Low Luminescence Research Articles

Green massive mechanical synthesis of highly efficient Zn-Doped Cs3Cu2I5 for LED and X-ray imaging applications

As a new generation of environmentally friendly halide materials, Cs3Cu2I5 shows up the promising application in scintillation, LED, and photoelectric detection fields. However, liquid phase methods cannot produce Cs3Cu2I5 on a large scale, and the preparation process is accompanied by serious pollution. Although the ball milling method can solve the problems caused by the liquid phase synthesis method, the Cs3Cu2I5 obtained has many surface defects and low luminescence efficiency. In this work, a strategy of doping-assisted ball-milling synthesis using ZnI2 is proposed. Similar to the chemical preparation of Cs3Cu2I5, the iodine-rich environment during the modified ball milling process can also play a role in repairing surface defects. And it has been demonstrated through experiments and first principles calculations that the distortion of [Cu2I5]3- under ground/excited state can be adjusted through doping Zn into the Cu1 site, the formation barrier of self-trapped excitons is reduced, and the luminous efficiency of Cs3Cu2I5 is significantly improved. Subsequently, using the simple hot-pressing method, the representative Cs3Cu2I5:1.0Zn sample was combined with commercially available polypropylene to fabricate Cs3Cu2I5:1.0Zn@PP film. Finally, the potential applications of the newly-developed film in portable and customizable WLED and scintillation fields were explored.

Simultaneous achieving color‐tuning long persistent luminescence and phosphorescent quantum yield of 81.05% in 2D organic metal halide perovskite

AbstractIonically bonded organic metal halide perovskite‐like luminescent materials, which incorporate organic cations and metal halides, have emerged as a versatile multicomponent material system. However, these materials still face challenges in terms of low phosphorescence quantum yields and limited long persistent luminescence (LPL) colors. Herein, we present the design and synthesis of an intraligand charge‐transfer organic‐based metal halide perovskite‐like material, in which organic cations form a compact supramolecular hydrogen‐bonded organic framework (HOF) structure, exhibiting crystallization‐induced phosphorescence emission of ligand, while metal halides form a unique two‐dimensional (2D) structure that displays intrinsic self‐trapped excitons (STE) emission under the radiation of UV light. Notably, the metal halide hybrid is found to exhibit enhanced phosphorescent photoluminescence efficiency of up to 81.05% and tunable LPL from cyan to orange compared to the pristine organic phosphor, due to the structural distortion and scaffolding effects of 2D metal halides as well as a well‐packed HOF structure. Optical characterizations and theoretical calculations reveal that charge transfer from organic cations and halogen to ligand as well as STE from inorganic layers are responsible for the tunable LPL. Meanwhile, the high‐efficiency phosphorescent quantum yield is attributed to stronger hydrogen bond stacking as well as structural distortion of metal halogen bands. Thus, the obtained LPL provides potentials in anti‐counterfeiting, security systems, and so on.

Two‐Photon Clusteroluminescence Enabled by Through‐Space Conjugation for In Vivo Bioimaging

AbstractClusteroluminescence (CL) materials without largely conjugated structures have gained significant attention due to their unique photophysical properties and potential in bioimaging. However, low luminescence efficiency and short emission wavelength limit their development. This work designs three luminogens with CL properties (CLgens) by introducing n‐electron‐involved through‐space conjugation (TSC) into diarylmethane. Apart from single‐photon excited long‐wavelength (686 nm) and high‐efficiency (29 %) CL, two‐photon clusteroluminescence (TPCL) is successfully achieved in such small luminogens with only two isolated heteroatomic units. TSC stabilized in the aggregate state has been proven to realize efficient spatial electron delocalization similar to conventionally conjugated compounds. Encouraged by the excellent TPCL properties, two‐photon imaging of blood vessels in vivo and biocompatibility verification utilizing CLgens are also achieved. This work illustrates the essential role of TSC in promoting nonlinear optical properties of CLgens and may facilitate further design and development of the next generation of bioprobes with excellent biocompatibility.

Comparative VUV Synchrotron Excitation Study of YAG: Eu and YAG: Cr Ceramics

Using synchrotron radiation, a comparative VUV excitation study of YAG ceramics doped with Eu3+ and Cr3+ ions under VUV excitation (10.5–3.7 eV) at 9 K was conducted in this work. Both ceramics exhibit distinct excitation peaks in the VUV region, indicating high-energy transitions related to the internal electronic levels of the dopants and interband transitions within the YAG matrix. For YAG:Eu, the main excitation peaks at 6–7 eV correspond to transitions within the 4f-shell of Eu3+ and Eu3+-O2− charge transfer states, showing weak dependence on the crystal field and high energy conversion efficiency. In contrast, YAG:Cr shows broad excitation bands due to transitions between levels influenced by strong crystal field interactions, resulting in lower luminescence efficiency. The study highlights the importance of crystal structure and dopant interactions in determining the spectral characteristics of YAG-based ceramics, offering potential for their application in advanced optoelectronic devices.

Enabling robust near-infrared afterglow polymers through cascade energy transfer

Near-infrared afterglow materials, which can significantly reduce background fluorescence and improve penetration in living organisms, are vital for precision imaging. However, the practicability of near-infrared afterglow materials has been hindered by their short lifetime and low luminescence quantum efficiency. Herein, we propose an effective strategy for doping water-soluble afterglow polymer host materials with fluorescent dyes, leveraging the step-by-step Förster energy transfer principle to realize near-infrared afterglow. Benefiting from the ultralong lifetime of 4.2 s and high quantum efficiency of 20.1 % for the blue host PAMCz as well as efficient cascade energy transfer efficiency of 83.3 %, the developed NIR afterglow exhibits luminescence peaked at 750 nm, a lifetime of 1.4 s, and a quantum efficiency of 17.1 %. A successful demonstration of near-infrared afterglow biological imaging with a penetration depth of 3.4 mm and signal-to-background ratio of 48.3, has been established. These advancements expand the scope of near-infrared afterglow materials by combining an ultralong lifetime with high quantum efficiency, providing a roadmap for designing robust near-infrared materials.

Exploration of red and deep red Thermally activated delayed fluorescence molecules constructed via intramolecular locking strategy

Red and deep red (DR) organic light-emitting diodes (OLEDs) have garnered increasing attention due to their widespread applications in display technology and lighting devices. However, most red OLEDs exhibit low luminescence efficiency, severely limiting their practical applications. To address this challenge, we theoretically design four novel TADF molecules with red and DR luminescence using intramolecular locking strategies building upon the experimental findings of DCN-DLB and DCN-DSP, and their crystal structures are predicted with the lower energy and higher packing density. The photophysical properties and luminescence mechanism of six molecules in toluene and crystal are clarified using the first principles calculation and thermal vibration correlation function (TVCF) method. The proposed design strategy is anticipated to offer several advantages: enhanced electron-donating capabilities, more rigid structures, longer emission wavelengths and higher luminescence efficiency. Specifically, we introduce oxygen atoms and nitrogen atoms as intramolecular locks, and the newly developed DCN-DBF and DCN-PHC have redshifted emission, narrow singlet–triplet energy gap (ΔEST), fast reverse intersystem crossing rate and enhanced photoluminescence quantum yield (PLQY). Notably, DCN-DBF achieves both long wavelength emission and high efficiency, with emission peaks at 598 nm and 587 nm corresponding to PLQY of 52.13 % and 43.42 % in toluene and crystal, respectively. Our work not only elucidates the relationship between molecular structures and photophysical properties, but also proposes feasible intramolecular locking design strategies and four promising red and DR TADF molecules, which could provide a valuable reference for the design of more efficient red and DR TADF emitters.

Maximizing Upconversion Luminescence of Co-Doped CaF₂:Yb, Er Nanoparticles at Low Laser Power for Efficient Cellular Imaging.

Upconversion nanoparticles (UCNPs) are well-reported for bioimaging. However, their applications are limited by low luminescence intensity. To enhance the intensity, often the UCNPs are coated with macromolecules or excited with high laser power, which is detrimental to their long-term biological applications. Herein, we report a novel approach to prepare co-doped CaF2:Yb3+ (20%), Er3+ with varying concentrations of Er (2%, 2.5%, 3%, and 5%) at ambient temperature with minimal surfactant and high-pressure homogenization. Strong luminescence and effective red emission of the UCNPs were seen even at low power and without functionalization. X-ray diffraction (XRD) of UCNPs revealed the formation of highly crystalline, single-phase cubic fluorite-type nanostructures, and transmission electron microscopy (TEM) showed co-doped UCNPs are of ~12 nm. The successful doping of Yb and Er was evident from TEM-energy dispersive X-ray analysis (TEM-EDAX) and X-ray photoelectron spectroscopy (XPS) studies. Photoluminescence studies of UCNPs revealed the effect of phonon coupling between host lattice (CaF2), sensitizer (Yb3+), and activator (Er3+). They exhibited tunable upconversion luminescence (UCL) under irradiation of near-infrared (NIR) light (980 nm) at low laser powers (0.28-0.7 W). The UCL properties increased until 3% doping of Er3+ ions, after which quenching of UCL was observed with higher Er3+ ion concentration, probably due to non-radiative energy transfer and cross-relaxation between Yb3+-Er3+ and Er3+-Er3+ ions. The decay studies aligned with the above observation and showed the dependence of UCL on Er3+ concentration. Further, the UCNPs exhibited strong red emission under irradiation of 980 nm light and retained their red luminescence upon internalization into cancer cell lines, as evident from confocal microscopic imaging. The present study demonstrated an effective approach to designing UCNPs with tunable luminescence properties and their capability for cellular imaging under low laser power.

Glow-type luminol chemiluminescence based on a supramolecular enhancer of cyclodextrin

BackgroundChemiluminescence (CL) bioassay is one of the most advanced and used detection method in clinical diagnosis and biomedical research because of the advantages of low background, easy operation, and wide-field imaging without a light source or microscope. The luminol/hydrogen peroxide/horseradish peroxidase (luminol/H2O2/HRP) system is the most popular CL system, but its application in high-throughput imaging detection is challenged due to its low luminescence efficiency and flash-type emission which is difficult in ensuring the reproducibility and consistency of detection results. ResultsWe reported a glow-type CL system of luminol@CD/H2O2/HRP by using a supramolecular enhancer of cyclodextrin (CD). This luminol@CD/H2O2/HRP system exhibited a luminescence lifetime of 41 min for sensitive and accurate imaging analysis. The long-lasting CL emission was attributed to the formation of a 1:1 host–guest complex between luminol and CD, which could stabilize the emitter and effectively reduce nonradiative relaxation. The formation of luminol@CD complex was determined through NMR experiments and theoretical analysis. Under optimum conditions, the luminol@CD/H2O2/HRP system showed higher sensitivity and much better precision than classical luminol/H2O2/HRP system for imaging detection of HRP. Especially, this glow-type luminol@CD/H2O2/HRP system realized CL imaging of microwell arrays on microfluidic chips. In addition, the luminol@CD/H2O2/HRP system was successfully applied for point-of-care detection of 17β-estradiol based on a competitive mechanism of host–guest recognition. SignificanceAn efficient CL system is crucial for obtaining reproducible and consistent results for accurate detection. Our luminol@CD/H2O2/HRP system emitted strong and persistent luminescence, resulting in reliability and efficiency at both CL macroscopic and microscopic imaging detection. We expected the luminol@CD/H2O2/HRP CL system to be applied in various detection fields.

Two-photon Clusteroluminescence Enabled by Through-Space Conjugation for In Vivo Bioimaging.

Clusteroluminescence (CL) materials without largely conjugated structures have gained significant attention due to their unique photophysical properties and potential in bioimaging. However, low luminescence efficiency and short emission wavelength limit their development. This work designs three luminogens with CL properties (CLgens) by introducing n-electron-involved through-space conjugation (TSC) into diarylmethane. Apart from single-photon excited long-wavelength (688 nm) and high-efficiency (29%) CL, two-photon clusteroluminescence (TPCL) is successfully achieved in such small luminogens with only two isolated heteroatomic units. TSC stabilized in the aggregate state has been proven to realize efficient spatial electron delocalization similar to conventionally conjugated compounds. Encouraged by the excellent TPCL properties, two-photon imaging of blood vessels in vivo and biocompatibility verification utilizing CLgens are also achieved. This work illustrates the essential role of TSC in promoting nonlinear optical properties of CLgens and may facilitate further design and development of the next generation of bioprobes with excellent biocompatibility.

Scale-Bridging Mechanics Transfer Enables Ultrabright Mechanoluminescent Fiber Electronics.

Mechanoluminescent (ML) fibers and textiles enable stress visualization without auxiliary power, showing great potential in wearable electronics, machine vision, and human-computer interaction. However, traditional ML devices suffer from inefficient stress transfer in soft-rigid material systems, leading to low luminescence brightness and short cycle life. Here, we propose a tendon-inspired scale-bridging mechanics transfer mechanism for ML composites, which employs molecular-scale copolymerized cross-linking and nanoscale inorganic nanoparticles as hierarchical stress transfer sites. This strategy effectively reduces the dissipation of stress in molecular chain segments and alleviates local stress concentration, increases luminescence by 9 times, and extends cycle life to more than 10,000 times. Furthermore, a scalable (kilometer-scale) anti-Plateau-Rayleigh instability manufacturing technology is developed for thermoset ML fibers, compatible with various existing textile techniques. We also demonstrate its system-level applications in motion capture, underwater interaction, etc., providing a feasible strategy for the next generation of smart visual textiles.

Rapid and dynamic detection of endogenous proteins through in locus tagging in rice

Understanding the behavior of endogenous proteins is crucial for functional genomics, yet their dynamic characterization in plants presents substantial challenges. Whereas mammalian studies have leveraged in locus tagging with the luminescent HiBiT peptide and genome editing for rapid quantification of native proteins, this approach remains unexplored in plants. Here, we introduce the in locus HiBiT tagging of rice proteins and demonstrate its feasibility in plants. We found that although traditional HiBiT blotting works in rice, it failed to detect two of the three tagged proteins, a result attributable to low luminescence activity in plants. To overcome this limitation, we engaged in extensive optimization, culminating in a new luciferin substrate coupled with a refined reaction protocol that enhanced luminescence up to 6.9 fold. This innovation led to the development of TagBIT (tagging with HiBiT), a robust method for high-sensitivity protein characterization in plants. Our application of TagBIT to seven rice genes illustrates its versatility on endogenous proteins, enabling antibody-free protein blotting, real-time protein quantification via luminescence, in situ visualization using a cross-breeding strategy, and effective immunoprecipitation for analysis of protein interactions. The heritable nature of this system, confirmed across T1 to T3 generations, positions TagBIT as a powerful tool for protein study in plant biology.

Inspection techniques in photovoltaic power plants: A review of electroluminescence and photoluminescence imaging

The growth of photovoltaic power plants in both size and number has spurred the development of new approaches in inspection techniques. The most commonly employed methods include visual inspections, current-voltage measurements, infrared thermography, and luminescence imaging. Luminescence, rooted in the electromagnetic radiation capture of semiconductor structures that make up solar cells, proves effective in detecting various failures that may occur throughout the lifespan of a photovoltaic module. This phenomenon can be induced either by injecting current into the photovoltaic module (Electroluminescence) or through optical excitation using an appropriate light source (Photoluminescence). This paper offers an overview of the conventional outdoor luminescence imaging technique, delving into its applications and limitations. Additionally, it provides a comprehensive review of innovative outdoor luminescence technique approaches. These novel techniques aim to address several limitations of conventional methods, such as the considerably lower luminescence emission intensity compared to solar radiation, the need for external energy sources for current injection, the required acquisition time, and the necessity of disconnecting the solar module.

Synthesis of stable fluorescent ethylene-vinyl acetate copolymers based on in-situ grafted rare-earth organic complexes and antioxidants through transesterification

The synthesis and application of rare earth organic complexes (REOCs) are gaining attention due to their advantages including low excitation thresholds and high luminescence efficiencies. However, their integration as functional fillers in polymer matrices is constrained by challenges related to poor dispersion and limited stability. This study introduces a novel method for synthesizing stable fluorescent polymers by co-grafting europium (Eu) complexes and the antioxidant 3,9-bis-{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl-)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5.5]-undecane (AO-80) onto an ethylene-vinyl acetate (EVA) matrix through an in-situ synchronous grafting strategy, aiming to address these dual challenges of poor dispersion and rapid aging. In this study, Eu complexes characterized by low excitation thresholds and high hexahydrate (EuCl3) and selected ligands - 1,10-phenanthroline (Phen), alpha-thienyl trifluoroacetone (HTTA), and 4-acetoxybenzoic acid (4-ABA). Through transesterifications, the Eu complexes were successfully grafted onto the EVA chain, achieving a uniform dispersion within the EVA matrix to form fluorescent polymers. Furthermore, the incorporation of antioxidant AO-80 as a radical scavenger can significantly mitigate fluorescence attenuation. Through detailed exploration of transesterifications under various conditions, optimal grafting rates of 11.34% for EVA with Eu complexes and 22.87% for EVA with AO-80 were achieved. The synthesized fluorescent polymers of EVA synchronously grafted with Eu complexes and AO-80 have been proven to obtain markedly improved fluorescence stability and aging resistance by outdoor aging tests. Our findings not only validate the in-situ reaction grafting method as an efficient strategy for producing polymer composites with excellent fluorescence stability but also pave the way for future research aimed at overcoming the limitations of REOCs in photovoltaic and agricultural applications.

Numerical demonstration of an efficient up-conversion enhancement strategy by plasmon excitations in a gap-mode nanocavity

Lanthanide-doped up-conversion nanoparticles (UCNPs) can be widely used as near-infrared absorbing photoactive materials in bioimaging and photovoltaic devices. However, the low absorption cross section and low luminescence quantum rate of UCNPs significantly limit its use. Therefore, a hexagonal gold pillar nano-array structure consisting of UCNPs, gold pillar arrays, gold film and silica layer is proposed. By optimizing the structural parameters, the surface plasmon resonance wavelengths are simultaneously matched with the 808 nm excitation wavelength and 450 nm emission wavelength of the UCNPs. The gap-mode nanocavity confines the incident excitation radiation to nanophotonic hotspots with greatly high field strengths, thus theoretically proposed an efficient strategy to enhance the up-conversion luminescence. The plasmonic structure investigated in this study combines the advantages of ease of processing, high absorption, low loss and good controllability of its localized surface plasmon resonance. It provides a new solution for up-conversion enhancement design of gap-mode nanocavities.

Enhancement of Upconversion Luminescence through Three-Dimensional Design of Plasma Ti3O5-Coupled Structural Domain-Limiting Effects.

Upconversion luminescence plays a crucial role in various technological applications, and among the various valence states of lanthanide elements, Ln3+ has the highest stability. The 4f orbitals of these elements are in a fully empty, semifull, or full state. This special 4f electron configuration allows them to exhibit rich discrete energy levels. However, the 4f-4f transition of Ln3+ rare earth ions itself is prohibited, resulting in a lower luminescence efficiency. This limitation greatly hinders the practical application of upconversion luminescence. In this study, we report nanostructured luminescence-enhanced substrate platforms with both semiconductive local surface plasmons and spatially confined domain effects on a single defect semiconductor substrate. By coupling NaYF4:Yb-Er nanoparticle emitters to the surface of Ti3O5 NC-arrays plasmonic nanostructures, an ultrabright luminescence with a 32-fold increase in green emission and a 40-fold increase in red emission was achieved. Furthermore, the fluorescence resonance energy transfer characteristics observed in the R6G/NaYF4/Ti3O5 NC-array composite film enable accurate detection of fluorescent molecules. The results provide an innovative and intelligent approach to enhance the upconversion luminescence intensity of rare-doped nanoparticles and develop highly sensitive molecular detection systems based on the above luminescence enhancement.

Zircon petrochronological evidences for diachronous tectonic switch and orogenic keel collapse of the Tongbai-Dabie-Sulu orogens

Migmatites can be produced in different stages of orogeny and thus have a great significance to constrain the evolution of an orogenic belt. Migmatites widely occur in the Tongbai orogen, but their formation ages and geological significance have not been well constrained. In this study, a combination of cathodoluminescence (CL) imaging, U-Pb-Hf-O isotopes and trace elements of zircons were carried for migmatites in the Tongbai orogen. Most inherited cores in a melanosome show variable UPb ages and Hf isotope compositions with high δ18O values, suggesting they might be detrital zircons from its protolith. Whereas other relict cores in this sample have nebulously zoning or no zoning, flat HREE patterns with insignificant Eu anomalies and relatively low formation temperatures, indicating their formation under eclogite-facies conditions. They yield UPb ages of 228 ± 3 Ma, providing direct evidence for the involvement of Triassic subducted continental materials. The overgrowth rims and some new grown grains in the migmatites show euhedral shapes, low CL luminescence, high Th/U ratios, clear negative Eu anomalies and steep HREE patterns, suggesting they are anatectic zircons formed during partial melting. They yield UPb ages from 139 ± 2 to 132 ± 1 Ma. Combined with previous studies, we suggest that migmatization mainly occurred at 139–130 Ma in the Tongbai orogen. The anatectic zircons in the leucosomes show much lower δ18O values (5.79 ± 0.23‰ vs. 8.94 ± 0.16‰) and higher 176Hf/177Hf ratios (0.282302–0.282648 vs. 0.281728–0.282504) than the zircons in adjacent melanosomes, suggesting that the leucosomes might be externally sourced. According to a compilation of the geochronological information of migmatite and magmatism, the Tongbai-Dabie-Sulu orogens have a spatial and temporal variation of partial melting and magma activities in the post-collisional stage. These might result from the diachronical tectonic switch and collapse of the orogenic lithospheric keels caused by the subduction and rollback of the Paleo-Pacific slab.

Development of a synthetic relaxin-3/INSL5 chimeric peptide ligand for NanoBiT complementation binding assays

INSL5 and relaxin-3 are relaxin family peptides with important roles in gut and brain function, respectively. They mediate their actions through the class A GPCRs RXFP4 and RXFP3. RXFP4 has been proposed to be a therapeutic target for colon motility disorders whereas RXFP3 targeting could be effective for neurological conditions such as anxiety. Validation of these targets has been limited by the lack of specific ligands and the availability of robust ligand-binding assays for their development. In this study, we have utilized NanoBiT complementation to develop a SmBiT-conjugated tracer for use with LgBiT-fused RXFP3 and RXFP4. The low affinity between LgBiT:SmBiT should result in a low non-specific luminescence signal and enable the quantification of binding without the tedious separation of non-bound ligands. We used solid-phase peptide synthesis to produce a SmBiT-labelled RXFP3/4 agonist, R3/I5, where SmBiT was conjugated to the B-chain N-terminus via a PEG12 linker. Both SmBiT-R3/I5 and R3/I5 were synthesized and purified in high purity and yield. Stable HEK293T cell lines expressing LgBiT-RXFP3 and LgBiT-RXFP4 were produced and demonstrated normal signaling in response to the synthetic R3/I5 peptide. Binding was first characterized in whole-cell binding kinetic assays validating that the SmBiT-R3/I5 bound to both cell lines with nanomolar affinity with minimal non-specific binding without bound and free SmBiT-R3/I5 separation. We then optimized membrane binding assays, demonstrating easy and robust analysis of both saturation and competition binding from frozen membranes. These assays therefore provide an appropriate rigorous binding assay for the high-throughput analysis of RXFP3 and RXFP4 ligands.

Facile synthesis of highly stable and efficient MAPbI3 perovskite quantum dots: Spectroscopic characterization and defect analysis

The hybrid methylammonium-based perovskite quantum dots (PQDs) have attracted tremendous attraction for display devices due to their low cost, high luminescence, and color purity. The large-scale production of PQDs is constrained due to the use of toxic and hazardous solvents such as dimethylformamide (DMF) in the synthesis process. Here, a novel approach to prepare PQDs using an environment-friendly solvent, gamma-valerolactone (GVL), is proposed. The synthesized PQDs were found to be uniform with less defect states as compared to the conventionally used DMF solvents, confirmed by different characterizing techniques. The stability of GVL-based PQDs was also found to be improved and proved the efficiency of the present method. Photoluminescence quantum yield (PLQY) of 98 % and single tetragonal CH3NH3PbI3 phase of GVL-derived sample retained over 15 days while the decomposition and degradation were observed in the DMF-derived sample within a short duration. A protocol for the preparation of CH3NH3PbI3 PQDs with less intrinsic defects and uniform optoelectronic properties is presented and paves the way for further modifications and applications.

Structural anatomy and thermal transitions of barium feldspars, BaAl2Si2O8

BaAl2Si2O8 (barium feldspar-based) materials are widely used in glass and ceramic industry due to high melting temperature, chemical resistance, low thermal expansion, low dielectric constants and attractive luminescence properties. The durability of barium feldspar ceramics strongly depends on reversible phase transitions between the low-temperature modification (celsian), and series of high-temperature (HT) polymorphs known as 'hexacelsian'. Numerous works have been devoted to the study of the thermal transitions of 'hexacelsian' by X-ray powder diffraction methods and transmission electron microscopy, the use of which provides limited information about structural changes. Here, the crystal structures, thermal properties and phase transitions of HT BaAl2Si2O8 polymorphs are characterized for the first time using in-situ HT X-ray single-crystal structural study (SCXRD), and micro-Raman spectroscopy up to 1000 °C. The crystal structure of α-hexacelsian under ambient conditions is monoclinic (I2/a). The alpha-form undergoes two polymorphic transformations upon heating: into an orthorhombic (Fmmm) β-modification above 300 °C and into a hexagonal (P–62m) γ-modification above 700 °C. These transitions lead to significant changes in the unit-cell volume: an obstacle in the production of BaAl2Si2O8-based ceramics.

Long Time Atmospheric Oxidation Followed by Hydrofluoric Etching and Hydrosilylation for High‐Efficiency Light‐Emitting Silicon Quantum Dots

AbstractTunable emission wavelength and excellent biocompatibility have positioned silicon quantum dots (Si QDs) as important optoelectronic materials in areas like displays, lighting, and biomedical imaging. However, the challenges of low luminescence efficiency impede the utilization of Si QDs, restraining the advancement of Si QDs‐based light‐emitting diode (LED) devices. This study primarily concentrates on optimizing the surface structure of Si QDs and refining the Si QDs‐based LED device structures. A strategy involving active oxidation followed by hydrofluoric etching and hydrosilylation is proposed to enhance the optical characteristics of Si QDs. A variety of characterization methods are employed to evaluate the impact of the active oxidation on the photoluminescence and surface structures of Si QDs. This approach ultimately achieves an impressive enhancement in the photoluminescence quantum yield (PL QY) of Si QDs from 6.7% to 60.3%. Furthermore, the atmospherically oxidized Si QDs with the highest PL QY are selected as the emitting‐layer material to fabricate LEDs with the structure of ITO/PEDOT:PSS/TFB/Si QDs/ZnMgO/Ag. The introduction of ZnMgO effectively balances charge injection in the Si‐QDs‐based LEDs. As a result, the devices achieve electroluminescence with an external quantum efficiency of 13.2%.