Search Results (1,158)

The synthesis of carbon dots (CDs) from coal represents a promising strategy for advancing both the efficient, low-carbon utilization of coal resources and the cost-effective production of CDs. To enable the controlled, high-quality conversion of CDs from coal, a comprehensive understanding of the relationship between the coal chemical structure and the properties of CDs is crucial. This study prepared CDs from nine kinds of coal using a chemical oxidation method, and the correlations between properties of coal-based carbon dots and the original materials were revealed. The results show that the luminescence sites of coal-derived CDs are mostly distributed around 435 nm or 500 nm, where the former one relates to the confined sp² domains and the latter one is associated with the defect structure. Coal with a volatile content of about 20–30% in the nine samples was found to produce higher CD yields, with a maximum mass yield of 19.96%, accompanied by stronger fluorescence intensity. During chemical oxidation processes, the unsaturated double bonds (C=C, C=O) and aliphatic chains firstly break, and then aromatic clusters are formed by dehydrocyclization between carbon crystallites, followed by the introduction of a C–O group. The growth of the C–O group in the CDs contributes to a stronger fluorescence property. Furthermore, strong correlations were found between the carbon skeleton structure of raw coal and photoluminescence characteristics of corresponding CDs, as reflected by Raman parameters A_D1/A_G, I_D1/I_G, and FWHM_D. The findings offer significant insights into the precise modulation and control of coal-based carbon dot structures. Full article

Effective in situ pH sensing holds exciting prospects in environmental and biomedical applications, but still faces a great challenge. Until now, pH sensors with small size, high sensitivity, good stability and repeatability, great biosafety, wide detection range, and flexible structure have rarely been reported. Herein, we propose a novel dual-emission ratiometric fluorescent pH sensor by decorating ethyl cellulose (EC)-encapsulated CdSe/ZnS quantum dots (QDs) and oxazine 170 perchlorate (O170 dye) on the surface of the spider silk. When a 473 nm excitation light is coupled into the pH sensor, the evanescent wave transmitting along the surface of the spider silk will excite the CdSe/ZnS QDs and then the O170 dye based on the fluorescence resonance energy transfer (FRET) effect from the QDs; thus, the pH sensing of the surrounding liquid environment can be achieved in real time by collecting the photoluminescence (PL) spectra of the pH sensor and measuring the emission intensity ratio of the two fluorescent materials. The sensor has also demonstrated a high sensing sensitivity (0.775/pH unit) within a wide pH range of 1.92–12.11, as well as excellent reusability and reversibility, structure and time stability, biocompatibility, and biosafety. The proposed pH sensor has a potential application in an in situ monitor of water microenvironments, cellular metabolism, tumor microenvironments, etc. Full article

A new family of highly uniform, cubic-shaped Cu₃VS_xSe_4−x (CVSSe; 0 ≤ x ≤ 4) nanocrystals based on earth-abundant materials with intermediate bandgaps (IB) in the visible range is reported, synthesized via a hot-injection method. The IB transitions and optical band gap of the novel CVSSe nanocrystals are investigated using ultraviolet-visible spectroscopy, revealing tunable band gaps that span the visible and near-infrared regimes. The composition-dependent relationships among the crystal phase, optical band gap, and photoluminescence properties of the novel IB semiconductors with progressive substitution of Se by S are examined in detail. High-resolution transmission electron microscopy and scanning electron microscopy characterization confirm the high crystallinity and uniform size (~19.7 nm × 17.2 nm for Cu₃VS₄) of the cubic-shaped nanocrystals. Density functional theory (DFT) calculations based on virtual crystal approximation support the experimental findings, showing good agreement in lattice parameters and band gaps across the CVSSe series and lending confidence that the targeted phases and compositions have been successfully realized. A current conversion efficiency, i.e., incident photon-to-current efficiency, of 14.7% was achieved with the p-type IB semiconductor Cu₃VS₄. These novel p-type IB semiconductor nanocrystals hold promise for enabling thin film solar cells with efficiencies beyond the Shockley–Queisser limit by allowing sub-band-gap photon absorption through intermediate-band transitions, in addition to the conventional direct-band-gap transition. Full article

BO₃³⁻, PO₄³⁻, and SO₄²⁻ anionic groups were used to study their effects on the structure and luminescence of Sm³⁺-doped ZnO. ZnO, ZnO:Sm³⁺, ZnO, Zn₄B₆O₁₃:Sm³⁺, and Zn₂P₂O₇:Sm³⁺ phosphors were successfully synthesized via combustion synthesis. While BO₃³⁻ and PO₄³⁻ ions led to the formation of new crystalline phases, the sulfate precursor decomposed during synthesis, yielding ZnO with only minor surface sulfur traces. The XRD results revealed the formation of wurtzite crystal structures in the ZnO, ZnO:Sm³⁺, and ZnO-SO₄:Sm³⁺ samples, while a complete change of structure was observed after the incorporation of borate (BO₃³⁻) and phosphate (PO₄³⁻) ions into ZnO:Sm³⁺ to Zn₄B₆O₁₃:Sm³⁺ and Zn₂P₂O₇:Sm³⁺, respectively. The structures for borate and phosphate ions were confirmed as cubic (Zn₄B₆O₁₃) and monoclinic (Zn₂P₂O₇) crystal structures, respectively. The morphological studies of ZnO:Sm³⁺ and ZnO-SO₄:Sm³⁺ were characterized by aggregated particles with different shapes and sizes. Zn₄B₆O₁₃ and Zn₂P₂O₇ samples were characterized by having cubic and rough surfaces, respectively. The oxidation state of the Sm ions was confirmed by XPS analysis. The photoluminescence studies revealed a broad-band emission for the ZnO:Sm³⁺ and ZnO-SO₄:Sm³⁺ materials and characteristic Sm³⁺ emissions (from the ⁴G_5/2 level to lower states ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2)) for the Zn₄B₆O₁₃ and Zn₂P₂O₇ samples. Enhanced emissions were observed after the incorporation of anionic group systems. The most intense PL emission was observed from the Zn₄B₆O₁₃ phosphor material. The CIE calculations revealed that the best color purity results were from Zn₄B₆O₁₃, which lay in the orange region with 98% color purity. Full article

This study presents a green synthesis of zinc oxide (ZnO) nanoparticles (NPs) capped with Haloxylon (P1) and Calligonum (P2) extracts. The use of plant-derived biomolecules as natural capping agents offers an environmentally friendly strategy to tune surface chemistry and to enhance the photocatalytic behavior of ZnO NPs. ZnO/plant extracts nanocomposites were prepared via a hydrothermal route and systematically characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis spectroscopy, and photoluminescence (PL), followed by evaluation of their photocatalytic performance against methylene blue (MB) under UV irradiation. XRD confirmed a wurtzite structure with crystallite sizes ranging from 8.95 to 10.93 nm, while PL spectra indicated an improved charge carrier separation in extract-capped ZnO. The characteristics and pollutant removal performance of the greenly synthesized ZnO composites were compared with those of a chemically synthesized ZnO nanoparticles reference sample. Adsorption tests under dark conditions revealed a strong difference between the materials: ZnO-P1 removed 48% of MB, whereas ZnO-P2 adsorbed only 7%, demonstrating a much higher affinity of the Haloxylon-derived surface groups toward MB. In comparison, the chemically synthesized ZnO exhibited an adsorption capacity of 54%, confirming that the Haloxylon-mediated surface provides a comparable efficient dye uptake prior to irradiation. After UV irradiation, all samples exhibited a photocatalytic activity with a total MB removal reached ~59% for the reference ZnO sample and ~53% for ZnO-P1 compared to about 13% for the ZnO-P2. Kinetic analysis also confirmed that ZnO-P1 possessed a high degradation rate constant, indicating a better intrinsic photocatalytic efficiency in addition to the strong adsorption contribution. The enhanced performance of plant-capped ZnO is attributed to phytochemical-induced surface defects, which facilitated charge separation and boosted the generation of reactive oxygen species (ROS). Overall, these results demonstrate that Haloxylon and Calligonum extracts are effective and sustainable capping agents, providing a low-cost, eco-friendly approach for designing ZnO nanocatalysts composites with promising applications in wastewater treatment and environmental remediation. Full article

This study presents the development of a smart packaging material utilizing garlic-derived nitrogen-doped carbon dots (CDs) integrated into a whey protein–starch (WP-S) emulsion. The research aimed to create a real-time, non-invasive biosensor capable of detecting microbial spoilage. The synthesized CDs demonstrated strong pH-sensitive photoluminescence, exhibiting distinct changes in CIE coordinates and fluorescence intensity in response to varying pH values. The WP-S-CDs emulsion was tested against E. coli, S. aureus, and C. albicans. The results showed that the composite film provided a clear colorimetric shift and fluorescence quenching, both of which are directly correlated with microbial metabolic activity. The physical and electronic properties of the composite were investigated to understand the sensing mechanism. Scanning electron microscopy (SEM) of the dried film revealed that the WP-S-CDs system formed a more porous structure with larger pore sizes (3.63–8.18 µm) compared to the control WP-S film (1.62–6.52 µm), which facilitated the rapid diffusion of microbial metabolites. Additionally, density functional theory (DFT) calculations demonstrated that the incorporation of CDs significantly enhanced the composite’s electronic properties by reducing its band gap and increasing its dipole moment, thereby heightening its reactivity and sensitivity to spoilage byproducts. In a practical application on apples, the WP-S-CDs coating produced a visible red spot, confirming its function as a dynamic sensor. The material also showed a dual-action antimicrobial effect, synergistically inhibiting C. albicans while exhibiting an antagonistic effect against bacteria. These findings validate the potential of the WP-S-CDs emulsion as a powerful, multi-faceted intelligent packaging system for food quality monitoring. Full article

Cerium (Ce³⁺)-doped gadolinium orthoborate (GdBO₃) phosphor powders were synthesized via an aqueous sol–gel route, with systematic variation in solution pH (2, 5, and 8) and annealing temperature (600–1200 °C, in 100 °C increments) to investigate their influence on structural, optical, and scintillation properties. The materials were comprehensively characterized using thermogravimetric and differential thermal analysis (TG–DTA) to assess thermal behavior, X-ray diffraction (XRD) for crystal structure determination, Fourier-transform infrared spectroscopy (FTIR) for vibrational analysis, and both photoluminescence (PL) and radioluminescence (RL) spectroscopies to evaluate optical and scintillation performance. All samples crystallized in the hexagonal GdBO₃ vaterite phase (space group P6₃/mcm). The PL and RL emission spectra were consistent with the Ce³⁺ 5d–4f transitions, and scintillation yields under X-ray excitation were quantified relative to a standard Gadox phosphor. A decrease in photoluminescence quantum yield (PLQY) was observed at annealing temperatures above 800 °C, which is attributed to the incorporation of Ce³⁺ into the host lattice. Scintillation decay profiles were recorded, enabling extraction of timing kinetics parameters. Overall, the results reveal clear correlations between synthesis conditions, structural evolution, and luminescence behavior, providing a rational basis for the optimization of Ce³⁺-doped GdBO₃ phosphors for scintillation applications. Full article

Magneto-photoluminescent hybrid materials (MPHMs) were prepared by incorporating cobalt ferrite nanoparticles (CFNs) into the fluorescent polymer poly(terephthalaldehyde-undecan-2-one) (PT2U). The CFNs, with a mean size of 3.95 nm, formed aggregates within the PT2U matrix (650–1042 nm) due to surface and interfacial interactions, modulating aggregate morphology and interparticle coupling. Magnetization studies revealed non-monotonic variations in saturation magnetization (30.3–16.2 emu/g), mean blocking temperature (39.3–43.1 K) and effective magnetic anisotropy energy density (2.14 × 10⁶–1.31 × 10⁶ erg/cm³) with increasing CFN content, consistent with the presence of canted surface spins and enhanced magnetizing interparticle interactions. Photoluminescence exhibited progressive quenching, dominated by collisional mechanisms at low CFN content and by interfacial CFN–PT2U interactions at higher loadings. Under a magnetic field (800 Oe), additional quenching occurred, attributed to magnetically induced polymer-chain rearrangements that disrupted the molecular stacking required for efficient aggregation-induced emission. These results demonstrate tunable magneto-photoluminescent coupling in MPHMs governed by surface and interfacial phenomena, providing insights for the design of functional and responsive hybrid materials. Full article

Development of new biologically active materials based on natural products has, over the years, attracted considerable attention due to their effectiveness in human health and disease. Polyphenolic compounds, particularly flavonoids, provide a wide range of health benefits, including antioxidant, anti-inflammatory, anticancer, and antibacterial properties. A series of novel Schiff base derivatives of flavonoids with amino-containing linkers was successfully designed and synthesized through condensation reactions. Naringin and naringenin derivatives with diamines, including ethylenediamine (EDA), 1,3-diamino-2-propanol (DA-2-PrOH), tetramethylenediamine (TMEDA), pentamethylenediamine (PMEDA), as well as polyamines spermidine (SPD) and spermine (SPM), were synthesized and well-characterized through FT-IR, UV–Visible, ESI–MS, ¹H and ¹³C NMR spectroscopy, and elemental analysis. The so confirmed and well-characterized derivatives were subjected to photoluminescence studies, exhibiting enhanced activity, especially for naringin-based derivatives, and quenching in some others, thus verifying the significance of chemically modifying the conjugated systems of these molecules. Their biological activity was examined in the case of their antimicrobial efficacy against two Gram (+) (Staphylococcus aureus and Bacillus cereus) and two Gram (−) (Escherichia coli and Xanthomonas campestris) bacterial strains. Antibacterial screening projected selectivity of modified flavonoids against E. coli, proposing new “dense” flavonoid-(poly)amine materials as multifunctional antimicrobial agents and fluorescent probes. Full article

Perovskite crystals, nanocrystals, quantum dots (QDs), and two-dimensional (2D) materials are at the forefront of optoelectronics and quantum optics, offering groundbreaking potential for a wide range of applications, including photovoltaics, light-emitting devices, and quantum information technologies. Perovskite materials, with their remarkable, tunable bandgaps, high absorption coefficients, and efficient charge transport, have revolutionized the field of light-emitting diodes, photodetectors, and solar cells. QDs, owing to their size-dependent quantum confinement and high photoluminescence quantum yields, are crucial for applications in display technologies, imaging, and quantum computing. The synthesis of QDs from perovskite-based materials yields a significant enhancement in the performance of optoelectronics devices. Furthermore, 2D perovskites have recently exhibited extraordinary carrier mobility, strong light–matter interactions, and mechanical flexibility, making them highly attractive for next-generation optoelectronic applications. Additionally, this review discusses the synergistic potential of hybrid material architectures, where perovskite crystals, QDs, and 2D materials are combined to enhance optoelectronic performance and their role in quantum optics. By analyzing the effects of material structure, surface modifications, and fabrication techniques, this review provides a valuable resource for harnessing the transformative potential of these advanced materials in modern optoelectronic applications. Full article

Wavelength-shifting (WLS) materials are used in radiation detectors to convert ultraviolet photons into visible light, enabling improved photon detection in systems such as scintillators and optical diagnostics for nuclear fusion devices. However, the long-term performance of these materials under radiation is still a critical issue in high-dose environments. In this work, we investigated the radiation tolerance of three WLS compounds (TPB, NOL1, and SB2001), each deposited on reflective substrates (ESR and E-PTFE), resulting in six distinct WLS/substrate systems. The samples underwent gamma irradiation at absorbed doses of 100 kGy, 500 kGy, and 1000 kGy, as well as fast neutron (14.1 MeV) irradiation up to a fluence of 1.9 × 10¹³ n/cm². Qualitative photoluminescence and reflectance measurements were performed before and after irradiation to assess changes in optical performance. Gamma exposure caused spectral broadening in several samples, particularly those with TPB and SB2001, with variations of the two metrics used to compare the performance of the materials exceeding 10% at the highest doses. Neutron-induced effects were generally weaker and did not exhibit a clear fluence dependence. Reflectance degradation was also observed, with variations depending on both the WLS material and the deposition method. These findings contribute to the understanding of WLS material stability under radiation and support their qualification for use in optical components exposed to harsh nuclear environments. Full article

Perovskite light-emitting diodes (PeLEDs) have garnered significant interest owing to their exceptional color purity, broadly tunable emission spectra, and cost-effective solution processability. However, blue PeLEDs continue to underperform in efficiency and operational stability compared to their red and green counterparts, primarily due to defect-induced non-radiative recombination losses and inefficient exciton management. Herein, we demonstrate a synergistic approach that integrates multi-cation compositional engineering with triplet exciton management by incorporating a high-triplet-energy material, mCBP (3,3-Di(9H-carbazol-9-yl)biphenyl), during film fabrication. Temperature-dependent photoluminescence reveals that mCBP incorporation significantly enhances the exciton binding energy from 49.36 meV to 68.84 meV and reduces phonon coupling strength, indicating improved exciton stability and suppressed non-radiative channels. The corresponding PeLEDs achieve a peak external quantum efficiency of 10.2% and a maximum luminance exceeding 12,000 cd/m², demonstrating the effectiveness of this solution-based triplet management strategy. This work highlights the critical role of scalable, solution-processed triplet exciton management strategies in advancing blue PeLED performance, offering a practical pathway toward high-performance perovskite-based display and lighting technologies. Full article

This study presents the synthesis and characterization of novel kaolinite niobium and kaolinite titanium niobium nanocomposites and their application as heterogeneous photocatalysts. Utilizing a hydrolytic sol–gel route, we combined kaolinite with isopropyl alcohol, acetic acid, titanium (IV) isopropoxide, and ammonium niobium oxalate, followed by heat treatment at 400, 700, and 1000 °C. X-ray diffraction confirmed the retention of kaolinite’s characteristic reflections, with basal spacings indicating the presence of semiconductors on the external surfaces and edges. Heating treatment not allowing the crystallization of anatase until 1000 °C reveals that Nb⁵⁺ could inhibit the transition to titanium crystalline phases (anatase and rutile). The bandgap energies decreased with clay mineral support, averaging 2.50 eV, and absorbing up to 650 nm. The model reaction of terephthalic acid hydroxylation accomplished by photoluminescence spectroscopy demonstrated that KaolTiNb400 presented a higher rate of *OH production, achieving 591 mmol L⁻¹ min⁻¹ compared to pure KaolNb400 173 mmol L⁻¹ min⁻¹. Photodegradation studies revealed significant photocatalytic activity, with the KaolTiNb400 nanocomposite achieving the highest efficiency, demonstrating 90% removal of methylene blue (combining adsorption and degradation) after 24 h of UV light irradiation. These materials also exhibited promising results for the degradation of the antibiotics Triaxon^® (40%) and Loratadine (8%), highlighting their potential for organic pollutants’ removal. In both cases the presence of byproducts is detected. Full article

Quantum sensing with nitrogen vacancy (NV) defects in diamond enables detection of extremely small changes in temperature, host material strain, and magnetic and electric fields. Action potential detection has previously been demonstrated with cardiac tissue and whole organisms using NV defects in bulk diamond crystals. Nanodiamonds (NDs) with NV defects were previously used as effective fluorescent markers, as they do not bleach under laser illumination like conventional fluorescent dyes. Subcellular-level action potential recording with NDs is yet to be demonstrated. Here, we report our results on the confocal imaging of NDs and the feasibility of optically detected magnetic resonance (ODMR) experiments with Cath.-a-differentiated (CAD) mouse brain cells. 10 nm and 60 nm NDs were shown to diffuse into cells within 30 min with no additional surface modification, as confirmed with confocal imaging. In contrast, 100 nm and 140 nm NDs were observed to remain localized on the cell surface. ND photoluminescence (PL) signals did not bleach over the course of 5 h long imaging studies. ODMR technique was used to detect externally applied millitesla-level magnetic fields with NDs in cell solutions. In summary, NDs were shown to be effective, non-bleaching fluorescent markers in mouse brain cells, with further potential for use in action potential recording at the subcellular level. Full article

This work presents a study of copper selenite nanocrystals, obtained for the first time by chemical deposition (template synthesis) in a SiO₂/Si track template, and investigates their properties. The obtained nanostructures were subjected to structural, optical, and electrical analysis. After deposition, X-ray diffraction (XRD) analysis confirmed the formation of the orthorhombic phase CuSeO₃. Subsequent annealing in a vacuum at 800 °C and 1000 °C led to successive phase transformations: to the monoclinic phase and, finally, to the triclinic polymorph of copper selenite. Photoluminescence (PL) analysis showed that the intensity and spectral position of the emission peaks vary depending on the crystal structure, which is associated with changes in defects and bandgap width as a result of heat treatment. Current–voltage characteristic (CVC) measurements showed that the phase composition significantly affects electrical conductivity. In particular, the transition to the triclinic phase after annealing at 1000 °C led to noticeable changes in optical and electrical properties compared to the initial material. Thus, a direct relationship has been established between heat treatment conditions, crystal structure, and functional properties of CuSeO₃-based materials, opening up possibilities for their application in photonics and electronics. Full article