Nanoemulsion-derived AlPO₄ ceramics: Densification and phase behavior under field-assisted sintering

An aluminum phosphate powder (AlPO4) was synthesized using a modified Ouzo nanoemulsion technique. Monolithic AlPO4 ceramics were subsequently produced via a field-assisted sintering technique (FAST) at temperatures 1300 °C and 1400 °C. Both the powder and sintered samples were comprehensively characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Structural characterization of the field-assisted sintered samples revealed stabilization of the high-temperature orthorhombic phase, which may have occurred due to the presence of oxygen vacancies. Mechanical and thermal characterizations of the sintered samples were also performed. Across various thermal treatments, the high-temperature orthorhombic phase gradually transformed to a tridymite monoclinic structure due to temperature-induced atomic displacements caused by shifting and tilting of adjacent layers of rigid AlO4 and PO4 tetrahedra. This study reveals that pressure-dependent polymorphism reflects temperature-dependent phase stability, influenced by external energy inputs from the applied current, which modulates structural rearrangements. The results demonstrate that the modified Ouzo nanoemulsion synthesis method is a highly effective technique for producing AlPO4 powders with favorable sintering properties

Machine learning-assisted luminescence thermometry using Mn5 + -doped near-infrared phosphor with improved accuracy and precision

This study provides a thorough investigation of machine learning-assisted luminescent thermometry using a Mn5+-doped Ca6Ba(PO4)4O phosphor. A novel, slightly modified Principal Component Analysis (PCA), where data normalization was observation-based rather than feature-based, was used to analyze near-infrared emission spectra collected over a temperature range of 293–373 K. This method showed significantly improved thermometric performance compared to traditional single-parameter and multiparametric approaches. Based on statistical analysis of cross-validation experimental data, the PCA-based method achieved exceptional average temperature resolution (δT = 0.135 K) and accuracy (ΔT = 0.077 K) across the entire temperature range, with even better performance in the physiological temperature range (δTphy = 0.074 K, ΔTphy = 0.032 K). This method utilizes full spectral data through dimensionality reduction, offering insights into the most thermometrically significant spectral regions while keeping the computation simple with basic mathematical operations. Compared to traditional thermometry techniques, which involve calculating emission band intensity ratios, finding spectral positions, and fitting emission decays, PCA-assisted thermometry greatly simplifies and speeds up the computational process, while also enhancing the accuracy and precision of temperature measurement

Single-source precursor synthesis of a compositionally complex early transitional metal nitride (V, Nb, Ta, Mo, W)Nx and its high temperature stability

Compositionally complex transitional metal nitrides are an interesting class of ceramics with superior chemical, thermal, and mechanical stability, with a high potential in ultra-high temperature applications and catalysis. The exceptionality in the properties may partly be explained as a consequence of their high configuration entropy. Although promising candidates, the bulk synthesis of compositionally complex metal (carbo)nitrides remains challenging, often limited by purity and scalability due to significant oxygen contamination from gaseous reactants or nitrogen loss. To offset these disadvantages, the current manuscript proposes an alternative synthesis route for the synthesis of a compositionally complex nitride (V, Nb, Ta, Mo, W)Nx, which deviates from the typical solid-state and sputtering methods by employing an organometallic precursor route and a double ammonolysis process. This is a first attempt to synthesize such ceramics with low oxygen contamination in compositionally complex (carbo)nitrides with a scalable production. Using a multidisciplinary approach consisting of theoretical methods and experiments, the current study elucidates the evolution and stability of the precursor at high temperatures under carbon, and thereby obtained ceramics at different temperatures

Gamma rays assisted synthesis of N doped-graphene quantum dots from multiwall carbon nanotubes

Gamma rays are the powerful tool for top-down synthesis of nitrogen doped graphene quantum dots (NGQDs) from multiwall carbon nanotubes. Different doses of gamma rays (100, 200 and 300 kGy) were applied to the multiwall carbon nanotubes suspended in mixture of sulfuric and nitric acid (3:1 ratio). After purification, NGQD were characterized to investigate their structure (morphology, particle size, nanomechanical and nanoelectrical properties, chemical composition, photoluminescence, reactive oxygen species production, antibacterial activity and biocompatibility). Viscoelastic measurements revealed that NGQDs nanoparticles had Young’ modulus of elasticity almost equal to single wall carbon nanotubes (SWCNTs (6,5)). Electrostatic force and scanning tunneling microscopy showed that all types of the NGQDs nanoparticles had negative charge distributed homogeneously. All NGQDs samples produced singlet oxygen and the NGQDs300 sample showed moderate antibacterial activity and good biocompatibility

The influence of ambient high pressure to structural features of barium hexaferrite

A comprehensive analysis of the magnetic properties, crystal structure and magnetic configuration of the ceramic BaFe12O19, prepared using the sol-gel method, was conducted over the temperature range from 4 K to room temperature. The impact of ambient pressure on the crystal and magnetic structures of ceramic BaFe12O19has enabled the determination of bulk modulusB0∼ 123.8 GPa and its first-order derivativeBp' ∼ 4.1, as well as the coefficients of linear compressibility of the lattice parameters for the hexagonal unit cell. The results of neutron diffraction collected at pressures ranging from 0.1 GPa to 5 GPa were analyzed in the framework of both centrosymmetric SG P63/mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The decrease in the total magnetic moment with an increase in ambient pressure was associated with a weakening of the exchange interaction in the ferrimagnetic structure, owing to a reduction in the bond angles (∠ Fe-O-Fe) of various iron sublattices

Er3+/Yb3+ co-activated YNbO4 nanocrystalline phosphors: Up-conversion luminescence under the 980 nm excitation and integrated lifetime thermometry

This paper presents the structure, morphology, optical and photoluminescent properties of erbium (1 at %) and ytterbium (2 at %) doped yttrium niobium oxide (YNbO4) as a potential temperature sensor material. Obtained powder samples of fergusonite-β-like monoclinic crystalline structure of YNbO4, confirmed by X-ray diffraction analysis, showed particles of about 1–3 μm in size. Photoluminescence emissions were detected in the visible (Vis) and near-infrared (NIR) regions after excitation at 980 nm as a result of the energy up-conversion (UC) process. The lifetime of the most intense Er3+ excited state 4S3/2 level measured at 300 K was 0.238 ms. Thermometric properties were recorded at different temperatures and analyzed for the first time using the luminescence emission decay method. The relative sensitivity decreases from 0.23 % to 0.085 % K−1, by varying the temperature from 300 to 600 K, indicating a good potential of this material for lifetime-based phosphor thermometry

Advanced nanosystem for target recognition and precise dual-mode imaging-guided photothermal therapy against triple-negative breast cancer

Triple-negative breast cancer (TNBC) presents significant diagnostic and therapeutic challenges due to the lack of targeted treatments, rapid progression, high recurrence and metastasis rates, and overall poorer prognosis. Herein, the targeted theranostic platform of cysteine-modified gold nanodots-sulfhydrated luteinizing hormone releasing hormone (CGN-SLR) nanosystem was designed for target recognition and precise dual-mode imaging-guided photothermal therapy (PTT) against TNBC. On the one hand, the CGN-SLR nanosystem can serve as an ideal targeting fluorescent probe and computed tomography (CT) enhancer to facilitate the accurate diagnosis and surgical guidance of TNBC. On the other hand, the CGN-SLR nanosystem with great targeting and PTT ability can significantly inhibit the growth of TNBC, without causing harm to normal tissues and healthy organs. It provides an effective strategy for the diagnosis and treatment of TNBC through the rational design of multifunctional nanoplatform with target recognition, multiple imaging guidance/monitoring, and high-efficiency PTT

High-color-purity orange luminescence from Sm³⁺-doped NaY₉Si₆O₂₆ oxyapatite nanophosphors for optoelectronic applications

Luminescent Sm³⁺-doped NaY₉Si₆O₂₆ oxyapatites were hydrothermally synthesized and studied for their structural, morphological, and optical properties, aiming for high-color-purity orange emission. X-ray diffraction confirmed a single-phase oxyapatite host lattice across 0.1–6 mol% Sm³⁺ doping, with nanoscale crystallites. Transmission electron microscopy revealed elongated sphere-like nanoparticles with an average size of ∼44 nm. All samples emitted intense orange light under 405 nm excitation, with chromaticity coordinates within the high-purity orange region of the CIE 1931 diagram. It was also shown that concentration quenching of Sm³⁺ emission in NaY₉Si₆O₂₆ host is predominantly governed by dipole–dipole electric multipolar interactions. The optimized NaY₉Si₆O₂₆:0.5 mol% Sm³⁺ sample demonstrated excellent thermal stability, maintaining 100 % of its emission intensity up to 200 °C and showing consistent luminescence during extended operation at 100 °C for 300 min. A prototype LED–phosphor device produced bright orange light under electrical excitation, confirming the potential of Sm³⁺-doped NaY₉Si₆O₂₆ nanophosphors for high-quality solid-state lighting

X-ray imaging dosimeter performance in standard and non-standard radiography radiation fields in terms of air kerma

Introduction X-ray medical imaging developments have introduced needs for updated dosimetry practices. Methods Performance of commercially available dosimeters used for air kerma measurements in diagnostic and interventional radiology was examined. Ionization chambers and X-ray multimeters were tested in a wide range of air kerma rates, photon energies (using standard and non-standard radiation qualities), and angles of incidence with different dosimeter orientation and rotation. Stability and repeatability of the measured value, the influence of pulse duration, non-linearity of dosimeter response, energy and angular dependence were studied against the IEC 61674:2024 limits of variation. Energy response was tested using the standard RQR and RQT radiation qualities defined in IEC 61267:2005, as well as non-standard copper-filtered beams with added 0.9 mm Cu filtration. Results Most dosimeters complied with the IEC 61674:2024 standard limits of variation, for both standard and non-standard radiation fields. In some cases, observed performance was significantly better than the current limits allowing for the introduction of more stringent values. Conclusion Modification of the performance requirements was proposed, considering differences between reference-class and field-class dosimeters, while introducing more stringent requirements for reference-class dosimeters

Novel N-doped carbon/Co/Co3O4 ternary composites derived by direct carbonization of ZIF-67: Efficient electrocatalysts for oxygen reduction reaction

Cobalt-containing zeolitic imidazole framework ZIF-67 was synthesized in high yield, and directly carbonized by different heating routes at 800 and 900 °C. The products of carbonization, C(ZIF-67)s, were comprehensively characterized in terms of elemental composition (FAAS, EDX, XPS), crystalline (XRD) and molecular structure (FTIR and Raman spectroscopies), morphology (SEM), electrical conductivity, textural (N2 physisorption), and electrochemical properties. It was found that C(ZIF-67)s represent novel meso/microporous ternary composites of the type N-doped carbon/Co/Co3O4, containing metallic Co nanoparticles (NPs) with cubic body-centred crystalline structure, and predominately amorphous Co3O4. They exhibited high electrical conductivity (up to 4.2 S cm−1), notable BET specific surface area (197–265 cm2 g−1), and almost doubled mesopore volume compared to the parent ZIF-67. The effects of carbonization conditions on the structure, physico-chemical properties, and performance of C(ZIF-67)s as electrode materials in electrocatalysis of oxygen reduction reaction (ORR) and charge storage were studied. All C(ZIF-67) composites showed excellent ORR electrocatalytic activity in 0.1 M KOH, with four-electron reduction pathway. The highest ORR activity (the onset potential of −0.13 V vs. SCE) showed the composite produced by gradual heating up to 800 °C followed by holding at that temperature for 3 h. This is attributed to its highest mesopore volume, appropriate meso/micropore structure, high surface content of heteroatom-containing active sites (C–O–C, Co–N, Co–O), high surface Co2+/Co3+ ratio and the presence of Co NPs. The applied direct carbonization of ZIF-67, without additives and post-synthetic modifications, was shown as a simple way to produce meso/microporous electroconducting composites with high potential in energy related applications