Evolution of organic phosphor through precision regulation of nonradiative decay.

Development of single-component organic phosphor attracts increasing interest due to its wide applications in optoelectronic technologies. Theoretically, activating efficient intersystem crossing (ISC) via 1(π, π*) to 3(π, π*) transitions, rather than 1(n, π*) → 3(π, π*) transitions, is an alternative access to purely organic phosphors but remains challenging. Herein, we designed and successfully synthesized the sila-8-membered ring fused biaryl benzoskeleton by transition metal catalysis, which served as a new organic phosphor with efficient 1(π, π*) to 3(π, π*) ISC. We first found that such a compound exhibits a record-long phosphorescence lifetime of 6.5 s at low temperature for single-component organic systems. Then, we developed two strategies to tune their decay channels to evolve such nonemissive molecules into bright phosphors with elongated lifetimes at room temperature: 1) Physic-based design, where quantitative analyses of electron-phonon coupling led us to reveal and hinder the major nonradiative channels, thus lighted up room temperature phosphorescence (RTP) with a lifetime of 480 ms at 298 K; 2) chemical geometry-driven molecular engineering, where a geometry-based descriptor ΔΘT1-S0/ΘS0 was developed for rational screening RTP candidates and further improved the RTP lifetime to 794 ms. This study clearly shows the power of interdiscipline among synthetic methodology, physics-based rational design, and computational modeling, which represents a paradigm for the development of an organic emitter.

Distinctive Patterns of Transcription and RNA Processing for Human lincRNAs.

Numerous long intervening noncoding RNAs (lincRNAs) are generated from the mammalian genome by RNA polymerase II (Pol II) transcription. Although multiple functions have been ascribed to lincRNAs, their synthesis and turnover remain poorly characterized. Here, we define systematic differences in transcription and RNA processing between protein-coding and lincRNA genes in human HeLa cells. This is based on a range of nascent transcriptomic approaches applied to different nuclear fractions, including mammalian native elongating transcript sequencing (mNET-seq). Notably, mNET-seq patterns specific for different Pol II CTD phosphorylation states reveal weak co-transcriptional splicing and poly(A) signal-independent Pol II termination of lincRNAs as compared to pre-mRNAs. In addition, lincRNAs are mostly restricted to chromatin, since they are rapidly degraded by the RNA exosome. We also show that a lincRNA-specific co-transcriptional RNA cleavage mechanism acts to induce premature termination. In effect, functional lincRNAs must escape from this targeted nuclear surveillance process.

High-Performance Tunable Near-Infrared Emitters of Cr3+-Activated Garnet Phosphor Enabled by Chemical Unit Co-Substitution.

The escalating demand for portable near-infrared (NIR) light sources has posed a formidable challenge to the development of NIR phosphors characterized by high efficiency and exceptional thermal stability. Taking inspiration from the chemical unit co-substitution strategy, high-performance tunable (Lu3- xCax)(Ga5- xGex)O12:6%Cr3+ (x = 0-3) phosphors are designed with an emission center from 704 to 780 nm and a broadest full width at half maximum (FWHM) of up to 172 nm by introducing Ca2+ and Ge4+ ions into the garnet structure. In particular, Lu3Ga5O12:6%Cr3+ demonstrates an anti-thermal quenching phenomenon (I423K = 113.1%). Compared to Lu3Ga5O12:6%Cr3+, Lu2CaGa4GeO12:6%Cr3+ exhibits significantly improved FWHM and IQE by 108 nm and 25.5%, respectively, while maintaining good thermal stability (I423K = 80.4%). Finally, Lu2CaGa4GeO12:6%Cr3+ phosphor is combined with a 465 nm blue LED chip to fabricate NIR LED devices, exhibiting a NIR electroluminescence efficiency of 13.31%@100 mA and demonstrating successful applications in nocturnal illumination and biomedical imaging technology. This work offers a fresh perspective on the design of highly efficient NIR garnet phosphors.

A phosphatase gene is linked to nectar dihydroxyacetone accumulation in manuka (Leptospermum scoparium).

Floral nectar composition beyond common sugars shows great diversity but contributing genetic factors are generally unknown. Manuka (Leptospermum scoparium) is renowned for the antimicrobial compound methylglyoxal in its derived honey, which originates from the precursor, dihydroxyacetone (DHA), accumulating in the nectar. Although this nectar trait is highly variable, genetic contribution to the trait is unclear. Therefore, we investigated key gene(s) and genomic regions underpinning this trait. We used RNAseq analysis to identify nectary-associated genes differentially expressed between high and low nectar DHA genotypes. We also used a manuka high-density linkage map and quantitative trait loci (QTL) mapping population, supported by an improved genome assembly, to reveal genetic regions associated with nectar DHA content. Expression and QTL analyses both pointed to the involvement of a phosphatase gene, LsSgpp2. The expression pattern of LsSgpp2 correlated with nectar DHA accumulation, and it co-located with a QTL on chromosome 4. The identification of three QTLs, some of the first reported for a plant nectar trait, indicates polygenic control of DHA content. We have established plant genetics as a key influence on DHA accumulation. The data suggest the hypothesis of LsSGPP2 releasing DHA from DHA-phosphate and variability in LsSgpp2 gene expression contributing to the trait variability.

Luminescence and Energy Transfer Properties of Color-Tunable Dy3+, Eu3+ co-Activated NaGdSiO4 Phosphor for WLED with Great Thermo-Stability.

A series of NaGd1-x-ySiO4: y Dy3+-x Eu3+ phosphors were synthesized by a high-temperature solid-phase method. The optimal doping ion concentration of Dy3+ ions for this phosphor was determined to be 1 % from the emission spectra. The energy transfer between Dy3+ and Eu3+ ions at 351 nm was investigated by photoluminescence spectra and fluorescence decay curves. At the excitation wavelengths of 275 nm, 351 nm, 366 nm, and 394 nm, a change from yellow to white to red light can be realized by adjusting the doping concentration of Eu/Dy ions. Particularly, by testing the temperature-dependent fluorescence spectrum of the phosphor, it can be found that the luminous intensity of the phosphor is as high as 96 % when 394 nm excitation is employed at 413 K. It was the maximum at this temperature comparing with other phosphors as far as we know. The color coordinate values show that the NaGd1-x-ySiO4:×Dy3+-y Eu3+ phosphors are very close to the white light color coordinates (x=0.33, y=0.33) under 351 nm excitation. Meanwhile, the correlated color temperature is between 5062-7104 K. These results indicate that this phosphor is a promising candidate for high-quality WLED.

Influence of Synthesis Temperature on the Structural, Morphological and Optical Properties of MoO3 Nanorods.

Molybdenum trioxide nanomaterials have attained notable attention in the recent past and are used in various optoelectronic and biomedical applications. Here blue and purple blue light emitting MoO3 nanophosphors were synthesized using the simple hydrothermal method at three different temperatures 100ºC, 150°C, and 200°C. Structural characterization using XRD along with Raman spectroscopy confirms the formation of a highly stable orthorhombic phase. Micro strain effects have been analyzed by employing the Williamson-Hall method using a uniform deformation model. Nanorod like morphology was obtained from FESEM. Optical analysis, using Tauc plot shows a decreasing trend in bandgap value with increasing temperature. Emission peaks in the photoluminescence spectrum are associated with the transition between the sub-bands of the Mo5+ defect state. From CIE coordinates it is confirmed that the characteristic light from the samples is blue and purple-blue. Being an excellent blue and purple blue light emitting phosphor, MoO3 is a suitable material for future LED and fluorescence imaging applications.

The Role of Anions in Rare-earth Activated Inorganic Host Materials for its Luminescence Characteristics.

This work is inspired from the comprehensive work done by our research team aimed at improving the efficiency of white light emitting diodes (LEDs) through improvements in the colour rendering index of the red light (CRI), one of the primary colours of white light. Such work is triggered through the incorporation of anions (BO33-, PO43-, SO42-), either individually or as an integral part of dopant activated inorganic phosphor host materials. Numerous host materials such as ZnO, Y2O3, Ca3(PO4)2, CaMoO4, ABPO4, ABSO4 (where A represents alkali metals and B alkaline earth metals) have been considered ideal hosts materials for studying luminescence properties of materials (including other phosphors). In addition, red emitting dopants such as Sm3+, Eu3+ and Ce3+ have been incorporated into these host materials to achieve a higher CRI of red colour, an essential component of white light. The role anions in various materials is multifaceted; firstly, it acts as sensitizer whereby it absorbs excitation energy and transfers it non-radiatively to the dopants, secondly, it acts as a charge compensator to dopants with a charge of + 3, thirdly, it creates crystal fields that affects the electronic transitions of the dopants and fourthly, it creates a stable crystal structure that allows for dopant embedding. By understanding the exact role of these anions and their interactions with the host lattice and dopant ions, we could further optimize the luminescent properties of these activated host materials, which leads to higher efficiencies and performances in white light-emitting diodes and other lighting technologies. This work is a comprehensive review of the work undertaken by our research team aimed at enhancing the luminescent properties of WLEDs.

Simple and Cost-effective Synthesis of a Rare-earth Free Long Afterglow Phosphor for Dark Visual Markings.

Materials with long afterglow (LAG) became very renowned in the field of luminescence due to their high ability to store energy. However, the development of LAG phosphors is mostly dependent on rare-earth activators, which are commercially expensive due to their limited availability across the world. On the other hand, LAG phosphors that are not based on rare-earth and are developed as an alternative cannot compete with existing rare-earth LAG phosphors. Copper-doped zinc sulfide (ZnS:Cu) phosphor developed long ago has considerable afterglow, but its development has been too tedious, and expensive, and contains usage of toxic gasses such as H2S, CS2, etc. and most of the literature refers to the cubic phase of ZnS. To overcome these issues and simplify the process, we have developed a cost-effective approach to synthesize the hexagonal phase of ZnS, without the involvement of hazardous gases. This is one of the very few reports that highlights the appearance of LAG phenomenon from the hexagonal ZnS:Cu phosphor system. Structural, morphological, and optical studies of the developed ZnS:Cu LAG phosphor have been carried out. The phosphor showed a strong green photoluminescence at 515 nm and an afterglow duration of ~ 1 h useful for specific applications of visual markings in dark conditions. The thermoluminescence spectrum shows a broad and intense glow peak at 377.15 K that indicates the electron trap depth to be at 0.75 eV, supporting our afterglow results.

Combustion Synthesis and Photoluminescence Properties of Novel Bi2Al4O9:Eu3+ Phosphor for n-UV w-LEDs.

The combustion procedure was used to synthesize Bi2Al4O9:Eu3+ phosphors. The XRD and photoluminescence properties are investigations. The XRD patterns consist of an orthorhombic crystal structure. At 395 nm, the maximum excitation intensity was obtained. Following 395 nm excitation, two different emission peaks at 593 and 615 nm were observed. Concentration quenching occurred at 0.5 mol % Eu3+ ions. The CIE coordinates for the Bi2Al4O9 phosphor with Eu3+ ion doped are 615 nm (x = 0.680, y = 0.319) falling in the red region. According to the photoluminescence results, Bi2Al4O9:Eu3+ phosphors might be useful in the fields of near UV-excited w-LEDs.

Effect of Tb3+ and Ce3+ Co-doping on the Structure and Photoluminescence Properties of Hexagonal Boron Nitride Phosphors.

In the paper, we have successfully prepared hexagonal boron nitride (h-BN:Tb3+, Ce3+) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P 6 ¯ m2 space group. It is interesting that the co-doping combination of Tb3+ and Ce3+ can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce3+ phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb3+, Ce3+ phosphors, the co-doping of Ce3+ not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce3+ to Tb3+ is about 55%. The fluorescence lifetime increases with the increase of Ce3+ and Tb3+ concentration, and the fluorescence lifetime of h-BN:0.025Tb3+, 0.05Ce3+ phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb3+, 0.05Ce3+ phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb3+, Ce3+ samples can be used as green phosphors for solid state lighting and fluorescent labeling.

Modulation and Enhancement of Red Luminescence in Ca2GdSbO6: Eu3+ Phosphor by Co-Doping with Bi3.

The double perovskite structure of Ca2GdSbO6 as a fluorescent phosphor matrix material possesses a stable structure, making it an excellent candidate for a matrix material. In this study, single-doped Ca2GdSbO6: Eu3+ fluorescent phosphors and Bi3+ sensitized Ca2GdSbO6: Eu3+, Bi3+ fluorescent phosphor materials were synthesized using the high-temperature solid-state method. The luminescence of this phosphor is based on the 5D0→4F2 transition emission of Eu3+ ions, which occurs at 612 nm. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, high-temperature fluorescence spectra, and fluorescence decay lifetimes to study the phase structure, optical properties, crystal structure, and chemical purity of the samples. The performance of the single-doped phosphor was significantly improved by the addition of Bi3+ sensitizer. The luminescence intensity increased by nearly 100% compared to Ca2GdSbO6: Eu3+ phosphor, with a quantum efficiency increase of 124%. The thermal quenching activation energy was found to be 0.299 eV, and the luminescence intensity remained at 70.3% of room temperature at 453 K. These results indicate that the co-doping of Bi3+ has a modulation and enhancement effect on the luminescence of Ca2GdSbO6: Eu3+ red phosphor, showing great potential for application in near-ultraviolet-excited white LED devices.

Studies on a novel SrZr2 CaLa2 O8 :Eu3+ phosphor for lighting applications emitting direct white light.

Direct white light emitting phosphors play a significant role in the display industry due to their ability to improve the quality, efficiency, and versatility of lighting sources used in most of the displays. The currently investigated phosphor SrZr2 CaLa2 O8 :Eu3+ was prepared by a conventional solid-state reaction method. It has been observed that the stoichiometric ratio of all precursors plays an important role in determining the characteristics of the final phosphor. From X-ray diffraction (XRD) analysis, the phosphor was observed to have a hexagonal phase and a crystal size of ~28 nm. Scanning electron microscopy (SEM) observations revealed a cluster of rod-like structures with an average diameter of ~0.2 µm. The excitation peak maximum observed at 280 nm is due to charge transfer between Eu3+ -O2- ions. The energy transitions 7 F0 → 5 L6 and 7 F0 → 5 D2 are responsible for the appearance of other excitation peaks at ultraviolet (UV) (395 nm), blue (~467 nm), green (~540 nm), orange (~590 nm), and red (~627 nm) attributed to 5 D0 → 7 FJ (J = 0-4) transitions of europium ion (Eu3+ ). The Commercial International de I'Eclairage (CIE) chromaticity coordinates were estimated to be (0.37, 0.0.33) and (0.67, 0.33) for the emissions corresponding to 395 and 590 nm, respectively. The characteristic emissions of Eu3+ ions allow this novel phosphor to be used to generate direct white light in light-emitting diodes (LEDs), which is otherwise difficult to achieve in single-component systems.

Site occupancy and tunable luminescence of Eu2+ and Eu3+ coactivated KCaY (PO4)2:Eu phosphors.

Utilizing the structure characteristic of KCaY (PO4)2 crystal, the site distribution of Eu2+ in KCaY (PO4)2:Eu phosphor coactivated with Eu2+ and Eu3+ ions is tuned. Upon 393-nm excitation, the as-prepared phosphor exhibits a broadband emission of Eu2+ peaked at ~ 475 nm and a typical red emission of Eu3+ with a strong 5D0-7F1 emission at ~ 591 nm. The luminescence color of the phosphor can be adjusted from blue to green, white, yellow, and red. The increasing concentration of Sr2+ and Eu2+ results in a blue shifting of Eu2+ emission. The increasing concentration of Eu3+ results in a red shifting of Eu2+ emission and an enhanced red emission of Eu3+. The luminescence behaviors of the phosphors are analyzed in terms of the site distribution of Eu2+ and Eu3+. A single-phase white light emitting was achieved in KCaY (PO4)2:Eu phosphor upon UV and NUV light excitation, indicating that the phosphor has potential application in white lighting.

Broadband near-infrared (NIR) emitting Cr3+ -doped La3 Ga5 SnO14 phosphor with long persistent and photostimulated persistent luminescence.

Recently, long persistent phosphors (LPPs) have attracted significant attention as promising candidates for biomedical applications. However, the serious decrease in luminescence intensity in tissue still remains a major challenge. Therefore, exploring more competitive LPPs and achieving reproducible tissue imaging is crucial. In this study, a new series of near-infrared (NIR) phosphors La3 Ga5 Sn1-x O14 :xCr3+ (x = 0.005-0.05) were synthesized using a high-temperature solid-state method. The as-synthesized samples were characterized using X-ray diffraction, diffuse/photoluminescence spectroscopy, fluorescence decay curves, and thermoluminescence spectroscopy. Upon excitation with ultraviolet light, strong emission bands were observed in the range 600-1200 nm with an optimal doping concentration of x = 0.02 mol. Moreover, La3 Ga5 SnO14 :Cr3+ exhibits persistent luminescence due to the presence of suitable energy traps, which prompted the phosphor to emit NIR light even after the removal of the excitation source.

A novel n-UV convertible colour-tunable emitting oxynitride phosphor: Realization based on Ce3+ -Tb3+ energy transfer.

In the present work, a novel n-UV convertible colour-tunable emitting phosphor was obtained based on the efficient Ce3+ -Tb3+ energy transfer in the Y10 Al2 Si3 O18 N4 host. By properly controlling the ratio of Ce3+ /Tb3+ , the colour hue of the obtained powder covered the blue and green regions, under excitation of 365 nm. The steady-state and dynamic-state luminescence measurement was performed to shed light on the related mechanism, which was justified by the electronic dipole-quadrupole dominating the related energy transfer process. Preliminary studies showed that Y10 Al2 Si3 O18 N4 :Ce3+ ,Tb3+ can be promising as an inorganic phosphor for white LED applications.

The synthesis and properties of Ca3 Sc2 Si3 O12 :Ce3+ (CSSG) phosphor are utilized for the development of human-centric lighting light-emitting diodes (HCL-LEDs).

In this study, cerium ion (Ce3+ )-doped calcium scandium silicate garnet (Ca3 Sc2 Si3 O12 , abbreviated CSSG) phosphors were successfully synthesized using the sol-gel method. The crystal phase, morphology, and photoluminescence properties of the synthesized phosphors were thoroughly investigated. Under excitation by a blue light-emitting diode (LED) chip (450 nm), the CSSG phosphor displayed a wide emission spectrum spanning from green to yellow. Remarkably, the material exhibited exceptional thermal stability, with an emissivity ratio at 150°C to that at 25°C reaching approximately 85%. Additionally, the material showcased impressive optical performance when tested with a blue LED chip, including a color rendering index (CRI) exceeding 90, an R9 value surpassing 50, and a biological impact ratio (M/P) above 0.6. These noteworthy findings underscore the potential applications of CSSG as a white light-converting phosphor, particularly in the realm of human-centered lighting.

Investigations of thermoluminescence characteristics of SrAlBO4 :Eu3+ phosphors irradiated with gamma rays and carbon ion beam.

A series of SrAlBO4 :Eu phosphors doped with different concentrations of Eu (0.1, 0.3, 0.5, 0.7, 1.0 mol%) was synthesized using a solid-state diffusion method, and their thermoluminescence (TL) properties were analyzed for gamma and carbon ion irradiation. The phase purity, morphological properties, vibrational features, and thermal stability of the prepared sample were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric/differential thermal analyzer (TG/DTA) techniques, respectively. The TL properties of the proposed materials showed broad dosimetric bands, peaking at 202°C for 0.12 kGy gamma irradiation. The highest TL intensity was obtained for a 0.7 mol% concentration of Eu ions under gamma irradiation. Furthermore, the glow curve of the proposed materials showed a broad emission band, centred at 148°C under carbon ion beam irradiation and exhibited the highest emission intensity for a 0.1 mol% Eu concentration. In addition, the dosimetric trapping parameters of the prepared samples such as symmetry factor, order of kinetics, activation energy, and frequency factor, were analyzed using various methods such as Chen's peak shape method, initial growth method, and the Ilich method. The obtained results of the samples showed the potential for dosimetric application.

Ho3+ -doped BaGd2 ZnO5 green-emitting phosphor for solid-state lighting: synthesis, characterization, and photoluminescence properties.

In this work, we present the synthesis of a green-emitting series of BaGd2 ZnO5 :xHo3+ (0.5-3 mol%) phosphors using a high-temperature solid-state reaction method. Phase purity and crystal structure information were evaluated through X-ray powder diffraction patterns. Optical properties were examined through diffuse reflectance spectra, revealing that the prepared phosphor exhibited a band gap of 4.65 eV. The effect of Ho3+ doping on the morphology and ion distribution on the surface was assessed using scanning electron microscopy and time-of-flight secondary ion mass spectrometry techniques, respectively. The excitation spectra of the synthesized phosphor exhibited a charge transfer band and strong absorption transitions. The emission spectra displayed typical holmium emission characteristics, featuring a strong green emission band associated with f-f transitions from 5 F4 + 2 S2 → 5 I8 . Decay dynamics of the synthesized phosphor exhibited a single-exponential decay pattern, with lifetimes ranging from 0.103 to 0.053 ms. The intrinsic radiative lifetime, calculated through Auzel's fitting was determined to be 0.14 ms. Using the emission spectra, colorimetric behaviour was analyzed, revealing that the Commission Internationale de l'éclairage (CIE) coordinates exclusively lay within the green region at (0.285, 0.705), with an impressive colour purity of 99.6%. Given these marked properties, the synthesized phosphor exhibits great potential for a wide range of green-emitting applications, including displays, white light-emitting diodes, and security signage.

Optical properties of blue-light-emitting Y2 O3 :Ce nanophosphor for solid-state lighting application.

The structural, surface morphological, optical absorption and emission features of Y2 O3 :Ce (0%-5%) were studied. The samples had a body-centred cubic crystal structure. The undoped sample had a crystallite size of 29.03 nm, and it varied after doping with Ce. The grain size of the samples varied from 23.00 to 50.78 nm. All the samples exhibited a strong absorption band at 206 nm due to F-centre absorption and absorption involving the delocalised bands. In addition, the doped samples exhibited a secondary band at ~250 nm due to 4f → 5d transitions of Ce3+ ions. The optical bandgap of the undoped sample was found to be ~5.37 eV, and it decreased to 5.20 eV with an increase in Ce concentration to 5%. The undoped sample under 350-nm excitation exhibited a broad photoluminescence (PL) emission band with the maxima at 406 nm and a secondary band at 463 nm. In contrast, multiple PL peaks were centred at ~397, 436, 466, 488 and 563 nm in all the doped samples. The average lifetime of the emission band at 406 nm was 1.05 ns and that of the emission band at ~466 nm was 1.63 ns. The material has potential for solid-state lighting applications.

Demystification of luminescence properties and the near imperceptible thermal quenching of Sm3+-doped tungstate phosphors.

Ultra-high thermally stable Ca2MgWO6:xSm3+ (x = 0.5, 0.75, 1, 1.25, and 1.5 mol%) double perovskite phosphors were synthesized through solid-state reaction method. Product formation was confirmed by comparing the X-ray diffraction (XRD) patterns of the phosphors with the standard reference file. The structural, morphological, thermal, and optical properties of the prepared phosphor were examined in detail using XRD, Fourier transform infrared spectra, scanning electron microscopy, diffused reflectance spectra, thermogravimetric analysis (TGA), photoluminescence emission, and temperature-dependent PLE (TDPL). It was seen that the phosphor exhibited emission in the reddish region for the near-ultraviolet excitation with moderate Colour Rendering Index values and high colour purity. The optimized phosphor (x = 1.25 mol%) was found to possess a direct optical band gap of 3.31 eV. TGA studies showed the astonishing thermal stability of the optimized phosphor. Additionally, near-zero thermal quenching was seen in TDPL due to elevated phonon-assisted radiative transition. Furthermore, the anti-Stokes and Stokes emission peaks were found to be sensitive toward the temperature change and followed a Boltzmann-type distribution. All these marked properties will make the prepared phosphors a suitable candidate for multifield applications and a fascinating material for further development.