Luminescence Characteristics Research Articles

Graphene oxide based Gd2O3:Eu3+ nanocomposites: A multifaceted approach to advanced energy storage and bio sensing applications

This investigation delves into the synthesis and characterization of graphene oxide (GO) based gadolinium oxide europium-doped nanocomposites (GO-Gd2O3:Eu3+ (1 mol %) NCs), emphasizing their utility in super capacitors and biosensors. Utilizing a hydrothermal process with graphene oxide, the study enhances Gd2O3 energy storage capabilities, complemented by europium’s luminescent features for real-time monitoring. Structural, morphological, and chemical analyses by X-ray diffraction (XRD), Transmission electron microscopy (TEM), and electrochemical (CH) Analyzer, reveal promising electrochemical performance, reaching specific capacitance values of 512.14 Fg−1 in 1 M H2SO4 electrolyte. The electrodes exhibit commendable rate capability, cycling stability, and a Coulombic efficiency of 94.54 % after 5000 galvanostatic charge–discharge (GCD) cycles. Impedance spectroscopy confirms low charge transfer resistance, contributing to enhanced electrochemical performance. Moreover, the integration of europium imparts luminescent properties, positioning these super capacitors for integrated sensing applications. The luminescence allows real-time monitoring, showcasing the versatility of GO-Gd2O3:Eu3+ based NCs for future technologies, particularly in smart sensors, wearables, and integrated electronics.

Impact of blue-shifted effective joint density of electronic states on the photoluminescence of nanostructured silicon

Light emission from nanostructured silicon has triggered tremendous research interest for three decades. Yet, the exact mechanism of photoluminescence from silicon-based nano-systems is still not completely understood. It is generally believed that quantum confinement and surface chemistry play a combined role in determining the luminescence characteristics on nano silicon. In this work, we show that the evolution of electron-hole effective joint density of states, resulting from the relaxation of k-selection rule, can account for the much-observed temperature dependent shift of the luminescence spectra of nanostructured silicon. Deconvolution of the emission characteristics reveals three distinct radiative recombination channels that can be attributed to band-to-band, band-to-trap and trap-to-trap transitions. At temperatures below ∼200 K, the peak due to band-to-band transition exhibit a nearly linear blue shift with increasing temperature while at higher temperatures this trend is reversed. The rate of variation of emission peak energy with temperature is also found to be dependent on average crystallite size. These results are explained in terms of shift in the effective joint density of state function of photogenerated electron-hole pairs. The shift provides experimental evidence of the pseudo-direct transitions in the quantum-confined nanostructure of silicon.

Color tunable emission and temperature sensing performance in Dy3+/Sm3+ co-doped transparent oxyfluoride glass ceramics containing K3YF6 nanocrystals

This paper presents the preparation and characterization of transparent oxyfluoride glass ceramics (GCs) that contain nanocrystals of K3YF6 co-doped with Dy3+ and Sm3+. The study investigates the luminescence characteristics, the process of energy transfer (ET) and the behavior of the ratio-metric temperature sensing. The formation of well-defined nanocrystals of K3YF6 in the glass substrate was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By varying Sm3+ concentration, a tunable emission ranging from pale yellow to orange-red was observed. Energy transfer from Dy3+ to Sm3+ ions was confirmed through fluorescence spectra and decay curves. Sample K3YF6, containing 0.5 mol%Dy3+/1.2 mol%Sm3+, showed an absolute sensitivity (Sa) of 0.635% K−1 and relative sensitivity (Sr) of 0.401% K−1. These findings underscore the promising applications of K3YF6: Dy3+, Sm3+ GCs in multicolor displays and high-performance temperature sensing devices.

Underestimated single-aliquot quartz OSL ages of Late-Pleistocene sediments due to the dominance of medium component

Optically stimulated luminescence (OSL) dating technique has increasingly been employed to establish chronologies for coastal deposits since the Late Pleistocene. However, the commonly used single-aliquot quartz OSL dating method may yield inaccurate ages due to factors such as partial bleaching, luminescence characteristics, and the age limit of quartz. In this study, taking the Yangtze River Delta (YRD) as an example, single-aliquot and single-grain OSL dating using varying grain-sized quartz and K-feldspar were cross-checked to establish appropriate dating method for Late-Pleistocene sediments in coastal areas. The quartz OSL signals of the upper 24 m Holocene sediments were dominated by the fast component, and the ages obtained through OSL and AMS 14C ages agree. Conversely, the lower 24–91 m section, representing the last glacial-interglacial cycle, reveals a notable underestimation of quartz OSL ages, with a maximum underestimation of 250%, attributed to the influence of signal components. For samples within the dating limit of quartz (less than 70 ka), the single-grain method effectively mitigates the issue associated with the signal component. Single-grain K-feldspar technique proves valuable for accurately determining the age of those older sediments exceeding 70 ka. Through cross-checking between different OSL dating methods, sediments initially attributed to marine isotope stage (MIS) 3 (36–60 ka) are re-identified as deposited during MIS 5 (80–130 ka). This study highlights the necessity of assessing the variability in luminescence characteristics before applying a single OSL dating protocol to all samples from different sedimentary facies within a single core.

Multistimuli‐Responsive Luminescent Porous Organic Polymers with Chiroptical Properties and Acid‐Induced Degradation

Comprehensive SummaryPorous organic polymers (POPs) have attracted great attention in past decades. Although diverse functional POPs have been developed, multistimuli‐responsive POPs with excellent aggregate‐state luminescence together with good chiroptical properties have rarely been reported. Herein, two pairs of Salen‐type enantiomeric POPs with multistimuli‐responsive luminescence and chiral features were designed and synthesized by facile polycondensation reactions between polyfunctional aggregation‐induced emission luminogen (AIEgen)‐containing salicylaldehyde derivatives and chiral diamines. With Salen units in polymer backbones as tetradentate ligands, a series of POP‐metal complexes were further prepared. The obtained POPs and metal complexes show good porosity, high thermal stability, and obvious circular dichroism signals. Moreover, benefiting from the coexistence of AIEgen and Salen units in polymer structures, these POPs exhibit excellent luminescence performance in aggregate states and tunable fluorescence behaviors in response to external stimuli of Zn2+ ion, mechanical forces, organic solvent, and acids. Due to the dynamic feature of Schiff base C=N bonds, the present POPs can efficiently undergo hydrolysis reactions under strong acidic conditions to reproduce the AIEgen‐ containing monomers, and such an acid‐induced degradation process can be directly visualized and dynamically monitored via fluorescence variation. These properties collectively make the POPs candidate materials for applications in heterogeneous asymmetric catalysis, fluorescence sensing, biomedicine, etc.

Luminescent/Temperature-Sensing Properties of Multifunctional Rare-Earth Upconversion Kevlar Nanofiber Composite under 1550 nm.

The unique properties of upconversion nanoparticles (UCNPs) are responsible for their diverse applications in photonic materials, medicine, analytics, and energy conversion. In this study, water-soluble rare-earth upconversion nanomaterials emitting green, yellow, and red light under 1550 nm excitation were synthesized. These nanomaterials were then integrated into water-soluble Kevlar nanofibers (KNFs) to fabricate ultra-thin composite films exhibiting favorable mechanical characteristics. The characterization of the products, along with their luminescent, mechanical, and temperature-sensing properties, was examined. The results indicate that the composite material exhibited varying colors based on the doped nanoparticles when subjected to 1550 nm excitation. The composite showed highly sensitive temperature-sensing properties, excellent luminescent characteristics, and superior mechanical strength. This study suggests that KNFs are effective carriers of UCNPs. This study offers a reference for the utilization of rare-earth upconversion in anti-counterfeiting displays, wearable health monitoring, and remote temperature sensing.

Luminescence features of Dy3+-doped B2O3 and B2O3-P2O5 hosts for optical devices: the linear and non-linear optical studies

Luminescence features of Dy3+-doped B2O3 and B2O3-P2O5 hosts for optical devices: the linear and non-linear optical studies

Synthesis, coating, and application of a novel cadmium-free red perovskite quantum dot for micro LED technology

This study successfully creats cadmium-free red perovskite QDs through a chemical solution method. The CsPb(Br0.2/I0.8)3 QDs were synthesized by adjusting the bromine-to-iodine ratio and was customized for red emission wavelengths. The QDs were coated with silicon dioxide (SiO2) using a sol-gel method to protect their luminescent characteristics from moisture and oxygenand enhancing interface modification. Finally, pixelated red perovskite QDs were applied to a blue light display as a color conversion layer. The excess blue light penetration was addressed using a 23-layer distributed Bragg reflector (DBR), which redirected surplus blue light back to the QDs, amplifying red light by 30% with a reduced blue light penetration rate of 0.5%. Future research may involve achieving a regionally colored display by precisely aligning and bonding pixelated perovskite QDs, processed for red and previously studied green quantum dots, onto a pre-prepared blue light display.

Self-Assembly-Induced Enhancement of Cathodic Electrochemiluminescence of Copper Nanoclusters for a Split-Type Matrix Metalloproteinase 14 Sensing Platform.

The unique optoelectronic and tunable luminescent characteristics of copper nanoclusters (Cu NCs) make them extremely promising as luminophores. However, the limited luminescence intensity and stability of Cu NCs have restricted their application in the field of electrochemiluminescence (ECL). Herein, a self-assembly-induced enhancement strategy was successfully employed to enhance the cathodic ECL performance of flexible ligand-stabilized Cu NCs. Specifically, Cu NCs form ordered sheetlike structures through intermolecular force. The restriction of ligand torsion in this self-assembled structure leads to a significant improvement in the ECL properties of the Cu NCs. Experimental results demonstrate that the assembled nanoscale Cu NC sheets exhibit an approximately three-fold increase in cathodic ECL emission compared to the dispersed state of Cu NCs. Furthermore, assembled nanoscale Cu NCs sheets were utilized as signal probes in conjunction with a specific short peptide derived from the catalytic structural domain of matrix metalloproteinase 14 (MMP 14) as the identification probe, thereby establishing a split-type ECL sensing platform for the quantification of NMP 14. The investigation has revealed the exceptional performance of assembled nanoscale Cu NCs sheets in ECL analysis, thus positioning them as novel and promising signal probes with significant potential in the field of sensing.

Aromatimide tetracarboxylate metal-framework materials: Fluorescence sensing application towards NACs and small drug molecules

Three multifunctional fluorescent Metal-Organic Framework (MOF) sensors are synthesized based on N, N’-bis(3, 5-dicarboxyphenyl)isophthalic diimide (H4BDCPPI) with Zn, Cu, and Cd ions. Structural analysis shows that although using the same organic conjugated aromatic imide tetracarboxylic acids ligand, their corresponding structures are different. Based on luminescence characteristics of the organic components, they exhibit good luminescent properties. They can sensitively detect nitro aromatic compounds (p-nitrophenol (PNP), 2,4-dinitrophenol (DNP) and 2,4,6-trinitrophenol (TNP)) and small drug molecules (colchicine and balsalazide disodium) with low limit of detection. The complex 1 is more sensitive for detection of TNP, compared to the other complexes. The mechanism of fluorescence sensing is proposed in detail based on analyses of PXRD, fluorescence lifetimes, and UV–vis spectra. This study explores the potential of MOFs based on H4BDCPPI in the field of fluorescence sensing for the first time, laying the theoretical foundation for application of complexes with conjugated aromatic imide tetracarboxylic acids.

On the Lanthanide Effect on Functional Properties of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 Ceramic.

The beneficial effects of lanthanide incorporation into 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (BNT-BT) matrix on its functional properties were investigated. The conventional solid-state method was used for synthesizing samples. The structural refinement revealed that all samples crystallized in R3c rhombohedral symmetry. Raman spectroscopy study was carried out using green laser excitation and revealed that no clear perceptible variation in frequency is observed. Dielectric measurements unveiled that the introduction of rare earth obstructed the depolarization temperature promoted in BNT-BT, the diffusive phase transition decreasing with increasing lanthanide size. Only dysprosium addition showed comparable diffusion constant and dielectric behavior as the unmodified composition. Further, the comparison of the obtained ferroelectric hysteresis and strain-electric field loops revealed that only Dy-phase exhibited interesting properties comparing parent composition. In addition, the incorporation of lanthanides Ln3+ into the BNT-BT matrix led to the development of luminescence characteristics in the visible and near infrared regions, depending on the excitation wavelengths. The simultaneous occurrence of photoluminescence and ferroelectric/piezoelectric properties opens up possibilities for BNT-BT-Ln to exhibit multifunctionality in a wide range of applications.

The Characteristics of Luminescence from High-Temperature- and High-Pressure-Treated Diamonds

High-temperature and high-pressure (HTHP)-treated diamonds have attracted attention all over the world due to their vivid colors. In order to explore a new method for the rapid and non-destructive identification of HTHP-treated diamonds, in this paper, five IaAB-type diamonds yielded in Russia were selected as the research object and treated with HTHP. The HTHP-treated diamonds were investigated by DiamondViewTM, cathodoluminescence, micro-infrared spectrometry (micro-IR), low-temperature photoluminescence (PL) spectrometry, and three-dimensional (3D) fluorescence spectrometry. The results show that under DiamondViewTM and cathode rays, the five samples were all non-phosphorescent with different luminous patterns, such as regular annular bands, multiple groups of intersecting linear stripes, or jagged stripes. In the low-temperature PL spectra, most HTHP-treated diamonds exhibited stronger luminescence peaks at 637 nm compared to 575 nm. But there were also exceptions, such as the purple-red sample showing the opposite luminescence peak. In the 3D fluorescence spectrum of the HTHP-treated diamonds, the fluorescence peak mainly appeared in the range of 440–450 nm, accompanied by a broad band of 350–500 nm and even longer wavelengths. Meanwhile, some samples also exhibited fluorescence peaks at longer wavelengths, such as 353 nm, 676 nm, and 665 nm. These results make it possible to identify HTHP-treated diamonds by using luminescence characteristics, providing a new method for the non-destructive and rapid detection of HTHP-treated diamonds.

Modulating the ESIPT Mechanism and Luminescence Characteristics of Two Reversible Fluorescent Probes by Solvent Polarity: A Novel Perspective.

As reversible fluorescent probes, HTP-1 and HTP-2 have favourable applications for the detection of Zn2+ and H2S. Herein, the impact of solvent on the excited-state intramolecular proton transfer (ESIPT) of HTP-1 and HTP-2 was comprehensively investigated. The obtained geometric parameters and infrared (IR) vibrational analysis associated with the intramolecular hydrogen bond (IHB) indicated that the strength of IHB for HTP-1 was weakened in the excited state. Moreover, structural torsion and almost no ICT behaviour indicated that the ESIPT process did not occur in HTP-1. Nevertheless, when the 7-nitro-1,2,3-benzoxadiazole (NBD) group replaced the H atom, the IHB strength of HTP-2 was enhanced after photoexcitation, which inhibited the twisting of tetraphenylethylene, thereby opening the ESIPT channel. Notably, hole-electron analysis and frontier molecular orbitals revealed that the charge decoupling effect was the reason for the fluorescence quenching of HTP-2. Furthermore, the potential energy curves (PECs) revealed that HTP-2 was more inclined to the ESIPT process in polar solvents than in nonpolar solvents. With a decrease in solvent polarity, it was more conducive to the ESIPT process. Our study systematically presents the ESIPT process and different detection mechanisms of the two reversible probe molecules regulated by solvent polarity, providing new insights into the design and development of novel fluorescent probes.

Photoactivated Circularly Polarized Luminescent Organic Radicals in Doped Amorphous Polymer

AbstractLuminescent organic radicals, especially those with photoactivated circularly polarized luminescence (CPL) features, hold great significance for cutting‐edge optoelectronic applications, but their development still remains a challenge. In this study, we propose a novel strategy to achieve photoactivated CPL radicals by bonding two phosphine centers within an axial chiral system, yielding a compound of R/S‐5,5‐bis(diphenylphosphino)‐4,4′‐bibenzo[d][1,3]dioxole (R/S‐BDP). The photoactivated R/S‐BDP molecules in polymer matrix display a robust quantum yield of 19.8 % and a dissymmetry factor (glum) of 1.2×10−4, marking this work as the first example of photoactivated CPL radicals. Furthermore, the glum is improved to 1.0×10−2 by using a liquid crystal as host. Experimental and theoretical analyses reveal that R/S‐BDP molecules, endowed with double phosphine cores in axial chirality, offer a direct way for intramolecular electron transfer upon photoirradiation. This leads to the generation of radical ionic pairs, which subsequently trigger the donor‐acceptor arrangement through intermolecular electron transfer, thereby resulting in stable radical emission. The extended photoactivated BDP‐F exhibits a remarkably high quantum efficiency of 57.8%. Ultimately, the distinctive photo‐responsive CPL radical luminescence has been successfully used for information displays and anti‐counterfeiting.

Photoactivated Circularly Polarized Luminescent Organic Radicals in Doped Amorphous Polymer.

Luminescent organic radicals, especially those with photoactivated circularly polarized luminescence (CPL) features, hold great significance for cutting-edge optoelectronic applications, but their development still remains a challenge. In this study, we propose a novel strategy to achieve photoactivated CPL radicals by bonding two phosphine centers within an axial chiral system, yielding a compound of R/S-5,5-bis(diphenylphosphino)-4,4'-bibenzo[d][1,3]dioxole (R/S-BDP). The photoactivated R/S-BDP molecules in polymer matrix display a robust quantum yield of 19.8 % and a dissymmetry factor (glum) of 1.2×10-4, marking this work as the first example of photoactivated CPL radicals. Furthermore, the glum is improved to 1.0×10-2 by using a liquid crystal as host. Experimental and theoretical analyses reveal that R/S-BDP molecules, endowed with double phosphine cores in axial chirality, offer a direct way for intramolecular electron transfer upon photoirradiation. This leads to the generation of radical ionic pairs, which subsequently trigger the donor-acceptor arrangement through intermolecular electron transfer, thereby resulting in stable radical emission. The extended photoactivated BDP-F exhibits a remarkably high quantum efficiency of 57.8%. Ultimately, the distinctive photo-responsive CPL radical luminescence has been successfully used for information displays and anti-counterfeiting.

On the Energy Dependence of the PL of RE Ions in LuBO3:RE (RE = Ce, Eu, Gd, or Tb)

LuBO3 crystallizes in the calcite type (CaCO3) structure and is a widely applied inorganic host for luminescent materials and scintillators. Even though many scientific works have been published concerning the optical properties of rare-earth-doped LuBO3, so far, no study of the emission spectra as function of the excitation energy of such orthoborates has been conducted. Therefore, this work elaborates on the photoluminescence of RE-doped LuBO3 with RE = Ce3+, Eu3+, Gd3+, or Tb3+, while an emphasize is laid on the energy dependence of these four luminescent compounds. The reflection, emission, and excitation spectra were additionally recorded, and the particle size distribution was determined. Calcite type LuBO3 was successfully obtained, and the characteristic RE luminescence was observed. Furthermore, the Gd3+-doped sample showed no scintillation due to its monovalence and a sensitizer is required to transfer the respective energy to the Gd3+-activator.

The crystal structure, energy transfer and tunable luminescence properties of NaLaMgWO6:Tm3+, Eu3+ phosphors

A series of NaLaMgWO6:Tm3+, Eu3+ phosphors with color-tunable emission were successfully synthesized by the solid-state reaction method. The crystal structure, luminescence characteristics and energy transfer of NaLaMgWO6:Tm3+, Eu3+ phosphors have been studied. It is observed that Tm3+ singly doped phosphors exhibit intense blue emission at 484 nm, and Eu3+ singly doped phosphors emit red light at 621 nm. The phosphors co-doped with Tm3+, Eu3+ exhibit fluorescence spectra composed by the characteristic emission peaks of Tm3+ ions and Eu3+ ions. A tunable emission color from blue to red can be obtained by adjusting the ratio of the doping concentration of Tm3+/Eu3+, indicating a significant energy transfer from Tm3+ to Eu3+. The energy transfer mechanism between Tm3+→Eu3+ in the NaLaMgWO6:Tm3+, Eu3+ phosphors is proved to be a quadrupole-quadrupole interaction. These results show that NaLaMgWO6:Tm3+, Eu3+ phosphors may have a potential application in white light emitting diodes.

Sr6Y(PO4)5: Nd3+ a novel whitlockite-type phosphor for optical temperature sensing applications: Synthesis and luminescence properties

Active research in science and technology is improving the development of materials that emit infrared light, with the aim of better optical thermometric sensors. In this paper we report the synthesis of a new NIR-emitting phosphate phosphor, Sr6Y(PO4)5:Nd3+ (SYP: Nd3+), at differing concentrations of Nd3+ using a conventional solid-state reaction route. X-ray diffraction analysis showed that the prepared phosphors exhibit a singular phase with a monoclinic whitlockite structure (space group I2/a). SEM images show micrometer-sized particle. FTIR and Raman spectroscopies confirm the presence of PO43− groups in the examined phosphates. Luminescence features, comprising emission spectra, concentration quenching, and fluorescence lifetime, were investigated for the prepared SYP: Nd3+ samples at various Nd3+ doping concentrations. Excited at 808 nm, the phosphors emitted near-infrared light with four distinct bands corresponding to specific Nd3+ transitions from 4F3/2 to (4I9/2,4I11/2 and 4I13/2) and 4F5/2 to 4I11/2, falling within the first and second biological windows (NIR-I and NIR-II). Importantly, Nd3+ emission characteristics are affected by concentration and temperature. The powders' effectiveness as optical temperature sensors using fluorescence intensity ratio (FIR) between coupled and non-coupled levels was researched across 303–473 K, resulting in two distinctive FIR-based temperature sensor strategies employing emissions at 874.8 nm (4F3/2 → 4I9/2) and 956 nm (4F5/2 → 4I11/2) transitions, all within the first biological window for excitation and emission. Using this method, SYP: Nd3+ revealed a notably elevated sensitivity of approximately 1.16 %K−1 at 303 K, surpassing other Nd3+-doped materials when stimulated within the infrared range. These results strongly suggest the prospective applicability of the analyzed material in monitoring the temperature of biological systems.

Study on pH dependent ON/OFF fluorescent switching behaviour of hydrothermally synthesised vanadium disulphide quantum dots (VS2-QDs)

It is fascinating to design and develop an inorganic quantum dot (QDs) which exhibit luminescence features with ion concentration, temperature, and pH sensitivity dependence. Vanadium disulphide (VS2) belongs to the family of transition metal dichalcogenides (TMDs), and is extensively studied owing to its layered characteristics features in sensing and filtrations technology, however, its fluorescence features have not been well studied so far. The current work describes a widely adopted eco-friendly hydrothermal approach for the synthesis of VS2-QDs. The average size of particles was determined to be ∼10 nm by transmission electron microscopy (TEM) and Zetasizer analysis. The synthetic approach adopted here facilitates in situ functionalization of QDs, which results in their high stability in aqueous medium and enhanced sensitivity towards their surroundings. As most of the QDs show the sensitivity towards pH, a thorough investigation of VS2 QDs for their pH dependent photoluminescence has been carried out. The VS2-QDs were discovered to exhibit a remarkable luminescence intensity that was found to be about 11 times higher in basic conditions (pH ∼ 13, QY = ∼4.80%) as compared to that in acidic conditions (pH ∼ 1, QY = ∼1.10%). The root cause of this ON/OFF florescence flipping may be related to the functional groups (such as −SO42−, −NH2, OH−, etc.) attached over the surface of QDs, acid etching, and protonation–deprotonation process. This paper highlights the pH dependent switching behaviour of VS2-QDs that could offer valuable information for designing a futuristic pH-based device for biomedical applications.

Luminescence characterization of rare earth (RE = Tb, Dy, Eu) ions activated Ca8NaGd(PO4)6F2 halophosphor synthesis by modified Pechini method

Luminescence characterization of rare earth (RE = Tb, Dy, Eu) ions activated Ca8NaGd(PO4)6F2 halophosphor synthesis by modified Pechini method