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A facial differential pulse voltammetric procedure using a glassy carbon electrode modified with zeolite imidazolate framework-67/graphitic carbon nitride (ZIF-67/g-C3N4) for the diclofenac (DCF) determination is demonstrated. ZIF-67/g-C3N4 with different mass ratios of the components was synthesized in a self-assembly process. The obtained materials were characterized by using X-ray diffraction, scanning electron microscopy (SEM), EDX-mapping, and nitrogen adsorption/desorption isotherms. The peak current varies linearly with the DCF concentration in the range of 0.2–2.2 μmol·L−1 and has a detection limit of 0.071 μmol·L−1. The modified electrode exhibits acceptable repeatability, reproducibility, and selectivity towards DCF. The proposed electrode allows determining DCF in human urine without pretreatment, and the results are comparable with those determined with HPLC.

A novel method was developed for the simultaneous determination of Pb(II), Cd(II), and Zn(II) based on the cathodic stripping response at a bismuth film electrode associated with oxine as a chelating agent. The developed method provided a high and sharp electrochemical response compared with the method without oxine. A linear response of peak currents was observed for Pb(II), Cd(II), and Zn(II) concentration in the range from 2 ppb to 110 ppb. The detection limits of Pb(II), Cd(II), and Zn(II) were 0.45, 0.17, and 0.78 ppb, respectively. This method was successfully applied to the determination of Pb(II), Cd(II), and Zn(II) in lake-water and river-water samples. The metals were detected at the ultratrace level, showing the feasibility of the proposed method for environmental applications.

The simultaneous electrochemical determination of Zn(II), Cd(II), Pb(II), and Cu(II) in the aqueous solution has been developed on the basis of the bismuth film glassy carbon electrode (GCE) using differential pulse anodic stripping voltammetry (DP-ASV). The bismuth film electrode (BiFE) was prepared by adding 500 ppb bismuth(III) directly to the sample solution and simultaneously depositing bismuth and the metal analytes on GCE. The optimal operational parameters, namely, accumulation potential (–1.6 V), accumulation time (110 s), pulsed amplitude (0.07 V), and scan rate (0.021 V·s−1), were found using a Box–Behnken design. Under the optimum conditions, a linear relationship exists between the current and the concentration of Zn(II), Cd(II), Pb(II), and Cu(II) in the range between 5.0 ppb and 110.0 ppb with the detection limits of 1.07 for Zn(II), 0.93 ppb for Cd(II), 0.65 ppb for Pb(II), and 0.94 ppb for Cu(II) calculated on the basis of a signal-to-noise ratio equal to 3 (S/N = 3). The interference experiments show that Co(II), Ni(II), and Fe(III) have a little influence on the DP-ASV signals of Zn(II), Cd(II), Pb(II), and Cu(II). In addition, a high reproducibility was indicated from small relative standard deviations (1.03%, 1.74%, 1.32%, and 4.74%) for 25 repeated measurements of 15 ppb copper, lead, cadmium, and zinc solutions. BiFE was successfully applied to determine Zn(II), Cd(II), Pb(II), and Cu(II) in river samples, and the results are in a good agreement with those determined with graphite furnace atomic absorption spectrometry (GF-AAS).

In the present paper, the synthesis of metal-organic framework-101 (MIL-101) and Remazol Deep Black RGB (RDB) adsorption on MIL-101 were demonstrated. The kinetics of RDB adsorption on MIL-101 was studied using Weber’s intraparticle diffusion model and the pseudo-first- and pseudo-second-order kinetic models. Particularly, the statistical method of piecewise linear regression and multi-nonlinear regression was employed to analyse the adsorption data according to the previously mentioned kinetic models. The results indicated that the adsorption process followed the three-step pseudo-first-order kinetic equation, which was consistent with the results of the intraparticle diffusion model with three linear segments. This model best described the experimental data. In addition, the adsorption isotherm data were studied using five adsorption models, namely, Langmuir, Freundlich, Redlich–Peterson, Toth, and Sips in nonlinear forms, and the Langmuir model is the most appropriate for the experimental data. The values of energies of activation of adsorption were calculated, and they revealed that the adsorption process was of endothermic chemical nature. A statistical comparison using Akaike information criterion to estimate the goodness of fit of the kinetic and isotherm models was presented.

Nuclear magnetic resonance (NMR) spectroscopy allows the determination of atomic-level information on intermolecular interactions, molecular structure, and molecular dynamics in the cellular environment. This may be broadly divided into studies focused on obtaining detailed molecular information in the intracellular context ('in-cell') or those focused on characterizing molecules or events at the cell surface ('on-cell'). In this review, we outline some key NMR techniques applied for on-cell NMR studies through both solution- and solid-state NMR and survey studies that have used these techniques to uncover key information. In particular, we focus on the application of on-cell NMR spectroscopy to characterize ligand interactions with cell surface membrane proteins such as G-protein coupled receptors (GPCRs) and receptor tyrosine kinases. These techniques allow for quantification of binding affinities, competitive binding assays, delineation of ligands involved in binding, ligand bound-state conformational determination, evaluation of receptor structuring and dynamics, and inference of distance constraints characteristic of the ligand-receptor bound state. Interestingly, it is possible to avoid the barriers of production and purification of membrane proteins while obtaining directly physiologically relevant information through on-cell NMR. We also provide a brief survey of the applicability of on-cell NMR approaches to other classes of cell surface molecules. Key words: NMR spectroscopy, ligand-receptor interactions, intact cells, atomic-level characterization, biophysics. La spectroscopie par résonance magnétique nucléaire (RMN) permet d'obtenir des informations à l'échelle atomique en matière d'interactions intermoléculaires, de structure moléculaire et de dynamique moléculaire dans l'environnement cellulaire. On peut distinguer les études axées sur l'obtention d'informations moléculaires détaillées dans le contexte intracellulaire (<< dans la cellule >>) et celles axées sur la caractérisation des molécules ou des événements à la surface de la cellule (<< sur cellule >>). Dans cette synthèse, les auteurs exposent certaines des principales techniques de RMN appliquées aux études de RMN sur cellule à travers la RMN tant à l'état de solution qu'à l'état solide, et passent en revue les études qui ont utilisé ces techniques pour obtenir des informations essentielles. Ils se concentrent en particulier sur l'application de la spectroscopie RMN sur cellule pour caractériser les interactions entre les ligands et les protéines membranaires de la surface cellulaire, comme les récepteurs couplés aux protéines G (RCPG), les récepteurs à tyrosine kinase, etc. Ces techniques permettent de quantifier les affinités de liaison, de réaliser des essais de liaison compétitive, de délimiter les portions de ligands impliquées dans la liaison, de déterminer la conformation de l'état lié du ligand, d'évaluer la structuration et la dynamique des récepteurs et de déduire les contraintes de distance caractéristiques de l'état lié ligand-récepteur. Il est intéressant de noter qu'il est possible d'éviter les obstacles liés à la production et à la purification des protéines membranaires tout en obtenant des informations directement pertinentes sur le plan physiologique grâce à la RMN sur cellule. Ils présentent également une étude plus succincte de l'applicabilité des approches de RMN sur cellule à d'autres classes de molécules de la surface cellulaire. [Traduit par la Rédaction] Mots-clés : spectroscopie RMN, interactions ligand-récepteur, cellules intactes, caractérisation à l'échelle atomique, biophysique., Introduction Membrane proteins account for ~26% of the human proteome (Fagerberg et al. 2010). This class of proteins includes a wide variety of cell surface receptors that mediate communication and [...]

Perovskite-type LaTiO2N with a bandgap energy of 2.1 eV is a promising semiconductor for solar (sea)water splitting to produce renewable hydrogen. However, the synthesis of an oxynitride with low defect density to achieve strong charge separation for high solar-to-hydrogen energy conversion is still challenging. Herein, we report less-defective, two-dimensional (2D) LaTiO2N crystals prepared from layered perovskite BaLa4Ti4O15 and their highly improved photoelectrochemical (PEC) seawater-splitting activity at neutral pH. The (111)-type layered perovskite BaLa4Ti4O15 has structural similarity to LaTiO2N and excess Ba species with a strong basicity, thus guaranteeing complete and fast nitridation accompanied by suppressed Ti4+ reduction. The prepared oxynitride, capable of absorbing visible light up to 610 nm, was highly crystalline and less-defective in both bulk and surface states, which is favorable for efficient photoreactions. Oxynitrides were also prepared from other layered perovskite oxides, namely La2Ti2O7 and La4Ti3O12, for comparison. Photoanodes using LaTiO2N were fabricated by spin-coating and then employed for driving PEC seawater splitting including chloride oxidation at neutral pH. The less-defective LaTiO2N exhibited a photocurrent density of approximately 2.4 mA cm−2 at 1.23 VRHE (4.9 mA cm−2 at 1.36 VRHE) in 0.5 M NaCl electrolyte at pH 6.4 under AM 1.5G simulated sunlight, indicating hitherto unreported remarkable activity. This work presents the first demonstration of the complete conversion of layered perovskite BaLa4Ti4O15 into perovskite LaTiO2N as well as the types of starting oxides that reduce the defect density of the resulting oxynitride, thereby improving the hydrogen evolution rate at neutral pH. [ABSTRACT FROM AUTHOR]

This paper demonstrates the preparation of ZnMn2O4 nanoparticles through thermal hydrolysis in different solvents, such as isopropanol, ethylene glycol, glycerol, and water, combined with pyrolysis. The obtained samples were characterised by using X-ray diffraction (XRD), infrared spectroscopy (FT‒IR), scanning electron microscopy (SEM), energy-dispersive X-ray mapping, nitrogen adsorption/desorption isotherms, and a vibrating sample magnetometer. The electrocatalytic activity of ZnMn2O4 nanoparticles was investigated toward the oxidation of uric acid (UA) and xanthine (XA). The ZnMn2O4-nanoparticle-modified electrode not only enhances the oxidation currents of the two purine derivatives but also successfully separates the voltammetric signals of the analytes in their binary mixture and, hence, is employed for their simultaneous determination. The factors affecting the analysis, such as pH, scan rate, linear range, detection limit, reproducibility, and interferents, were also investigated. The results show that the UA and XA limits of detection are as low as 0.55 and 1.28 µM, and the modified electrodes have satisfactory repeatability and reproducibility. The practical application of the modified electrode was demonstrated by simultaneously determining the concentrations of UA and XA in urine samples with exceptional accuracy. [ABSTRACT FROM AUTHOR]