Luminescence Characteristics Research Articles

Synthesis and Luminescence Characterization of Novel Red-Emitting Phosphors Based on Eu3+-Activated K2Sr(MoO4)2 Molybdates for w-LEDs.

In this work, trivalent europium (Eu3+) ion activated K2Sr(MoO4)2 red phosphors have been synthesized through high-temperature solid-state reaction method at 750 ℃. Detailed analysis was conducted on the phase purity, morphology, and luminescence properties of the synthesized phosphors. X-ray diffraction (XRD) confirmed the successful formation of K2Sr(MoO4)2:Eu3+ phosphors with pure phase with space group С2/c. The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated K2Sr(MoO4)2 phosphor. Under the excitation of 280nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0→7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 35mol%. Concentration quenching mechanism was identified as the interaction of near-neighbor ions. The chromaticity coordinates of K2Sr(MoO4)2:35mol%Eu3+ were (0.659, 0.340) with a corresponding high color purity of 99.8%. The prepared K2Sr(MoO4)2:35mol%Eu3+ phosphor had good thermal stability with temperature quenching temperature (T0.5 > 420K) and high activation energy (Ea = 0.267eV). The exhaustive findings from this study form the basis for advocating the application of these phosphors in light-emitting devices.

Synthesis and luminescence characterizations of Ag and Na doped LiAlO2 for OSL dosimetry

Optically Stimulated Luminescence (OSL) materials are advanced technology materials widely used in critical applications from radiation dosimetry, biomedicine, and optical data storage to archaeometry. These materials store energy by trapping charge carriers and convert this energy back into light by optical stimulation. However, there are significant challenges such as control of trap distribution and complete understanding of luminescence mechanisms. This study aims to overcome these challenges by comprehensively investigating the luminescence characteristics of lithium aluminate (LiAlO2) pellet materials produced by the sol-gel method and enabling the development of a new OSL dosimetric material. The crystal structures of the synthesized materials were confirmed by X-Ray Diffraction (XRD) method and their morphologies were investigated by Scanning Electron Microscope (SEM). Detailed discussions on defect concentrations and lattice parameters of LiAlO2 are presented. To obtain promising luminescence signals for passive dosimetry, LiAlO2 were doped with various lanthanides (Ce and Gd) and metals (Cu, Ag, Na, Mg and Ca). Especially, the co-doping of Ag and Na ions provided a significant increase in Thermoluminescence (TL) and OSL signals. The effects of dopant elements on TL and OSL signals were investigated comprehensively, and the OSL components and lifetimes were analyzed in detail. As a result, it was determined that TL traps of the developed LiAlO2:Ag,Na pellets at 100 °C were the main source of OSL signals. The reusable OSL signals and almost linear dose-response ratio up to 2 Gy of this material make it a candidate for radiation dosimetry applications. While the developed LiAlO2:Ag,Na material exhibits promising OSL sensitivity and low fading over 2 weeks, the signal stability is dependent on an initial preheat treatment at 100 °C, which reduces around 80 % of the initial OSL signal associated with shallow traps. This characteristic supports the material’s application in dosimetry but may limit sensitivity in low-dose contexts.

Microdiagnostic characteristics of the herb Artemisia austriaca Jacq. (Artemisia austriaca Jacq.)

Introduction. Artemisia austriaca Jacq. is a perennial herbaceous plant of the Asteraceae family, popular in folk medicine due to its various biological activities, in particular: wound-healing, anticonvulsant, analgesic, antipyretic and others. In addition, this plant is in the same section as the pharmacopoeial species – wormwood bitter. In the dynamically developing pharmaceutical field, one of the aspects of expanding the base of medicinal plants as sources of phytopreparations is the study of wild plants close to officinal species. One of the initial stages on the way to the development of regulatory documentation for medicinal plant raw materials is the identification of their authenticity criteria that allow reliable identification. Objective: Study of anatomical-diagnostic features of Artemisia austriaca Jacq. of the Saratov region. Material and methods. The objects of the study were samples of Artemisia austriaca Jacq. herbs harvested in 2021 in the Saratov region. The study of the structure of A. austriaca herbs was performed according to the instructions of GPA.1.5.3.0003 "Microscopic and microchemical analysis of medicinal plant raw materials and drugs of plant origin" in the 15th edition of the Russian Federation’s State Pharmacopoeia. Results. The anatomical-histological study of stem, petiole, inflorescence of Artemisia austriaca growing on the territory of Saratov region has been carried out. As a result of the work the markers, luminescent characteristics of tissues, which help to authenticate the raw materials of this taxon, were revealed and clearly presented. Conclusion. The results obtained provide the possibility to identify the mentioned raw material, as an individual, and in addition, in a complex multicomponent phytocomposition.

Optically active persistent luminescence in supramolecular nanoassemblies constructed from entirely achiral building blocks

Optically active persistent luminescent materials have attracted significant attention due to their distinctive luminescent characteristics and ability to exhibit rich circular polarization information. Despite extensive efforts to develop circularly polarized persistent luminescence (CPPL) materials using chiral molecules or polymers, fabricating CPPL materials from achiral units remains a big challenge. In this work, we introduce an efficient co-assembly strategy to create CPPL materials using entirely achiral organic molecules. The optical activities of co-assembled complexes are attributed to structural chirality, which arises from chiral nanohelices formed during symmetry breaking in the self-assembly process of C3-symmetric molecules. Achiral molecules with long-lasting phosphorescence can adhere to these chiral nanostructures via hydrogen bonding, and during the drying phase, form nanocrystals that align along helical fibers, resulting in circularly polarized, long-lasting phosphorescence. Enhanced CPPL efficiency, ranging from blue to yellow with a dissymmetry factor over 1.2 × 10−2 and lifetime of up to 0.6 s at room temperature, is achieved through hydrogen bonding driven co-assembly. Additionally, the CPPL spectra of these co-assemblies are captured using a homemade time-resolved circularly polarized long afterglow detection platform. This study not only presents a new approach for the high-efficiency design of CPPL materials from achiral building blocks but also significantly broadens the research possibilities in real-time CPPL analysis, offering a horizon in the exploration of CPPL materials.

Robust red-emitting glass phosphors with high color purity achieved through a novel energy transfer pathway in Pr3+/Sm3+ co-activation

For the first time, a series of Pr3+/Sm3+ co-activated Multicomponent Borosilcate glasses were prepared by melt-quench technique with a fixed concentration of Pr3+ ions (0.5 mol%) and varied concentrations of Sm3+ ions (0.1–1 mol%). An energy transfer route is predicted from the spectral overlap diagram of absorption band (Pr3+:3H4→1D2) and emission (Sm3+:4G5/2→6H5/2, 4G5/2→6H7/2) bands of the singly doped glasses. A comprehensive analysis of photoluminescence features imparted by the Pr3+/Sm3+ co-activation in Multicomponent Borosilcate glasses was investigated with 402 and 444 nm excitation wavelengths and confirmed the existence of energy transfer from Pr3+ to Sm3+ ions with red light emission of high color purity (100 %). Decay profiles and colorimetry analysis further revealed that this dazzling red luminescence feature, achieved via novel energy transfer pathways in the as-prepared glasses, could be useful for red emission applications.

Luminescence and scintillation characteristics of Ce3 + and Tb3+ co-doped SiO2 fiber for low-dose gamma radiation

Ce3+ and Tb3+ co-doped SiO2 optical fibers (SCTF) were prepared using the modified chemical vapor deposition method. The optical and structural properties of the SCTF samples were investigated using refractive index measurements, energy dispersive X-ray spectroscopy, photoluminescence (PL), transmission loss, and fluorescence lifetime. The SCTF was fabricated into a radiation dosimeter, and its gamma radioluminescence (RL) response was studied over a dose rate range of 424.27–2095.16 mGy/min and a total dose range of 424.27–2095.16 mGy. The radiation response exhibited good linearity. To verify the repeatability of the dosimeter, repeated experiments were conducted at a fixed dose rate of 2095.16 mGy/min. The results demonstrated that the dosimeter has good repeatability. An energy transfer model in SCTF was established, and Ce/Tb-doped SiO2 was prepared using a sol-gel method. The energy transfer model was verified by measuring its PL spectrum. The above results verify that the SCTF shifts the RL to a longer wavelength due to the energy transfer of radioluminescence, which is more conducive to the remote sensing and transmission of SiO2 optical fiber in an irradiated environment.

Trap Assisted Dynamic Mechanoluminescence Toward Self-Referencing and Visualized Strain Sensing.

Strain sensors utilizing mechanoluminescent (ML) materials have garnered significant attention and application due to their advantages, such as self-powering, non-contact operation, and real-time response. However, ML-based strain sensing techniques typically rely on the establishing of a mathematical relationship between ML intensity and mechanical parameters. The absolute ML intensity is vulnerable to environmental factors, which can result in measurement errors. Herein, an color-resolved visualized dynamic ML and self-referencing strain sensing is investigated in Ca9Al(PO4)7: Tb3+, Mn2+. By analyzing the ML performance under various mechanical stimulations and adjustable strain parameters, a relationship between strain and the ML intensity ratio of Tb3+/Mn2+ is aimed to bed established. This will enable the development of a self-referencing and visualized strain sensing technology. Through a comparison of luminescence characteristics under continuous mechanical stimulation (stretching) and continuous X-ray irradiation, it is discovered that the ratiometric dynamic ML is primarily driven by the dynamic filling and continuous release of carriers form traps, which compensates for the ML of Mn2+. Leveraging the self-referencing and color-resolved (from green to red) visualized ML characteristics, an application scenario for monitoring human joint movement is developed. This approach offers new insights into the use of dynamic ML materials in strain sensing and human-machine interaction.

Impact of exciton fine structure on the energy transfer in magic-sized (CdSe)13 clusters

Magic-sized (CdSe)13 clusters (MSCs) represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure. The characteristic photoluminescence is composed of exciton bandgap emission and a spectrally broad mid-gap emission related to surface defects. Here, we report on a thermally activated energy transfer from fine-structure split exciton states to surface states by using temperature dependent photoluminescence excitation spectroscopy. We demonstrate that the broad mid-gap emission can be suppressed by a targeted Mn-doping of the MSC leading to the characteristic orange luminescence of the 4T1 → 6A1 Mn2+ transition. The energy transfer to the Mn2+ states is found to be significantly different than the transfer to the surface defect states, as the activation of the dopant emission requires a spin-conserving charge carrier transfer that only dark excitons can provide.

Tuning the bandgap and photoluminescence properties of Ge/Al2O3 multilayer thin films using annealing and ion beam irradiation

Abstract The present work reports high energy ion beam irradiation induced modifications in Ge/Al2O3 multilayers (MLs). Ge and Al2O3 multilayer thin films were deposited using the electron beam evaporation technique. Afterward, the as-deposited films were annealed using Rapid thermal annealing (RTA) at different temperatures ranging from 500 to 800°C under high vacuum. At a constant fluence of 5×1012 ions /cm2, the annealed films were subjected to irradiation with 80 MeV Ag ions. X-ray diffraction patterns show the crystalline nature of films that were annealed above 500°C, and the increase in crystallite size of Ge nanocrystals from 4.5 to 5.7 nm is observed for annealed samples. After Ag ion irradiation, the crystallinity of the films deteriorates. The crystallinity and optical bandgap are found to vary with Ag ion irradiation. The band gap of annealed films decreased from 1.1 to 0.97 eV with increase in crystallite size. The band gap of irradiated samples increased than that of pristine films. In addition, photoluminescence (PL) measurements were carried out to investigate the luminescence characteristics of annealed and irradiated multilayer films, and a wide emission band in the visible region was observed. The basic mechanism for tailoring the optical band gap and PL emission using RTA and ion irradiation is discussed.


Ultra-broadband bismuth-doped fiber amplifier with 170 nm bandwidth using a two-stage configuration.

We present a two-stage bismuth-doped fiber amplifier (BDFA) that achieves ultra-broadband amplification from 1280 to 1480 nm. The two-stage BDFA is designed to limit the reabsorption of bismuth-doped silica fiber (BDSF) by high-power pumps pulled fluorescence. A peak gain of 37.9 dB was obtained at 1340 nm for a -23 dBm input signal, with >23 dB gain from 1300 to 1470 nm. Furthermore, the gain of 40.0 and 36.1 dB was measured at small signal power for 1340 and 1430 nm, respectively, and the 3 dB saturation output power reaches 16.0 and 14.6 dBm, respectively. In addition, the basic properties and luminescence characteristic of two types of BDSFs fabricated using atomic layer deposition and modified chemical vapor deposition technique worked in the configuration were investigated.

High-throughput point-of-care serum iron testing utilizing machine learning-assisted deep eutectic solvent fluorescence detection platform

In this study, a high-throughput point-of-care testing (HT-POCT) system for detecting serum iron was developed using a hydrophobic deep eutectic solvent (HDES) fluorescence detection platform. This machine learning-assisted portable platform enables intelligent and rapid detection of trace iron ions. Blue fluorescent hydrophobic carbon quantum dots (CQDs) were synthesized using the solvothermal method. The CQDs exhibit a notable quantum yield (QY) of 36.6%, demonstrating exceptional luminescent characteristics and precise, sensitive detection capabilities for Fe3+ ions. By incorporating CQDs into specially filtered HDESs, this blend serves a dual function of concentrating iron ions from the sample and facilitating their detection. The collaboration between the two enhances the fluorescence detection signal significantly, while reducing interference from hydrophilic substances. The limit of detection can be as low as 33 nM. The principles of synthesizing HDESs and the process of extracting Fe3+ using HDESs fluorescence detection system were modeled using density functional theory (DFT). As the concentration of Fe3+ increases, the fluorescence signal detected from the sample decreases, accompanied by visible color changes when exposed to ultraviolet light. The machine learning-assisted portable platform is designed to capture fluorescence images of samples directly. The application developed using the YOLOv8 algorithm efficiently analyzes multiple samples in single or multiple images, simultaneously extracting color data from each sample and determining the concentration of iron ions. The Relative Standard Deviations (RSDs) for both single-sample and multi-sample tests were less than 10%. The machine learning-assisted portable platform provides a reliable method for detecting trace iron ions.

Multifunctional Dy3+ Complexes with Triphenylmethanolates: Structural Diversity, Luminescence, and Magnetic Relaxation.

The coordination environment of magneto-luminescent Dy3+-based Single-Molecule Magnets (SMM) is a crucial factor influencing both magnetic and luminescent properties. In this work, we explore how triphenylmethanolate (Ph3CO-), in combination with other ligands, can modulate the structure and, therefore, the magnetic properties of Dy3+-based SMM. Using triphenylmethanolate in combination with THF and pyridine (Py) as co-ligands, we synthesized a series of mononuclear cis-[Dy(OCPh3)2(THF)4][BPh4]·(2,6-Me2C5H3N) (1), trans-Dy(OCPh3)3(THF)2 (2), fac-Dy(OCPh3)3(py)3 (3) and dinuclear [(Ph3CO)Dy(THF){(μ2-Cl)2Li(THF)2}μ2-Cl]2 (4) complexes where the Dy3+ ion presents five- or six-coordinate geometries. Dinuclear compound 4 exhibits a genuine SMM behavior with a relatively high energy barrier of 421 cm-1, while mononuclear complexes 1-3 are field-induced SMM. These complexes also present Dy3+-characteristic luminescence, highlighting their multifunctional character.

Investigating Quantum Confinement and Enhanced Luminescence in Nanoporous Silicon: A Photoelectrochemical Etching Approach Using Multispectral Laser Irradiation

This study explores electrochemical etching to form porous silicon (PS), which has diverse biomedical and energy applications. Our objective is to gain new insights and drive significant scientific and technological advancements. Specifically, we study the effect of electrochemical etching of P-type silicon using laser irradiation in a hydrofluoric acid (HF) solution. The formation of the nanoscale PS structure can be successfully controlled by incorporating laser irradiation into the electrochemical etching process. The wavelength and power of the laser influence the formation of nanoporous silicon (NPS) on the surface during the electrochemical etching process. The luminous flux is monitored with the help of a customized integrating sphere system and an LED-based excitation source to find the light flux values distributed across the P-type nanolayer PS wafers. Analysis of the NPS and luminescence characteristics shows that the laser bandwidth controls the band gap energy absorption (BEA) phenomenon during the electrothermal reaction. It is demonstrated that formation of the NPS layer can be controlled in this combined laser irradiation and electrochemical etching technique by adjusting the range of the laser wavelength. This also allows for further precise control of the numerical trend of the luminous flux.

Thermal and Luminescent Properties of Multi-Ligand Complexes of Europium(III) with Pyrazine-2-carboxylic Acid

Eu(III) compounds with pyrazine-2-carboxylic acid and nitrogen- and phosphorus-containing neutral ligands were synthesized. Using the methods of chemical elemental and thermal analysis and IR spectroscopy, the composition of the complexes and the method of coordination of carboxylate ions were established. The most thermally stable compounds have been identified. The luminescent characteristics of complex compounds have been studied. It was found that the maximum luminescence intensity is characteristic of europium(III) pyrazinate with triphenylphosphine oxide. The morphological structure and dispersion of the complexes were determined.

Tri‐ and Hexanuclear Gold(I) Systems Based on Tribenzotriquinacene

A tridentate trimethylstannyl substituted alkyne based on the tribenzotriquinacene (TBTQ) scaffold has been transformed into several gold(I)phosphane complexes by tin‐gold exchange. While the molecular structures of the gold(I) derivatives with less bulky trimethyl and dimethylphenylphosphane ligands exhibit intermolecular aurophilic interactions, the sterically demanding triphenylphosphane ligands inhibit the occurrence of Au···Au contacts. In addition, a hexanuclear gold(I) system was synthesised by terminal functionalisation of the hexaalkynyl TBTQ. Investigations of the photophysical properties of the gold(I)phosphane TBTQ compounds revealed their luminescent character at room temperature.

Nonaqueous Contact-Electro-Chemistry via Triboelectric Charge.

Mechanochemistry revolutionizes traditional reactions through mechanical stimulation, but its reaction efficiency is limited. Recent advancements in utilizing triboelectric charge from liquid-solid contact electrification (CE) have demonstrated significant potential in improving the reaction efficiency. However, its efficacy remains constrained by interfacial electrical double-layer screening in aqueous solutions. This study pioneered chemistry in nonaqueous systems via CE for catalysis and luminescence. Density functional theory simulations and experiments revealed varying electron transfer capabilities and chemoselectivity of CE across different solvents. Phenol degradation via CE in dimethyl sulfoxide (DMSO) exhibited a rate over 40 times faster than that of traditional mechano-driven chemistry. A more intuitive comparison revealed that CE degradation of phenol in DMSO exhibits a 30-fold rate improvement compared to deionized water, where the degradation remains incomplete. Luminol oxidation by radicals generated solely via CE in DMSO eliminates the dependence on traditional catalysts and side reactions, establishing a pure and simple system for investigating the reaction mechanisms. A high and stable luminescence characteristic was maintained for 3 months, enhancing the imaging accuracy and stability exponentially. This study underscores the impact of triboelectric charge on reaction efficiency and chemoselectivity, establishing a new paradigm in nonmetal catalysis, mechanoluminescence, and providing profound insights into reaction kinetics.

Enhancing luminescence in bio-cellulose derived carbon microcoils through europium incorporation: A pathway to high-performance UV luminophores

Bio-cellulose derived carbon microcoils (BCMC) are renowned for their distinctive helical structure, sustainability, and renewability, making them highly versatile for applications such as microwave absorption, water purification, and energy storage. Despite extensive research on carbon microcoils or nanocoils, the luminescent properties of BCMC remain largely unexplored. This study delves into the luminescence characteristics of BCMC extracted from recycled tea leaves, revealing a broad spectrum of multicolor emissions including ultraviolet (355 nm, 396 nm), blue (467 nm), and near-infrared (764 nm). These emissions are attributed to BCMC's distinctive three-dimensional helical configuration and its rich array of oxygen-containing functional groups. Incorporating europium further tailors the photoluminescent properties of BCMC, significantly amplifying UV and blue light emissions. Additionally, annealing improves UV emission, showcasing the potential for enhanced luminescence performance. This research not only deepens our understanding of sustainable luminescent materials but also paves the way for developing advanced UV luminophores with diverse applications.

Synthesis and Characterization of Boron Nitride Thin Films Deposited by High-Power Impulse Reactive Magnetron Sputtering.

In the present research, hexagonal boron nitride (h-BN) films were deposited by reactive high-power impulse magnetron sputtering (HiPIMS) of the pure boron target. Nitrogen was used as both a sputtering gas and a reactive gas. It was shown that, using only nitrogen gas, hexagonal-boron-phase thin films were synthesized successfully. The deposition temperature, time, and nitrogen gas flow effects were studied. It was found that an increase in deposition temperature resulted in hydrogen desorption, less intensive hydrogen-bond-related luminescence features in the Raman spectra of the films, and increased h-BN crystallite size. Increases in deposition time affect crystallites, which form larger conglomerates, with size decreases. The conglomerates' size and surface roughness increase with increases in both time and temperature. An increase in the nitrogen flow was beneficial for a significant reduction in the carbon amount in the h-BN films and the appearance of the h-BN-related features in the lateral force microscopy images.

Thermoluminescence characteristics of BeO doped with Si, Mg, and Cr: Density functional theory calculations and One trap – One recombination center model simulations

The incorporation of first principles computational methods in Thermoluminescence (TL) enables the comprehensive investigation of the luminescent characteristics exhibited by solid materials. These calculations offer valuable insights into the electronic structures and thermal behavior, providing a deeper understanding of the underlying mechanisms. Density Functional Theory (DFT) is a powerful tool for predicting the electronic structure properties, as the Density of States (DOS) of materials. By theoretically depicting the electronic states arising from electron transitions, the present study focuses on the DFT study of undoped BeO and of BeO with substitutional Si4+,Mg2+ and Cr3+,Mg2+ doping, and the connection of TL emission caused by recombination of electrons in centers, as outlined in the One Trap – One Recombination (OTOR) center model. This approach offers essential details regarding the origins of electron traps, facilitating a deeper exploration of the intrinsic contribution of DFT in Stimulated Luminescence (SL) analysis.

Cr3+-Activated Deep Trap Electron-Trapping Biphasic Mixture of Zn (Al,Ga)2O4 and Zn2GeO4 for Multilevel Information Storage by Trap Multiplexing and Wavelength Multiplexing.

Double wavelength emitting phosphors with hypersensitive thermal response are important for optical/thermal sensors and multiplexing optical data storage technology. However, it is a daunting challenge to develop multicolor electron-trapping materials with superheat sensitivity and anomalous quenching luminescence characteristics for information storage. Here, based on the selection of host lattice and the control of doping ion types, we have designed Mn2+- and/or Cr3+-activated persistent materials with excellent fluorescence properties. Among these phosphors, Mn,Cr co-activated biphasic mixture exhibits not only sensitive anomalous thermosensitive fluorescence properties but also multicolor and multimode fluorescence emission characteristics derived from Mn and Cr simultaneously. The corresponding multimode fluorescence mechanism is proposed based on afterglow energy transfer and deepening trap effect. Especially, based on the excellent fluorescence performances, these phosphors as information storage medium demonstrate multilevel information storage by a combination of the trap multiplexing and wavelength multiplexing technologies. The study here provides not only the ideas for designing and synthesizing new electronic materials but also a material foundation for the fourth generation of optical information storage and encryption.