White Light-emitting Diodes Research Articles

Dual-Emission Organic-Inorganic Hybrids (2,6-DTP)2ZnCl4·DMF:Sb3+ Unlocking High-Efficiency Luminescence and Stability for Advanced White Light-Emitting Diodes.

The development of high-performance luminescent materials is essential for advancing optoelectronic applications, particularly in the field of solid-state lighting and displays. This study investigates the structural, optical, and thermal properties of the 0D organic-inorganic hybrid metal halides (OIHMHs) (2,6-DTP)2ZnCl4·DMF and its Sb3+-doped derivatives, aiming to enhance the luminescent efficiency and stability for potential applications in white light-emitting diodes (WLEDs). The Sb3+-doped (2,6-DTP)2ZnCl4·DMF samples showed broad emission spectra covering the entire visible region, with distinct peaks at 505 and 647 nm with the photoluminescence quantum yield (PLQY) of 91.9% and high thermal stability. Furthermore, the (2,6-DTP)2ZnCl4·DMF-based WLEDs exhibited stable white light emission with a high color rendering index (CRI) of 91 and a correlated color temperature (CCT) of 5635 K. This research provides valuable insights into the design and optimization of efficient luminescent materials for optoelectronic applications, contributing to the development of next-generation lighting technologies.

Investigation of the Role of Gd3+ in Energy Transfer Mechanism of Eu3+ Activated LaNbO4 Phosphors for Solid-State Lighting

Abstract In the field of illumination and energy, phosphor-converted white light-emitting diodes (pc-WLEDs) have emerged as critical lighting sources due to their longevity, high efficiency, exceptional brightness, reliability, and eco-friendliness. Phosphors in pc-WLEDs are based on different combinations of host and dopant ions. Designing a single matrix with dual-emitting centers and color-tunable properties has become a trend in the development of phosphors for such applications. Lanthanum niobate (LaNbO4), due to its remarkable chemical and thermal stability, is an excellent host material and Europium (Eu3+) ion is a key red activator in several inorganic phosphor materials. Herein we studied the role of Gd3+ in the energy transfer mechanism in Eu3+-doped LaNbO4. Using a solid-state reaction route, we initially synthesized La(1-x)NbO4:xGd3+ by varying concentrations of Gd3+. The optimal concentration of Gd3+ was determined from the emission studies. Subsequently, fixing that optimal Gd3+ concentration, we prepared Gd3+ and Eu3+ co-doped La(1-x-y)NbO4:xGd3+/yEu3+ by varying the Eu3+content. XRD analysis was performed to identify the structure and phase purity of all synthesized phosphors. The vibrational and absorption characteristics were examined through FTIR and reflectance spectroscopy, respectively. Gd3+ doped LaNbO4 displayed a sharp emission at 313 nm due to Gd3+ transitions and a broad blue emission around 410 nm from the host. Along with the aforementioned emissions, Gd3+/Eu3+ codoped phosphors exhibited orangish-red emission with a maximum emission at 614 nm with 5D0 to 7F2 transition of Eu3+ ion. Upon excitation at 273 nm, we observed energy transfer from the host and Gd3+ to Eu3+, leading to an enhancement in red emission. Additionally, we performed morphology and elemental analyses using SEM and EDAX, confirming that no impurities other than the initial precursors were present. CIE chromaticity coordinates of LaNbO4:Gd3+/Eu3+ phosphors correspond to the orangish-red region, making them promising red-emitting materials for lighting and displays.

Navigating antiBlackness: a critical race exploration of Black community leaders perspectives on university-community partnerships (UCPs)

ABSTRACT This article employs Critical Race Theory and Community-Based Educational Leadership as frameworks to explore how anti-Blackness manifests in university-community partnerships (UCPs) between predominantly white institutions (PWIs) and majority Black communities. Drawing from semi-structured interviews with six Black community leaders, the study reveals their complex experiences navigating these partnerships. A thematic analysis of the data identified the overarching theme of ‘Navigating the Neo-Plantation’, with sub-themes of antiBlackness, plantation politics, and white leadership by Black proxy. The findings highlight the pervasive nature of racial hierarchies within these partnerships and ‘how under the guise of “community engagement”, these UCPs often perpetuate exploitive dynamics that have historically marginalized Black communities’ (27). The article concludes by discussing the implications for scholars and practitioners engaging in critical community-engaged research, focusing on advancing racial justice and equity in UCPs.

Gram-Scale Synthesis of Mn2+/Octadecylamine Codecorated Carbon Dots with Ultrabroadband Yellow Emission for High-CRI White LEDs.

Exploiting environment-friendly and efficient phosphors is crucial to constructing high-quality and sustainable white light-emitting devices. Here, we demonstrate a facile and high-yield approach to synthesize Mn2+/octadecylamine (ODA)-codecorated carbon dots (CDs) with ultrabroadband and efficient yellow fluorescence in the solid state. The dots are prepared from anhydrous citric acid (CA), 1-ODA, and manganese acetate through a simple one-step hydrothermal process, with a production yield of 80%, a full width at half maxima (FWHM) of 98nm, and a solid-state quantum yield up to 62.8%. Utilizing the synthetic CDs powder as a phosphor to directly coat on a blue light-emitting chip, the device exhibits warm white emission, with a high color rendering index (CRI) of 88, correlated color temperature (CCT) of 4215K, and Commission International de l'Éclairage (CIE) coordinates of (0.33, 0.31), endowing great potential applications in green and health lighting.

TiO2, SiO2, CaF2, and CaCO3: the Influence of Particles’ Concentration on Luminous Efficiency of the Conformal Geometry MCW-LEDs

In this research, the influence of scattering enhancement particle TiO2, SiO2, CaF2, and CaCO3 concentration, which adds to the YAG:Ce phosphor compounding, on the luminous efficiency of multichip white LEDs (MCW-LEDs) was proposed and analyzed. Firstly, the physical model of MCW-LEDs is simulated and demonstrated by using commercial LightTools 8.4 program. After that, the effect of scattering enhancement particles on the luminous efficiency is calculated and analyzed. Then, the luminous output of the 8500K W-LEDs are demonstrated convincingly by the Monte Carlo simulation and the Mie-scattering theory. The simulation results indicated that the highest luminous output could be accomplished with CaCO3 particles. The results and discussion provided a prospective approach for higher-quality manufacturing W-LEDs in the near future.

Investigation on Optical Properties of Cool White Light Emitting Dy3+ Doped SrZrSi2O7 Luminescent Materials for WLEDs and TLD Applications.

In this study, the optical properties of Dy3⁺-doped SrZrSi₂O₇ (SZSO) luminescent materials were synthesized via a high-temperature solid-state reaction method and investigated for the first time. The crystal structure and phase purity of the synthesized phosphors were examined using the X-ray diffraction (XRD) technique. The XRD results matched the standard JCPDS suggesting that the prepared samples comprise a monoclinic phase structure. The structure of the synthesized phosphor was validated using the Rietveld refinement technique. Vibrational modes, surface morphology, and chemical composition were examined using Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive X-ray (EDX) spectroscopy, respectively. Under 354nm excitation, the phosphors exhibit three emission peaks at 492, 580, and 723nm, corresponding to the transitions 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, and4F9/2 → 6H11/2. The PL intensity of the samples increased with rising Dy3⁺ ion concentration until concentration quenching occurred at x = 1.0mol% and the critical distance (Rc) was calculated to be 24Å. By doping Dy3⁺ ions into the phosphors capable of emitting white light were synthesized, exhibiting CIE chromaticity coordinates of (0.2883, 0.3123) which are in close agreement with the standard white light coordinates of (0.333, 0.333). The CCT analysis revealed that the emitted light from these phosphors is cool in nature. The diffuse reflectance spectroscopy (DRS) analysis was conducted to calculate the band gap of the prepared phosphor, which was found to be 5.04eV. The thermoluminescence (TL) properties of SZSO: Dy3⁺ phosphors were also studied, and relevant trapping parameters-including the order of kinetics (b), shape factor (μg), trap density (n₀), frequency factor (s), and activation energy (Ea)-are determined using Chen's peak shape method. The thermoluminescence (TL) of UV-irradiated (254nm) samples was recorded at a constant heating rate of 5°C/s. The sample doped with 2mol% Dy3⁺ and irradiated for 50min exhibited optimal thermoluminescence (TL) intensity in the temperature range of 100-150°C, characterized by a single broad TL glow peak extending from 45 to 300°C. Using the TL glow curve deconvolution method, five distinct deconvoluted peaks were identified, indicating the presence of five separate trap centers. All these parameters prove that this material is a potential candidate for applications in thermoluminescent dosimeters (TLDs) and white light-emitting diodes (WLEDs).

Thermally stable Sm3+ doped SrCeO3 single-phase white phosphor with Y3+ sensitization for fabricating wLEDs

The pioneering study reveals the transformative power of co-doping in enhancing phosphor performance, focusing on the development of a cutting-edge white phosphor: SrCeO3:0.02Sm3+ co-doped with Y3+ (0–2 wt%) for high-CRI white LED applications. These innovative perovskites were synthesized using a low-temperature fuel-excess gel combustion technique, with citric acid as the fuel and ammonium nitrate as an additional oxidizer. By examining the impact of Y3+ sensitization on the crystalline phases, morphology, elemental composition, band gap energy, and luminescence properties, the study discovered that orthorhombic SrCeO₃:0.02Sm3+: Y3+ perovskites exhibit exceptional crystallinity and peak luminescence at 1.5 wt% Y3+. The CIE color diagram confirmed their bright white light emission across all samples. This breakthrough positions nano-perovskite SrCe0.965Sm0.02O3:1.5 wt% Y3+ as a top candidate for direct phosphor coatings on near-UV LED chips, and its practical utility promises significant advancements in energy-efficient lighting technology.

Green Light Enhances the Postharvest Quality of Lettuce During Cold Storage

The postharvest quality of lettuce (Lactuca sativa) is significantly influenced by the lighting environment during storage. This study evaluated the effects of green LEDs at 500 nm and 530 nm, white LEDs (400–700 nm), and dark storage on lettuce quality over 14 days at 5 °C. All treatments were applied at 10 µmol m−2 s−1 under a 12 h photoperiod. Quality parameters measured included moisture loss, relative water content (RWC), photosynthetic rate, chlorophyll content (SPAD), total soluble solids (TSSs), electrolyte leakage (EL), color change (∆E), texture (crispness), and overall visual quality (OVQ). Lettuce stored under green LEDs, particularly 530 nm, exhibited superior postharvest quality. Compared to dark storage, 530 nm reduced moisture loss by 7.1%, increased RWC by 9.2%, and reduced transpiration rate. The green light preserved photosynthetic activity (43% decline vs. 77% in the dark), increased TSS, reduced color change by 42%, improved crispness by 46.1%, and limited EL to 54.5%. Shelf life was extended by approximately four days. The 500 nm treatment showed notable improvements, including an 8.4% reduction in moisture loss, 8.2% higher RWC, a smaller photosynthesis decline (25%), and the lowest EL (53.1%). It improved color retention (∆E reduced by 45.3%) and crispness (46.8%). Both green wavelengths effectively maintained lettuce quality during cold storage, with 530 nm being the most effective overall. These results suggest that targeted green LED lighting is a promising, energy-efficient strategy to preserve postharvest quality and extend shelf life in leafy greens.

The Effect of Light on the Germination of Raphanus sativus Seeds and the Use of Sprout Extracts in the Development of a Dermatocosmetic Gel

This study investigates the influence of different light sources (sunlight, green, red, and white LED) on the germination of Raphanus sativus L. sprouts and the potential use of their sprout extracts in the development of natural dermatocosmetic gels. The bioactive fractions were extracted using simple methods and analyzed for total polyphenol content and antioxidant activity. Statistical analysis of weight, total phenolic content, and antioxidant activity of Raphanus sativus L. sprouts was performed using ANOVA. Sprouts exposed to green LED light showed the highest biomass (16.13 ± 0.38 g), while red LED light resulted in the highest total polyphenol content (3.28 ± 0.03 mg GAE/g fresh weight). The highest antioxidant activity (6.60 ± 0.08 mM Trolox/g fresh weight) was obtained under white LED. Although variations were observed, ANOVA analysis revealed that only sprout weight differed significantly among treatments (p < 0.001), while differences in polyphenol content and antioxidant activity were not statistically significant (p > 0.05). The extract with the highest antioxidant activity was incorporated as an active ingredient into Carbopol-based hydrogel formulations containing natural gelling agents and gentle preservatives. The resulting gels demonstrated favorable pH (4.85–5.05), texture, and stability. The results indicate that the light spectrum influences the germination process and the initial development of seedlings. Moreover, radish sprout extracts, rich in bioactive compounds, show promise for dermatocosmetic applications due to their antioxidant, soothing, and antimicrobial properties. This study supports the use of natural resources in the development of care products, in line with current trends in green cosmetics.

Effects of Red and Blue LEDs Light on Growth and Development of Chrysanthemum Callus

Effects of LED illumination on callus induction from petals of Karaked and Scarlet chrysanthemums cultivated in MS medium supplemented with 2 mg/I NAA and 4 mg/l Kinetin, under white LED light (PPFD 30±2 µmol/m2/s) and red to blue light in the ratios 30:10, 40:15, and 30:3 (PPFD 50±2 µmol/m2/s) for 16 h. It was determined that a light ratio throughout 4 weeks culture period had no impact on the fresh weight of callus. Conversely, varying light proportions yield distinct callus dry weights. Upon evaluating cultivar parameters, it was determined that ‘Karaked’ exhibited more fresh and dry weight compared to the callus of the ‘Scarlet’. Analysis of Karaked's callus showed that callus cultured under 30:3 red to blue LED light exhibited the largest concentrations of all photosynthetic pigments, the greatest levels of malondialdehyde (MDA) and total phenolic compounds, and the lowest EC50 value for DPPH free radical inhibition. In the case of the Scarlet chrysanthemum, following 8 weeks of callus induction, it was observed that a light ratio of red to blue at 40:15 yielded the maximum concentrations of chlorophyll a and carotenoids. No statistical difference was seen in the quantity of chlorophyll b. The MDA content of Scarlet’s callus cultivated under white LED light was the highest, and the EC50 value for DPPH free radical inhibition was also the highest. Callus produced under red to blue LED light ratios of 30:10, 40:15, and 30:3 exhibited greater quantities of phenolic compared to callus cultured under white LED light.

Graphitic-C3N4 modified by 9-phenylcarbazole groups and used as a metal-free phosphor in white light-emitting diodes

Graphitic-C3N4 modified by 9-phenylcarbazole groups and used as a metal-free phosphor in white light-emitting diodes

Visible Light Driven Knoevenagel Condensation Reaction Using Functionalized Graphene Oxide, Fe3O4, and Graphitic Carbon Nitride Heterojunction‐Based Photocatalyst Within Short Duration

Abstract A well‐known C─C bond forming reaction, Knoevenagel condensation, has received less attention to perform it photocatalytically. A handful studies have been conducted to investigate how photocatalysis influences processes that generate C─C bonds. This study presents the synthesis of a photoactive system through the combination of ethylene diamine functionalized graphene oxide (EDG), Fe3O4 and graphitic carbon nitride (GCN), resulting in the formation of EDG/Fe‐GCN ternary heterojunction and characterized through various techniques, for instance, XRD, FTIR, TGA, HR‐TEM, FE‐SEM, XPS analysis, and so on. The results of several characterizations indicate the formation of heterojunctions. The EDG/Fe‐GCN depicts type II heterojunction photocatalyst, where EDG works as a surface provider for photogenerated charge carriers. The relatively less explored photo‐condensation C─C bond forming reaction was successfully executed utilizing synthesized EDG/Fe‐GCN photocatalyst. The model reaction between benzaldehyde and malononitrile resulted in the desired product (benzylidene malononitrile) with remarkable conversion of (>99.9%) and selectivity (98.5%) using ethanol as a green solvent in concise short span just 45 min, employing a 200 W white LED. Furthermore, the EDG/Fe‐GCN photocatalyst exhibited exceptional reusability for over six cycles with minimal reduction in conversion and selectivity of the resulting product.

Retired AD influenced many to follow in his footsteps

ORLANDO, Fla. — There's something about Kevin White's leadership that's contagious. As he looks back on his career spanning almost five decades in college athletics, he takes pride in the fact that nearly 40 of his former team members went on to serve as athletics directors and commissioners.

White and blue LED irradiation effectively inhibit postharvest decay in citrus caused by Cladosporium cladosporioides

White and blue LED irradiation effectively inhibit postharvest decay in citrus caused by Cladosporium cladosporioides

Highly luminescent green-emitting AgInS2/ZnS quantum dots enabled by controlling Zn ion exchange for white light-emitting diodes

Highly luminescent green-emitting AgInS2/ZnS quantum dots enabled by controlling Zn ion exchange for white light-emitting diodes

Investigation of molybdate-tungstate based phosphors enriched with Dy3+ and Sm3+ ions: From synthesis to white LED applications

Investigation of molybdate-tungstate based phosphors enriched with Dy3+ and Sm3+ ions: From synthesis to white LED applications

Cold sintering of CsPbBr3 quantum dots embedded KBr ceramics for LED displays

Cold sintering of CsPbBr3 quantum dots embedded KBr ceramics for LED displays

Orange-red oxyapatite-type Ba2La3(SiO4)2(PO4)O:Sm3+ phosphors with good moisture resistance and excellent thermal stability for white LEDs and plant-growth LEDs

Orange-red oxyapatite-type Ba2La3(SiO4)2(PO4)O:Sm3+ phosphors with good moisture resistance and excellent thermal stability for white LEDs and plant-growth LEDs

Twenty years of infectious disease dynamics research: gender and race imbalances in publication and citation practices.

Publication practices accumulate to affect credibility and career advancement. Understanding authorship and citation practices is critical to addressing inequities. While citation bias has been demonstrated in several fields, it remains uncharacterized in infectious disease dynamics (IDD), a quantitative, interdisciplinary domain highly visible during the COVID-19 pandemic. We analyse IDD articles and their bibliographies from 2000 to 2019 using machine-learning algorithms to infer the gender and race/ethnicity of each article's lead and senior authors. We examine authorship and citation patterns by gender and racial group across geographic scales, including characterizing the author composition of each article's bibliography relative to the field. Our analysis reveals persistent gender and race imbalances in IDD research. Man-authored and White-authored publications dominate the field, with little progress in racial diversification of US and UK publications over the last two decades. Woman-authored articles have the most representative citation practices but are undercited, especially when women are senior authors. In the USA and UK, most citations feature White lead and senior authors, even when citing articles have lead or senior authors of colour. These findings underscore the urgent need for more inclusive IDD research practices. We discuss possible mechanisms and solutions to create opportunities for researchers from underrepresented groups.

Influences from MgO-doped phosphors on optical properties of white light-emitting diodes

MgO was produced utilizing Andrographis paniculata (A. paniculata), which forms cubic crystallites having a median dimension of 35 nm. SEM analysis shows the development of nano-bars (diameter - length: 46 nm - 185 nm). The illuminating spectra revealed oxygen deficiencies at 467 nm. This has high antimicrobial properties, having zones of restriction of 19 mm and 29 mm versus disease-causing agents from seafood and food. The compound has anti-udder cancer effect (IC50: 15.76 μg/mL for human mammary adenocarcinoma MCF-7) and is biocompatible.