A three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrate was fabricated as an array of poly (diethylene glycol dimethacrylate - glycidyl methacrylate) [poly(DEGDMA-GMA)] microparticles synthesized via gamma radiation-initiated polymerization technique and decorated with silver nanoparticles (AgNPs). The morphological characterization of the substrate showed a highly uniform distribution of the AgNPs on the microparticle surface. Two localized surface plasmon resonance peaks were observed in the optical absorption spectrum of the array, corresponding to standalone and assembled nanoparticles. The evaluation of the SERS performance showed a 10-11 M detection limit for Rhodamine 6G, and a SERS analytical enhancement factor of 1.26 x 108. The excellent SERS detection sensitivity and spatial uniformity of the platform were validated with SERS measurements on deoxyribonucleic acid strand.

The intrinsic defects in lithium niobate (LiNbO3) bulk crystals have been investigated with experimental and theoretical methods for many years. According to the most widely accepted model for the intrinsic defects in LiNbO3 bulk crystals, antisite niobium (NbLi) and lithium vacancy (VLi) defects are present in the lattice in concentrations depending on the composition, i.e., the Li/Nb ratio of the crystal. But nowadays, scientific attention has turned to nanocrystals. One of the methods to produce nanosized LiNbO3 crystals is the frequently used ball-milling procedure. In the present work, sintered lithium niobate with congruent composition was ground under wet conditions in a high-energy ball mill for different grinding times. After that, thermal treatments were performed on the powder samples at temperatures of 300 and 500 degrees C. The structural changes were monitored by Raman spectroscopic measurements. Atomistic computer simulations based on classical potential models have long been used for understanding intrinsic defect formation in various crystal lattices. In this work, a Li245Nb245O735 unit, constructed from a 5 x 5 x 5 supercell with sharp corners cut away to achieve a size of about 24 x 24 x 52 & Aring;3, was chosen for GULP force-field calculations as the starting configuration. The relaxation of the unit was achieved by first using the conjugate gradient and then the Newton-Raphson optimization methods. This process was repeated for the relaxed nano-LiNbO3 structure by placing one or two NbLi + 4 VLi, or one LiNb3O8-type neutral intrinsic defect into the supercell. The total energies were compared in terms of both the defect positions and their relative locations.

In addition to the network structures, bulk As2S3 glass contains a small amount of various cage-like molecular inclusions. In contrast, the As4S4 and As4S5 cage-like molecules make up the majority of the structures in As-S thin films freshly prepared by thermal evaporation of the glass. Thermal annealing or white light irradiation of these films leads to polymerization of the molecular cages and formation of a structure similar to that of the bulk material. However, the near-band gap laser irradiation of As-S films results in structural rearrangements of the As4S4 isomer (realgar-to-pararealgar transition). This transformation is reversible during “laser irradiation”—“thermal annealing” cycles. It was found that As-S crystallites can be grown using thermally activated and gold nanoparticle-assisted synthesis. Moreover, under specific synthesis conditions, selective growth of crystallites consisting solely of photosensitive As4S4 or As4S5 cage-like molecules can be achieved. The structure of various As-S crystallites was examined using Raman spectroscopy and density functional theory calculations. The selective growth of microcrystallites and their laser-induced transformation are discussed in detail.

It was observed in recent magnetoresistance studies on elongated strip-shaped thin foil samples that the MR(H) hysteresis curves have different shapes and widths in the longitudinal (L) configuration (field H parallel with the measuring current) and in the transverse (T) configuration (field H transverse to the measuring current). Subsequent magnetic measurements [L.F. Kiss et al., Eur. Phys. J Plus 139, 844 (2024)] of similar strip-shaped samples taken with different field orientations (corresponding either to the LMR or TMR configurations of the magnetoresistance measurements) revealed differences also in the M(H) magnetization curves, which are attributed to demagnetizing effects. After correcting for the demagnetizing field, the transverse M(H) curves could be brought in fairly good overlap with the measured longitudinal M(H) curves. In the present work, results of MR(H) measurements are reported on strips of the same Ni-Co alloys and pure Ni metal which were used in the M(H) study. Based on this recent work on the M(H) curves, one can now explain the differences in the shape and width of the LMR(H) and TMR(H) curves of a given material in a fully quantitative manner by taking into account the demagnetizing effects. Similarly to the transverse M(H) curves, the TMR(H) curves could also be corrected for the demagnetizing field, yielding good agreement with the LMR(H) curves. Furthermore, whereas the LMR(H) curves exhibited a normal hysteresis corresponding to the hysteresis behavior of the M(H) curve, the TMR(H) curves showed an anomalous behavior which can also be ascribed to demagnetizing effects. The same holds true also for the polar magnetoresistance curves PMR(H) measured in a magnetic field perpendicular to the strip plane.

Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.

A surface-wave microwave discharge is applied to deposit reactive oxygen and nitrogen species (RONS) into the liquid subsequently used as a medium for laser ablation of a Zn metallic target. It is shown that during laser ablation in plasma-treated liquids the H2O2 concentration decreases, while in deionized water (DIW) significant H2O2 is produced. Meanwhile, the pH-initially adjusted by applying reductive metals-increases in the acidic liquids and decreases in the alkaline ones. During months of storage the pH of colloids stabilize around pH 6, which insures the long-term stability of RONS. It is demonstrated that in DIW metallic Zn NPs are created, which gradually oxidize during storage, while in the plasma-treated liquids ZnO NPs are produced with the mean size of 18 nm. In the alkaline plasma-treated liquid the NPs form large aggregates, which slows the dissolution of NPs. In the acidic and neutral solutions besides NPs nanosheets are also formed, which during storage evolve into nanosheet networks as a result of the dissolution of NPs. The band gap of the colloidal ZnO is found to decrease with the formation of aggregates and nanosheet networks. The ZnO NPs ablated in plasma-treated liquids exhibit a high-intensity visible emission covering the green-to-red spectral region. The photoluminescence spectra is dominated by the orange-red emission-previously not detected in the case of laser-ablated ZnO NPs and attributed to the interstitial Zn and oxygen sites-and the yellow emission, which can be attributed to the OH groups on the surface. It is shown that during months of storage, due to the dissolution of NPs and formation of nanosheets, the intensity of the visible emission decreases and shifts to the blue-green spectral region.

The cross-section of various substrate–deposit metal pairs obtained with a laser-assisted additive manufacturing process has been studied by observing the composition profile with energy-dispersive spectroscopy (EDS). The EDS composition profiles observed with a sufficiently high data acquisition time revealed that the composition profile is asymmetric. By scanning toward the growth direction, a sudden composition variation was observed, which was followed by a slow decay. The character of the composition profile was the same for a number of substrate–deposit pairs, and similar trends were found in various earlier publications as well. A mathematical model for the composition variation is suggested based on the assumption that a spontaneous homogenization process takes place in the intermixing (dilution) zone of the remelted top layer of the substrate. The equation obtained makes it possible to quantitatively describe the composition profile of each component that exhibits a concentration difference between the substrate and the deposit, provided that the mole fraction difference much exceeds the scattering of the data measured. The suggested model has also been applied successfully to composition profiles published in other works, hence exhibiting general relevance. Since the variation in some physical parameters (such as hardness) along the growth direction has been reported to follow the same pattern, it is assumed that the root cause in these cases may also be the composition variation.

In the present work, a detailed field dependence of the resistivity of Ni75Co25 and Ni40Co60 bulk alloys was measured at T = 3 K and 300 K up to high magnetic fields. The focus of the study was to determine the anisotropic magnetoresistance (AMR) and to get a quantitative description of the field-induced resistivity change, the latter not yet being available for Ni -Co alloys. The AMR parameters were derived from the resistivity data in the magnetically saturated (monodomain) state by using the Kohler analysis. The values of the AMR ratio were found to be close to the relevant previous data both at low and high temperatures. Due to the measurement precision and careful data evaluation, our AMR data obtained on well-characterized samples can be considered as reference values for the bulk state of the investigated compositions. In addition, also the resistivity anisotropy splitting was determined. The experimentally found field dependence of the resistivity at both T = 3 K and 300 K turned out to be at variance with the current theoretical descriptions both for the resistivity increase due to the ordinary magnetoresistance effect being significant at T = 3 K and for the resistivity decrease due to the magnon suppression process at T = 300 K, invoking for a refinement of theory in both cases.

Mesoporous materials containing heteroelements have a huge potential for use as catalysts, exchangers, and adsorbents due to their tunable nanometer-sized pores and exceptionally large internal surfaces accessible to bulky organic molecules. In the present work, ordered mesoporous silica containing Ni atoms as active sites was synthesized by a new low-temperature method of condensation of silica precursors on a micellar template from aqueous solutions in the presence of nickel salt. The homogeneity of the resulting product was achieved by introducing ammonia and ammonium salt as a buffer to maintain a constant pH value. The obtained materials were characterized by nitrogen sorption, X-ray and neutron diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analysis. Their morphology consists of polydisperse spherical particles 50–300 nm in size, with a hexagonally ordered channel structure, high specific surface area (ABET = 900–1200 m2/g), large pore volume (Vp = 0.70–0.90 cm3/g), average mesopore diameter of about 3 nm, and narrow pore size distribution. Adsorption tests for methylene blue show sorption capacities reaching 39–42 mg/g at alkaline pH. The advantages of producing nickel silicates by this method, in contrast to precipitation from silicon alkoxides, are the low cost of reagents, fire safety, room-temperature processing, and the absence of specific problems associated with the use of ethanol as a solvent, as well as the absence of the inevitable capture of organic matter in the precipitation process.

Multi-principal element alloys (MPEAs) are at the forefront of materials science due to their large variety of compositions, which can yield unexplored properties. Mapping the structure and properties of a compositional MPEA library in a reasonable time can be performed with the help of gradient samples. This type of specimens has already been produced in both bulk and layer forms. However, combinatorial MPEA coatings have not been synthesized by electroplating, although this method has a great potential to deposit a coating on components with complex shapes. In this study, a combinatorial Co-Fe-Ni-Zn coating with the thickness of 4 μm was synthesized by electrodeposition. The material exhibited a well-defined Zn gradient; therefore, the investigation of the effect of Zn concentration on the microstructure and mechanical properties was feasible without the production of an excessively large number of specimens. The Zn concentration was controlled laterally through mass transfer due to the unique geometry of the substrate, and it covered a concentration range of 18–44 at%. The chemical and phase compositions as well as the morphology of the as-processed samples were investigated in multiple locations using X-ray diffraction and scanning electron microscopy. The mechanical performance was characterized by nanoindentation. It was found that for any composition, the structure is face-centered cubic and the lattice constant scaled with the Zn concentration of the deposit. The hardness and the elastic modulus were consistent with values of about 4.5 and 130 GPa, respectively, in the Zn concentration range of 25–44 at%.

According to some recent studies, the magnetoresistance curves of ferromagnetic strip-shaped samples can significantly differ depending on whether the in-plane external applied magnetic field H is oriented in parallel to either the long or the short edge of the strip. To address this problem, in the present work magnetization curves M(H) were measured for similarly shaped samples with both magnetic field orientations used in the magnetoresistance measurements. It was found that the M(H) curves strongly depend on the saturation magnetization and shape of the samples as well as on the magnetic field orientations. For some samples with sufficiently large saturation magnetization, the effective demagnetizing factors could be deduced from the measured M(H) curves. By considering the investigated samples as a ferromagnetic slab, and approximating them with a general ellipsoid, the demagnetizing factors were calculated from known formulae and compared to the experimental values. A fairly good matching was observed, although the latter data were systematically slightly larger, certainly due to the not completely homogeneous magnetization within the rectangular slab as opposed to the case of a general ellipsoid. The differences in the M(H) curves for the two orientations of the magnetic field could be completely attributed to demagnetizing effects.

The intrinsic and extrinsic defects in LiNbO 3 (LN) bulk crystals have been investigated with experimental and theoretical methods for many years. However, nowadays, scientific attention has turned to nanocrystals (e.g., for quantum nanophotonic applications). Herein, the results of spectroscopic measurements and theoretical calculations on Yb 3+ ‐ or Er 3+ ‐doped LN nanocrystals are presented. A series of congruent LN nanocrystals doped with Er 3+ or Yb 3+ have been produced by grinding process under wet conditions in a high‐energy ball mill. The effect of size reduction on the rare‐earth (RE) ions has been followed by absorption measurement of the characteristic electronic transitions using a Fourier‐transform infrared spectrometer. Out‐diffusion of the RE ions from the nano‐LN particle and the appearance of an unordered phase have been concluded from the experimental results. GULP software has been used to make force‐field calculations on a Li 245 Nb 245 O 735 unit to model the nano‐LN structure containing Er 3+ or Yb 3+ dopants. From the calculations taking into account, one Er 3+ or Yb 3+ ion, their out‐diffusion, and the appearance of the ions in the unordered phase have been demonstrated, while in the double‐doped case, independent RE incorporation has been found.

The optimization of the parameters of the solvothermal synthesis of lithium niobate (LiNbO3, LN) nanocrystals from Nb2O5 and LiOH was performed. The effects of polyol media, reaction time and Li excess of the starting reagents were investigated. According to the X-ray diffraction phase analysis, Li3NbO4 and Nb2O5 were also detected besides the LN phase in many samples depending on the ratio of the starting components and the reaction time. The best yield and the most homogeneous LN phase was prepared by using diethylene glycol medium with a Li/Nb ratio of 1.5 and a 72 h reaction time. The size and the shape of the LN particles were characterized by scanning electron microscopy. The particle size distribution was narrow and under 100 nm for all cases.

In a previous work [El-Tahawy et al., J. Magn. Magn. Mater. 560 , 169660 (2022)], we reported that from a sulfate type bath, hcp-Co can be electrodeposited at high pH and low current density and investigated the structure and magnetoresistance (MR) characteristics of such hcp-Co electrodeposits. Based on this earlier work, Co-rich Co-Cu and Co-Ni alloy electrodeposits were prepared under the same conditions by adding varying amounts of CuSO 4 and NiSO 4 , respectively, to the CoSO 4 bath. According to the results of detailed structural studies by various X-ray diffraction (XRD) geometries, in both the Co-Cu and Co-Ni systems an hcp phase formed exclusively up to about 2 at% of the alloying element. Above this concentration, a significant fcc phase fraction appeared in Co-Cu and a minor fcc fraction in Co-Ni up to about 8 at%. This means that the destabilization effect of Cu on hcp-Co is higher than that of Ni. Although the reduction of the stability of hcp-Co with increasing Cu and Ni content is a well-known phenomenon, a quantitative comparison of this effect in Co-Cu and Co-Ni alloys is missing from the literature. The measured lattice constants are analyzed in comparison with Vegard’s law for the Co-Cu and Co-Ni element pairs deduced from data previously reported for the hcp and fcc phases of all three pure elements. For Co-rich Co-Ni alloys, the concentration dependence of the lattice parameters was found to follow Vegard’s law for both the hcp and fcc phases due to the miscibility of the two components. For the Co-rich Co-Cu alloys, the data indicate a positive deviation from Vegard’s law for both the hcp and fcc phases in agreement with the known similar behavior of fcc Co-Cu alloys for the whole composition range. The positive deviation from Vegard’s law in the Co-Cu system is due to the excess mixing volume required for solid solution alloy formation of these immiscible elements in either phases. The MR data are discussed in the light of the observed phases and of the MR parameters reported in our previous work on the hcp and fcc phases of pure Co.

A Co-Fe-Ni-Zn multi-principal element alloy (MPEA) film with the thickness of about 2.5 & mu;m is processed by electrodeposition. The layer has a nanocrystalline microstructure with the grain size of about 12 nm as determined by transmission electron microscopy. The structure of the majority of the film is face-centered cubic (fcc); however, body-centered cubic (bcc) and amorphous phases with small fractions are also detected. The average hardness and elastic modulus of the coating are 9.2 and 197 GPa, respectively, as determined by nano-indentation. The hardness value is superior compared to other fcc MPEA layers processed by different deposition methods. The enhanced hardness can be attributed to the strengthening effect of the very small grain size and the presence of nanocrystalline bcc and amorphous minority phases. This study demonstrates the ability of electrodeposition for producing hard MPEA layers with the desired composition.

Studies of sessile droplets and fluid bridges of a ferroelectric nematic liquid crystal in externally applied electric fields are presented. It is found that above a threshold, the interface of the fluid with air undergoes a fingering instability or ramification, resembling to Rayleigh-type instability observed in charged droplets in electric fields or circular drop-type instabilities observed in ferromagnetic liquids in magnetic field. The frequency dependence of the threshold voltage was determined in various geometries. The nematic director and ferroelectric polarization direction was found to point along the tip of the fingers that appear to repel each other, indicating that the ferroelectric polarization is essentially parallel to the director. The results are interpreted in connection to the Rayleigh and circular drop-type instabilities.

This paper presents a handful of electrochemical experiments related to one single system that opens up the way to teach a bunch of topics related to physical and inorganic chemistry, hence serving experience-oriented education of otherwise hard-to-understand fields. The key idea is the electrodeposition of metals from the same bath containing Cu 2+ and Ni 2+ ions onto electrodes that differ from each other either in size or position within the electrochemical cell. With the proper optimization of the current densities, pure Cu and a Ni-rich coating with shiny silver colour can be obtained on electrodes of large and small surface area, respectively. It will be explained in detail how to drive the discussion on the experiment so that the audience learns which processes can be treated as parallel ones (i.e. the deposition of two metals, Cu and Ni), the mass transport taking place in serial with the electrochemical reaction, and the occurrence of the mass transport limitation in an electrode process. Didactic aspects of the experiment are presented for both high school and undergraduate levels, and control experiments are also suggested to verify the conclusions achieved. Collateral topics of chemistry and materials science that can be brought up in connection with the experiment are also enumerated.

Citric acid plays an ubiquitous role in the complexation of essential metals like iron and thus it has a key function making them biologically available. For this, iron(III) citrate complexes are considered among the most significant coordinated forms of ferric iron that take place in biochemical processes of all living organisms. Although these systems hold great biological relevance, their coordination chemistry has not been fully elucidated yet. The current study aimed to investigate the speciation of iron(III) citrate using Mössbauer and electron paramagnetic resonance spectroscopies. Our aim was to gain insights into the structure and nuclearity of the complexes depending on the pH and iron to citrate ratio. By applying the frozen solution technique, the results obtained directly reflect the iron speciation present in the aqueous solution. At 1:1 iron:citrate molar ratio, polynuclear species prevailed forming most probably a trinuclear structure. In the case of citrate excess, the coexistence of several monoiron species with different coordination environments was confirmed. The stability of the polynuclear complexes was checked in the presence of organic solvents.

The edition of this special issue started in early 2022-that is, at a time when the decay of the COVID-SARS-19 pandemic could already be foreseen, but before a new war broke out in the region, impacting also scientific research and international collaborations.We are grateful to all our colleagues who contributed to this issue prepared in such a difficult period.The present issue inherits the spirit of the book "Electrochemistry in the Divided World" [1], but with an essential difference: we try to highlight the development of electrochemistry in both "large" and "small" countries and to accent individual scientific features of the electrochemical research of particular countries and/or regions.The issue starts a new collection, which will hopefully be extended by colleagues from various countries mentioned below.Eastern Europe is a conditional term which is closely associated with the former "socialist" countries .Fortunately, nowadays, many of them solidly belong to the European Union and undergo the development of their research in the absence of limitations described in Ref. [1].Great electrochemical schools which existed in Eastern Europe even under "soviet" pressure are undergoing natural evolution.However, currently, active generations of electrochemists are still under the influence of the professional traditions of these schools, and their international integration still allows them to keep certain individuality.This is in favor of further dissemination of basic knowledge.We also noticed a lot of joint publications of electrochemists from different Eastern European countries.Sometimes, this stems from long-term cooperations started even before the collapse of the soviet political block but may also stem from more recently established networks like the Association of South-East European Electrochemists (ASEEE) [2].Following the approximate geographic definition, we invited the authors from the countries mentioned below in alphabetic order.The issue collects the reviews covering electrochemistry in either various countries and-in the case of larger or less homogeneous communities-in some separate regions, or related to separate topical branches.Original articles are presented as well.Although we strived for completeness and committed everything to recruit contributions from each single part of the Eastern Europe, it was impossible to collect the reviews from all the countries for various reasons.In such instances, we present our obviously non-exhaustive brief comments in this introductory article.Electrochemistry in Albania is mostly presented by corrosion/protection studied by individual researchers, typically in cooperation with other countries.There are also some publications in the field of electroanalysis.Albanian publications in specialized electrochemical journals are very rare, and there are no ISE members from Albania.This is also the case for Armenia, where electrochemical techniques and approaches are mostly applied in frames of interdisciplinary research (e.g., medical diagnostics, materials for various devices, organic electrosynthesis).The most noticeable electrochemical publications from Azerbaijan address the electrodeposition of binary alloys and compounds.This country tends to cooperate mostly with Asian partners in scientific research .