Clarification of ATR-FTIR spectra of graphene oxide (GO) remains challenging due to overlapping vibrational modes of oxygenated groups and variability introduced by synthesis and processing. Here, we present the first comprehensive ATR-FTIR study of size-separated GO fractions combined with modern statistical, machine learning (ML) analysis. A dataset of 75 GO samples prepared via multiple routes and post-treatments was assembled, followed by size fractionation (0.2-70 mu m) and reproducible ATR-FTIR measurements. Rigorous preprocessing, peak detection, and feature engineering were applied to extract interpretable spectral descriptors, and logistic regression models were trained in both the fingerprint (1900-800 cm-1) as most examined and high-frequency (3800-2500 cm-1) regions. The fingerprint region yielded high accuracy and revealed chemical correlations between particle size and functionalities such as carbonyls, epoxides, alcohols, and aliphatic moieties. In contrast, the high-frequency region, though containing only a few informative bands, provided nearly comparable predictive performance, particularly for small and large fractions, underscoring its value for rapid classification. A practical guide to SHAP analysis highlighted size-dependent spectral contributions and confirmed the chemical plausibility of the models. Together, these results establish a reproducible, explainable framework for linking FTIR spectral features to GO particle size, clarifying band assignments, and supporting the development of standardized protocols for GO characterization and quality control.

Although vanadium-containing phosphates with the NASICON-related structure are promising cathode materials for lithium-ion batteries, the issues of structural degradation associated with the complete extraction of Li+ and/or complete oxidation of vanadium remain unclear. Here, we present novel monoclinic (m-LVScP) and rhombohedral (r-LVScP) polymorphs of Li3VSc(PO4)(3) as model objects to study structural transformations occurring upon oxidation and reduction of vanadium cations. The structure of m-LVScP obtained by direct high-temperature synthesis belongs to the anti-NASICON type. Ion Li+ -> Na+ exchange from NASICON type Na3VSc(PO4)(3) leads to the formation of the rhombohedral polymorph of Li3VSc(PO4)(3) and is accompanied by a strong distortion of the NASICON type polyanion framework. The BVSE study of Li-3(V,Sc)(2)(PO4)(3) indicates faster diffusion of Li+ ions within the anti-NASICON framework; moreover, the activation energy of cation migration in the substituted phase m-Li3VSc(PO4)(3) is lower than that of the corresponding non-substituted vanadium and scandium phosphates. Carbon-coated m-LVScP and r-LVScP demonstrate a specific capacity up to similar to 175 mA h g(-1) which corresponds to a complete three-electron V2+/V3+/V4+/V5+ process within the voltage range of 1-4.65 V vs. Li/Li+, following a predominantly solid-solution mechanism, as shown by operando and ex situ powder X-ray diffraction. Electrochemical and chemical deintercalation of 2Li(+) per formula unit from m-LVScP and r-LVScP results in the formation of a short V5+ = O bond, revealed by V-51 NMR and Fourier-transformed infrared spectroscopy. This is accompanied by strong distortion of the frameworks, which impedes the complete reversibility of the phase transformations and leads to capacity degradation during long time cycling.

Background In biomedicine, a promising direction is the use of graphene oxide (GO) as a platform material or as a nanozyme. A key challenge for the application of GO is precise control of its interaction with reactive oxygen species, since this activity may influence the overall therapeutic outcome. Insignificant variations in material origin and processing can translate into measurable differences in its redox behavior. Peroxyl radical (ROO•)-generating assays are of particular interest, as ROO• are major contributors to oxidative stress in vivo, while kinetic chemiluminescence readouts sensitively track antioxidant effects of complex probes. This study addresses the need for a more biologically informed and comparable assessment of aqueous GO dispersions in relation to ROO•. Results A chemiluminescence (CL) assay based on the well-known AAPH/luminol free radical generation system is presented. Buffer oxygenation is identified as a critical controllable factor: under otherwise identical conditions, oxygenation increased the analytical signal and stabilized the kinetic readout. Platinum-assisted conditioning is introduced as a diagnostic step to suppress peroxide-driven CL enhancement and reveal intrinsic GO behavior. A phenotype-guided strategy is developed and applied. Reproducibly Trolox-like traces are quantified in restricted Trolox-equivalent terms, whereas slow or non-Trolox-like responses are compared using fixed-time reactivity descriptors, enabling comparative series across a diverse set of GO dispersions, including commercial and laboratory-prepared samples as well as fractionated and non-fractionated materials. Significance The combined workflow (buffer saturation & artefact removal & phenotype-guided quantification) improves robustness and interpretability of CL-based peroxyl radical assays for GO dispersions. It enables analytically justified comparison of GO samples differing in origin and processing history, while restricting Trolox-equivalent reporting to kinetically justified cases.

Although vanadium-containing phosphates with the NASICON-related structure are promising cathode materials for lithium-ion batteries, the issues of structural degradation associated with the complete oxidation of vanadium remain unclear.

The NaNbTi(PO4)3 material with the NASICON structure (space group R3-c) was prepared by the Pechini-type technique followed by spark plasma sintering. XANES measurements revealed mixed-valence states of niobium (Nb5+/4+) and titanium (Ti4+/3+). The material exhibits reversible electrochemical intercalation of about 1.67 Na+ per formula unit at a C/10 rate, with a gradual decrease in capacity, which could be attributed to the mixing of Na+ and Ti3+ cations in the structure.

This study investigates the relationship between stress coping ability, salivary antioxidant capacity (AOC), and trace element concentrations, focusing on zinc (Zn) and potassium (K). A cohort of 73 participants, divided into groups based on stress coping ability (SCA) (“adaptive”, “intermediate”, and “maladaptive”), underwent cognitive tasks while physiological and behavioral data were collected. Saliva samples were analyzed for AOC and trace elements, including Zn, K, total phosphorus (P), and total sulfur (S). Results revealed that individuals with effective stress coping strategies (the “adaptive” group) exhibited significantly higher AOC and Zn levels, along with lower K levels, compared to those with maladaptive coping abilities. Positive correlations were observed between Zn and AOC, while K showed a negative correlation with AOC. Behavioral data indicated that the “maladaptive” group demonstrated a pronounced decline in self-assessment as task difficulty increased, despite similar task performance across groups. These findings suggest that stress coping ability is a stable trait influencing physiological homeostasis, with effective coping associated with enhanced antioxidant defenses and balanced trace element regulation. The study highlights the importance of stress management in maintaining oxidative balance and emotional resilience, offering potential pathways for interventions targeting stress-related physiological and cognitive dysregulation.

Three chemiluminescent (CL) systems for superoxide anion radical (SAR) generation were evaluated using two probes: luminol (Lum), responsive to detecting a broad range of reactive oxygen species (ROS), and lucigenin (Luc), most selective to SAR. The Co(II)/H2O2 system, in both Lum- and Luc-based assays, showed good repeatability and reproducibility (sr < 15%), suitable for routine screening, whereas the enzymatic system using xanthine/xanthine oxidase (Xa/XO) provided higher SAR generation selectivity but markedly poorer reproducibility (sr > 20%). An operational threshold for detectable CL response changes was estimated for the Lum/Co(II)/H2O2 system, whereas the Luc/Xa/XO system is suitable for selective same-day SOD-referenced comparative assays. Thirty aqueous graphene oxide dispersions (aqGO), including pristine (unpurified) and purified by a dialysis bag membrane, were studied in these CL-based assays. The CL intensity decreased by 50-70% in the presence of pristine aqGO and by 80-90% with purified samples, resulting in an operational detectable-response threshold of 1-2 mg L-1 depending on aqGO type under the Lum/Co(II)/H2O2 protocol. Compared to SOD, aqGO exhibits antioxidant activity up to 106 times less efficiently. The obtained results show the advantages and limitations of each CL system for SAR-based antioxidant/prooxidant assessment and validate the strong modulatory role of GO. A practical quantitative criterion of inhibitory activity based on half-suppression of CL intensity (or integrated area) is proposed to evaluate antioxidant and prooxidant activity across a batch of GO samples. An approach to estimate the concentration of accessible sorption-active oxygen-containing sites is proposed. A metrological scheme for Co(II)/H2O2 systems in both probes, standardized assessment of the "antioxidant activity" and nanozyme-like behavior of graphene-based materials, suitable for interlaboratory comparison and batch quality control, is outlined.

BACKGROUND:Graphene oxide (GO) is widely used in biomedicine and biotechnology due to its aqueous dispersibility and potential nanozyme activity. However, it remains analytically challenging because of structural heterogeneity and metallic inclusions, which affect its functional performance. GO therefore requires precise trace metal analysis, as even minor compositional variations can be critical. Modern multi-element analysis demands results that are both reliable and accurate, yet sound laboratory practice is not always followed. Although ICP-OES offers high sensitivity and precision, metrological rigor is often lacking. This work addresses the need for validated and robust elemental analysis of GO bulk material and particle-size fractions. RESULTS:ICP-OES was employed to quantify metals in bulk GO and to characterize Mn and Ti distribution in GO fractions. A fast algorithm was developed to identify robust plasma conditions by mapping the Mermet coefficient (Mg II/Mg I intensity ratio) across a range of flow rates and RF power levels. Concentrations for selected elements in the bulk material ranged from 10-1 to 103 mg kg-1; in aqueous dispersions, values reached up to 103 mg L-1. Validation parameters for Mn, Ti, and Fe included recoveries of 85-115 %, detection limits of 0.1-0.3 ng kg-1 (for used weight ca. 50 mg), and intra-/inter-day RSDs not exceeding 7 %. The Mermet coefficient exhibited an RSD of ∼0.6 %, indicating minimal matrix interference. Fraction analysis revealed a monotonic decrease in Mn toward fractions with smaller lateral-size cut-offs. ATR-FTIR spectra were obtained for stirred, purified, and ultrasound-treated GO fractions to assess whether purification altered the surface functional groups. SIGNIFICANCE:This study provides a validated approach for trace metal analysis in GO, combining sensitivity, robustness, and reproducibility across both bulk solid and aqueous dispersion forms. By experimentally examining the influence of plasma conditions on analytical performance, it offers the first systematic assessment of GO-specific ICP-OES parameter optimization. The results support more reliable characterization of GO materials and enable improved quality control in applications where elemental composition critically affects functionality.

Phosphate-based cathode materials represent a major class of compounds used in the manufacturing of low-cost and safe lithium-ion batteries (LIBs). A significant challenge in this field is developing scalable and cost-effective synthesis routes that yield battery-grade materials meeting industrial standards. This study addresses this challenge by focusing on reagent selection for the hydrothermal synthesis of near-commercial-grade phosphate cathodes. Specifically, we used hematite-type iron oxide (alpha-Fe2O3) and pyrolusite-type manganese dioxide (beta-MnO2) as cost-effective and chemically stable sources of iron and manganese. We investigated phase evolution pathways by adjusting the reducing strength of complexing agents, including citric acid, ascorbic acid, oxalic acid, and ethylenediaminetetraacetic acid, as well as the reaction medium (water or ethylene glycol). This approach allowed us to identify crystallization routes leading to the formation of tavorite (LiFePO4(OH)), triphylite (LiFePO4), and lithiophilite (LiMnPO4). During hydrothermal treatment, the formation of LiFePO4 proceeded through sequential phase transformations from hematite to lipscombite and then triphylite. In addition, we showed that the synthesis conditions and phase transformation pathways were correlated with the resulting electrochemical properties, which explains the origin of the limited electrochemical activity. This study lays the groundwork for future research aimed at optimizing the production of high-performance phosphate-based cathode materials.

The present study investigated the influence of ultrasonication and humic substances (HS) on the colloidal-chemical characteristics and enzyme activity of alkaline phosphatase (AP). Specifically, the distribution of AP in immiscible liquid systems, its adsorption at the liquid-liquid interface, and its enzyme activity were examined. The latter was assessed by measuring both the enzyme's ability to hydrolyze 4-nitrophenyl phosphate and its capacity to catalyze the synthesis of calcium phosphate. Under alkaline pH conditions, HS preserved the enzyme activity of AP during ultrasonication. Ultrasonication did not alter the secondary structure of the protein, and the observed loss of enzyme activity is reversible for both free AP and its mixture with HS. This reversibility was further supported by the enzymatic synthesis of calcium phosphate, which yielded comparable results for both treated and untreated AP samples. The following mechanism of HS action in the AP-HS system is proposed: (1) HS fragments form complexes with AP, resulting in higher enzyme activity; (2) continued ultrasonic treatment leads to a sharp decline in the activity of free AP; and (3) after the ultrasonic treatment is completed, the enzyme activity remains reduced; however, complexes between HS fragments and AP may begin to reform and exert their effect again.

Novel solubility (SLE) and vapor-liquid phase equilibria data were obtained for ternary aqua systems containing calcium methanesulfonate and sodium (or magnesium) methanesulfonate. The isothermal solubility method was used to obtain an isothermal cross-section at 298.15 K for the Ca(CH3SO3)2-NaCH3SO3-H2O and the Ca(CH3SO3)2-Mg(CH3SO3)2-H2O systems. As expected, there are neither solid solutions nor double salts in both systems. The Mg(CH3SO3)212H2O hydrate is the only solid phase containing magnesium in the Ca(CH3SO3)2-Mg(CH3SO3)2-H2O system at 298.15 K. Water activity was determined at 298.15-323.15 K to expand the temperature range for NaCH3SO3-H2O by two methods (static vapor pressure measurement and hygrometer). Water vapor pressure was measured in the 288.15-308.15 K range in both ternary systems to calculate water activity. The Zdanovskii rule is applicable to both ternary systems in the composition range under investigation. The Pitzer-Simonson-Clegg model is used for liquid-phase modeling. Binary parameters for NaCH3SO3-H2O were evaluated for the first time, as well as the solubility constant for NaCH3SO3, in the 250-323 K temperature range. Ternary parameters of the PSC model were evaluated for the first time, too, needed for a correct solubility prediction. The water activity was predicted with a higher accuracy without ternary parameters.

The enzyme-catalyzed synthesis of calcium phosphate is a promising method for producing calcium-based nanomaterials for biomedical applications. The purpose of this work was to determine the type of phosphate that forms when alkaline phosphatase catalyzes the reaction, and to identify the role of natural biopolymers in calcium phosphate formation. In this research, we analyzed calcium phosphates that were synthesized in the presence of alkaline phosphatase from either E. coli or calf intestinal, analyzed the obtained nanoparticles and compared them by functional composition, elemental ratio, and morphology. Since all syntheses were performed in Tris buffer with the addition of MgCl2, the final depleted hydroxyapatite incorporated magnesium. It was found that in the first 24 h, the reaction product form is determined by the enzyme source as well as the presence of other biopolymers (in particular, humic acid) in the reaction mixture. Hollow nanospheres of the depleted hydroxyapatite were obtained as a final product for both E. coli and calf-intestinal alkaline phosphatase during a 7-day reaction. When humic acid was added into the reaction mixture, separate spheres of the depleted hydroxyapatite were observed during a 24-h reaction. When Mg ions are present in the reaction mixture as a buffer component, they are evenly incorporated into the structure of the resulting calcium phosphate. The data obtained can be useful in understanding the calcification process of bioobjects and in applying the enzymatic method of calcium phosphate synthesis to biomedical applications.

The feasibility of saturating aqueous anoxic solutions with in situ-generated high-purity nitric oxide (NO) is shown herein. A methemoglobin assay estimated the average nitric oxide concentration to be ca. 20 ± 3 µM. Graphene oxide aqueous dispersions were prepared by ultrasound-assisted extra exfoliation. These dispersions, including unpurified (pristine) samples and samples purified from transition metal impurities (bulk) fractions (bulkGO) and (nano) separated fractions (nanoGO) in a range of 0.5 to 14 kDa were prepared with ppm level concentrations. A robust and reproducible chemiluminescence (CL) assay validated the interaction between graphene oxide and NO in a luminol-based system. The results showed a significant increase in NO scavenging activity within the bulkGO fractions to nanofractions ranging from 14 to 3.5 kDa. The different reaction pathways underlying the transformation of nitric oxide are being evaluated, focusing on understanding how its presence or absence affects these processes. Our kinetic model suggests a significant difference in nitric oxide regulation; nanoGO demonstrates an interception rate seventy-times higher than that achieved through CL quenching.

Tungsten oxides and related compounds have been known as negative electrode materials for metal-ion batteries for decades. Despite their structural flexibility, most studies has largely focused on lithium-based energy storage systems. Here, we investigated KMxW2_xO6 (M = Ta, Nb, Ti, Cr, Al) oxides adopting a defect pyrochlore structure as intercalation-type anodes for potassium-ion batteries. Crystal structure, chemical composition, and thermal behavior of all representatives were comprehensively characterized. Electrochemical testing in K half-cells revealed average operating potentials of the considered pyrochlores to be in the range of-1.1-1.3 V vs. K+/ K, consistent with density functional theory predictions. The variation in the electrochemical performance among the KMxW2_xO6 was correlated with differences in electronic conductivity of M dopants, as validated by M density of states calculations. Through regression analysis of Rietveld-refined structural data, a strong linear dependence (rho =0.96) between the average intercalation potential of KMxW2_xO6 and the intrinsic parameters (ionic radius and electronegativity) of the M metal was established. This work not only advances fundamental understanding of tungsten-based oxygen-deficient pyrochlores but also paves the way for their development as potassium-ion intercalation hosts.

The NaNbTi(PO4)3 material with the NASICON structure (space group R3c) was prepared by the Pechini-type technique followed by spark plasma sintering. XANES measurements revealed mixed-valence states of niobium (Nb5+/4+) and titanium (Ti4+/3+). The material exhibits reversible electrochemical intercalation of about 1.67 Na+ per formula unit at a C/10 rate, with a gradual decrease in capacity, which could be attributed to the mixing of Na+ and Ti3+ cations in the structure.

We report on the deposition of Prussian blue nanoparticles onto the carbon black supports in course of reduction of FeCl3/K3Fe(CN)6 equimolar mixture by hydrogen peroxide. This one-pot synthesis eliminates the use of volatile organic solvents as well as additional synthetic or mixing steps. With an increase of carbon black loading, the hydrodynamic size of the resulting nanocomposites displays the well-defined maximum and reaches the plateau at 115 ± 10 nm. Modified electrodes were fabricated by simple drop-casting of the nanoparticle suspensions onto the surface of screen-printed carbon structures. The highest electroactivity of Prussian blue was achieved at a carbon-to-iron molar ratio of 35. The corresponding hydrogen peroxide sensors exhibit ultra-high sensitivity (1.5 ± 0.1 A·M-1·cm-2), approximately 1.5-2 fold higher than sensors based on solely adsorbed Prussian blue nanoparticles or the same mixed with carbon black after synthesis. The low-cost and easily prepared carbon black/Prussian blue nanoparticles are promising for application in various fields of electroanalysis.

The variation of graphene oxide preparation techniques and the often occurring similarity of spectral information in molecular spectroscopy data for tested samples pose challenges for reliable data interpretation, especially when conservative "manual" analysis methods are used. This work employs a machine learning (ML)-based approach to develop an algorithm to solve cluster analysis issues of the infrared spectroscopy data for the graphene oxide: as-prepared, purified (by dialysis bag), and reduced samples. We propose an ML-based model to provide fully-automated qualitative analysis and a semi-automated pipeline for functional groups speciation analysis on graphene oxide, developed by simultaneously combining statistical analysis and data processing, optimization algorithms, and applying unsupervised learning techniques. Also, the study examines the possibilities of applying ML to analyze and cluster data from UV/vis and Dynamic Light Scattering (DLS).

Due to their biocompatibility, biodegradability, injectability, and self-setting properties, calcium–magnesium phosphate cements (MCPCs) have proven to be effective biomaterials for bone defect filling. Two types of MCPC powders based on the magnesium whitlockite or stanfieldite phases with MgO with different magnesium contents (20 and 60%) were synthesised. The effects of magnesium ions (Mg2+) on functional properties such as setting time, temperature, mechanical strength, injectability, cohesion, and in vitro degradation kinetics, as well as cytocompatibility in the MG-63 cell line and the osteogenic differentiation of BM hMSCs in vitro, were analysed. The introduction of NaHA into the cement liquid results in an increase in injectability of up to 83%, provides a compressive strength of up to 22 MPa, and shows a reasonable setting time of about 20 min without an exothermic reaction. These cements had the ability to support MG-63 cell adhesion, proliferation, and spread and the osteogenic differentiation of BM hMSCs in vitro, stimulating ALPL, SP7, and RUNX2 gene expression and ALPL production. The combination of the studied physicochemical and biological properties of the developed cement compositions characterises them as bioactive, cytocompatible, and promising biomaterials for bone defect reconstruction.

The thermal and optical properties of aqueous dispersions of magnetite nanoparticles were studied by dual-beam thermal-lens spectrometry. Surface-modified magnetite nanoparticles with an average crystal size of 7.5 nm were synthesized by a simple, one-stage method of coprecipitation followed by surface functionalization. For this purpose, the most popular and promising modifiers based on surfactants, polyelectrolytes, biopolymers and organic acids were used. The effect of the concentration of nanoparticles (in the range from 0.01 to 5 mg/L) and the nature of the surface modifier on the thermal diffusivity of the dispersion was studied. It was found that at concentrations of 0.4–0.6 mg/L, the dispersions exhibit heat-accumulating properties, which may be promising in the development of a magnetically controlled heat-conducting liquid. Thermal lens spectrometry in the steady-state measurement mode was used to reveal the processes of deposition and adsorption of magnetite nanoparticles on the surface of a quartz cell, leading to an apparent increase in thermal diffusivity by more than 30%. The paper touches upon the issues of accuracy and precision of temperature diffusion measurements, processing, and presentation of measurement results of time-resolved transient and steady-state signals for dispersed systems. The ratio of the change in the steady-state thermal-lens signals to the change in concentration regarding the concentration (dϑ/dc vs. c) provides a way to identify a systematic error at a low level (less than 5%) of thermal-lens measurements caused by a high concentration (or optical absorption) of the object. Various options for signal normalization (in terms of power, absorbance, and pure-solvent signal) are considered, and their advantages and disadvantages are discussed. An approach to using thermal diffusivity as a function of the steady-state signal of the sample is proposed. This approach allows for a comparative thermal-lens analysis of objects with different optical and thermal properties.