Crystals, Volume 13, Issue 12 (December 2023) – 92 articles

The present study demonstrates the synthesis of phase pure hematite (α-Fe₂O₃) nanoparticles (NPs) using collagen protein and calcium carbonate extracted from eggshell membranes and eggshells, respectively, as organic additives. To test the influence of organic additives on the quality of the resulting NPs, the amount of eggshell powder was varied between 1 to 5 g in aqueous iron nitrate solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and RAMAN analysis confirmed the formation of hematite NPs without any impurities. FTIR spectra revealed the presence of polyphenolic constituents on the surface of the resulting NPs as stabilizers, which may potentially be responsible for the observed antioxidant and antibacterial properties. Furthermore, the stable phase and the presence of low defects divulged the high hardness value (~983 HV) and fracture toughness (8.59 MPa m^1/2), which can be exploited for bone implantation. The FE-SEM results demonstrate the formation of spherical particles, which are well-separated NPs. The results of a biodegradation study which was carried out in phosphate-buffered saline (PBS) revealed that the as-prepared NPs retained their hardness even after 72 h of soaking. These prepared NPs showed 95% radical scavenging activity (RSA) and were good carriers against S. aureus bacteria. Moreover, the SEM images of the mineralization of iron oxide NPs confirmed the formation of new bone. After 5 weeks, all pores were filled, and the minerals were deposited on the surfaces of the scaffolds. Full article

The protection of implant surfaces from biofilm and corrosion is crucial for osteogenesis and tissue engineering. To this end, an L-glutamine-based green corrosion inhibitor with recently established anticancer properties has been applied onto antibacterial Cu(111) surfaces that usually cover the Ti-based implants. Among several configurations, L-glutamine prefers the parallel to the surface orientation with the carbon chain along the [110] direction having the heteroatoms N and O atoms on top of Cu surface atoms, which is important for the creation of a planar two-dimensioned (2d) stable coating. L-glutamine forms well-localized, directional covalent-like bonded states (below −3 eV) with the Cu surface atoms, using mainly its backbone’s N₁ atom that interestingly also shows electron charge occupation in the single-molecule highest occupied state, denoting its ability as an active center. The Mulliken analysis shows charge transfer from the molecule’s N, C and Cu neighboring atoms towards the O atoms revealing the strong bond tendency of L-glutamine and therefore its ability to act as a corrosion inhibitor on the Cu surface. Additional L-glutamine adsorption results in intermolecular covalent bonding between the molecules, proving the ability of this amino acid to form a stable protective 2d organic coating on Cu(111). These results could be used for the design of a multifunctional hybrid (organic–metallic) coating with anticorrosion, anticancer and antibacterial properties suitable for many technological applications. Full article

Among short donor–acceptor molecules with a central benzothiadiazole fragment, 4,7-di-2-thienyl-2,1,3-benzothiadiazole (T-BTD) is one of the most well-known compounds, valued for its photophysical and semiconductor properties. We have synthesized a derivative of 4,7-di-2-thienyl-2,1,3-benzothiadiazole with trimethylsilyl end-substituents, 4,7-bis(5-(trimethylsilyl)thiophen-2-yl)benzothiadiazole (TMS-T-BTD). The phase transition parameters and thermal stability of T-BTD and TMS-T-BTD were investigated using DSC and TGA methods. The presence of the trimethylsilyl end-groups in TMS-T-BTD significantly enhances solubility, increases the melting temperature, and improves the resistance of TMS-T-BTD to evaporation in the liquid state. Single crystals of T-BTD and TMS-T-BTD were grown from solutions, with the largest sizes being 7 × 2 × 0.5 mm³ and 8 × 1 × 0.45 mm³, respectively. Using single-crystal X-ray diffraction at 293 K, the crystal structure of T-BTD was refined in the rhombic system (sp.gr. P_cab, Z = 8), while for TMS-T-BTD, it was determined for the first time in the monoclinic system (sp.gr. P2₁/c, Z = 4). The relationship between observed growth anisotropy and molecular packing in the crystals was analyzed. The results of investigations into the spectral-fluorescent properties of solutions in hexane and THF are presented. The solvatochromic effect was studied in a series of solvents, including hexane, THF, dichloromethane, and acetonitrile. The photostability of the compounds in hexane solutions was examined. It was found that the quantum yield of photodestruction for T-BTD is 13 times higher than that of TMS-T-BTD. The fluorescent properties of T-BTD and TMS-T-BTD crystals were investigated. Full article

Depending on operating conditions, metals and alloys are exposed to various factors: wear, friction, corrosion, and others. Plasma surface alloying of machine and tool parts is now an effective surface treatment process of commercial and strategic importance. The plasma surface alloying process involves adding the required elements (carbon, chromium, titanium, silicon, nickel, etc.) to the surface layer of the metal during the melting process. A thin layer of the compound is pre-applied to the substrate, then melted and intensively mixed under the influence of a plasma arc, and during the solidification process, a new surface layer with optimal mechanical properties is formed. Copper-based alloys—Cu-X, where X is Fe, Cr, V, Nb, Mo, Ta, and W—belong to an immiscible binary system with high mechanical strength, electrical conductivity, and magnetism (for Fe-Cu) and also high thermal characteristics. At the same time, copper-based alloys have low hardness. In this article, wear tests were carried out on coatings obtained by plasma alloying of CuSn10 and CrxCy under various friction conditions. The following were chosen as a modifying element: chromium carbide to increase hardness and iron to increase surface tension. It is noted that an increase in the chromium carbide content to 20% leads to the formation of a martensitic structure. As a result, the microhardness of the layer increased to 700 HV. The addition of CuSn10 + 20% CrxCy and an additional 5% iron to the composition of the coating improves the formation of the surface layer. Friction tests on fixed abrasive particles were carried out at various loads of 5, 10, and 50 N. According to the test results, the alloy layer of the Fe-Cr-C-Cu-Sn system has the greatest wear resistance under abrasive conditions and dry sliding friction conditions. Full article

The early loss of dental implants can be avoided with systemic antibiotics, however there are potentially significant side effects. Consequently, the use of local drug administration techniques is necessary to make dental implant therapy more practical. In this study, Y-branched nanotubes were prepared by non-expensive and simple anodization in two steps. Tests were performed to highlight their potential for local antibiotic administration. Y-branched nanotubes were able to incorporate a dose of Tetracycline and ensure its electrochemical stability. The presence of tetracycline significantly enhanced antibacterial efficacy, resulting in an increase of up to 55% for Escherichia coli and Pseudomonas aeruginosa and 50% for Staphylococcus aureus. The comparable antibacterial effects of the nanostructured surfaces highlight the potential of tetracycline in promoting antimicrobial action. Moreover, the addition of tetracycline does not influence the structural, morphological and stability properties of the nanostructured deposited TiO₂ films. Full article

The crystallographic-orientation relationship between GaN crystals grown via hydride vapor phase epitaxy (HVPE) on 6H-SiC was investigated. This study employed electron backscatter diffraction (EBSD) Kikuchi diffraction patterns and pole figures to identify this relationship and calculate lattice mismatches. Comparing the misorientation of GaN crystals on different substrates along the growth direction using EBSD mapping, we identify the strain in GaN based on crystallographic-orientation results. Raman spectroscopy results correlate residual stress in GaN with lattice mismatches, aligning with our previous works. Residual stress of GaN on different substrates identified using PL spectrum also confirmed these results. The HRXRD characterized the dislocation density of GaN crystals grown on these substrates. Full article

This study investigated the crystallographic and electronic properties of 1,5-benzodiazepine compounds, namely: cis-(3S,4S)-3-hydroxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-1,5-benzodiazepin-2-one 3b, trans-(3R,4R)-1-ethyl-3-hydroxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-one 4, and trans-(3S,4S) 1-ethyl-3-ethoxy-7,8-dimethyl-4-phenyl-1,3,4,5-tetrahydro-1,5-benzodiazepin-2-one 5. Hirshfeld surface analysis was also applied to discern the intermolecular interactions, highlighting the significance of hydrogen bonding, van der Waals forces, and the influence of specific substituents. Furthermore, the MESP maps created using the density functional theory revealed the electrostatic nature of these molecules. The absence of dark blue regions on the MESP maps and variations due to different functional groups and substitutions were noteworthy findings. Collectively, this research offers crucial insights into the behaviour, interactions, and potential applications of new compounds. Finally, the anticancer effects of compounds 3b, 4, and 5 were evaluated against three cancer cell lines and one normal cell line, and the results showed that 3b and 4 had potent antiproliferative effects against all three cancer cell lines. Full article

The aim of the research campaign was to simulate in vitro the typical conditions for the corrosion in biofluid of a femoral bone implant manufactured with AZ31 alloy. The samples were immersed in biofluid (alpha-MEM) for time intervals of up to 56 days. For each immersion time, the chemical compositions and morphologies of the samples were studied with SEM, EDX, XRD, Raman spectroscopy, and XPS. The weight losses of the samples caused by corrosion were also measured. The results highlighted the formation of calcium phosphate crystals on the surface of the samples. This type of coating is well-known for its excellent corrosion resistance and for its ability to accelerate tissue regeneration. The deceleration of the corrosion process, observed after 28 days of immersion in biofluid, confirms the anti-corrosive effect of the coating that was spontaneously formed during the immersion tests. Full article

Recent advancements in experimental approaches have made it possible to synthesize silver (Ag₅) atomic quantum clusters (AQCs), which have shown a great potential in photocatalysis. This study employs the generalized gradient approximation (GGA) density functional theory (DFT) to explore the adsorption of CO₂, CH₄, and H₂O molecules on the Ag₅ AQC. Our investigations focus on the structural and electronic properties of the molecules in Ag₅ AQC systems. This involves adsorption energy simulations, charge transfer, charge density difference, and the density of states for the modelled systems. Our simulations suggest that CH₄ and H₂O molecules exhibit higher adsorption energies on the Ag₅ AQC compared to CO₂ molecules. Remarkably, the presence of CH₄ molecule leads to a significant deformation in the Ag₅ AQC structure. The structure reforms from a bipyramidal to trapezoidal shape. This study also reveals that the Ag₅ AQC donates electrons to CO₂ and CH₄ molecules, resulting in an oxidation state. In contrast, gaining charges from H₂O molecules results in a reduced state. We believe the proposed predictions provide valuable insights for future experimental investigations of the interaction behaviour between carbon dioxide, methane, water molecules, and Ag₅ sub-nanometre clusters. Full article

Using a hierarchy of three sigmoid growth models with increasing complexity, i.e., number of parameters, we reanalyzed kinetic data for heterogeneous nucleation—the number of nuclei N(t) vs. time t—from archetypical experiments on the electrodeposition of mercury on platinum by I. Markov and E. Stoycheva, to obtain two scales: N_max and τ. The universal character of the studied phenomenon was revealed when replotting the original data as α ≡ N(t)/N_max vs. t/τ. Yet the simplest model, the recently introduced α₂₁ model which is aimed to describe diffusion-limited growth in 2D, α₂₁ = tanh²(2t/τ₂₁), fits all datasets with an R² ≥ 0.989. This can be rationalized by attracting the non-classical notion of two-step nucleation—the nuclei form in a metastable phase which, in this case, grows on the electrode surface. Beyond the universality, we find the dependence of the two obtained scales on the overvoltage, which is increased systematically from 83 to 88 mV to generate the six N(t) datasets for each of the two electrode types—planar and hemispherical. Surprisingly, for one of them, the planar electrode, there is a discontinuity in the dependence—an almost horizontal jump from 85 to 86 mV, while for the hemispherical electrode, τ decreases smoothly. Full article

We describe an all-optical method to achieve—prior to further advanced processing steps—a perfect match of the relevant wavelength-sensitive parameters of an InGaN/GaN semiconductor distributed feedback laser. Instead of permanently etching and epitaxially over-growing a waveguide-based diffraction grating for the definition of an index-coupled distributed feedback laser, we suggest here—by employing a powerful ultraviolet pump laser—a non-permanent, photoinduced generation of an optical diffraction grating. The resulting complex refractive index modulation then forms a gain-coupled distributed feedback laser. Such an approach has the advantage of remaining flexible as long as possible—both in terms of the correct grating period and the ideal coupling constant. This flexibility is maintained until the definitive etch and the epitaxial over-growth of the diffraction grating are completed. Such devices can—like their dye laser counterparts in the early seventies—also be used as ultra-broadly tunable single-mode sources. Full article

Thermal expansion of metatorbernite, Cu(UO₂)₂(PO₄)₂(H₂O)₈ (1), and metazeunerite, Cu(UO₂)₂(AsO₄)₂(H₂O)₈ (2), has been investigated using single-crystal and powder X-ray diffraction. Both minerals are prone to dehydration, which proceeds already at ambient conditions. According to the single-crystal XRD data, 1 is stable up to 300(50) K, while 2 is stable up to 250(50) K. Powder XRD studies at various temperatures suggest that 1 dehydrates in three stages at ca. 353, 373, and 483 K, while 2 in two stages at ca. 283 and 543 K. Calculation of the main coefficients of thermal expansion reveals strong anisotropy. The expansion is maximal in the direction normal to the autunite-type layers. This correlates with the anisotropy in thermal evolution of Cu–O bond lengths and differences in the thermal behavior of PO₄ and AsO₄ tetrahedra. Full article

In recent years, rare earth silicate compounds have attracted the extensive attention of researchers owing to their potential for applications in scintillation crystals in gamma ray or X-ray detectors, as well as in thermal or environmental barrier coatings. Large high quality crystals of three members of the rare earth monosilicates family of compounds, $R_2{\mathrm{SiO}}_5$ (with R = Dy, Ho, and Er), have been grown by the floating zone method, using a laser-diode-heated floating zone furnace. Crystal growths attempts were carried out using different parameters in order to determine the optimum conditions for the growth of these materials. The phase purity and the crystalline quality of the crystal boules were analysed using powder and Laue X-ray diffraction. Single crystal X-ray diffraction experiments were carried out to determine the crystal structures of the boules. The optimum conditions used for the crystal growth of $R_2{\mathrm{SiO}}_5$ materials are reported. The phase purity and high crystalline quality of the crystals produced makes them ideal for detailed investigations of the intrinsic physical and chemical properties of these materials. Full article

The strain engineering effects induced by different means, e.g., the substrate lattice mismatch and/or chemical doping, on the functional properties of perovskite thin films have triggered interest in the use of these materials in different applications such as energy storage/generation or photonics. The effects of the film’s thickness and strain state of the structure for the lead-free perovskite ferrite-based materials (BiFeO₃-BFO; Y-doped BiFeO₃-BYFO; LaFeO₃-LFO) on their functional properties are highlighted here. As was previously demonstrated, the dielectric properties of BFO epitaxial thin films are strongly affected by the film thickness and by the epitaxial strain induced by the lattice mismatch between substrate and film. Doping the BiFeO₃ ferroelectric perovskite with rare-earth elements or inducing a high level of structural deformation into the crystalline structure of LaFeO₃ thin films have allowed the tuning of functional properties of these materials, such as dielectric, optical or photocatalytic ones. These changes are presented in relation to the appearance of complex ensembles of nanoscale phase/nanodomains within the epitaxial films due to strain engineering. However, it is a challenge to maintain the same level of epitaxial strain present in ultrathin films (<10 nm) and to preserve or tune the positive effects in films of thicknesses usually higher than 30 nm. Full article

Mechanochemical synthesis for the preparation of bimetallic catalysts is gaining increasing interest, and in recent years, some important milestones have been reached. However, the complexity of mechanochemically prepared bimetallic supported catalysts still leaves many open questions that need a systematic approach to be solved. In this work, we summarize our experience of mechanochemically milling bimetallic catalysts, introducing some key parameters that should be taken into account, particularly the thermal stability and hydrophilicity of precursor salts, and the effect of the milling order, highlighting the differences with wet synthesis methods. Finally, we will provide some suggestions on the application of the design of experiments approach to the rationalization of the milling procedure for the preparation of supported bimetallic catalysts. Full article

Magnesium alloys possess a high strength-to-density ratio, thereby increasingly being utilized as lightweight structural materials in a range of industrial applications. Nevertheless, to compete with established materials like aluminum alloys, it is essential to understand the corrosion behavior of Mg and its alloys, as their high reactivity hampers industrial application. The addition of Ca to wrought Mg-Al alloys has gained attention for its ability to improve mechanical properties while also enhancing processing behavior. However, the wide range of alloy compositions within the class of Mg-Al-Ca alloys results in a variety of different corrosion properties. Consequently, this study contributes by investigating the corrosion behavior of two Mg-Al-Ca alloys, highlighting the influence of chemical composition and microstructure. Full article

This article presents the results of a study to identify intermetallic phases whose role is to limit austenite grain growth in the low-pressure carburizing process. A drawback of high-temperature low-pressure carburizing is the austenite grain growth during the process. Using low-pressure carburizing with pre-nitriding technology (PreNitLPC^®) offers the possibility of reducing austenite grain growth. This technology involves the application of doses of ammonia during the heating stage of the steel, at the carburizing temperature, to introduce nitrogen into the surface layer of the steel and to form nitrides. It is these phases that cause restrictions on austenite grain growth during carburizing. The research carried out in this article was aimed at identifying these phases. The research was carried out on one of the basic steels used for carburizing—16MnCr5 steel. The carburizing of this steel with and without pre-nitriding was performed, followed by an evaluation of the austenite grain size after these processes and the identification of the intermetallic phases present in the surface layer of the steel. Full article

It is known that the meso- and microstructures of metals determine the physical, mechanical and operational properties of their final products. Scientific and technological progress of recent decades has given impetus to the elaboration and use of models capable of describing the evolving structure of materials. The most promising are multilevel models that include internal variables and are based on physical theories of elastoplasticity (elastoviscoplasticity). This paper presents the structure and basic relationships of a three-level (macro-, meso-1 and meso-2 levels) elastoviscoplastic model. The developed model operates on such internal variables as dislocation densities on slip systems, barriers on split dislocations and sources of edge dislocations. The model describes the mechanisms of production, annihilation, formation of barriers and sources of dislocations. The law of hardening directly takes into account the densities of dislocations and barriers. The mechanism of inelastic deformation is the gliding of edge dislocations along slip systems. Special emphasis is placed on the influence of split dislocations (prone to forming hard Lomer–Cottrell and Hirth barriers) on the deformation of the material. The model is used to describe the behavior of an elastoviscoplastic polycrystalline aggregate with an FCC lattice. Geometric nonlinearity is taken into account by utilizing decomposition of the crystallite motion into quasi-rigid and deformation components. For this purpose, a rigid moving coordinate system for the crystal lattice is introduced. Examples of the application of the model for analyzing the simple and complex deformation mechanisms of materials with different stacking fault energies and, consequently, with different tendencies toward the decomposition of dislocations and barrier formation are given. Full article

Two 3D Zn(II) and Cd(II) coordination polymers, [Zn₂(µ₄-dppa)(µ-dpe)(µ-H₂O)]_n·nH₂O (1) and [Cd₂(µ₈-dppa)(µ-dpe)(H₂O)]_n (2), have been constructed hydrothermally using 4-(3,5-dicarboxyphenoxy)phthalic acid (H₄dppa), 1,2-di(4-pyridyl)ethylene (dpe), and zinc or cadmium chlorides. Both compounds feature 3D network structures. Their structure and topology, thermal stability, catalytic, and anti-wear properties were investigated. Particularly, excellent catalytic performance was displayed by zinc(II)-polymer 1 in the Knoevenagel condensation reaction at room temperature. Full article

Interactions between liquid crystal molecules and target analytes open up various biosensing applications for quick screening and point-of-care applications. In this review, we categorized biosensors by type, depending on the liquid crystal mesophase, and considered several applications for the detection of biomolecules, point-of-care diagnostics and environmental monitoring. We also discuss interactions between polarized light and target pathogens dispersed in biological fluids, which result in the change of the polarization state. An array of the Stokes parameters can be compared with the pattern, and a proper pathogen can be manifested. We suggest that a combination of a micropolarizer array and a complementary metal oxide semiconductor sensor is an optimal setup for the detection of pathogens. Herein, we discuss the working principles of liquid crystal biosensors and their fabrication principles. In addition, relevant theoretical and practical issues related to liquid crystal biosensors are outlined. In general, this review gives an in-depth survey of the research on liquid crystal-based sensors, making it easier for researchers to locate their niche and make contributions to this subject from multiple viewpoints. Full article

The sintering process can improve the microstructure of Al₂O₃ composite ceramics and enhance their comprehensive properties, but the effects of the sintering process on Al₂O₃ composite ceramics are still unclear. Herein, a novel Al₂O₃ composite ceramic was printed using the material extrusion and photo-polymerization combined process, and the final ceramic was obtained using one-step sintering (TS) and two-step sintering technology (TSS). Based on the testing results, such as the relative density (D_rel), average grain size (AGS), hardness, bending strength, and fracture toughness, TSS was suitable for the refinement of commercial Al₂O₃ ceramics. Moreover, the highest sintering temperature of the second step (T₂) was at 1550 °C, while that of the shortest holding time (t) was at 4 h (TSS₈), which was to ensure densification before rapid grain growth. The D_rel and AGS of the best ceramics obtained via TSS₈ were 97.65% and 1.52 µm, respectively. Their hardness, bending strength, and fracture toughness were also enhanced, and they were affected by T₂, t, and the interaction. In sum, the TSS obtained better fracture toughness and bending strength, which had great potential in the application of the additive manufacturing field. Full article

Lead halide perovskites have been widely used in optoelectronic devices due to their excellent properties; however, the toxicity of lead and the poor stability of these perovskites hinder their further application. Herein, we report a zero-dimensional (0D) lead-free organic manganese (II) bromide hybrid compound of (TBA)₂MnBr₄ (TBA⁺ = tetrabutylammonium cation) single crystals (SCs) with great environmental stability. The (TBA)₂MnBr₄ SCs show a strong green emission peak at 518 nm with a high photoluminescence quantum yield (PLQY) of 84.98% at room temperature, which is attributed to the d-d transition of single Mn²⁺ ions, as also confirmed through density functional calculation. A green light-emitting diode was produced based on (TBA)₂MnBr₄ SCs, which exhibited CIE coordinates (0.17, 0.69) close to those of standard green. A photodetector fabricated by the (TBA)₂MnBr₄ SCs shows an obvious photo response with a rapid millisecond rise/decay response time (at 365 nm). Our findings promote the research of Mn(II)-based organic–inorganic hybrid materials and pave the way by using these materials for future high-performance optoelectronic devices. Full article

The recently discovered Mida nephrite deposit, located in the East Kunlun Mountains, Qiemo County, Xinjiang, Northwest China, contains new types of white and greenish white nephrite formed by limestone replacement, which shows microstructures, macroscopic features and country rocks typologies that are quite different from those of the other deposits along the Kunlun–Altyn Tagh Mountains. The gemological and mineralogical characteristics of Mida nephrite are presented here. These nephrites show an ivory white color and a porcelain-like appearance, with semitranslucent-to-opaque transparency and a porcelain-to-greasy luster. Petrographic study, electron probe microanalysis (EPMA) data and scanning electron microscopy (SEM) images have indicated that the nephrite is composed of tremolite, accompanied by minor quartz, calcite and diopside. Tremolite aggregates have shown different textures, like flaky, granular, fibrous–felted, bundle, radial and metasomatic relict textures. Quartz has appeared in granular or disseminated form, dispersed in the tremolite matrix. Calcite has shown a metasomatic relict texture in the white nephrite samples. Diopside has shown euhedral grains, with some distributed with a certain geometric appearance. Based on our observations, it is suggested that the quartz in the nephrite originated from Si-rich hydrothermal fluids. We propose that the substantial size difference of mineral grains, together with uncompacted grains with inter-particle pores, are the main reasons for the internal reflection and refraction under transmitted light, which allow less transmitted light to pass through the nephrite body and generate the appearance of a semitranslucent-to-opaque transparency, ivory white color and porcelain luster. Our study has unveiled that the Mida nephrite is not typical of the two known types (D-type: dolomite-related; S-type: serpentinite-related) and is overlapped by quartz grains dispersed throughout the less compact tremolite matrix. These observations would help set it apart from the majority of nephrite jades found in the Kunlun Mountains region and provide valuable insights for enhancing comprehension of the diversity of the nephrite deposits. Full article

The determination of the three-dimensional structures of viral proteins is a necessary step both for understanding the mechanisms of virus pathogenicity and for developing methods to combat viral infections. This study aimed to explore the folding and oligomeric state of the major component of the virion surface of the tick-borne encephalitis virus (TBEV), the ectodomain of the envelope E protein (ectoE), which was expressed in E. coli in a soluble form and purified from inclusion bodies as a mixture of dimeric and monomeric forms. The time-dependent assembly of monomers into dimers was detected using size-exclusion chromatography. An X-ray diffraction study of the ectoE crystals grown at pH 4.5 confirmed the dimeric folding of the recombinant protein typical for ectoE. The ability of ectoE dimers to self-assemble into tetramers was detected via small-angle X-ray scattering (SAXS) in combination with molecular dynamics. Such self-assembly occurred at protein concentrations above 4 mg/mL and depended on the pH of the solution. In contrast to stable, specific dimers, we observed that tetramers were stabilized with weak intermolecular contacts and were sensitive to environmental conditions. We discovered the ability of ectoE tetramers to change conformation under crystallization conditions. These results are important for understanding the crystallization process of viral proteins and may be of interest for the development of virus-like particles. Full article

In the evolving landscape of pharmaceutical manufacturing, a comprehensive continuous production process is being crafted for the small-scale production of active pharmaceutical ingredients. This study focuses on continuous crystallization with separate nucleation and crystal growth units, as well as continuous downstream processing, encompassing filtration, washing, and drying until the formation of free-flowing particles. We introduce a novel continuous nucleator designed based on solubility data and produced via 3D printing, enabling the fast and precise small-scale manufacturing of a nucleator meeting the requirements for nucleation and further growth processes. The nucleator is evaluated with regard to its suitability for continuous long-term operation across various coupled crystallizers. As a practical application example, it is connected to a slug flow crystallizer to enable high-quality continuous crystallization. Additionally, the full integration of downstream processes using a continuous vacuum screw filter to achieve free-flowing product particles is realized. Even under non-optimized process conditions, with the help of the in situ generation of nuclei, free-flowing product particles are successfully obtained. This is particularly useful during drug development when no material is available for seed addition and to quickly obtain products for further characterization. Full article

Cordierite-based supported noble-metal-free catalysts for ozone decomposition are elaborated. The cordierite ceramic surface is pretreated with oxalic acid and NaOH, and Mn-Cu-Ni oxide catalysts are prepared by the impregnation method. The mass ratio of the supported oxides in the resulting catalysts is MnO₂:CuO:NiO = 3:2:1, and their loadings are from 1.8 to 7.0 wt.%. The pretreated supports and catalysts are characterized by low-temperature N₂ adsorption, scanning electron microscopy (SEM), powder X-ray diffraction analysis (XRD), and temperature-programmed reduction with H₂ (TPR-H₂). The catalysts are tested in ozone decomposition with high airflow rates (20 and 50 L/min) and with initial ozone concentrations of 1 and 2 ppm at temperatures in the range of 25–120 °C. It is shown that a combined treatment of cordierite with oxalic acid and NaOH leads to a developed porous structure and stabilization of supported Mn-Cu-Ni oxides in a highly dispersed state. The high activity of catalysts in ozone decomposition at room temperature and high airflow is demonstrated. The developed catalysts can be recommended for application in purification of air from the ozone because of their high catalytic activity, high mechanical stability, and relatively low weight and cost. Full article

This study proposes an automated method for estimating the uncertain parameters of the solidification model in response to the inefficient and time-consuming problem of manually estimating multiple uncertain parameters of the solidification model. The method establishes an uncertain parameter estimation model based on the relationship between the simulated images equiaxed crystal ratio and the uncertain parameters of the solidification model, fits the parameters of the model by the least squares method, and finally estimates the uncertain parameters in the solidification model using the parameters of the fitted model. In comparison with the traditional method of calculating uncertain parameters manually through empirical formulas, this method reduces the difficulty of tuning parameters and solves the problem of tuning multiple parameters simultaneously in the nonlinear solidification model. The experimental results show that the proposed method can accurately estimate the uncertain parameters of the solidification model, improve the efficiency and accuracy of the solidification model estimation parameters, and play a guiding role in simulating the solidification process of continuously casting billet to control the solidification structure. Full article

Zinc oxide nanopowder was synthesized by the coprecipitation method. FT-IR and EDS analyses were performed to qualitatively determine the composition of the nanopowder. FE-SEM images revealed the morphology of the nanopowder formed by clusters of nanoparticles. An XRD analysis confirmed the wurtzite structure with a crystallite size of ~21.2 nm. UV–Vis measurements were performed to determine the ZnO bandgap (~3.05 eV) using the Tauc plot method in the absorbance spectra. The ZnO nanopowder and two comb-like metal contacts were confined and compacted between two polymeric layers by a low-temperature thermal lamination method, resulting in a flexible Polymer/ZnO/Metal/ZnO/Polymer structure. Part of each comb-like metal was kept uncovered by a polymeric layer in order to be used for electrical characterization. I-V measurements of the flexible structure were performed in the dark and under UV illumination, showing the capacity to detect UV radiation and its potential application as a visible-blind UV sensor. A facile and low-cost flexible optoelectronic device is presented, avoiding using high-vacuum or high-temperature technology. This new and novel approach to developing optoelectronic devices proposes using powder materials as semiconducting active regions instead of thin films; this could eliminate the cracking and delamination problems of flexible devices based on thin film technology. Full article

The study focuses on investigating the relationship between the ultrasonic effect and microstructure of ultrasonic-assisted gas tungsten arc welding (UA-GTAW) Inconel690 alloy joints. The influence of ultrasonic vibrations on Inconel690 plates was examined, while also clarifying the distribution pattern of the ultrasonic effect across the plate. Furthermore, actual welding experiments were performed by varying the distance between the ultrasonic horn and the welding torch. The results revealed that there were changes in both grain growth direction within the weld zone and refinement effects achieved under different distances. The optimal refinement of primary and secondary dendrite arm spacing was observed at distances of 60 mm and 180 mm between the welding torch and ultrasonic horn. The hardness of weld zone reached 235HV₁ when the distance between ultrasonic horn and welding torch is 180 mm. Full article

Layered nickelate oxides containing Ni¹⁺/Ni²⁺ are isoelectronic to Cu²⁺/Cu³⁺ compounds and of present interest with respect to recent findings of superconductivity in a series of different compositions. It is thereby questionable why superconductivity is still rare to find in nickelates, compared to the much larger amount of superconducting cuprates. Anisotropic d_z² vs. d_x²−y² orbital occupation as well as interface-induced superconductivity are two of the main advanced arguments. We are here interested in investigating the feasibility of synthesizing layered nickelate-type oxides, where the Ni¹⁺/Ni²⁺ ratio can be tuned by oxygen and/or cation doping. Our strategy is to synthesize Sr-doped n = 1 Ruddlesden–Popper type Nd_2−xSr_xNiO_4+δ single crystals, which are then reduced by H₂ gas, forming Nd_2−xSr_xNiO_4−δ via a topotactic oxygen release at moderate temperatures. We report here on structural studies carried out on single crystals by laboratory and synchrotron diffraction using pixel detectors. We evidence the general possibility to obtain reduced single crystals despite their increased orthorhombicity. This must be regarded as a milestone to obtain single crystalline nickelate oxides, which further on contain charge-ordering of Ni¹⁺/Ni²⁺, opening the access towards anisotropic properties. Full article