Green Emission Research Articles

Inhibiting the Appearance of Green Emission in Mixed Lead Halide Perovskite Nanocrystals for Pure Red Emission.

Mixed halide perovskites exhibit promising optoelectronic properties for next-generation light-emitting diodes due to their tunable emission wavelength that covers the entire visible light spectrum. However, these materials suffer from severe phase segregation under continuous illumination, making long-term stability for pure red emission a significant challenge. In this study, we present a comprehensive analysis of the role of halide oxidation in unbalanced ion migration (I/Br) within CsPbI2Br nanocrystals and thin films. We also introduce a new approach using cyclic olefin copolymer (COC) to encapsulate CsPbI2Br perovskite nanocrystals (PNCs), effectively suppressing ion migration by increasing the corresponding activation energy. Compared with that of unencapsulated samples, we observe a substantial reduction in phase separation under intense illumination in PNCs with a COC coating. Our findings show that COC enhances phase stability by passivating uncoordinated surface defects (Pb2+ and I-), increasing the formation energy of halide vacancies, improving the charge carrier lifetime, and reducing the nonradiative recombination density.

Sb3+ dopant triggered highly efficient emission in zero-dimensional organic-inorganic hybrid metal halides.

Hybrid luminescent metal halides have attracted considerable attention for their structural diversity and versatility in photonic applications. Herein, we fabricate Sb3+ doped organic-inorganic hybrid metal halides (DMA)2CsInCl6 (DMA = [CH3NH2CH3]+) single crystal. Under ultraviolet light excitation, the crystals yield bright green emission at 550 nm with near-unity photoluminescence quantum efficiency (PLQY), which is attributed to the strong electronegativity and ns2 lone pairs of Sb3+ dopants. Given the slender rod-shaped semblance, bright green emission, near-unity PLQY, and large Stokes shift, Sb3+-doped (DMA)2CsInCl6 allows the potential optical waveguide applications.

Caged AIEgens: Multicolor and White Emission Triggered by Mechanical Activation.

Aggregation-induced emission luminogens (AIEgens) that respond to mechanical force are increasingly used as force probes, memory devices, and advanced security systems. Most of the known mechanisms to modulate mechanoresponsive AIEgens have been based on changes in aggregation states, involving only physical alterations. Instances that employ covalent bond cleavage are still rare. We have developed a novel mechanochemical uncaging strategy to unveil AIEgens with diverse emission characteristics using engineered norborn-2-en-7-one (NEO) mechanophores. These NEO mechanophores were covalently integrated into polymer molecules and activated in both the solution and solid states. This activation resulted in highly tunable fluorescence upon immobilization through solidification or aggregation, producing blue, green, yellow, and orange-red emissions. By designing the caged and uncaged forms as donor-acceptor pairs for Förster resonance energy transfer (FRET), we achieved multicolor mechanofluorescence, effectively broadening the color spectrum to include white emission. Additionally, we computationally explored the electronic structures of activated NEOs, providing insights into the observed regiochemical effects of the substituents. This understanding, together with the novel luminogenic characteristics of the caged and activated species, provides a highly tunable reporter that traces progress with continuous color evolution. This advancement paves the way for future applications of mechanoresponsive materials in areas like damage detection and bioimaging.

Suppressed concentration quenching and tunable photoluminescence in Eu2+-activated Rb3Y(PO4)2 phosphors for full-spectrum lighting

Highly efficient inorganic phosphors are desirable for lighting-emitting diode light sources, and increasing the doping concentration of activators is a common approach for enhancing the photoluminescence quantum yield (PLQY). However, the constraint of concentration quenching poses a great challenge for improving the PLQY. Herein, we propose a fundamental design principle by separating activators and prolonging their distance in Eu2+-activated Rb3Y(PO4)2 phosphors to inhibit concentration quenching, in which different quenching rates are controlled by the Eu distribution at various crystallographic sites. The blue-violet-emitting Rb3Y(PO4)2:xEu (x = 0.1%–15%) phosphors, with the occupation of Rb1, Rb2 and Y sites by Eu2+, exhibit rapid luminescence quenching with optimum external PLQY of 10% due to multi-channel energy migration. Interestingly, as the Eu concentration increases above 20%, Eu2+ prefer to occupy the Rb1 and Y sites with separated polyhedra and large interionic distances, resulting in green emission with suppressed concentration quenching, achieving an improved external PLQY of 41%. Our study provides a unique design perspective for elevating the efficiency of Eu2+-activated phosphors toward high-performance inorganic luminescent materials for full-spectrum lighting.

Synthesis, Structure, Photoluminescence, and Optical Properties of (Co/B) Co‐Doped ZnO Nanoparticles

AbstractCo/B co‐doped ZnO nanoparticles, denoted as Zn0.95‐xBxCo0.05O, are synthesized using the sol–gel method to explore the effects of the defects on optical properties. The stoichiometry is adjusted by varying the doping levels (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05). X‐ray diffraction is employed to analyze the structural characteristics of all Co/B co‐doped ZnO nanoparticles, confirming the presence of a hexagonal Wurtzite structure by assessing the c/a ratios. To investigate structural defects, photoluminescence properties are measured using the Fluorescence Spectrophotometer, revealing violet, blue, green, and red emissions. With the doped of boron (B), a shift from green emission to blue emission occurs, indicating a transformation of singly charged oxygen vacancies (VO+) to VZn vacancies. Fourier Transform Infrared (FTIR) spectra (4000–400 cm−1) are acquired using the Perkin Elmer Spectrum Two FTIR‐ATR spectrophotometer. The surface morphology, crystallite size, and nanoparticle shapes are characterized through Transmission Electron Microscope (TEM) analysis. Elemental compositions are determined using Electron Dispersive Spectroscopy (EDAX). The Shimadzu 2600 UV‐Spectrophotometer is used to examine optical characteristics. The samples' energy band gaps are calculated, and the impact of dopant elements on these optical characteristics is examined. Five different models are used to compute the refractive index.

Regional Load Forecasting Scheme for Security Outsourcing Computation

Smart grids generate an immense volume of load data. When analyzed using intelligent technologies, these data can significantly improve power load management, optimize energy distribution, and support green energy conservation and emissions reduction goals. However, in the process of data utilization, a pertinent issue arises regarding potential privacy leakage concerning both regional and individual user power load data. This paper addresses the scenario of outsourcing computational tasks for regional power load forecasting in smart grids, proposing a regional-level load forecasting solution based on secure outsourcing computation. Initially, the scheme designs a secure outsourcing training protocol to carry out model training tasks while ensuring data security. This protocol guarantees that sensitive information, including but not limited to individual power consumption data, remains comprehensively safeguarded throughout the entirety of the training process, effectively mitigating any potential risks of privacy infringements. Subsequently, a secure outsourcing online prediction protocol is devised, enabling efficient execution of prediction tasks while safeguarding data privacy. This protocol ensures that predictions can be made without compromising the privacy of individual or regional power load data. Ultimately, experimental analysis demonstrates that the proposed scheme meets the requirements of privacy, accuracy, and timeliness for outsourcing computational tasks of load forecasting in smart grids.

Insights into the structural and optical properties of [formula omitted] substituted [formula omitted]

Y2−xTbxMo4O15(x=0,0.1,0.2,0.3,0.4,0.5,0.6,0.7) were successfully synthesized using citrate nitrate combustion method. The characterization techniques used in the present study involves X-ray Diffraction, Raman and FTIR spectroscopy, transmission electron microscopy, UV-Visible spectroscopy and photoluminescence spectroscopy. Structural analysis concludes that the compound crystallizes in monoclinic phase with space group P21/c as confirmed through Rietveld refinement. Diffuse reflectance spectra show a high absorption in the wavelength range 250 – 400 nm and the band gap energy values are evaluated. Photoluminescence spectra show an intense green emission at 545 nm and luminescence quenching of Y2−xTbxMo4O15 occurs beyond the concentration, x=0.4.The critical distance evaluated using Blasse’s expression is 9.24 Å and dipole-dipole interaction exists between the Tb3+ions which is confirmed through Dexter theory. The optimized nanophosphor has internal and external quantum yields equal to 11.01 % and 9.91 %, respectively, and has a decay time of 0.101 ms. These results strongly suggest that the prepared nanophosphor can be used as a green phosphor in pc-LEDs.

Unveiling the Photoluminescence of Carbon Quantum Dots with Controlled Cyan or Green Emission: Synthesis and Photophysics Investigation

Unveiling the Photoluminescence of Carbon Quantum Dots with Controlled Cyan or Green Emission: Synthesis and Photophysics Investigation

Structural and optical investigation of Nb5+-doped Sn3O4 for photoelectrochemical hydrogen production

We report herein, the microwave-assisted hydrothermal (MAH) synthesis of Nb5+-doped Sn3O4 nanoparticles for the photoelectrochemical production of hydrogen (H2). Nb5+ ions inside the Sn3O4 created structural defects, contributing to a local structural disorder, as confirmed by micro-Raman spectra. Photoluminescence spectroscopy indicated the decrease of the violet-blue–green visible emission after adding Nb5+, revealing the formation of alternative energy pathways for the electron/hole recombination. Through the morphological analysis, it was observed that the Nb5+ dopant slightly changed the morphology of nano-petals in Sn3O4. We demonstrate that the 3 % Nb5+ doped-Sn3O4 photoanode presented higher charge carrier mobility, higher photocurrent density, and an impressive H2 production of 1.50 mmol L−1 in a 3 h experiment, compared to the pure Sn3O4 material. The best performance of the Nb5+ doped Sn3O4 nanomaterial could be ascribed to the formation of new energy levels in the Sn3O4 band gap, thereby inhibiting the electron-hole pair recombination and positively affecting the photoelectrochemical response of the doped material.

Enhancing Optical Properties of Zn-Mn Solid Solution Hybrid Halides for Wide Color Gamut Backlight Displays.

Hybrid metal halides display a range of optical properties and hold promise for various applications such as solid-state lighting, anti-counterfeiting measures, backlight displays, and X-ray detection. The incorporation of zinc into (C13H26N)2MnBr4 aims to enhance its structural rigidity and improve its narrow band green light emission properties. The resulting (C13H26N)2ZnBr4 compound exhibits an identical crystal structure to (C13H26N)2MnBr4, indicating the potential for a solid solution of varying Zn and Mn ratios within this structural framework. (C13H26N)2Zn0.2Mn0.8Br4 exhibits significantly enhanced properties, including a photoluminescence quantum yield of 92%, a minimum full width at half maximum of 43nm, and 85% retention of room temperature emission at 420K. Additionally, crystals of (C13H26N)2ZnCl4 and (C7H18N)2ZnX4 (X = Br, I) are synthesized, with (C7H18N)2ZnBr4 displaying luminescent color changes dependent on excitation. (C7H18N)2Zn0.2Mn0.8Br4 demonstrates reversible phase transitions and alterations in optical properties. A white light-emitting diode utilizing (C13H26N)2Zn0.2Mn0.8Br4 and commercial phosphors exhibited a color gamut of 112.2% of the National Television Standards Committee 1931 Standard. This investigation introduces a stable and highly efficient narrow-band green phosphor suitable for displays.

Synthesis, characterization, photophysical and electrochemical properties of new thiadiazole-based olefins for OLED applications

A three–step synthetic approach was employed to synthesize new thiadiazole-based olefins integrating customized functional groups. This methodology consistently delivered satisfactory overall yields ranging from 44 % to 57 %. Comprehensive structural characterization of the synthesized compounds was conducted using FT–IR and NMR (1H, 13C) spectroscopic techniques. The resulting thiadiazole-based olefins exhibited notable UV absorption (λmax = 309–382 nm). Among these, one compound displayed a green emission, while others exhibited red-orange emission, indicating a Stokes shift ranging from 5423 to 6835 cm–1. Their electrochemical behavior was analyzed, revealing an irreversible redox-active response and experimentally determined HOMO and LUMO energy levels indicated an electrochemical gap of <2.32 eV. Our comprehensive investigation, integrating experimental and theoretical methodologies with TD–DFT calculations, aimed to deepen the understanding of the photophysical properties of the target compounds. This comparative analysis between computational results and experimental data highlights the potential of these N-heteroaromatic compounds as organic small-molecule fluorophores for applications in electroluminescent devices.

Stability and photophysical study of bright day light fluorescent material and its fabrication in laser patterning and LED application

Developing aggregation-induced emission (AIE) active highly visible fluorescent dyes is of great importance because of its numerous applications. We have successfully developed and synthesized two novel napthalimide based molecules PU1 and PU2, that exhibit bright greenish yellow in day light and vivid green emission when exposed to UV light. Compounds PU1 and PU2 exhibit variable emission behavior at different solvent polarities. Upon raising the solvent polarity from ether to DMF, emission maxima of PU1 and PU2 underwent a bathochromic shift. Additionally, compounds PU1 and PU2 show signs of AIE, which cause a restriction in intramolecular mobility. A distinct self-assembled structure was generated at 30 % aqueous DMF solution following aggregation, as demonstrated by experiments using dynamic light scattering and field emission scanning electron microscopy. Compounds PU1 and PU2 have been blended with poly(urethane) to develop a polymeric film. Tensile strain studies, and TGA, DSC analyses were used to examine the thermal/mechanical stability of PU films. The photostability of PU1 and PU2 in both solution and polymeric film was examined using a 5-h UV-beam irradiation. Furthermore, in the presence of trifluoroacetic acid, the blended polymeric film and 365 nm LED light coated material exhibits distinct colorimetric and fluorimetric transformations. Finally, laser-induced periodic surface structure (LIPSS) pattern processing on PU1 coated substrates can be extended for optical applications.

Tb3+-doped a zero-dimensional all-inorganic metal halide perovskite scintillator Cs2ScCl5·H2O for X-ray imaging

All-inorganic zero-dimensional (0D) metal halide perovskite materials have been widely studied in solid-state lighting due to their unique optical properties. However, there are few researchs on their potential applications in X-ray imaging. Herein, we synthesized an all-inorganic 0D metal halide perovskite scintillator, Cs2ScCl5·H2O:Tb3+, was prepared by using a hydrothermal method. Upon 240 nm excitation, the emission spectrum of Cs2ScCl5·H2O:Tb3+ is primarily composed of characteristic emissions from Tb3+, with the strongest emission peak at 548 nm. Additionally, under X-ray excitation, it exhibits blue light showing an intense emission band centered at 425 nm due to self-trapped (STE) emission, and a rather weaker green emission caused by energy transfer from STE emission to Tb3+ ions. Based on this, a flexible film prepared by using the as-obtained scintillator Cs2ScCl5·H2O:Tb3+ demonstrates real-time X-ray imaging with a resolution of 9.5 lp mm−1. These results suggest the potential application prospect of Cs2ScCl5·H2O:Tb3+ in X-ray detection and imaging.

Self-assembled fluorescent Zn-MOF with high specific surface area based on the coordination interaction for sensitive detection and selective removal of tetracycline antibiotic in water

As one of most common used antibiotics, tetracyclines (TCs) have been widespread used in many fields. However, the abuse of antibiotics resulted in serious environmental pollutants. Therefore, it is of great significance to develop new materials for rapid detection and effective removal of tetracyclines. In this study, a step-by-step synthesis strategy was adopted to prepare a fluorescent LMOF material Znq2@ZIF-8, and it was well characterized. Znq2@ZIF-8 showed strong green emission and has large specific surface area, with excellent stability and good recyclability. The fluorescence of Znq2@ZIF-8 can be quenched with the addition of tetracycline (TC) in the aqueous environment, demonstrating good selectivity and strong interference resistance, with a limit of detection (LOD) of 0.13 μmol∙L−1. In addition, Znq2@ZIF-8 exhibits excellent adsorption and removal abilities for TC. As a result, Znq2@ZIF-8 enables the simultaneous detection and removal of TC in aqueous environments, providing a solution for future TC pollution in water.

Strategic engineering of cationic systems for spatial & temporal anti-counterfeiting applications in zero-dimensional Mn(II) halides

While spatial and time-resolved anti-counterfeiting technologies have gained increasing attention owing to their excellent tunable photoluminescence, achieving high-security-level anti-counterfeiting remains a challenge. Herein, we developed a spatial-time-dual-resolved anti-counterfeiting system using zero-dimensional (0D) organic–inorganic Mn(II) metal halides: (EMMZ)2MnBr4 (named M−1, EMMZ=1-Ethyl-3-Methylimidazolium Bromide) and (EDMMZ)2MnBr4 (named M−2, EDMMZ=1-Ethyl-2,3-Dimethylimidazolium Bromide). M−1 shows a bright green emission with a quantum yield of 78 %. It undergoes a phase transformation from the crystalline to molten state with phosphorescence quenching at 350 K. Reversible phase and luminescent conversion was observed after cooling down for 15 s. Notably, M−2 exhibits green light emission similar to M−1 but undergoes phase conversion and phosphorescence quenching at 390 K, with reversible conversion observed after cooling down for 5 s. The photoluminescence switching mode of on(green)-off–on(green) can be achieved by temperature control, demonstrating excellent performance with short response times and ultra-high cyclic reversibility. By leveraging the different quenching temperatures and reversible PL conversion times of M−1 and M−2, we propose a spatial-time-dual-resolved photoluminescence (PL) switching system that combines M−1 and M−2. This system enables multi-fold tuning of the PL switch for encryption and decryption through cationic engineering strategies by modulating temperature and cooling time. This work presents a novel and feasible design strategy for advanced-level anti-counterfeiting technology based on a spatial-time-dual-resolved system.

Highly efficient green and blue emitters exhibiting thermally activated delayed fluorescence with 4,6-substituted dibenzo[b,d]thiophene-S,S-dioxide as electron acceptor and their electroluminescent properties

Through attaching electron donors to the 4, 6-positions of dibenzo[b,d]thiophene-S,S-dioxide (DBTDO), three organic emitters (SO-OZ, SO-AD and SO-CZ) with D-A-D configuration have been designed and synthesized. They not only show high thermal stability with decomposition temperature (Td) higher than 460 °C, but also exhibit photoluminescent quantum yield (PLQY) as high as 0.9. Despite that SO-CZ with carbazole unit as electron donor cannot furnish thermally activated delayed fluorescence (TADF) emission, both SO-OZ with 10H-phenoxazine as electron donor and SO-AD bearing electron donor of 9,9-dimethylacridine exhibit typical TADF behaviors due to their small energy difference between S1 and T1 excited states (ΔEST). Critically, SO-OZ can show very fast revers intersystem crossing (RISC) process with rate constant of RISC (kRISC) ca. 1.8 × 106 s−1. The cyclic voltammetry (CV) results indicate their decent electrochemical stability by showing reversible oxidation and reduction processes. When doped into the emission layer of organic light-emitting diodes (OLEDs), they can show good potential as highly efficient emitters, showing electroluminescent efficiencies of the maximum current efficiency (CE) of 53.4 cd A−1, the maximum power efficiency (PE) of 52.4 lm W−1 and the maximum external quantum efficiency (EQE) of 20.5 %. These encouraging results can provide critical information for developing highly efficient TADF emitters based on DBTDO electron acceptor.

Mn2+ doped Zn2SiO4 phosphors: A threefold-mode sensing approach for optical thermometry in the visible region at 525 nm

Optical functional materials such as nanostructured silicates have been studied for photonics applications involving energy conversion. In this scenario, we studied Zn2SiO4:Mn2+ nanostructured powders prepared by combustion synthesis for optical thermometry based on photon downshifting. The structural analysis showed that Zn2SiO4 particles were found embedded in clustered silica nanoparticles. The photoluminescence analysis showed that the samples exhibit intense green emission (centered around 525 nm), corresponding to the electronic transition 4T1 → 6A1 of Mn2+, when exposed to a low power ultraviolet lamp (centered around 255 nm). The temperature sensing performance of this material was evaluated using three different methodologies, i.e. the luminescence decay time constant, the spectral full width at half maximum, and the luminescence peak intensity from the 4T1 → 6A1 radiative transition. The thermometric analysis based on luminescence peak intensity provided a maximum relative sensitivity of ∼4.9x10−3 K−1 at 498 K, while the decay lifetime and the spectral width at half maximum provided maximum relative temperature sensitivities of ∼2.9x10−3 K−1 at 523 K and ∼1.7x10−3 K−1 at 298 K, respectively.

L-cysteine capped MoS2 QDs for dual-channel imaging and superior Fe3+ ion sensing in biological systems.

MoS2 quantum dots (MQDs) with an average size of 1.9 ± 0.7 nm were synthesized using a microwave-assisted method. Absorbance studies confirmed characteristic transitions of MoS2, with absorption humps at 260-280 nm and 300-330 nm, and a band gap of 3.6 ± 0.1 eV. Fluorescence emission studies showed dominant blue and some green emissions under 315 nm excitation, with an absolute quantum yield of ∼9%. The MQDs exhibited fluorescence stability over time after repeated quenching cycles across various pH and media systems. In vitro toxicity tests indicated cytocompatibility, with around 80% cell survival at 1000 mg L-1. Confocal imaging demonstrated significant uptake and vibrant fluorescence in cancerous and non-cancerous cell lines. The MQDs showed strong selectivity towards Fe3+ ions, with a detection limit of 27.61 ± 0.25 nM. Recovery rates for Fe3+ in phosphate buffer saline (PBS) and simulated body fluid (SBF) systems were >97% and >98%, respectively, with a relative standard deviation (RSD) within 3%, indicating precision. These findings suggest that MQDs have high potential for diagnostic applications involving Fe3+ detection due to their fluorescence stability, robustness, enhanced cell viability, and dual-channel imaging properties.

A Water‐Soluble Fluorescent Probe Derived from Pyridine‐2,6‐Dicarboxylic Acid: Synthesis, Interaction with Ions, and Two‐Photon Microscopy

AbstractTwo‐photon excited fluorescence is a process in which the excited fluorophore relaxes and emits fluorescence after two‐photon absorption. Combined with appropriate two‐photon fluorescent probes, two‐photon microscopy enables observation deep inside tissue without damage. Former reports showed that the two‐photon absorption cross sections of donor–acceptor (D–A) dipoles, as well as D‐π‐D and D–A–D quadrupoles can be strengthened by using strong D–A groups. In this study, a novel water‐soluble fluorescent probe with D‐π‐A structure containing pyridine‐2,6‐dicarboxylic acid unit was synthesized. The maximum excitation wavelength and emission wavelength of the probe in aqueous solution were 328 nm and 471 nm, respectively. The fluorescence emitted by the probe can be quenched by various metal cations. The pyridyl N and carboxyl O in the probe formed chelates with Cu2+, which resulted in a fluorescence quenching response, and showed a linear relationship between fluorescent intensity and Cu2+ concentration with wide linear range and low limit of detection. CCK‐8 tests showed the probe had no obvious toxicity to 4T1 cells in the range of 0.4–50 μmol L−1, and the cell survival rate was above 86 %. The probe had a large two‐photon absorption cross section ranging from 680 nm to 820 nm. The two‐photon absorption cross section reached 100 GM at 760 nm of excitation wavelength. By means of microscopic imaging of 4T1 cells stained with the probe, one‐photon fluorescence represented blue emission, while two‐photon fluorescence represented bright green emission. The probe was proved to have good cell permeability, and preferred to target nucleus, showing application potential in two‐photon fluorescence imaging technology.

Superior Circularly Polarized Luminescence Brightness Achieved with Chiral Heteroleptic Nine-Coordinate Coumarin-Based Tb3+ Complexes.

In order to facilitate the practical application of circularly polarized luminescence (CPL) active molecules, the CPL brightness (BCPL) must be optimized. We have applied a binary modular strategy to synthesize two chiral organo-Tb3+ complexes, [Tb(Coum)3(1R,2R-Ph-PyBox)] (2) and [Tb(Coum)3(1S,2S-Ph-PyBox)] (5), combining 3-acetyl-4-hydroxy-coumarin (Coum) and enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine (1R,2R/1S,2S-Ph-PyBox). The photophysical properties of these novel complexes have been fully characterized. The combined point-chiral induction capability of chiral bis(oxazoline) derivatives and the outstanding photophysical properties of the coumarin-derived ligand have resulted in an intense excited-state chiroptical activity (|glum| = 0.097-0.103) for both Tb3+ enantiomers, with a bright Tb3+-centered high-purity green emission (ΦPL = 74%) and enhanced antenna-centered absorption behavior (ε320nm = 47820-47940 M-1 cm-1). A superior BCPL (1132.7-1205.8 M-1 cm-1 at 5D4 → 7F5) has been established for complexes 2 and 5. The strategy adopted in this work provides a new route to chiroptical organo-Tb3+ luminophores with outstanding comprehensive performance.