Chemistry and Materials Science

Abstract: Limited access to analytical instrumentation motivates the development of affordable alternatives. This study describes the construction and evaluation of two ESP32-based optical prototypes: an RGB colorimeter using a TCS34725 sensor and an ultraviolet radiometer using an AS7331 sensor. The RGB device combined a darkened chamber with a mirror-assisted optical path and was evaluated using colored papers and solutions of potassium permanganate, methylene blue, rhodamine B, zinc phthalocyanine, and free-base tetraphenylporphyrin. Paper measurements distinguished colors but differed from nominal RGB codes due to factors as print configuration and paper type. Comparisons with a benchtop spectrophotometer revealed analyte- and channel-dependent linear ranges, with R² values of 0.950-0.999 for selected RGB fits. In a test using an unfocused UV flashlight, the recorded signal decreased with increasing source-sensor distance, exhibiting behavior close to that predicted by the inverse-square law. Solar monitoring yielded temporal profiles qualitatively similar to commercial records obtained at a different location and date. Dedicated applications supported data acquisition, visualization, and storage. Artificial intelligence assisted development under human supervision. The results indicate potential for accessible instrumentation, experimental teaching, and connected monitoring, while emphasizing application-specific calibration and the limitations of the evaluated configurations.

Abstract: Excessive blue light exposure might severely threaten retinal health and disrupt circadian rhythms. To mitigate these hazards, candlelight-style sources were developed; however, fabricating high-efficiency, large-area, wet-processed candlelight organic light-emitting diodes (OLEDs) remains challenging. This study demonstrates a high-efficiency, blue-light-free candlelight OLED fabricated via wet-process by incorporating a [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayer between hole injection and emissive layers. At 1,000 cd/m², the resultant power efficacy, current efficiency and external quantum efficiency can be increased by 22%, 15% and 12%, respectively. Notably, at a high luminance of 10,000 cd/m², the corresponding efficiencies remain enhanced by 34%, 22%, and 19%, respectively. This device exhibits a color temperature of 1,991 K, permitting at 100 lx a maximum exposure limit of 71,211 seconds, 130 times longer than a cold-white OLED. The enhancement of device efficiencies may be attributed to the reduction of hole injection resistance and the suppression of non-radiative electron leakage.

Abstract: Optical response is commonly regarded as an intrinsic property of a photonic structure. Here we show that, in curved photonic systems, geometry plays a dual role: the photonic architecture defines the optical-state landscape, whereas the illumination–observation geometry determines which optical states become experimentally accessible. Self-assembled, millimeter-scale, free-standing curved silica opals coupled to spherical water droplets on Teflon or planar mirrors reveal simultaneous access to multiple Bragg diffraction bands, together with distance-controlled spectral redistribution, spatially organized halos, and pseudo-collimated beams under different illumination–observation geometries. Natural illumination further reveals optical responses relevant to biological and biomimetic photonic structures. Key aspects of this optical functionality are transferred to a graded curved photonic heterostructure formed by partial polystyrene infiltration of a curved silica opal, demonstrating that the underlying geometrical principle extends beyond liquid-confined systems. Curved photonic architectures therefore provide an experimental platform for geometry-controlled optical-state accessibility.

Abstract: Ferromagnetic-ferroelectric composites are of interest for studies of magneto-electric (ME) coupling between the two phases, which is mediated by mechanical strain arising from magnetostriction and the piezoelectric effect. A strong ME response in such composites typically requires an external DC bias magnetic field to compensate for weak zero-bias piezomagnetic deformation in the ferromagnetic phase. This reliance on an external field remains a key barrier to device miniaturization. Here we report strong, self-biased ME coupling achieved in a bilayer structure consisting of lead zirconate titanate (PZT) and a dual-phase ferromagnetic composite. The composite pairs hard barium hexaferrite BaFe12O19 (BaM), with its high magneto-crystalline anisotropy field, with soft nickel-zinc spinel ferrite Ni0.8 Zn0.2 O4 (NZFO), with its high magnetostriction. Samples consisting of (100-x) wt.% BaM- x wt.% NZFO (BNZx) were prepared via conventional solid-state sintering, and x-ray diffraction confirmed phase purity. Magnetic characterization revealed an in-plane anisotropy field (HA) ranging from 4.8 kOe to 8.3 kOe, which decreased systematically with increasing spinel content, alongside a high saturation magnetostriction of -25 ppm. The ME coupling strength of the BNZx-PZT bilayers was evaluated via the ME voltage coefficient (MEVC) across both low-frequency and electromechanical resonance regimes. The MEVC increased markedly with higher x-values, peaking at x=90. Under zero external DC bias, the bilayer showed a low-frequency (100 Hz) MEVC of 114 mV/cm Oe and a remarkably high MEVC of 3.6 V/cm Oe at resonance (10.6 kHz). The corresponding MEVC values under an external bias were 161 mV/cm Oe and 6 V/cm Oe. This pronounced self-biased behavior, driven by the internal field of the hard BaM phase, eliminates the need for external biasing elements and provides a practical framework for compact magnetic sensors, imaging arrays, and energy harvesters.

Abstract: This study analyzes the structural and magnetic properties of a new composite material with a lithium borate glass matrix loaded with electric arc furnace slag, with a composition of 50Li₂O- 50B₂O₃- 80 wt.% Slag. The amorphous nature of the obtained glass is confirmed by X-ray diffraction analysis (XRD). Differential scanning calorimetry (DSC) indicates that the material has an extremely high thermal stability as evidenced by its high glass transition temperature which is due to the reinforcing role of the slag metallic oxides. Additionally, magnetic studies reveal a highly frustrated magnetic state in the disordered system. The significant addition of mixed-valence iron ions (Fe²⁺/Fe³⁺) in the slag forms antiferromagnetic interactions in the system. These factors result in the stabilization of the spin-glass state. The incorporation of slag within the lithium borate matrix is a promising route to valorize this industrial by-product and to develop new functional materials.

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.