Chemistry and Materials Science

Abstract: Three novel D–π–A dyes (PtD 1–3) based on a [1,2,4]triazolo[1,5-a]pteridine (TPt) acceptor–anchoring unit and a thiophene π-bridge were synthesized through a modular approach involving nucleophilic aromatic substitution of hydrogen and Suzuki–Miyaura cross-coupling. The electron-donating fragments were varied to investigate their influence on the electronic structure and photophysical properties of the resulting compounds. Their optical and electrochemical properties were examined using experimental and computational methods, including DFT, TD-DFT, and quantitative hole–electron analysis. All three dyes exhibited absorption bands with intramolecular charge-transfer character and energy-level alignment compatible with electron injection into TiO2, consistent with the estimated electron injection efficiencies of 77.7–91.5%. The synthesized dyes were further subjected to a preliminary evaluation as sensitizers in dye-sensitized solar cells (DSSCs). Among the investigated compounds, PtD 1 showed the highest power conversion efficiency of 1.28%. Differences in photovoltaic performance were associated with variations in light harvesting, dye regeneration, and other device-relevant parameters rather than dye loading alone. These findings demonstrate the feasibility of using the TPt framework as an acceptor–anchoring platform and provide a basis for further development of organic dyes for DSSC applications.

Abstract: High-pressure high-temperature (HPHT) transformation of organic and heteroorganic systems has emerged as a versatile platform for the synthesis of diamond materials with tailored structural, optical, isotopic, spin, and biomedical functionalities. This work summarizes the results of our investigations on the synthesis and characterization of diamond materials produced via HPHT-induced transformations of hydrocarbon, fluorinated hydrocarbon, and heteroorganic systems. Particular attention is devoted to the mechanisms of diamond formation, the hydrogen–fluorine synergy responsible for stabilizing nanoscale diamond fractions, and the incorporation of optically active color centers during crystal growth. The formation and photophysical properties of nanodiamonds containing silicon-vacancy (SiV), germanium-vacancy (GeV), and nitrogen-vacancy (NV) centers are discussed together with size-dependent optical and quantum phenomena, spatial distributions of color centers, and light–matter interaction effects arising in nanoscale diamond particles. The review further examines isotopically engineered ¹³C-enriched diamonds and core–shell nanodiamond architectures designed for spin-based applications and hyperpolarization technologies. The capability of HPHT synthesis to independently control particle size, impurity incorporation, isotopic composition, and spin environment provides a versatile platform for engineering advanced diamond materials optimized for quantum photonics, nanoscale sensing, biomedical imaging, and spin-based technologies.

Abstract: Fluorescent ionic liquids (FILs) are an emerging class of tunable luminescent materials that combines the versatile physicochemical properties of ILs with highly fluorescent organic dyes. While the inherent fluorescent properties of ILs containing imidazolium and pyridinium cations have been previously explored, their optical properties are not strong enough to serve relevant applications as FILs. This review explores the synthesis, physical and optical properties, and applications of FILs, with emphasis room-temperature FILs (RTFILs), which fluorescence in the neat state, and find applications in chemical sensing. RTFILs are a relatively new class of materials that exhibit highly intense fluorescence properties in the neat state, which is a unique phenomenon as opposed to the aggregation induced quenching of fluorescence that usually occur in either the liquid state or in the solid state. Applications in chemical sensing, including the detection of metal ions, organic compounds, gases, pH, and chiral analytes are also discussed alongside a wide breadth of applications. Challenges of FILs will be delved, including the lack of universality in reporting fluorescence quantum yields in the neat state. This review aims to identify opportunities for expanding design strategies of FILs to accelerate their development for chemical sensing, photonics, and advanced functional materials.

Abstract: Missing values in materials datasets can compromise both data reconstruction and the prediction of material properties. However, an imputation method that accurately reconstructs individual descriptors does not necessarily maximise downstream predictive performance. Here, we investigate this distinction using 2,363 phosphor records from the Inorganic Phosphor Optical Properties database and compare three descriptor representations: a combined set of 88 features, a 13-feature physics-informed set, and a 75-feature data-driven set. Mean, K-nearest-neighbour, iterative Bayesian-regression and random-forest-based imputation methods are evaluated under artificially generated MCAR, MAR and MNAR mechanisms at missingness rates of 10–50%. Reconstruction error is assessed separately from emission-wavelength prediction using five regression algorithms and host-grouped cross-validation. In the evaluated configurations, random-forest regression performs best after feature-count selection, while the physics-informed representation approaches the predictive performance of the combined feature set. The iterative random-forest imputer achieves the lowest average normalised reconstruction error across all three representations. Nevertheless, the imputer minimising reconstruction error does not consistently maximise downstream predictive performance, with agreement between the two criteria in only 50.2% of the examined model-specific comparisons. These findings highlight the need to evaluate imputation according to its intended use rather than relying on reconstruction metrics alone. The reported performance remains conditional on the descriptor-selection procedure, host grouping and simulated missingness mechanisms; independent validation is required before extrapolation to chemically novel phosphors.

Abstract: Industrialization and urbanization have increased emissions of toxic atmospheric pollutants (CO, NO2, NH3), threatening ecological security and human health. Twin graphene (TG) features large specific surface area and excellent electronic transport properties, but its practical gas-capture performance is limited by weak physisorption. Silicon doping serves as an eco-friendly strategy to modulate TG’s electronic structure and generate surface active sites. Herein, first-principles calculations based on density-functional-theory were implemented. Six Si-modified TG models were built, among which the most stable ring-substituted TG-Si1 and short-chain central-doped TG-Si6 were further investigated. Their adsorption-sensing behaviors toward CO, NO2, NH3 as well as interfering H2O and O2 were systematically explored, and adsorption-desorption features at 298 K, 398 K and 498 K were evaluated. Results show that TG-Si1 produces strong chemisorption for NO2 and NH3 (Eads <  −2.35 eV) suitable for long-term gas capture, though suffering from severe cross-interference. In comparison, TG-Si6 exhibits high selectivity for NO2; interfering gases can be readily desorbed at 498 K to realize good recyclability. Both Si-doped configurations possess favorable resistance against H2O and O2 interferences. This work provides theoretical support for Si-modified TG applied in toxic-gas adsorption-sensing and offers new insights into modification of two-dimensional carbon-based materials.

Abstract: The present study focuses on the preparation and comprehensive characterization of HgSr₁.₆Y₀.₄Ca₂Cu₃O₈₊δ superconductors synthesized via the solid-state reaction method. The structural and surface characteristics of the prepared material were examined using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). XRD analysis established the formation of a tetragonal crystal structure associated with the Hg-1223 phase, from which the lattice parameters, density, and superconducting phase volume fraction were determined. AFM and SEM investigations revealed a heterogeneous surface morphology characterized by dome-like and flake-like grains with different dimensions. The electrical resistivity was evaluated using the four-probe technique within the temperature range of 100–300 K, yielding Tc (onset) = 136 K and Tc (offset) = 121 K. Thermal conductivity measurements performed by Lee’s disc method between 300 and 560 K demonstrated a progressive increase with temperature. Additionally, the dielectric response was examined at room temperature over the frequency range of 50 Hz–1 MHz using an LCR meter. The real and imaginary dielectric constants, dielectric loss coefficient, and AC electrical conductivity were determined and exhibited distinct frequency-dependent behavior. These findings confirm the successful formation of the Hg-1223 phase and demonstrate its promising superconducting, thermal, and dielectric properties.

Abstract: Ti₃C₂Tₓ MXene was synthesised via an optimised low-temperature molten salt method using ammonium bifluoride. Complete MAX (Ti3AlC2) phase etching was achieved within 5 minutes at a temperature of 150 °C. Structural and compositional characterisation of Ti₃C₂Tₓ MXene confirmed well-exfoliated Ti3C2Tx sheets with com-plete Al removal. The synthesised Ti₃C₂Tₓ MXene was integrated as the active switch-ing layer in lateral and vertical memristor geometries. Both geometries exhibited non-linear bipolar resistive switching. The vertical device exhibited an on-state current of ~10 mA and stable resistance retention of over 120 minutes. UV-Ozone treatment of lateral devices resulted in the I-V characteristics changing from bipolar to asymmetric with rectifying characteristics. These results establish a broadly accessible, low-cost prototyping framework for Ti₃C₂Tₓ MXene -based memristor devices.

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.