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In the recycling of end-of-life rare-earth magnets, the recovery of non-rare earth constituents is often neglected. In the present study, strong cation and anion exchange resins were tested batchwise for the recovery of the non-rare-earth constituents of permanent magnets (copper, cobalt, manganese, nickel and iron) from synthetic aqueous and ethanolic solutions. The cation exchange resin recovered most of metal ions from aqueous and ethanolic feeds, whereas the anion exchange resin could selectively recover copper and iron from ethanolic feeds. The highest uptake of iron and copper was found for 80 vol% and 95 vol% multi-element ethanolic feeds, respectively. A similar trend in selectivity of the anion resin was observed in breakthrough curve studies. Batch experiments, UV-Vis, FT-IR and XPS studies were performed to elucidate the ion exchange mechanism. The studies indicate that the formation of chloro complexes of copper and their exchange by the (hydrogen) sulfate counter ions of the resin have an important role in the selective uptake of copper from the 95 vol% ethanolic feed. Iron(II) was largely oxidized to iron(III) in ethanolic solutions and was expected to be recovered by the resin in the form of iron(II) and iron(III) complexes. The moisture content of the resin did not have a significant role on the selectivity for copper and iron., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Catalytic materials are the greatest challenge for the commercial application of water electrolysis (WEs) and fuel cells (FCs) as clean energy technologies. There is a need to find an alternative to expensive and unavailable platinum group metal (PGM) catalysts. This study aimed to reduce the cost of PGM materials by replacing Ru with RuO 2 and lowering the amount of RuO 2 by adding abundant and multifunctional ZnO. A ZnO@RuO 2 composite in a 10:1 molar ratio was synthesized by microwave processing of a precipitate as a green, low-cost, and fast method, and then annealed at 300°C and 600°C to improve the catalytic properties. The physicochemical properties of the ZnO@RuO 2 composites were investigated by X-ray powder diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The electrochemical activity of the samples was investigated by linear sweep voltammetry in acidic and alkaline electrolytes. We observed good bifunctional catalytic activity of the ZnO@RuO 2 composites toward HER and OER in both electrolytes. The improved bifunctional catalytic activity of the ZnO@RuO 2 composite by annealing was discussed and attributed to the reduced number of bulk oxygen vacancies and the increased number of established heterojunctions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Aleksić, Stojković Simatović, Stanković, Veselinović, Stojadinović, Rac, Radmilović, Rajić, Škapin, Mančić and Marković.)

This paper reports a detailed study of crystal structure and dielectric properties of ruthenium-substituted calcium-copper titanates (CaCu 3 Ti 4- x Ru x O 12 , CCTRO). A series of three samples with different stoichiometry was prepared: CaCu 3 Ti 4- x Ru x O 12 , x = 0, 1 and 4, abbreviated as CCTO, CCT3RO and CCRO, respectively. A detailed structural analysis of CCTRO samples was done by the Rietveld refinement of XRPD data. The results show that, regardless of whether Ti 4+ or Ru 4+ ions are placed in B crystallographic position in AA ' 3 B 4 O 12 (CaCu 3 Ti 4- x Ru x O 12 ) unit cell, the crystal structure remains cubic with Im3¯ symmetry. Slight increases in the unit cell parameters, cell volume and interatomic distances indicate that Ru 4+ ions with larger ionic radii (0.62 Å) than Ti 4+ (0.605 Å) are incorporated in the CaCu 3 Ti 4- x Ru x O 12 crystal lattice. The structural investigations were confirmed using TEM, HRTEM and ADF/STEM analyses, including EDXS elemental mapping. The effect of Ru atoms share in CaCu 3 Ti 4- x Ru x O 12 samples on their electrical properties was determined by impedance and dielectric measurements. Results of dielectric measurements indicate that one atom of ruthenium per CaCu 3 Ti 4 -x Ru x O 12 unit cell transforms dielectric CCTO into conductive CCT3RO while preserving cubic crystal structure. Our findings about CCTO and CCT3RO ceramics promote them as ideal tandem to overcome the problem of stress on dielectric-electrode interfaces in capacitors.

W n O 3n-1 nanotiles, with multiple stoichiometries within one nanotile, were synthesized via the chemical vapour transport method. They grow along the [010] crystallographic axis, with the thickness ranging from a few tens to a few hundreds of nm, with the lateral size up to several µm. Distinct surface corrugations, up to a few 10 nm deep appear during growth. The {102} r crystallographic shear planes indicate the W n O 3n-1 stoichiometries. Within a single nanotile, six stoichiometries were detected, namely W 16 O 47 (WO 2.938 ), W 15 O 44 (WO 2.933 ), W 14 O 41 (WO 2.928 ), W 13 O 38 (WO 2.923 ), W 12 O 35 (WO 2.917 ), and W 11 O 32 (WO 2.909 ), with the last three never being reported before. The existence of oxygen vacancies within the crystallographic shear planes resulted in the observed non-zero density of states at the Fermi energy.

The paper reports the synthesis of nickel tellurides via a mechanochemical method from elemental precursors. NiTe, NiTe 2 , and Ni 2 Te 3 were prepared by milling in stainless steel vials under nitrogen, using milling times from 1 h to 12 h. The products were characterized by powder X-ray diffraction (pXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), UV-VIS spectrometry, and thermal analysis (TGA and DSC). The products were obtained in the form of aggregates, several hundreds of nanometers in size, consisting of smaller nanosized crystallites. The magnetic measurements revealed a ferromagnetic behavior at room temperature. The band gap energies calculated using Tauc plots for NiTe, NiTe 2 , and Ni 2 Te 3 were 3.59, 3.94, and 3.70 eV, respectively. The mechanochemical process has proved to be a simple and successful method for the preparation of binary nickel tellurides, avoiding the use of solvents, toxic precursors, and energy-consuming reaction conditions.

Eco-friendly and rapid microwave processing of a precipitate was used to produce Fe-doped zinc oxide (Zn1-xFexO, x = 0, 0.05, 0.1, 0.15 and 0.20; ZnO:Fe) nanoparticles, which were tested as catalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a moderately alkaline solution. The phase composition, crystal structure, morphology, textural properties, surface chemistry, optical properties and band structure were examined to comprehend the influence of Zn2+ partial substitution with Fe3+ on the catalytic activity of ZnO:Fe. Linear sweep voltammetry showed an improved catalytic activity of ZnO:5Fe toward the ORR, compared to pure ZnO, while with increased amounts of the Fe-dopant the activity decreased. The improvement was suggested by a more positive onset potential (0.394 V vs. RHE), current density (0.231 mA cm-2 at 0.150 V vs. RHE), and faster kinetics (Tafel slope, b = 248 mV dec-1), and it may be due to the synergistic effect of (1) a sufficient amount of surface oxygen vacancies, and (2) a certain amount of plate-like particles composed of crystallites with well developed (0001) and (0001[combining macron]) facets. Quite the contrary, the OER study showed that the introduction of Fe3+ ions into the ZnO crystal structure resulted in enhanced catalytic activity of all ZnO:Fe samples, compared to pure ZnO, probably due to the modified binding energy and an optimized band structure. With the maximal current density of 1.066 mA cm-2 at 2.216 V vs. RHE, an onset potential of 1.856 V vs. RHE, and the smallest potential difference between the OER and ORR (ΔE = 1.58 V), ZnO:10Fe may be considered a promising bifunctional catalyst toward the OER/ORR in moderately alkaline solution. This study demonstrates that the electrocatalytic activity of ZnO:Fe strongly depends on the defect chemistry and consequently the band structure. Along with providing fundamental insight into the electrocatalytic activity of ZnO:Fe, the study also indicates an optimal stoichiometry for enhanced bifunctional activity toward the OER/ORR, compared to pure ZnO.

Quasi-two-dimensional tungsten oxide structures, which nucleate by epitaxial growth on W19O55 nanowires (NW) and grow as thin platelets, were identified. Both the nanowires and the platelets accommodate oxygen deficiency by the formation of crystallographic shear planes. Stoichiometric phases, W18O53 (WO2.944), W17O50 (WO2.941), W16O47 (WO2.938), W15O44 (WO2.933), W14O41 (WO2.929), W10O29 (WO2.9), and W9O26 (WO2.889), syntactically grow inside a single platelet. These layered crystals show a new kind of polycrystallinity, where crystallographic shear planes accommodate oxygen deficiency and at the same time stabilize this multi-stoichiometric structure.

The mineral composition and surface physico-chemical properties, i.e., specific surface area (SSA), cation exchange capacity (CEC), and surface charge of recent sediments and their submicron mineral fractions from different sedimentological environments of the Eastern Adriatic were investigated. The influence of organic matter on these properties was also investigated. It was shown that illite and mixed-layered clay minerals (MLCM) were ubiquitous and showed no size-related preferences while the occurrence of smectites, chlorites, and kaolinites varied. The smectites content increased and the chlorites decreased slightly with decreasing particle size. The sediments from the carbonate-rich environment contained no smectites or chlorites and had the highest kaolinite content. For the first time, in the recent sediments of the Adriatic Sea the poorly- and the well-crystallised kaolinite (Kl and Kl D ) were distinguished. While Kl predominates in the submicron-sized fraction, Kl D occurred only in micron-sized fractions. Authigenic aragonite of submicron-sized was determined in a distinct environment of the semi-enclosed marine lake. The differences in mineral composition and particle size of sediments and their separated fractions were reflected in a wide range of the SSA and CEC values obtained. The highest values of SSA and CEC were determined in the phyllosilicates-rich submicron-sized fractions range, 109 m 2 g -1 and 87.4 cmol + kg -1 , respectively. The submicron-sized fraction from aragonite-rich marine lake showed the lowest values of SSA (56.4 m 2 g -1 ) and CEC (38.8 cmol + kg -1 ), which are still unexpectedly high for carbonate-rich environments. The removal of organic matter resulted in a significant increase in SSA and CEC, up to 150% and 76%, respectively., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

ZnO nanopowders were produced using microwave processing of a precipitate and applied as a photoanode for photoelectrochemical water splitting. Two different surfactants, cetyltrimethylammonium bromide (CTAB) as the cationic and Pluronic F127 as the non-ionic one, were employed to in situ adjust the surface-to-bulk defect ratio in the ZnO crystal structure and further to modify the photo(electro)catalytic activity of the ZnO photoanode. The crystal structure, morphological, textural, optical and photo(electro)catalytic properties of ZnO particles were studied in detail to explain the profound effects of the surfactants on the photoanode activity. The ZnO/CTAB photoanode displayed the highest photocurrent density of 27 mA g -1 , compared to ZnO (10.4 mA g -1 ) and ZnO/F127 photoanodes (20 mA g -1 ) at 1.5 V vs. SCE in 0.1 M Na 2 SO 4 under visible illumination of 90 mW cm -2 . A significant shift of the overpotential toward lower values was also observed when photoanodes were illuminated. The highest shift of the overpotential, from 1.296 to 0.248 V vs. SCE, was recorded when the ZnO/CTAB photanode was illuminated. The ZnO/CTAB photoanode provides efficient charge transfer across the electrode/electrolyte interface, with a longer lifetime of photogenerated electron-hole pairs and reduced possibility of charge recombination. The photoconversion efficiency was improved from 1.4% for ZnO and 0.9% for ZnO/F127 to 4.2% for ZnO/CTAB at 0.510 mV. A simple procedure for the synthesis of ZnO particles with improved photo(electro)catalytic properties was established and it was found that even a small amount of CTAB used during processing of ZnO increases the surface-to-bulk defect ratio. Optimization of the surface-to-bulk defect ratio in ZnO materials enables increase of the absorption capacity for visible light, rendering of the recombination rate of the photogenerated pair, as well as increase of both the photocurrent density and photoconversion efficiency., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Copper nanoparticles (Cu NPs) have proven to own excellent antimicrobial efficacy, but the problems of easy oxidation and aggregation limit their practical application. Here, nanocomposite based on polyaniline (PANI) and Cu NPs solved this problem and brought additional physicochemical properties that are markedly advantageous for antimicrobial applications. Current work exploits this potential, to examine its time- and concentration-dependent antimicrobial activity, employing E. coli, S. aureus, and C. albicans as a model microbial species. Regarding the presence of polaronic charge carriers in the fibrous polyaniline network, effects of Cu NPs' size and their partially oxidized surfaces (the data were confirmed by HRTEM, FESEM, XRD, Raman and XPS analysis), as well as rapid copper ions release, Cu-PANI nanocomposite showed efficient bactericidal and fungicidal activities at the concentrations ≤1 ppm, within the incubation time of 2 h. Beside the quantitative analysis, the high levels of cellular disruption for all tested microbes were evidenced by atomic force microscopy. Moreover, the minimum inhibitory and bactericidal concentrations of the Cu-PANI nanocomposite were lower than those reported for other nanocomposites. Using such low concentrations is recognized as a good way to avoid its toxicity toward the environment. For this purpose, Cu-PANI nanocomposite is tested for its genotoxicity and influence on the oxidative status of the human cells in vitro., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This study describes and examines the structural and morphological properties of the hierarchically organized, aragonite cuttlebone forms for the common cuttlefish (Sepia officinalis, L.), including its main structural parts, the dorsal shield, and the chambers. Specifically, it complements the mechanism for the self-organized formation of aragonite, identifies the presence, and determines the role of soluble organic matrix (SOM) proteins in the morphogenesis of the cuttlebone's biomineral structures on the nanoscale. The structure and morphology of the cuttlebone were examined using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), and their thermal properties by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). Proteins from the SOM were investigated using two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (2D-PAGE), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS), nano liquid chromatography tandem mass spectrometry (nano-LC ESI-MS) and Edman degradation. The results showed that the cuttlebone exhibited several diverse biomineral structures characterized by complex morphologies. Their formation is governed by the organic matrix, particularly proteins, which at the earliest stage of development provide templates for the initial extracellular nucleation of the aragonite nanocrystals. This is followed by a bottom-up morphogenesis, based on the nanoscale oriented aggregation and coalescence of primarily formed aragonite nanograins, which results in the hierarchically organized, nanostructured, aragonite forms. The molecular masses of the most pronounced SOM proteins from the dorsal shield were about 10, 15, 40 and 60kDa, while from the chambers they were 10, 20, 25, 30 and 45kDa. Peptide fragments corresponding to Sep7, Sep8, chitin synthase 1, ficoline-2, polyubiquitin and the ubiquitin carboxyl-terminal hydrolase 32-like protein were detected in the SOM, with these proteins having functional properties related to the biomineralization processes. In general, there are mostly acidic proteins present in alternatively glycosylated forms, which are common attributes of biomineralization-related proteins., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This study investigates the geochemical characteristics of recent shallow-water aragonite-rich sediments from the karstic marine lakes located in the pristine environment on the island of Mljet (Adriatic Sea). Different trace elements were used as authigenic mineral formation, palaeoredox and pollution indicators. The distribution and the historical record of trace elements deposition mostly depended on the sedimentological processes associated with the formation of aragonite, early diagenetic processes governed by the prevailing physico-chemical conditions and on the recent anthropogenic activity. This study demonstrated that Sr could be used as a proxy indicating authigenic formation of aragonite in a marine carbonate sedimentological environment. Distribution of the redox sensitive elements Mo, Tl, U and Cd was used to identify changes in redox conditions in the investigated lake system and to determine the geochemical cycle of these elements through environmental changes over the last 100 years. The significant enrichment of these elements and the presence of early formed nanostructured authigenic framboidal pyrite in laminated deeper parts of sediment in Malo Jezero, indicate sporadic events of oxygen-depleted euxinic conditions in the recent past. Concentrations of trace elements were in the range characteristic for non-contaminated marine carbonates. However, the increase in the concentrations of Zn, Cu, Pb, Sn, Bi in the upper-most sediment strata of Veliko Jezero indicates a low level of trace element pollution, resulting from anthropogenic inputs over the last 40 years. The presence of butyltin compounds (BuTs) in the surface sediment of Veliko Jezero additionally indicates the anthropogenic influence in the recent past., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Structurally and morphologically different colloidal manganese oxide solids, including manganosite (MnO), bixbyite (Mn2O3) and hausmannite (Mn(2+)[Mn(3+)]2O4), were obtained through the initial biomimetically induced precipitation of a uniform, nanostructured and micron-sized rhodochrosite (MnCO3) precursor phase and their subsequent thermally controlled transformation into oxide structures in air and Ar/H2 atmospheres. The structures and morphology of the obtained precipitates were investigated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). Their surface properties were investigated by electrophoretic mobilities (EPM) and specific surface area (SSA) measurements. The results showed that the structurally diverse, micron-sized, spherical manganese oxide particles exhibit unusual and fascinating nanostructured surface morphologies. These were developed through the coalescence of an initially formed, nanosized, crystalline, manganese carbonate precursor phase which, during the heating, transformed into coarser, irregular, elongated, micron-sized, manganese oxide solids. It was also shown that structural transformations and morphological tailoring were followed by significant changes in the physico-chemical properties of the obtained solids. Their SSA values were drastically reduced as a result of the progressive coalescence at the particle surfaces occurring at higher temperatures. The isoelectric points (IEPs) of the obtained manganese oxides were diverse. This is the consequence of their range of crystal-chemical properties that governed the complex physico-chemical processes at the interface of the manganese oxide solid and the aqueous solution. The results of this study may lead to a conceptually new method for the synthesis of high-performance, nanostructured, manganese oxide solids with desirable structural, morphological and surface properties., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Because of the abounded presence of the silver-containing products in the market and intensively studied silver-containing biomaterials in the literature, we investigated a hypothesis that stabilizing silver within bioactive hydroxyapatite composite is capable to provide safe and effective antibacterial action. For that purpose nanocomposite made of bioactive, mineral hydroxyapatite (HAp) and antibacterial silver (Ag) is studied for interactions with both, bacterial and human cells. The nanocomposite provides controlled release of Ag ions; induces severe damages in bacterial cells and is capable for strong bacteriostatic and bactericidal action. On the other hand, investigations of the material's interactions with human cells confirm that lower concentrations are highly compatible with osteosarcoma and fetal lung fibroblasts, but at higher concentrations (that provide bacteriostatic and bactericidal influences in bacteria) the material is toxic and capable of inducing morphological changes similar to those observed in bacterial cells.

The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400-650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti(4+) to Ti(3+). The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.

This study explores different mechanisms of antimicrobial action by designing hybrid nanomaterials that provide a new approach in the fight against resistant microbes. Here, we present a cheap copper-polyaniline (Cu-PANI) nanocomposite material with enhanced antimicrobial properties, prepared by simple in situ polymerization method, when polymer and metal nanoparticles are produced simultaneously. The copper nanoparticles (CuNPs) are uniformly dispersed in the polymer and have a narrow size distribution (dav = 6 nm). We found that CuNPs and PANI act synergistically against three strains, Escherichia coli, Staphylococcus aureus, and Candida albicans, and resulting nanocomposite exhibits higher antimicrobial activity than any component acting alone. Before using the colony counting method to quantify its time and concentration antimicrobial activity, different techniques (UV-visible spectroscopy, transmission electron microscopy, scanning electron microscope, field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrophotometry, and inductively coupled plasma optical emission spectrometry) were used to identify the optical, structural, and chemical aspects of the formed Cu-PANI nanocomposite. The antimicrobial activity of this nanocomposite shows that the microbial growth has been fully inhibited; moreover, some of the tested microbes were killed. Atomic force microscopy revealed dramatic changes in morphology of tested cells due to disruption of their cell wall integrity after incubation with Cu-PANI nanocomposite.