxide solutions at 100 °C. The incorporation of chitosan (from 0.01–0.05 g/l) into the coating composition results in a smooth and uniform coating structure. SEM, EDS, and an X-ray diffractometer were utilized to analyze coated samples' surfaces to evaluate their surface morphology, chemical composition, and crystalline structures. The in vitro degradation behavior of the composite-coated samples in simulated body fluid at pH 7.4 and 37 °C was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization. The outcomes showed that microwave-derived coatings provided superior corrosion resistance for zinc implants as compared to electrodeposited coatings. Furthermore, the use of chitosan in hydroxyapatite coatings increased electrochemical corrosion performance. Low chitosan concentrations (0.01–0.03 g/l) exhibit superior anti-corrosion properties than higher concentrations (0.05 g/l). Against Staphylococcus aureus, the coatings demonstrated strong antibacterial efficacy. These corrosion outcomes and the fruitful deposition of a hydroxyapatite/chitosan composite coating on zinc substrate indicate that the coating is efficient for the creation of new composite coatings for either functional implants or regenerative medicine. The resultant coating may be an excellent option for bone implants.

Chemoconvection of miscible solutions in an inclined layer

This paper presents an experimental and numerical investigation of the chemoconvective flow of two miscible reacting solutions that generate a plain layer oriented at some angle to the gravity field. In the experiments, the aqueous solutions of nitric acid and sodium hydroxide were used. The system evolves from an initial state, in which each homogeneous solution occupies half of the layer, and the contact surface between the layers is flat. When the reacting solutions come into contact with each other, an acid-base neutralization reaction occurs, forming salt and water. The system configuration is chosen so that the acid solution of lower density rests on top of the denser base. This excludes the development of the Rayleigh–Taylor instability. The experiments were performed for such initial concentrations of the reagents at which a wave regime is realized in the system. The wave comprises a density jump rapidly advancing in the direction of gravity and separating the immobile alkali solution and the layer of acid and salt mixture, the convective motion of which feeds the frontal reaction with fresh acid. The visualization of the flow in the experiments was performed using a Fizeau interferometer. The numerical study of a complete three-dimensional problem was carried out using the ANSYS CFX hydrodynamic simulation program. We studied the flow evolution at a gradual increase in the angle of inclination from 0° to 70°. We found that the layer inclination leads to a significant change in the structure and intensity of the convective motion. Already at small inclination angles (up to 30°), the flow becomes three-dimensional, which makes the Hele-Shaw approximation inapplicable to this case. We show that there is a spontaneous stratification of salt and acid concentration fields in the cocurrent wave flow. With an increase in the angle of inclination, the wave velocity decreases, and chemoconvection in the cocurrent flow becomes less intense and acquires a certain vortex structure. At larger angles (from 50° to 70°), the wave front is strongly deformed or the wave breaks up. We demonstrate that an up-and-down fluid flow develops in the layer above the density jump. This flow eventually loses its stability with respect to the vertical rolls of solutal Rayleigh convection. There is a good agreement between the experimental measurements and the results of numerical simulation of the 3D problem.

Conversion of Lithium Chloride into Lithium Hydroxide by Solvent Extraction

A hydrometallurgical process is described for conversion of an aqueous solution of lithium chloride into an aqueous solution of lithium hydroxide via a chloride/hydroxide anion exchange reaction by solvent extraction. The organic phase comprises a quaternary ammonium chloride and a hydrophobic phenol in a diluent. The best results were observed for a mixture of the quaternary ammonium chloride Aliquat 336 and 2,6-di-tert-butylphenol (1:1 molar ratio) in the aliphatic diluent Shellsol D70. The solvent extraction process involves two steps. In the first step, the organic phase is contacted with an aqueous sodium hydroxide solution. The phenol is deprotonated, and a chloride ion is simultaneously transferred to the aqueous phase, leading to in situ formation of a quaternary ammonium phenolate in the organic phase. The organic phase, comprising the quaternary ammonium phenolate, is contacted in the second step with an aqueous lithium chloride solution. This contact converts the phenolate into the corresponding phenol by protonation with water extracted to the organic phase, followed by a transfer of hydroxide ions to the aqueous phase and chloride ions to the organic phase. As a result, the aqueous lithium chloride solution is transformed into a lithium hydroxide solution. The process has been demonstrated in continuous counter-current mode in mixer–settlers. Solid battery-grade lithium hydroxide monohydrate was obtained from the aqueous solution by crystallization or by antisolvent precipitation with isopropanol. The process consumes no chemicals other than sodium hydroxide. No waste is generated, with the exception of an aqueous sodium chloride solution.Graphical

In Situ Monitoring of the Surface Evolution of a Silver Electrode from Polycrystalline to Well-Defined Structures.

Capturing the surface-structural dynamics of metal electrocatalysts under certain electrochemical environments is intriguingly desired for understanding the behavior of various metal-based electrocatalysts. However, in situ monitoring of the evolution of a polycrystalline metal surface at the interface of electrode-electrolyte solutions at negative/positive potentials with high-resolution scanning tunneling microscopy (STM) is seldom. Here, we use electrochemical STM (EC-STM) for in situ monitoring of the surface evolution process of a silver electrode in both an aqueous sodium hydroxide solution and an ionic liquid of 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl) amide driven by negative potentials. We found silver underwent a surface change from a polycrystalline structure to a well-defined surface arrangement in both electrolytes. In NaOH aqueous solution, the silver surface transferred in several minutes at a turning-point potential where hydrogen adsorbed and formed mainly (111) and (100) pits. Controversially, the surface evolution in the ionic liquid was much slower than that in the aqueous solution, and cation adsorption was observed in a wide potential range. The surface evolution of silver is proposed to be linked to the surface adsorbates as well as the formation of their complexes with undercoordinated silver atoms. The results also show that cathodic annealing of polycrystalline silver is a cheap, easy, and reliable way to obtain quasi-ordered crystal surfaces.

Improving the color strength of poly(ethylene terephthalate) fabrics with a turmeric natural dye

PurposeThis study aims to enhance the dyeability of polyester fabrics with turmeric natural dyes through plasma and alkaline treatments. The aim is to achieve better color strength in dyed samples without significant changes in their other properties. This is done while the weight loss is kept in a range with no considerable effect on those properties.Design/methodology/approachThe surface of a poly(ethylene terephthalate) fabric was modified using oxygen plasma at a low temperature. The alkaline hydrolysis of that polyester fabric was also done through treating it with an aqueous sodium hydroxide (NaOH) solution. The untreated and treated polyester fabrics were studied for the changes of their physical characteristics such as weight loss, wetting behavior, strength loss, bending length, flexural rigidity and K/S and wash fastness. The samples were treated with plasma and sodium hydroxide and dyed with a turmeric natural dye.FindingsIn comparison to the untreated sample, the plasma-treated, alkaline-treated and plasma treatment followed by alkaline hydrolysis polyester experienced 9.3%, 68.6% and 102.3% increase in its color depth as it was dyed with a turmeric natural dye, respectively. The plasma treatment was followed by alkaline hydrolysis. The improvement in the color depth could be attributed to the surface modification.Originality/valueIn this paper, investigations were conducted of the separate effects of plasma treatment and alkaline hydrolysis as well as their synergistic effect on the dyeing of the polyester fabric with a natural dye obtained from turmeric.

A New Force Field for OH- for Computing Thermodynamic and Transport Properties of H2 and O2 in Aqueous NaOH and KOH Solutions.

The thermophysical properties of aqueous electrolyte solutions are of interest for applications such as water electrolyzers and fuel cells. Molecular dynamics (MD) and continuous fractional component Monte Carlo (CFCMC) simulations are used to calculate densities, transport properties (i.e., self-diffusivities and dynamic viscosities), and solubilities of H2 and O2 in aqueous sodium and potassium hydroxide (NaOH and KOH) solutions for a wide electrolyte concentration range (0-8 mol/kg). Simulations are carried out for a temperature and pressure range of 298-353 K and 1-100 bar, respectively. The TIP4P/2005 water model is used in combination with a newly parametrized OH- force field for NaOH and KOH. The computed dynamic viscosities at 298 K for NaOH and KOH solutions are within 5% from the reported experimental data up to an electrolyte concentration of 6 mol/kg. For most of the thermodynamic conditions (especially at high concentrations, pressures, and temperatures) experimental data are largely lacking. We present an extensive collection of new data and engineering equations for H2 and O2 self-diffusivities and solubilities in NaOH and KOH solutions, which can be used for process design and optimization of efficient alkaline electrolyzers and fuel cells.

Cellulose/glucomannan blends prepared from aqueous sodium hydroxide solution and their practical use as food materials

Aqueous sodium hydroxide solution is one of the simplest and most environmentally friendly solvents of cellulose. Regenerated cellulose/glucomannan blends were prepared from an aqueous sodium hydroxide solution, and the mechanical properties and structure of the blends were investigated. In addition, the noodle-shaped blends were sensory evaluated as food materials. The blends exhibited porous structures, which corresponded with high water and oil absorption. The strength and modulus of the blends were markedly low, probably due to the highly porous structure. The viscoelastic measurement indicated that cellulose and glucomannan existed in a rubbery state under wet conditions. The blends had a good oral sensation, probably derived from the remarkable porous structure, high water content, low strength and modulus, and rubbery state in wet conditions. The sensory evaluation suggested that the noodle-shaped blends can be used as a food material with a texture similar to capellini pasta.

INTERACTION OF BARIUM AND MAGNESIUM CONTAINING SOLIDS WITH CARBONATE LOADED SOLUTIONS

Bu çalışmada, baryum (Ba(OH)2·8H2O ve BaSO4) veya magnezyum (Mg(OH)2 ve MgSO4·7H2O) içeren katıların, yerel bir simitsonit (ZnCO3) cevher örneğinin sulu sodyum hidroksit çözeltilerinde liçi sonrasında oluşan çözünmüş karbonat yüklü çözeltilerle etkileşimi, bu yüklü çözeltilerdeki çözünmüş karbonatın (BaCO3 veya MgCO3 olarak) uzaklaştırılması amacıyla, X-ışını kırınımı analizleri kullanılarak incelenmiştir. Çözünmüş karbonat yüklü çözeltilerin Ba(OH)2·8H2O ve MgSO4·7H2O katılarıyla etkileşimini takiben, sırasıyla, tek faz olarak BaCO3 ve ana faz olarak Mg(OH)2 içeren katıların oluştuğu gözlenmiştir. Diğer taraftan, BaSO4 ve Mg(OH)2 katılarının yüklü çözeltilerle herhangi bir etkileşime girmediği ve dönüşmeden kaldıkları belirlenmiştir. Bununla birlikte, çalışılan tüm deneysel koşullar altında, baryum veya magnezyum zinkat fazlarına dönüşümün olmadığı da ortaya çıkarılmıştır. Bu çalışma kapsamında, toprak alkali baryum ve magnezyum içerikli katıların çözünmüş karbonat yüklü çözeltilerle etkileştirilmeleri sonrasında ilgili karbonat fazlarına dönüşüm özellikleri, bu katıların çözünürlükleri dikkate alınarak tartışılmıştır. Ayrıca, seçilmiş deneyler sonrasında elde edilen bazı dönüşmüş katıların kızılötesi spektrumları ve taramalı elektron mikroskop görüntüleri de bu çalışma kapsamında sunulmuştur.

The effect of Marangoni convection on mass transfer in a rising droplet with surface reaction

Dispersing of the medium from which the desired component is extracted is still one of the main approaches to liquid extraction. However, despite its high efficiency, this approach is still of empirical nature, since the choice of the main parameters - the average drop diameter and the residence time of the drop in the surrounding liquid (the extractant) - is determined by experiment in relation to the initial concentration of the extracted substance (reagent). The main difficulty with a full-scale theoretical treatment and numerical simulation is a three-dimensional shape of the droplet and, accordingly, the lack of experimental data on the structure of convective flows and the dynamics of reagent concentration fields in the moving droplet. The situation can get worse when the extracted component is a surfactant or reactive against the extractant. The paper presents the results of an experimental study of the structure and evolution of flows and distribution of a reagent (acetic acid) diffusing from a rising cylindrical droplet with an insoluble base component into a chemically active medium (aqueous sodium hydroxide solution). The motion of the droplet is accompanied by the development of Marangoni convection and neutralization reaction on the droplet surface.

Synthesis and characterization of alkali-activated zeolite-poor rocks

Zeolite-geopolymer composite materials were obtained through mechanical activation using planetary ball mill followed by chemical activation using an aqueous solution of sodium hydroxide (NaOH), these materials integrate the beneficial features of both zeolites and geopolymers. In this present work, the morphological characteristics, microstructure, phase determination of raw materials and the generated ceramic samples were studied by several characterization methods such as SEM, EDS and XRD. The microstructural analysis confirms the formation of needle-like structure in sub-micron and nanostructure, while the phase identification reveals the creation of single-phase zeolite (heulandite).

Physical, mechanical, and sliding wear behavior of epoxy composites filled with surface modified walnut shell particulate

AbstractThe current study aims to examine the influence of surface‐modified micro‐sized walnut shell particulates (WSP) with an aqueous solution of sodium hydroxide (NaOH) on epoxy composites. For that, epoxy/WSP composites are prepared by varying the WSP content up to 20 wt%. In this investigation, the physical properties (surface morphology, density, voids percentage, water uptake), mechanical properties (tensile, flexural, compressive, hardness), and sliding wear behavior of the composites are reported. From the micrographs, it is clear that WSP established good adhesion with the epoxy matrix. Further, it is found that the density, void content, water intake capacity, compressive strength, and hardness increase with WSP loading. Against that, the tensile and flexural strength is somewhat reduced at higher filler loading. Sliding wear tests are performed as per L25 Taguchi's orthogonal array. From the analysis, it is observed that WSP content is the most significant factor and sliding distance is the least significant factor for minimizing the wear rate. For analyzing the sliding wear performance under varied conditions, a prediction model is proposed using an artificial neural network to forecast the sliding wear rate of epoxy/WSP composites over a wide range of experimental domains.

Doping of Carbon Nanotubes with Encapsulated Phosphorus Chains

Single-walled carbon nanotubes (SWCNTs) are a perfect host for the formation of one-dimensional phosphorus structures and to obtain hybrid materials with a large P-C ratio. This work presents a procedure for high-yield phosphorus filling of commercial Tuball SWCNTs and efficient removal of phosphorus deposits from the external nanotube surface. We probed white and red phosphorus as precursors, varied the synthesis temperature and the ampoule shape, and tested three solvents for sample purification. High-resolution transmission electron microscopy and Raman spectroscopy indicated crystallization of interior phosphorus in a form resembling fibrous red phosphorus. An aqueous sodium hydroxide solution allowed removing the majority of external phosphorus particles. Thermogravimetric analysis of the product determined ∼23 wt % (∼10 atom %) of phosphorus, and the X-ray photoelectron spectroscopy (XPS) data showed that ca. 80% of it is in the form of elemental phosphorus. Externally purified SWCNTs filled with phosphorus were used to study the interaction between the components. Raman spectroscopy and core-level XPS revealed p-type SWCNT doping. Valence-band XPS data and density functional theory calculations confirmed the transfer of the SWCNT electron density to the encapsulated phosphorus.

Sensitive Ion-Chromatographic Determination of Citric Acid in Urine

Urine citrate analysis is relevant in the screening and monitoring of patients with calcium nephrolithiasis. A sensitive, fast, easy, and low-maintenance ion chromatographic (IC) method with conductivity detection for the analysis of urine citrate is developed and validated. Its application on true samples is also reported. Sample urine is diluted with a water solution containing internal standard (IS) before the chromatographic assay. The isocratic chromatographic run time is twenty-five minutes, using sodium hydroxide aqueous solution as the mobile phase. The method is fully validated as a quantitative method to objectively demonstrate its applicability for the intended use. The analytical response is linear in the 0.08–10.4 mmol/L concentration range. Precision and accuracy studies carried out on spiked urine and internal quality control samples reveal an imprecision CV% lower than 11% and an accuracy between 85 and 103%. The stability of citrate in urine samples is also evaluated. An easy, rapid, and low-maintenance, cost-effective IC method for urinary citrate determination is developed and validated. Internal standardization improves reliability and precision. The method has been currently used in our laboratory over recent years to analyze more than 1000 samples per year.

An azine-linked 2D porphyrinic covalent organic framework for red light photocatalytic oxidative coupling of amines

The construction of two-dimensional covalent organic frameworks (2D COFs) with robust stability for photocatalysis has gained intensive attention recently. Herein, we report the design and synthesis of a highly crystalline azine-linked porphyrinic 2D COF (Por-HZ-COF). Our results clearly show that Por-HZ-COF adopts an eclipsed AA stacking structure with a high Brunauer-Emmett-Teller (BET) specific surface area of 1586 m2/g. In addition, Por-HZ-COF is chemically stable under various conditions, even in 12 M sodium hydroxide aqueous solution or 9 M hydrochloric acid. Moreover, Por-HZ-COF can be used for the photocatalytic aerobic oxidative coupling of benzylamines under red light irradiation with high activity and good reusability. This study demonstrates a novel robust 2D COF with azine linkage that has promising applications in photocatalysis.

Wet-spun PEDOT:PSS/CNT composite fibers for wearable thermoelectric energy harvesting

Fiber-based thermoelectric materials have received increased attention as they are light weight and can be sewn and woven for portable and wearable thermoelectric generators. In this work, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/single-walled carbon nanotube (SWCNT) composite fibers were fabricated by a continuous wet spinning process using concentrated sulfuric acid as a coagulation bath, which could effectively remove the excess PSS and result in improved electric conductivity. With a SWCNT content of 50 wt%, the PEDOT:PSS/SWCNT composite fibers show a high electric conductivity of 2982 S cm−1 and a Seebeck coefficient of 27.1 μV K−1, leading to a promising power factor of 219 μW m−1 K−2. By further treated with sodium hydroxide aqueous solution, the PEDOT:PSS/SWCNT fibers exhibit an enhanced Seebeck coefficient of 36.4 μV K−1 and a power factor of 280 μW m−1 K−2, which is higher than most PEDOT:PSS-based thermoelectric fibers. The mechanism of the enhancement of thermoelectric properties for the composite fibers was discussed. A flexible thermoelectric generator with five pairs of PEDOT:PSS/SWCNT fibers and copper wires were assembled and the electrical power generation capability were evaluated, demonstrating its potential application in wearable electronic devices.