Chemistry and Materials Science

Abstract: This study investigates the use of magnetoelastic sensing for vibration-based structural health monitoring (SHM) of cementitious beam specimens under intact and damaged conditions. Prismatic mortar beams with dimensions of 160x40x40 mm3 were fabricated following standardized preparation procedures and equipped with annealed amorphous ferromagnetic ribbons, Metglas 2826MB3, for nondestructive magnetoelastic vibration sensing. The specimens were tested under free-vibration conditions in a simply supported configuration, and their vibration response was measured using a detection coil and subsequently analyzed using MATLAB software. The undamaged specimen exhibited a dominant resonance frequency at 6531 Hz, which closely corresponded to the fourth bending mode predicted by Euler–Bernoulli beam theory. Controlled notch-shaped cracks with varying locations and depths were subsequently introduced to evaluate the sensitivity of the sensing system to structural damage. Experimental results showed that the frequency shift is strongly influenced by the location of damage relative to the modal nodes, with maximum sensitivity observed between nodal regions and minimal variation near the nodes. Furthermore, increasing notch-shaped crack depth produced progressively larger frequency shifts, revealing a monotonic and non-linear relationship between damage severity and dynamic response. Polynomial fitting and 3D surface analysis further highlighted the combined influence of crack location and depth on the measured frequency variation. The findings confirm that the magnetoelastic sensor is capable of accurately detecting and magnetically transmitting the vibration state and damage-induced changes of cementitious structures, demonstrating high sensitivity and strong potential for application in vibration-based SHM systems.

Abstract: The particular microstructure of hot-deformed Nd-Fe-B magnets leads to difficulties in finding a direct recycling route. In this work, a combination of field assisted sintering technology/spark plasma sintering (FAST/SPS) and spark plasma texturing (SPT) are used as pre-compaction and deformation techniques, respectively, for the consolidation of crushed, hot-deformed Nd-Fe-B scrap. Field assisted sintering has the unique advantage of maintaining fine microstructures during material densification, making it an ideal candidate for direct recycling of this material. Recycled magnets, made from 100 wt% crushed magnet scrap, were able to achieve energy products of over 200 kJ m^-3 after FAST/SPS pre-compaction and SPT deformation. These recycled magnets could then be smoothed and cut to the size of industrial bar magnets for testing in the motor of a water pump. When tested, the recycled magnets could achieve 95% of the electromotive force compared to industrial standard magnets.

Abstract: Zn₂SnO₄ is a promising anode for lithium-ion batteries owing to its high theoretical capacity, yet its pratical utilization is severely limited by sluggish reaction kinetics, large volume expansion, and unstable electrode/electrolyte interfaces. Here, we intro-duce a dimensionality-reduction strategy that simultaneously boosts capacity and cy-cling stability. Through surfactant-directed crystal growth, acid-etching reconstruction, and hydrothermal carbon coating, compact Zn₂SnO₄ octahedra are controllably trans-formed into sheet-assembled structures and finally into a core–shell composite with a continuous carbon layer (C@M-Zn₂SnO₄ (H⁺)). The continuous structural evolution shortens Li⁺ diffusion paths, buffers mechanical stress, and stabilizes the sol-id-electrolyte interphase without altering the intrinisic lithium-storage mechanism of Zn₂SnO₄. As a result, the optimized C@M-Zn₂SnO₄ (H⁺) electrode delivers a reversible capacity of 650 mAh g⁻¹ after activation and retains 620 mAh g⁻¹ after 600 cycles at 200 mA g⁻¹, with Coulombic efficiency approaching 100% throughout. This work demon-strates that dimensionality-reduction-assisted structural engineering is an effective strategy for developing high-capacity, long-cycle-life anode materials.

Abstract: Benefiting from tunable emission from ultraviolet to near-infrared windows, long luminescence lifetimes, and exceptional photostability, rare-earth-doped nanomaterials overcome the limitations of conventional dyes and quantum dots, enabling deep-tissue, high-resolution, and low-background imaging. As multifunctional fluorescent probes, rare-earth-doped nanomaterials are driving the development of next-generation biomedical imaging. This review summarizes recent advances in the structural design of rare earth-doped nanomaterials, surface engineering for biocompatibility, and targeting strategies for improved performance, and highlights their integration into advanced imaging modalities, including NIR-I/II fluorescence, FLIM, PAI, super-resolution STED, multimodal FL/MRI/CT, X-ray-excited luminescence, and persistent luminescence. Meanwhile, mechanistic insights, material innovations, and comparative advantages are discussed. Furthermore, challenges related to quantum yield, scalable synthesis, imaging resolution, and clinical translation are considered, while future directions—centered on multifunctional probe design, NIR-II imaging, and AI-assisted data analysis—are proposed, offering a versatile platform for precise multimodal imaging with significant potential to advance early diagnosis, personalized therapy, and clinical applications.

Abstract: Integration of lead zirconate titanate (PZT) films on metallic substrates is important for flexible piezoelectric devices, but achieving highly textured crystallinity without detrimental interfacial diffusion or oxidation remains challenging. In this work, PZT thick films (~1.3 μm) were deposited on titanium substrates using radio-frequency magnetron sputtering at 400 °C followed by rapid thermal processing at 640 °C for 2.5 min. A conductive LaNiO₃ buffer layer was introduced to promote nucleation of the perovskite phase and suppress interfacial degradation. The resulting PZT films on LNO/Pt/Ti substrates exhibit a strong (001) preferred orientation and dense micro-structure. The films show a large remnant polarization Pr of ~61 μC cm^-2 and a low coercive field E_c of ~56 kV cm⁻¹ at 60 V, together with dielectric constants ε_r of ~1350–1612 and dielectric loss tanδ ≤ 0.06 in the frequency range of 1 kHz–1 MHz. Patterned Pt/PZT/LNO/Pt/Ti cantilevers yield a transverse piezoelectric coefficient e_31,f of ~ –6.7 C m^-2, significantly outperforming reported piezoelectric films deposited on Ti. These results demonstrate that controlled nucleation and rapid thermal crystallization enable highly textured PZT films on reactive metallic substrates, providing a viable route for flexible piezoelectric MEMS devices.

Abstract: Poor moisture resistance represents a critical bottleneck restricting the practical application of K2TiF6:Mn4+ phosphors in white light-emitting diodes (WLEDs). In this work, phosphorous acid was employed as a reducing agent to eliminate surface Mn4+ species and passivate the phosphor surface, followed by ethanol-induced surface deposition. This approach successfully constructed a thick K2TiF6 matrix coating layer on the phosphor particles. After 6 hours of water immersion, the treated phosphors maintained 88.11% of their initial fluorescence intensity; even after boiling treatment, the internal quantum yield (IQY) still reached as high as 76.78%. WLED devices encapsulated with the modified phosphors exhibited outstanding stability during continuous operation for 432 hours under high-temperature and high-humidity conditions. This effective surface modification strategy significantly broadens the application prospects of Mn4+-doped fluoride red phosphors in WLEDs.

Abstract: To meet the requirement of the current integrated circuit industry, atomic layer etching (ALE) technology has been broadly studied and developed. By dividing the whole etching process into several independent and self-limiting sub-process, ALE can achieve etching in atomic-level precision and better control in the etching process than traditional continuous etching technology, such as reactive ion etching. In this review, the characteristics of ALE are briefly summarized and five ways to improve the performance of ALE are introduced in detail. Attentionally, the main problem of the industrial application of ALE is how to make the trade-off between the time-consuming and the quality of etching. An improved ALE method with multiple temperature windows is proposed in this paper, which can theoretically shorten the time of each etching cycle in ALE.

Abstract: The optimization of the energy product in permanent magnets presents a complicated multi-parametric problem that encompasses a large variety of intrinsic and microstructural properties. As both high remanent magnetization and coercivity are required, the main concern in optimizing a given material is often how to deal with the trade-off between these two properties. A promising approach is to combine high anisotropy and high magnetization phases in chemically synthesized magnetically hard-soft nanoparticles. The magnetization reversal in such systems has been studied by micromagnetics, but most of the solutions are given for a magnetically hard shell surrounding a magnetically soft core, though synthetically the opposite may be more convenient. Here we review and summarize the basic general design rules for such systems and we present specific calculations for the FePt/CoFe system. Though in larger particles complex reversal modes appear that are scientifically interesting and may even include topological configurations, these are not relevant to the problem of achieving high energy products. The optimal size and phase content are within the simple homogeneous exchange-spring regime and must be determined under the contradictory requirements of achieving homogeneous reversal and avoiding thermal fluctuations.

Abstract: In recent years, rare earth (RE) ion-doped vanadate materials have garnered signifi-cant attention due to their promising applications in everyday technologies. Vanadate-based compounds, typically containing V⁵⁺ ions within oxide structures, form VO₄ tet-rahedra that enable broad ultraviolet absorption and wide-range visible light emission. These materials serve as versatile hosts for RE ions, namely, the 15 lanthanides (lan-thanum (La) to lutetium (Lu)) plus scandium (Sc), and yttrium (Y), which act as lumi-nescent centers when incorporated into the matrix. The unique electronic configura-tion of RE ions, particularly their unpaired 4f electrons, makes them ideal for diverse applications in luminescence, magnetism, electronic and magnetic relaxation, and ca-talysis. While RE ions exhibit sharp and intense emission peaks in the visible and near-infrared regions, vanadate hosts contribute broad-band spectra through charge trans-fer transitions within the VO₄ units. These complementary luminescent properties are critical for the advancement of optoelectronic devices. To enhance performance and broaden the applicability of RE-doped vanadate materials, ongoing research focuses on developing innovative synthesis techniques and structural designs. This paper pre-sents a comprehensive review of recent progress in synthesis strategies, luminescent behavior, and sensing applications of RE ion-doped vanadate materials.

Abstract: This study explores the effects of sputtering pressure and power on FeCoNi high‑entropy alloy films prepared by DC magnetron sputtering, focusing on microstructure, surface morphology, and static/high‑frequency magnetic properties. In situ Lorentz TEM (LZ‑TEM) was used to directly observe magnetic domain evolution. Results show that low sputtering pressure (1 mTorr) promotes strong FCC (111) crystallization, smooth and dense surfaces. Increasing pressure leads to amorphization, higher roughness, and degraded magnetic performance. Under optimized pressure, 100 W sputtering power yields the best crystallinity, smoothest surface, and optimal soft magnetic properties, including high remanence ratio, low coercivity, and clear ferromagnetic resonance in the 2–7.5 GHz range. The optimal parameters are confirmed as 1 mTorr and 100 W, producing uniform nanocrystalline FeCoNi films. In situ LZ‑TEM reveals river‑like domain walls, vortex–antivortex structures, and uniform magnetic moment precession, indicating weak domain pinning and excellent high‑frequency magnetization consistency. This study provides experimental and theoretical support for the controllable fabrication of high‑performance FeCoNi soft magnetic films for high‑frequency devices.

Abstract:

Although noninvasive glucose monitoring in sweat is a promising, pain-free method for diabetes management, it requires highly sensitive and stable sensors to overcome practical limitations. To overcome this challenge, a photoelectrochemical sensor based on a plasmon-enhanced black phosphorus (BP)/gold (Au) heterojunction was developed in this study. BP nanosheets possess a unique layered structure and intrinsic catalytic activity, but their instability and limited efficiency hinder direct use. Therefore, BP/Au was synthesized using the one-pot method. First-principles calculations revealed that single-layer BP behaved as a quasi-direct bandgap semiconductor. In comparison, the BP/Au heterojunction exhibited metallic characteristics, with anisotropic electron mobility reaching 1.62 cm²·V⁻¹·s⁻¹ along one direction. Charge density analysis confirmed directional charge transfer. Au donated electrons to adjacent P atoms, whereas P atoms forming shorter bonds lost charge. This process was associated with plasmon-assisted photoexcitation at the Au/BP interface, which modulated interfacial charge distribution and enhanced photoelectrochemical activity. By leveraging the Au component’s surface plasmon resonance, the heterojunction considerably augmented light absorption, accelerated interfacial electron transfer, and utilized the wrinkled BP layers to provide abundant active sites. This synergistic effect substantially lowered the oxidation activation energy of glucose. The resulting sensor achieved exceptional performance, with a sensitivity of 266.9 μA·μM⁻¹·cm⁻², a low detection limit, and a wide linear range well-suited for detecting glucose in sweat. The findings emphasized the potential of plasmon–semiconductor coupling for advancing noninvasive glucose monitoring and provided valuable design principles for sweat sensors based on metal–semiconductor heterojunctions.

Abstract: Bismuth ferrite (BiFeO₃) is a promising material for developing the next generation of multifunctional electronic devices. However, the production of high-quality BiFeO₃ thin films is compromised by the tendency for structural and electronic defects to form during synthesis, which degrades their functional properties. In this work, BiFeO₃ thin films were prepared by chemical solution deposition to determine optimal conditions for minimizing oxygen vacancies and to evaluate the impact of these point defects on their physical properties. The films were pyrolyzed at 300 °C for 60 min and 360 °C for 10 min, and crystallized in air and in an O₂ atmosphere, at 600 °C and 640 °C for 40 min. High oxygen vacancies were observed in films prepared at low pyrolysis temperatures and crystallized in air, whereas oxygen vacancies were minimized in the film pyrolyzed and crystallized at high temperatures in an O₂ atmosphere. The oxygen vacancies markedly affected the films’ physical properties, leading to increased dielectric loss, dielectric dispersion, dc conductivity, and leakage current, with consequent degradation of photovoltaic and magnetic performance. These findings highlight the critical importance of controlling synthesis parameters to suppress oxygen vacancy formation and achieve high-quality BiFeO₃ thin films.

Abstract: Polymeric hole-transport materials (HTMs) play a pivotal role in improving the efficiency, stability, and scalability of perovskite solar cells (PSCs). Owing to their structural tunability, polymeric HTMs enable effective control over energy-level alignment, charge transport, interfacial interactions, and film formation. This review summarizes recent advances in polymeric HTMs, including conjugated-backbone polymers, donor–acceptor (D–A) copolymers, and emerging architectures such as hyperbranched, ionic, chelating, and anchorable polymer systems. Particular emphasis is placed on structure–property–performance relationships and interfacial engineering strategies that govern device efficiency and long-term operational stability in PSCs. Finally, the key challenges and future directions for developing scalable and robust polymeric HTMs are discussed.

Abstract: All-inorganic metal halide perovskites exhibit excellent morphology-dependent pho-tophysical properties. Thus, detailed knowledge of photophysical behavior and mor-phological dependence of CsPbBr3 crystals is crucial for device engineering. However, the inability to directly control the morphology of CsPbBr3 crystals arises from a lim-ited understanding of their crystallization mechanism. Herein, we varied the prepara-tion parameters to investigate the perovskite growth mechanism and the impact of these parameters on size and shape of CsPbBr3 single crystals. By optimizing the solu-tion processing, the shape was tuned from the typical cubic microcrystals to more ir-regular ones. We have shown that three main factors favor the growth and formation of CsPbBr3 microcubes, namely high precursor concentration, high temperature and the use of DMSO solvent. The crystal size and density can be tuned by adjusting the precursor concentration, heating temperature, heating time and drop volume. The ob-tained crystals were of high quality and exhibited a strong photoluminescence at room temperature. This work not only introduces a distinct new morphology within the CsPbBr3 microcrystals family but also provides a fundamental understanding of the growth mechanism of these newly emerging functional materials.

Abstract: In this study, we investigated the effect of annealing ultrathin silver (Ag) films of varying thicknesses (1–6 nm) on both their optical absorption and the performance of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) organic solar cells (OSCs). The Ag films were deposited on indium tin oxide (ITO) anodes and annealed at 300 °C for 1–2 hours to modify the anodic interface. The optical and electrical properties of the resulting devices were systematically characterized and optimized. The results revealed that a 1 nm AgO layer annealed for 2 hours significantly enhanced the device performance, yielding a 6% increase in power conversion efficiency compared to the standard configuration. This improvement is attributed to two main factors: (i) a 25% increase in light absorption of the AgO/P3HT:PCBM film due to localized surface plasmon resonance of Ag nanoparticles, and (ii) an 11% reduction in series resistance resulting from the favorable alignment of the Ag work function with the ITO anode and the polymer HOMO, which facilitates efficient hole extraction. These findings highlight the potential of ultrathin, annealed Ag/AgO interfacial layers as an effective strategy to enhance light absorption and charge transport in OSCs.

Abstract: Thesol-gel auto-combustion method has emerged as a versatile and efficient technique for synthesizing magnetic nanomaterials with controlled structural and functional properties. This review comprehen sively examines the fundamental principles, reaction mechanisms, and process parameters governing the sol-gel auto-combustion synthesis of magnetic nanoparticles, with particular emphasis on ferrite materials. The method exploits the exothermic redox reaction between metal nitrates (oxidizers) and organic fuels such as citric acid, glycine, and urea to produce nanocrystalline powders at relatively low temperatures. Critical parameters including fuel-to-oxidizer ratio, pH, complexing agents, calcination temperature, and heating rate are systematically analyzed for their influence on phase purity, crystal lite size, morphology, and magnetic properties. The review covers the synthesis of various magnetic materials including spinel ferrites (MFe₂O₄, where M = Co, Ni, Zn, Mn), hexagonal ferrites (BaFe₁₂O₁₉, SrFe₁₂O₁₉), and mixed ferrite systems. Characterization techniques commonly employed for product evaluation, including X-ray diffraction, electron microscopy, and vibrating sample magnetometry, are discussed. Applications of sol-gel derived magnetic nanomaterials in data storage, biomedical fields, catalysis, environmental remediation, and electromagnetic interference shielding are highlighted. Finally, current challenges and future perspectives for advancing this synthesis methodology are outlined.

Abstract: Extreme environments such as low pressure, high temperature, and intense radiation pose severe challenges for humidity sensors, causing conventional hygroscopic materials to exhibit sluggish responses, drift, and instability. In response, recent research has adopted multi-level strategies involving material modification, structural engineering, and packaging optimization to enhance the adaptability of humidity-sensitive materials in extreme environments. This review examines humidity sensing from an environmental perspective, integrating sensing mechanisms, material classifications, and application scenarios. The performance, advantages, and limitations of six major categories of humidity-sensitive materials, including carbon-based, metal oxides, conductive and insulating polymers, two-dimensional (2D) materials, and composites, are systematically summarized under extreme conditions. Finally, emerging development trends are discussed, highlighting a shift from material-driven to system-driven approaches. Future progress will rely on multidisciplinary integration, including interface engineering, multiscale structural design, and intelligent algorithms, to achieve higher accuracy, stability, and durability in extreme-environment humidity sensing.

Abstract: A comprehensive study of the thermodynamic conditions (temperature, composition) of the existence of the cubic phase within the limits of homogeneity region in the quasi-binary PbF2-EuF3 system was carried out. Solid solution samples were obtained by solid-phase synthesis and co-precipitation technique from aqueous nitrate solutions. Phase equilibria were investigated in two regions: the solvus line in the range of 0-10 mol% EuF3 and the region of existence of the ordered rhombohedral R-phase in the range of 35-45 mol% EuF3. The structure of phases in the PbF2-EuF3 system was examined at temperatures below the phase transition temperature in lead fluoride (365°C). The possibility of obtaining a single-phase preparation of a cubic phase of high purity in 0-37 mol% EuF3 composition range has been demonstrated. The region of existence of the ordered rhombohedral R-phase in the concentration range from 37-39 to 43-44 mol% EuF3 was defined using X-ray phase analysis, optical probing, and Raman scattering.

Abstract:

β-Gallium oxide (β-Ga₂O₃) offers considerable potential for next-generation power electronics due to its ultrawide bandgap (~4.9 eV) and established n-type conductivity. Nevertheless, realizing stable p-type doping remains a significant challenge, primarily due to the deep acceptor levels associated with conventional dopants. This article presents a co-doping strategy involving tellurium (Te) and magnesium (Mg), implemented via metal-organic chemical vapor deposition (MOCVD), aimed at addressing this challenge. Density-functional-theory (DFT) calculations suggest that Te incorporation could induce an intermediate band near the valence band maximum (VBM), potentially lowering the acceptor ionization barrier for Mg impurities. Initial experimental results indicate encouraging transport properties: the optimized Te-Mg co-doped thin film showed a room-temperature resistivity as low as 32.4 Ω·cm, with a measured Hall hole concentration of 1.78 × 10¹⁷ cm⁻³ and mobility of up to 5.29 cm²/V·s at lower carrier concentrations (5.72 × 10¹⁴ cm⁻³). Characterizations reveal evidence of VBM elevation via Te-Ga orbital hybridization and suggest a shift in the Fermi-level toward the valence band compatible with p-type behavior. While these preliminary findings show promise for enabling p-type Ga₂O₃ homoepitaxy, further research is necessary to optimize carrier concentrations below 1 Ω·cm, fully elucidate the Te-Mg doping dynamics, and provide more comprehensive device-level validation. This work introduces a pathway worthy of further exploration for achieving p-type conductivity in this critical semiconductor.

Abstract:

A recent theoretical study of CsMnF₄ under pressure [Inorg. Chem. 2024, 63(29), 13231] presents conclusions on its structural, optical, and magnetic behavior that conflict with established experimental evidence. Crucially, this work omits key prior experimental results on CsMnF₄ and related Mn³⁺ fluorides under pressure. This perspective examines the resulting discrepancies, arguing that the omissions of this data undermines the theoretical estimates and methodological validity of Ref. [1]. This paper provides a critical overview centered on two main points: the contested nature of the pressure-induced high-spin to low-spin transition observed in CsMnF₄ at ~37 GPa and a detailed discussion of Jahn-Teller physics in this archetypal system. By reconciling the existing literature with the new theoretical claims, this work aims to clarify the high-pressure behavior of CsMnF₄.