Search Results (233)

Optimizing artificial lighting in controlled-environment agriculture is crucial for enhancing crop productivity and resource efficiency. This study presents a spectral–spatial co-optimization strategy for LED lighting tailored to the physiological needs of Italian lettuce (Lactuca sativa L. var. italica). A miniature plant factory system was developed with dimensions of 400 mm × 400 mm × 500 mm (L × W × H). Seven customized spectral treatments were created using 2835-packaged LEDs, incorporating various combinations of blue and violet LED chips with precisely controlled concentrations of red phosphor. The spectral configurations were aligned with the measured absorption peaks of Italian lettuce (450–470 nm and 640–670 nm), achieving a spectral mixing uniformity exceeding 99%, while the spatial light intensity uniformity surpassed 90%. To address spatial light heterogeneity, a particle swarm optimization (PSO) algorithm was employed to determine the optimal LED arrangement, which increased the photosynthetic photon flux density (PPFD) uniformity from 83% to 93%. The system operates with a fixture-level power consumption of only 75 W. Experimental evaluations across seven treatment groups demonstrated that the E-spectrum group—comprising two violet chips, one blue chip, and 0.21 g of red phosphor—achieved the highest agronomic performance. Compared to the A-spectrum group (three blue chips and 0.19 g of red phosphor), the E-spectrum group resulted in a 25% increase in fresh weight (90.0 g vs. 72.0 g), a 30% reduction in SPAD value (indicative of improved light-use efficiency), and compared with Group A, Group E exhibited significant improvements in plant morphological parameters, including a 7.05% increase in plant height (15.63 cm vs. 14.60 cm), a 25.64% increase in leaf width (6.37 cm vs. 5.07 cm), and a 6.35% increase in leaf length (10.22 cm vs. 9.61 cm). Furthermore, energy consumption was reduced from 9.2 kWh (Group A) to 7.3 kWh (Group E). These results demonstrate that integrating spectral customization with algorithmically optimized spatial distribution is an effective and scalable approach for enhancing both crop yield and energy efficiency in vertical farming systems. Full article

Herein, we study a method for developing a broad-emission emitter that can emit radiation from the visible light to NIR regions. Firstly, an NIR phosphor’s optical properties (e.g., scattering vs. weight concentration, conversion efficiency, and emission spectra under blue and red light excitation) are investigated. Then, pcW-LEDs encapsulated with NIR down-conversion phosphor samples are prepared to test these optical properties. The results show that pcW-LEDs encapsulated with the NIR phosphor at different weight concentrations of 10.0%, 12.5%, and 15.5%, respectively, emit a broadband emission from 400 nm to 900 nm. The EQE values of the pcW-LEDs encapsulated with NIR phosphor at weight concentrations of 10%, 12.5%, and 15.0% are 26%, 23%, and 19%, respectively. The correlated color temperatures of these samples are 5767 K, 5940 K, and 6068 K, respectively. The obtained radiant fluxes of the samples are 26 mW, 22 mW, and 18 mW, respectively, at an injection current of 50 mA. Full article

Silver nanoclusters that are confined inside zeolites can give off intensive tunable emission across the visible region under UV excitation. In this research, a series of silver nanoclusters loaded with R-FAU/Ag (R = Li, Na, K) zeolites were synthesized and then applied as phosphors for LEDs. The XRD and SEM measurements showed the R-FAU/Ag (R = Li, Na, K) zeolites have high crystallinity and a size distribution of 0.7–1.25 μm. Under excitations of 310–330 nm ultraviolet radiation, Li-FAU/Ag, Na-FAU/Ag, and K-FAU/Ag exhibit monotonically declining emission intensities and red-shifted emissions with peak wavelengths of 520, 527, and 535 nm, respectively. By using silicone-based epoxy resin as the packaging material, a series of LEDs were fabricated by mixing R-FAU/Ag (R = Li, Na, K) phosphors. It is indicated that the Li-FAU/Ag-LED shows the strongest intensity of 94.9 mcd, much higher than that of the LEDs made from Na-FAU/Ag (63.7 mcd) and K-FAU/Ag (74.2 mcd) phosphors. Additionally, the chromaticity coordinate of the Li-FAU/Ag-LED is located at (0.2651, 0.4073) and has a high color temperature of 7873 K. Thermal test data showed that upon heating to 440 K, the intensities of R-FAU/Ag (R = Li, Na, K) LEDs decreased to 81%, 79%, and 75% of their initial intensities measured at 280 K, respectively. This research proposes a method for regulating the luminescent properties of silver nanoclusters in FAU zeolite by modifying the extra-framework cations and demonstrates excellent performance in LED products. Full article

Red mud (RM) is a strongly alkaline waste residue produced during alumina production, and its high alkali and fine particle characteristics are prone to cause soil, water, and air pollution. Phosphogypsum (PG), as a by-product of the wet process phosphoric acid industry, poses a significant risk of fluorine leaching and threatens the ecological environment and human health due to its high fluorine content and strong acidic properties. In this study, RM-based cemented paste backfill (RCPB) based on the synergistic curing of PG and ordinary Portland cement (OPC) was proposed, aiming to achieve a synergistic enhancement of the material’s mechanical properties and fluorine fixation efficacy by optimizing the slurry concentration (63–69%). Experimental results demonstrated that increasing slurry concentration significantly improved unconfined compressive strength (UCS). The 67% concentration group achieved a UCS of 3.60 MPa after 28 days, while the 63%, 65%, and 69% groups reached 2.50 MPa, 3.20 MPa, and 3.40 MPa, respectively. Fluoride leaching concentrations for all groups were below the Class I groundwater standard (≤1.0 mg/L), with the 67% concentration exhibiting the lowest leaching value (0.6076 mg/L). The dual immobilization mechanism of fluoride ions was revealed by XRD, TGA, and SEM-EDS characterization: (1) Ca²⁺ and F⁻ to generate CaF₂ precipitation; (2) hydration products (C-S-H gel and calixarenes) immobilized F⁻ by physical adsorption and chemical bonding, where the alkaline component of the RM (Na₂O) further promotes the formation of sodium hexafluoroaluminate (Na₃AlF₆) precipitation. The system pH stabilized at 9.0 ± 0.3 after 28 days, mitigating alkalinity risks. High slurry concentrations (67–69%) reduced material porosity by 40–60%, enhancing mechanical performance. It was confirmed that the synergistic effect of RM and PG in the RCPB system could effectively neutralize the alkaline environment and optimize the hydration environment, and, at the same time, form CaF₂ as well as complexes encapsulating and adsorbing fluoride ions, thus significantly reducing the risk of fluorine migration. The aim is to improve the mechanical properties of materials and the fluorine-fixing efficiency by optimizing the slurry concentration (63–69%). The results provide a theoretical basis for the efficient resource utilization of PG and RM and open up a new way for the development of environmentally friendly building materials. Full article

Sr₂LaF₇:xPr³⁺ (x = 0.2, 1, 2, 3, 5, 10, and 25 mol%) nanophosphors with a cubic Fm3m structure were hydrothermally synthesized, forming nearly spherical nanoparticles with an average diameter of approximately 32 nm. Diffuse reflectance measurement and excitation spectra showed a primary excitation peak of Pr³⁺ at 443 nm, corresponding to the ground state to the ³P₂ level transition. Upon blue light excitation, Pr³⁺-activated Sr₂LaF₇ nanophosphors showed rich emission structure across the visible region of the spectrum, with blue (~483 nm), green (~525 nm), orange (~600 nm), and red (~640 nm) emissions, blue and orange being the most prominent ones. The relative intensities of these emissions varied with Pr³⁺ concentration, leading to tunable emission colors. The chromaticity showed slight variation with the Pr³⁺ content (0.350 < x < 0.417, 0.374 < y < 0.380), while the CCT value increased from 3118 K to 4901 K as the doping concentration increased. The optimized Sr₂LaF₇ with 2 mol% Pr³⁺ had the most intense emission with correlated color temperature (CCT) of 3628 K, corresponding to the warm white color. The proposed Pr³⁺-doping strategy offers valuable insights into discovering or optimizing single-phase phosphors for white-light-emitting applications. Full article

We report a monolithic GaN-based light-emitting diode (LED) platform capable of color-tunable white-light emission via LED size scaling. By varying the LED size from 800 µm to 50 µm, the injection current density was effectively controlled under constant driving current, enabling precise modulation of carrier distribution within a dual-composition multi-quantum well (MQW) structure. The active layer consists of five lower In_0.15Ga_0.85N/GaN QWs for blue emission and strain induction, and an upper In_0.3Ga_0.7N/GaN single QW engineered for red-orange emission. The strain imposed by lower QWs promotes indium segregation in the last QW through spinodal decomposition, resulting in a broadened emission spanning from ~500 nm to 580 nm. High-resolution TEM and EDX analyses directly confirmed the indium segregation and phase-separated structure of the last QW. Spectral analysis revealed that larger devices exhibited dominant emission at 580 nm with a correlated color temperature (CCT) of 2536 K and a CIE coordinate of (0.501, 0.490). As LED size decreased, increased hole injection allowed recombination to occur in deeper QWs, resulting in a blueshift to 450 nm and a CCT of 9425 K with CIE (0.224, 0.218) in the 50 × 50 µm² LED. This approach enables phosphor-free white-light generation with tunable color temperatures and chromaticities using a single wafer, offering a promising strategy for compact, adaptive solid-state lighting applications. Full article

In recent years, rare earth ion and transition metal ion co-doped fluorescent materials have attracted a lot of attention in the fields of WLEDs and optical temperature sensing. In this study, I successfully prepared the dual-emission Mg₃Ga₂SnO₈:Eu³⁺,Mn⁴⁺ red phosphors and the XRD patterns and refinement results show that the prepared phosphors belong to the Fd-3m space group. The energy transfer process between Eu³⁺ and Mn⁴⁺ was systematically investigated by emission spectra and decay curves of Mg₃Ga₂SnO₈:0.12Eu³⁺,yMn⁴⁺ (0.002 ≤ y ≤ 0.012) phosphors and the maximum value of transfer efficiency can reach 71.2%. Due to the weak thermal quenching effect of Eu³⁺, its emission provides a stable reference for the rapid thermal quenching of the Mn⁴⁺ emission peak, thereby achieving good temperature measurement performance. The relative thermometric sensitivities of the fluorescence intensity ratio and fluorescence lifetime methods reached a maximum value of 2.53% K⁻¹ at 448 K and a maximum value of 3.38% K⁻¹ at 473 K. In addition, the prepared WLEDs utilizing Mg₃Ga₂SnO₈:0.12Eu³⁺ phosphor have a high color rendering index of 82.5 and correlated color temperature of 6170 K. The electroluminescence spectrum of the synthesized red LED device by Mg₃Ga₂SnO₈:0.009Mn⁴⁺ phosphor highly overlaps with the absorption range of the phytochrome P_FR and thus can effectively promote plant growth. Therefore, the Mg₃Ga₂SnO₈:Eu³⁺,Mn⁴⁺ phosphors have good application prospects in WLEDs, temperature sensing, and plant growth illumination. Full article

Stable and efficient inorganic lead-free double perovskites are crucial for high-reliability optoelectronic devices. However, dual-doped perovskite phosphors often suffer from poor color stability due to differences in thermal activation energies and electron–phonon interactions between the doped ions. To address this, single-doped Sb³⁺-incorporated Rb₂HfCl₆ perovskite crystals were synthesized via a co-precipitation method. Under UV excitation, Rb₂HfCl₆:Sb exhibits broad dual emission bands, attributed to singlet and triplet self-trapped exciton radiative transitions induced by Jahn–Teller distortion in [SbCl₆]³⁻ octahedra. This dual emission endows the material with high sensitivity to excitation wavelengths, enabling tunable luminescence from cyan to orange-red across 400–800 nm. Utilizing this dual emission, a white LED was fabricated, showcasing a high color rendering index and excellent long-term stability. Remarkably, the material exhibits breakthrough thermal stability, maintaining more than 90% of its emission intensity at 100 °C, while also exhibiting remarkable resistance to humidity and oxygen exposure. Compared to co-doped phosphors, Rb₂HfCl₆:Sb offers advantages such as environmental friendliness, simple fabrication, and stable performance, making it an ideal candidate for WLEDs. This study demonstrates notable progress in developing thermally stable and reliable optoelectronic devices. Full article

The aim of this study was to investigate the possibility of Ag nanoparticle crystallization in B₂O₃–Bi₂O₃ glass using a heat treatment method and to investigate the possible influence of the obtained nanoparticles on the emission intensity of Eu³⁺ ions. Borate–bismuth glasses with different B₂O₃:Bi₂O₃ molar ratios of 50:50, 60:40 and 70:50 with Ag and Eu³⁺ ions were successfully synthesized. The structure of the glasses was studied using XRD and FTIR methods. The XRD results exhibited a characteristic amorphous halo, confirming the absence of long-range order in the samples. The glass transition temperatures of various compositions, required to select the annealing temperature, were measured using DTA analysis. The strong maximum in the UV–Vis spectrum of the sample with the highest Bi₂O₃ content clearly indicated the presence of Ag nanoparticles in the glass. Moreover, a color change was observed for this sample, from slightly yellow to red. The presence of Ag nanoparticles was further confirmed via TEM and XPS studies. However, with a high content of Ag nanoparticles in the matrix, their positive effect on luminescence intensity was not observed. The obtained results show that B₂O₃–Bi₂O₃ glass and glass ceramics, with Ag nanoparticles and rare-earth (Re) ions, could be considered as a new phosphor for light-emitting diodes (LEDs). Full article

Dye wastewater poses significant risks to human health and aquatic ecosystems, necessitating efficient remediation strategies. This study developed a magnetic Fe₂O₃ nanocomposite (MNC) derived from phosphoric acid-treated walnut shell biomass carbon to remove Alizarin red S (AR) dye from polluted water. Characterization techniques confirmed the nanocomposite’s mesoporous structure, superparamagnetic properties (61.5 emu/g), and high crystallinity. Optimization using Response Surface Methodology (RSM) revealed a maximum adsorption efficiency of 94.04% under the following optimal conditions: A pH of 2, AR dye concentration of 85 mg/L, adsorbent dose of 1.5 g/L, and particle size of 448.1 nm. Adsorption followed pseudo-second-order (PSO) kinetics (R² = 0.9999) and Langmuir isotherm models (R² = 0.9983), with thermodynamic studies indicating spontaneous and endothermic chemisorption. The intra-particle diffusion model, Bangham, and Boyd plots describe the adsorption process, and external boundary layer diffusion of AR dye molecules in the aqueous phase limits the adsorbate removal rate. Regeneration tests demonstrated reusability over three cycles, with a desorption efficiency of 50.52% using 30 mM HCl. The MNC exhibited a maximum adsorption capacity (Q_max) of 115.35 mg/g, outperforming other adsorbents, making it an efficient and sustainable alternative solution for AR dye removal from water bodies. Full article

Red melilite structure CaY_1−xAl₃O₇: Eu_x (x = 0.04–0.24) phosphors for white LEDs were synthesized through a straightforward solid-state reaction process. These phosphors exhibit efficient excitation under near-ultraviolet light at 398 nm (⁷F₀ → ⁵L₆), producing the desired emission peak at 622 nm from the transitions of ⁵D₀ → ⁷F₂. The Eu doping concentration was also optimized as x = 0.16. The complete 3003 × 3003 energy matrix was constructed based on an effective Hamiltonian including both free-ion and crystal-field interactions within a complete diagonalization method (CDM). Eighteen experimental fluorescent spectra for Eu³⁺ ions at the Y³⁺ site of CaYAl₃O₇ crystal were quantitatively identified with high accuracy through fitting calculations. The fitting values are in reasonable agreement with the experimental results, thereby showcasing the efficacy of the CDM in probing luminescent phosphors for white LEDs. Full article

We investigated the thermoluminescence (TL) properties of Mn-doped zinc zirconate (ZnZrO₃:Mn) phosphors under beta (β) radiation. SEM revealed morphological changes with varying levels of Mn doping (0–5%), while XRD confirmed a pure cubic phase. Mn doping introduced luminescent centers, enhancing emission efficiency. Mn²⁺ ions facilitated green/red emissions (⁴T₁ → ⁶A₁), while Mn⁴⁺ contributed to deep-red emissions (²E → ⁴A₂), making the material suitable for optoelectronic applications. Compared to conventional phosphors, ZnZrO₃:Mn exhibited superior thermal stability, enhanced luminescence, and tunable emissions. The TL dose−response showed a systematic peak shift to higher temperatures with increasing radiation dose, confirming its potential for use in accurate dosimetry. The TL glow curves displayed primary (349 K) and secondary (473 K) peaks that were influenced by heating-rate variations, which led to peak shifts and increased intensity. An innovative thermal-cleaning approach (110–336 °C) refined luminescence by stabilizing deeper traps while erasing shallow-trap signals. This combined effect of Mn doping and thermal treatment optimized ZnZrO₃ phosphors’ structural, optical, and TL properties. These findings provide insights into their potential use in radiation dosimetry and display technologies, offering a new strategy for future perspective luminescent materials Full article

Europium(III) β-diketone and organic carboxylic acid complexes are designable, easy to prepare, and easy to modify and have excellent fluorescence properties (narrow emission spectral band, high colour purity, long fluorescence lifetime, high quantum yield, and a spectral emission range covering both the visible and near-infrared regions). These complexes play important roles in popular fields such as laser and fibre-optic communications, medical diagnostics, immunoassays, fluorescent lasers, sensors, anticounterfeiting, and organic light-emitting diodes (OLEDs). In the field of light-emitting materials, europium complexes are especially widely used in OLED lamps, especially because of their high-efficiency emission of red (among the three primary colours); accordingly, these complexes can be mixed with blue and green phosphors to obtain high-efficiency white phosphors that can be excited by near-ultraviolet light. This paper reviews the red-light-emitting europium complexes with β-diketone and organic carboxylic acid as ligands that have been studied over the last five years, describes the current problems, and discusses their future application prospects. Full article

Red mud and phosphogypsum are two typical industrial by-products. The preparation of red mud/phosphogypsum-based artificial soils offers a promising novel solution to the efficient synergistic disposal of them. Fungi, as key drivers, can promote the continuous development and ecological improvement of artificial soils. This study is first to report the characteristics of fungal communities in three artificial soils after one year of incubation. The preliminary formation of fungal communities (with relatively low diversity) resulted in a total of 3 fungal phyla, 81 fungal genera, and 144 operational taxonomic units (OTUs) in artificial soils. Ascomycota was the dominant fungal phylum in each artificial soil (>99.5%), and the high-abundance fungal genera included Unclassified_c_Sordariomycetes, Unclassified_o_Sordariales, Emericellopsis, Kernia, Unclassified_f_Nectriaceae, Ramophialophora, Schizothecium, and Iodophanus. There were significant differences among the three artificial soils in the compositions of fungal genera, which affected material cycling, ecological succession, and soil development and maturation to varying extents. According to the FUNGuild prediction of fungal communities, saprotrophic fungi (such as undefined saprotroph, dung saprotroph–undefined saprotroph, and dung saprotroph) played dominant roles in promoting the degradation and humification of organic matter and the cycling of carbon in artificial soils. Fungal communities in the three artificial soils had strong correlations with many environmental factors (such as pH, organic matter, available nitrogen, total nitrogen, available phosphorous, sucrase, urease, acid phosphatase, alkaline phosphatase, and catalase), indicating significant interactions between them. This is not only conducive to the continuous optimization of the structure of fungal communities in artificial soils but also promotes the balanced and homogeneous distribution of various substances, promoting continuous soil development and maturation and gradual improvement in its ecological functions. This study provides an important scientific basis for clarifying the mechanisms of mycogenesis during the continuous development and maturation of artificial soils. Full article

The co-precipitation method was successfully used to synthesize Ba₃(Y_0.6−xGd_0.4Eu_x)₄O₉ (0.01 ≤ x ≤ 0.09) phosphors with heavy Gd³⁺ doping, resulting in significantly enhanced thermal stability and luminescence performance. Structural analyses confirm that Gd³⁺ and Eu³⁺ ions substitute Y³⁺ in the lattice, causing lattice expansion and improving crystal asymmetry, which enhances Eu³⁺ emission. The incorporation of Gd³⁺ creates efficient energy transfer pathways to Eu³⁺ while suppressing non-radiative relaxation, leading to stable fluorescence lifetimes even at elevated temperatures. With a thermal activation energy of ~0.3051 eV, the Ba₃(Y_0.55Gd_0.4Eu_0.05)₄O₉ phosphor exhibits superior resistance to thermal quenching compared to Ba₃(Y_0.95Eu_0.05)₄O₉ and many conventional red phosphors. Furthermore, the reduced color temperature and stable emission spectra across a wide temperature range highlight its potential for advanced lighting and display technologies in high-temperature environments. Full article