Borate Buffer Solution Research Articles

A molecular cobaloxime cocatalyst and ultrathin FeOOH nanolayers co-modified BiVO4 photoanode for efficient photoelectrochemical water oxidation

BiVO4 has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions. So far, sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance of BiVO4. In this study, a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporous BiVO4 electrode, followed by modification with a cobaloxime (Co(dmgH)2(4-COOH-py)Cl) molecular cocatalyst. Under irradiation of a 100 mW cm−2 (AM 1.5G) Xe lamp, the photocurrent density of the cobaloxime/FeOOH/BiVO4 composite photoanode reached 5.1 mA cm−2 at 1.23 V vs. RHE in 1.0 M potassium borate buffer solution (pH = 9.0). The onset potential of the optimal cobaloxime/FeOOH/BiVO4 photoanode exhibited a 460 mV cathodic shift relative to bare BiVO4. In addition, the surface charge injection efficiency of the composite photoanode reached ∼80% at 1.23 V vs. RHE and the incident photon-to-current efficiency (IPCE) reached ∼88% at 420 nm.

Self-assembly and cleaning and wettability of a polysaccharide-surfactant system formed from the cationic hydroxypropyltrimethyl ammonium chloride chitosan and nonionic sucrose lauric acid ester

Contact lens care solution was prepared via hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and sucrose lauric acid ester (SML) via self-assembly in borate buffer solution (BBS). The elution efficiency of lipids, micellization, and wettability properties of HACC-SML in BBS was studied systematically using high-performance liquid chromatography (HPLC), dynamic light scattering (DLS), zeta potential, surface tension, and contact angles methodologies. The elution efficiency of the lipid increased from 46.98% to 65.68%, whereas DLS and zeta potential data varied with the addition of SML. These caused the shrinkage of micelles, and the system became stable, and further revealed that SML was a non-ionic biosurfactant with excellent performance. The result of surface tension at water-air and contact angles on silicone hydrogel lens at 25 °C showed that SML has outstanding adsorption capacity with an increased degree of wetting, ensuring the comfort and safety of wearing.

THEOBROMINE AND THEOPHYLLINE DETERMINATION IN BLACK TEA BY CAPILLARY ZONE ELECTROPHORESIS USING LARGE VOLUME SAMPLE STACKING

Some features of the formation of methylxanthines during growth and development of tea leaves are discussed, and the information about the content of minor methylxanthines, theobromine (TB) and theophylline (TF), in tea products is summarized. The expediency of using TB and TF as marker substances characterizing the quality of tea is substantiated. Possibility and limitations of using electrophoretic methods for TB and TF determination in tea products were investigated. Experimental studies were carried out to develop a method for TB and TF determination in black tea by capillary zone electrophoresis using the procedure of analytes online concentration – large volume sample stacking (LVSS-CZE-UV). Optimized conditions for the analytes separation were using the borate buffer solution (pH = 9.8, 90 mM concentration) and 20 kV voltage in the system. The following conditions for the analytes concentrating were proposed: time for introducing a 40-fold diluted tea extract (1.0 g per 100 ml of water) was 200 s at 50 mbar; the polarity reversal time was 1.5–1.7 min at a voltage of –10 kV. Under the selected conditions, the TB and TF concentration efficiency factors were 28 and 38, respectively. The analysis time did not exceed 22 min. For the developed method, the repeatability, intralaboratory precision, trueness and accuracy of the results of analytes determination in black tea samples were evaluated. Determining TB (0.04–4.0 mg/g concentration range) and TF (0.04–1.0 mg/g concentration range) in tea showed that the relative standard deviation of the results of the analytes determination σ(Δ) did not exceed 7 and 12 %, respectively. Analysis of various samples of black tea using the developed method showed that TB content ranged from 0.14 to 2.32 mg/g and TF content ranged from "< 0.040" to 0.15 mg/g.

Sorption of Yb(III) from aqueous solution on Na-clinoptilolite

The sorptive properties of the Na-modified Transcarpathian clinoptilolite towards Yb(III) under dynamic conditions were investigated. The sorption capacity of the Na-form of Transcarpathian clinoptilolite towards Yb(III) significantly depends on the concentration of ytterbium salt, the pH of solution and the temperature of the preliminary calcination of the sorbent. The buffer solution has been used to maintain the constant value of pH, ioniс strength of the solutions and to improve the metrological characteristics of preconcentration methods of Yb. The trace amounts of Yb(III) most effectively are sorbed with borate buffer solution. The final concentration of the borate buffer in the sample solution is 4·10 - 4 М. The sorption capacity of Na-clinoptilolite under optimal conditions (diameter of zeolite grains was 0.20–0.31 mm; flow rate of ytterbium(III) solution with concentration 1.0 µg/mL through sorbent was 5 mL/min; temperature of preliminary thermal treatment ~ 50 ºC and pH 9.5) was 8.1 mg ytterbium per 1 g of Na-modified clinoptilolite. The sorption of Yb(III) is carried out mainly by means of the adsorption of soluble hydrolyzed forms of Yb(III) on the zeolite surface. The influence of the most common water ions on the preconcentration of Yb(III) on the Na-form of Transcarpathian clinoptilolite has been established. The solutions of 1 M KCl acidified by a hydrochloric acid to pH 4.0 are the most effective desorbents of ytterbium(III) ions from Na-clinoptilolite. It provides a 99 % withdrawal of Yb from the zeolite matrix. The method for ytterbium trace amounts preconcentration from aqueous solutions in a solid phase extraction mode with a further determination of this rare earth element by a spectrophotometric method was developed. Keywords: sorption, solid phase extraction, ytterbium, Na-clinoptilolite.

Influence of Homogenization and Annealing Temperatures on the Microstructure, Mechanical Properties, and Passive Properties of Cold Rolled 2205 Duplex Stainless Steel

The effects of homogenization, cold working, and subsequent annealing treatment were studied on the microstructural evolution, mechanical properties, and passive properties of duplex stainless steel (DSS). A hot-rolled 2205 DSS was subjected to two processing routes. In one, the DSS goes through an extra homogenization step at 1100 °C for 1800 s before cold rolling. After cold deformation (~75%) the specimens were isothermally annealed at 900, 1000, and 1100 °C for 180 s. The microstructure evolution was studied by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XDR). Mechanical properties were evaluated by microhardness and tensile tests. The electrochemical behaviors were investigated by potentiodynamic measurements, electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis (MS). Chemical composition of the lowest corrosion resistant passive film was assessed by X-ray photoelectron spectroscopy (XPS). Homogenization before cold rolling lowered strain hardening, slowing the microstructural transformation process. The thermomechanical process did not change the semiconductor type of the passive films. However, grain refinement after annealing improved the corrosion resistance in borate buffer solution. Cold rolling significantly decreased the corrosion resistance. The passive film of the specimen homogenized before cold rolling had the lowest corrosion resistance and high amounts of Cr(OH)3 and FeO.

Analyses of electrochemical behavior of plasma electrolytic oxidation film on Zirlo alloy in lithium borate buffer solution at 25–300 °C

The electrochemical behavior of plasma electrolytic oxidation (PEO) film on Zirlo alloy in 25–300 °C lithium borate buffer solution was evaluated by in-situ electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. As the solution temperature rose to a critical value (150 °C), a new relaxation process related to the distinguishable maximum in phase angle vs. frequency curves was observed at medium frequency and became more pronounced with increasing temperature. This relaxation process almost disappeared after a short exposure time under 300 °C. The transition of the relaxation process was closely related to the impedance of PEO film. The new relaxation process was ascribed to the diffusion of corrosion product through the PEO film. In addition, the degradation of the protective properties of PEO film was observed with increasing temperature, which resulted from the enhanced ionic conductivity of doped zirconia under high temperature. Finally, the PEO film hardly changed in morphology and microstructure after in-situ EIS tests at 25–300 °C. • Electrochemical behavior of PEO film was evaluated by in-situ electrochemical impedance spectroscopy. • A new relaxation process was observed at medium frequency. • The new relaxation process was ascribed to the diffusion of corrosion product. • The conduction mechanism of corrosion species through PEO film was analyzed based on a mix-conduction model.

High-Throughput Analysis of Amino Acids for Protein Quantification in Plant and Animal-Derived Samples Using High Resolution Mass Spectrometry.

Current methods for measuring the abundance of proteogenic amino acids in plants require derivatisation, extended run times, very sensitive pH adjustments of the protein hydrolysates, and the use of buffers in the chromatographic phases. Here, we describe a fast liquid chromatography–mass spectrometry (LC–MS) method for the determination of amino acids that requires only three steps: hydrolysis, neutralisation, and sample dilution with a borate buffer solution for pH and retention time stability. The method shows excellent repeatability (repeated consecutive injections) and reproducibility (repeated hydrolysis) in the amino acid content, peak area, and retention time for all the standard amino acids. The chromatographic run time is 20 min with a reproducibility and repeatability of <1% for the retention time and <11% for the peak area of the BSA and quality control (QC) lentil samples. The reproducibility of the total protein levels in the hydrolysis batches 1–4 was <12% for the BSA and the lentil samples. The level of detection on column was below 0.1 µM for most amino acids (mean 0.017 µM).

On the implication of mobile hydrogen content on the surface reactivity of an austenitic stainless steel

The Influence of hydrogen on the corrosion behavior of an AISI 316 L austenitic stainless steel in borate buffer solution is studied after a cathodic pre-charging step. A high amount of hydrogen is absorbed and forms a concentration gradient from the surface to the bulk with a path length of about 80 µm. The surface reactivity in the passive regime after the cathodic charging and during the hydrogen desorption is investigated with a large set of electrochemical and physico-chemical technics: electrochemical polarization, EIS, Mott-Schottky analysis and XPS. This approach allows to demonstrate that surface reactivity increases drastically with hydrogen absorption. This effect is mostly due to mobile hydrogen and is mainly reversible with its desorption. Hydrogen absorption and desorption have a small impact on the passive layer composition and thickness. However, the hydrogen induces an increase in the dissolution rate, which is discussed based on the Point Defect Model. Present results suggest that the impact of hydrogen on the surface reactivity is a consequence of a strong increase in the mobility of anionic vacancy and/or hydrogen oxidation.

Effect of surface roughness on the characteristics of passive film formed on 5083 Al alloy in pH 8.4 Borate Buffer Solution

Effect of surface roughness on the characteristics of passive film formed on 5083 Al alloy in pH 8.4 Borate Buffer Solution

Passivation kinetics of a high nitrogen face-centered-cubic phase formed on AISI 304L austenitic stainless steel in borate buffer solutions by photo- and electrochemical methods

The passive film thickening on a high nitrogen face-centered-cubic phase (γN) layer in a series of borate buffer solutions is in-situ characterized by the transient corrosion current and potential with the structure evolution in the photoelectrochemistry and electrochemical noise analyzes. The real-time nitrogen effect on the passivation is intended by controlling the proton concentration of the borate buffer solutions at the pH values of 6.5–8.9 with the immersion time up to 8 h. The γN phase layer on the nitrided AISI 304L austenitic stainless steel has a transitional maximum thickness with the firstly immersion time, and then gradually achieves a steady thickness value. Seven components, such as α-Fe2O3, FeO, Cr(OH)3, γ-FeOOH, CrOOH, Cr2O3 and γ-Fe2O3, are observed with 8 h, although no CrNx and FeNx compounds are detected due to lack of references in photoelectrochemistry. The nitrogen dissolving from the γN phase layer in the borate buffer solutions is clarified, according to the real-time photocurrent and transient corrosion current at the controllable pH values. The passivation transition period dependent on the nitrogen dissolving in the borate buffer solutions is proposed by the point defect model. The nitrogen hydrolysis to ammonia with a fast reaction rate is determined by the nitrogen concentration on the surface of the γN phase layer. The ammonia is further hydrolyzed to ammonium with a lower reaction rate which is mainly affected by proton concentration in the solutions. Therefore, the two-step nitrogen hydrolysis from the γN phase layer is in-situ discovered as an effect mechanism in the borate buffer solutions.

High-resolution TEM characterization of epitaxial passivation for a high nitrogen face-centered-cubic phase formed on AISI 304L austenitic stainless steel in borate buffer solution

The real-time composition and structure of the passive film formed on a high nitrogen face-centered-cubic phase (γN) layer at the characterized transient corrosion currents from the electrochemical noise analyses in the borate buffer solution with the pH = 7.7 are investigated by the transmission electron microscope (TEM) with energy dispersion X-ray spectrum (EDS) using the focused ion beam (FIB) sampling. The thicker passive film of the γN phase layer on the nitrided AISI 304L in the borate buffer solutions is observed as two regions structure of O enriched n-type defect spinel γ-Fe2(N,O)3 and hydroxides in the outer region and Cr and N enriched p-type defect spinel (Fe,Cr)3(N,O)4 in the inner region, although few β-(Fe,Cr)OOH compounds are detected due to dehydration. The defect spinel in directions of < 112 >, < 213 > and < 110 > is epitaxially growing on the γN phase matrix during the passivation up to 8 h with a decreasing lattice mismatch from 5.9 to 1%, which is attributed to lattice expansion of the γN phase and the defect spinel. The lattice expansion of the γN phase at the interface with growing passive film is affected by dissolving nitrogen outward to the borate buffer solution. The dissolving nitrogen in the defect spinel induces its lattice expansion by hydrolysis at the interface. The dense and low-defective passive films on the γN phase layer have a significant effect on the corrosion resistance due to inhibition of the absorption of aggressive ion and limitation of the carrier density.

Role of Alloying Elements in Passive and Transpassive Behavior of Ni–Cr-Based Alloys in Borate Buffer Solution

The role of the alloy composition of binary Ni–xCr alloys (x = 16, 20, 24, 28 wt.%) and ternary Ni–xCr–8Fe alloys (x = 14, 22, 30 wt.%) in borate buffer solution on the passive and transpassive behavior was investigated using successive electrochemical impedance measurements. These measurements supplement conventional polarization curves by enabling monitoring of the evolution of the electrochemical parameters extracted from impedance diagrams (thickness, resistivity at interfaces, etc) during the polarization. The polarization curves and evolution of the impedance parameters revealed that the Cr content and addition of Fe did not significantly affect the behavior of the alloys within the passive potential domain but directly affected the transpassivation process at higher potentials. For the Ni–xCr alloys, a higher Cr content resulted in a higher current-density peak for the transpassivation–second passivation processes. Conversely, the addition of Fe reduced or even prevented the appearance of this current-density peak. X-ray photoelectron spectroscopy analysis provided complementary information to help explain the role of alloying elements in the passivation (and secondary oxidation) mechanisms of Ni-based alloys in borate buffer solution.

Influence of electrolyte selection on performance of tantalum anodic oxide memristors

Anodic memristors obtained by electrochemical anodization of Ta in phosphate, borate and citrate buffer solutions are studied. Memristive behaviour is demonstrated by electrical switching between high and low conductive states. The endurance and retention of devices are analysed. The use of phosphate leads to 4 switching levels and the highest ratio between high and low resistive states. All studied oxides are stoichiometric Ta2O5 and only P is detected inside anodic memristors. The improved memristive characteristics of oxides anodized in phosphate are attributed to an increase of O vacancies due to the presence of Ta oxyphosphate, which is believed to mediate spatial pinning of conductive filaments positions during read/write. The anodic memristors show high stability, enhanced endurance and retention that combined with their active layer low fabrication cost makes them ideal candidates for industrial implementation.

Comparative study on corrosion behavior of Cu and Sn under UV light illumination in chloride-containing borate buffer solution

Corrosion behaviors of copper and tin in chloride-containing borate buffer solutions (pH 8.4) were investigated through electrochemical and spectroscopic techniques in the presence and absence of UV illumination. Concerning effects of UV light on the corrosion processes, in a borate buffer solution containing 0.025 M NaCl, photo-enhanced pitting corrosion was observed on copper while photo-induced passivation was found on tin. The effect of UV illumination on corrosion was dependent on the interaction between the photo-generated carriers and the metal oxides, as well as the photostability of the oxide film. Chloride anions can decrease the photostability of the oxide film.

Lead Borate Nanoparticles Induce Apoptotic Gene Activity in P53 Mutant Cancer Cells.

Cancer is a complex and multistage disease that causes suffering worldwide. Several mutations in tumor suppressor proteins are mostly responsible for tumorigenic development. Thus, determination of the mutations and developing a mutation targeted therapy are crucial in order to cure cancer. Moreover, since healthy cells do not have mutations in their tumor suppressor genes, mutation-specific treatment is responsible for selective treatment without harming a healthy tissue in the body. In this current study, lead borate nanoparticles (LB-Np) have been synthesized, and their effects on P53 mutant cancer cells were investigated. The synthesis method includes steps of mixing a borate buffer solution with the lead nitrate solution, washing the resulting precipitate with distilled water and eventually preparing stable LB-Np solutions. Cell viability analysis was conducted to identify the toxicity of LB-Np in HaCaT, A549, MCF7, and T47D cell lines. The changes in morphologies of breast cancer cell lines were demonstrated by using microscopical analysis. Additionally, alterations in gene expressions were determined in breast cancer cell lines after LB-Np treatment. This multidisciplinary study also identified the selective effect of LB-Np in cancer cell lines, in vitro. MTS and quantitative polymerase chain reaction assays demonstrated the effect of LB-Np were specific for p53 mutation cell line, T47D. Breast cancer cell line T47D has 580 C/T mutation which affects the activation of p53 tumor suppressor protein. However, LB-Np treatment effectively killed T47D cell lines and did not affect any other cell lines that have no p53 mutations such as MCF7, A549, and healthy HaCaT. Overall, synthesized LB-Np were found to be effective in p53-mutated cell lines and showed a remarkable selective anti-cancer activity.

Electrochemical stability, physical, and electronic properties of thermally pre-formed oxide compared to artificially sputtered oxide on Fe thin films in aqueous chloride

The electrochemical stability and corrosion behavior of the thermally pre-oxidized and sputter deposited variant of an oxide single-crystalline Fe thin film were compared. Thermal oxides formed Fe2O3 over an inner layer of Fe3O4 while the sputtered oxides were found to have grown Fe3O4 instead of the target stoichiometry of Fe2O3. Oxide films of both types were stable in pH = 9.3 borate buffer solution, however, were altered in pH = 9.3, 0.1 M NaCl solution in the case of thermally pre-oxidized Fe thin film. The stability of the oxide differed in pH = 4, 0.1 M NaCl where sputtered Fe films were more stable against acidic chemical dissolution than the thermally formed Fe oxide film. These differences were traced by AC/DC electrochemical analysis including electronic defect densities, and molecular identity characterized by ex-situ X-ray photoelectron spectroscopy.

Corrosion Resistance of Finer/Coarser Pearlitic Structures of Carbon Steel

Corrosion performance on pearlite structures of carbon steels has been researched using scanning Kevin probe force microscopy and energy-dispersive X-ray spectroscopy. The corrosion test was conducted by immersing in borate buffer solution containing NaCl. In the coarser pearlite structure, we detected an increase in the Volta potential at pearlitic cementite–ferrite boundaries after corrosion, in accordance with the following: increasing C concentration, and decreasing Mn concentration. We detected little change in the Volta potential and inorganic element concentrations in the finer pearlite structures. Crack-like trenches, with a depth less than several nanometers, formed along the boundaries where the Volta potential increased in the coarser pearlite structures. We demonstrated the importance of the concentration of inorganic elements (such as Mn and C) in promoting the initiation of corrosion, and higher corrosion susceptibility for the coarser pearlite structures.

Efficient suppression of surface charge recombination by CoP-Modified nanoporous BiVO4 for photoelectrochemical water splitting

BiVO4 is a promising photoanode material for water splitting due to its substantial absorption of solar light as well as favorable band edge positions. However, the poor water oxidation kinetics of BiVO4 results in its insufficient photocurrent density. Herein, we demonstrate the use of CoP nanoparticles for facile surface modification of nanoporous BiVO4 photoanode in potassium borate buffer solution (pH 9.0), which can generate a tremendous cathodic shift of ~430 mV in the onset potential for photoelectrochemical water oxidation. In addition, a remarkable photocurrent density of 4.1 mA cm−2 is achieved at 1.23 V vs. RHE under AM 1.5G illumination. The photoelectrochemical measurement using sodium sulfite as a hole scavenger clearly shows that the greatly improved performances are attributed to the efficient suppression of interfacial charge recombination through loading of CoP catalyst. Moreover, the maximum surface charge injection yield can reach >81% at 1.23 V vs. RHE and the maximum IPCE of CoP/BiVO4 can reach 75.8% at 420 nm, suggesting the potential application of CoP-modified BiVO4 photoanode for overall solar water splitting in cost-effective tandem photoelectrochemical cells.

Utility of solid-phase extraction coupled with spectrophotometry for a novel green nano determination of copper(II) using 4-((furan-2-ylmethylene) amino)-5-methyl-4H-1,2,4-triazole-3-thiol

ABSTRACT A highly sensitive, selective and accurate method has been developed to determine ultra trace amounts of copper(II) by solid-phase extraction (SPE). The following parameters such as pH, concentration of the reagent, Triton X-100, reversed-phase Amberlite IR-120, equilibrating temperature and centrifuging time were evaluated to enhance the sensitivity and extraction efficiency of the proposed method. The method has been based on copper(II) and 4-((furan-2-ylmethylene) amino)-5-methyl-4 H-1,2,4-triazole-3-thiol (FAMT) reaction, followed by solid-phase extraction (SPE) of Cu(II)-FAMT with a reversed-phase Amberlite IR-120. This was performed by using borate buffer solution of pH 7.6 in the presence of Triton X-100 medium. FAMT reacts with copper(II) to form a deep green complex with molar ratio of (2: 1) (FAMT: copper). An enrichment and improvement factor of 200 and 540, respectively, were obtained by elution of the complex from the resin with a minimal amount of dimethylsulfoxide (0.5 mL). The molar absorptivity of the complex was 6.49 × 106 L mol−1 cm−1 at 499 nm. Beer’s law was obeyed in the range 5.0–190 ng mL−1 of the measured solution. After optimising the instrumental and experimental parameters, the maximum values for quantification and detections limits of 100 mL sample system were 5.40 and 1.64 ng mL−1. The suggested method has been successfully applied for determination of copper ions in various environmental (water, vegetables, food, and biological) samples.

Adhesion barriers in laparoscopic myomectomy: Evidence from randomized clinical trials.

To evaluate the effectiveness of different adhesion barriers in the prevention of de novo adhesion development after laparoscopic myomectomy. A systematic review was performed by searching seven electronic databases for all randomized clinical trials (RCTs) comparing the use of any absorbable adhesion barrier (i.e. intervention group) with either no treatment or placebo (i.e. control group) in the prevention of adhesion development after laparoscopic myomectomy. Eight RCTs with a total of 748 participants (392 in the intervention group and 356 in the control group) were included. The assessed adhesion barrier methods were: oxidized regenerated cellulose (ORC) in two studies, auto-crosslinked hyaluronic acid (HA) gel in two studies, 4% icodextrin solution in one study, modified HA and carboxy-methylcellulose in one study, polyethylene glycol ester trilysine amine solution plus a borate buffer solution in one study, and polyethylene glycol amine plus dextran aldehyde polymers in another study. Adhesion barrier methods showing the most promising results were: ORC, auto-crosslinked HA gel, and polyethylene glycol amine plus dextran aldehyde polymers.