Emission Properties Research Articles

Dual-emissive BT-CP-TD covalent organic polymers for detecting furacillin, white light emission and information encryption

Recently, luminescent covalent organic polymers (LCOPs) are garnering more and more attention owing to their excellent emissive properties. However, the precise control of LCOPs’ luminescence behaviors remains a formidable challenge. Here, a dual-emissive CP-(BTxTD100-x) COP which was composited of CP, BT and TD (x is the added molar ratio of BT to total feed aldehyde) were synthesized by Knoevenagel condensation reaction between 1,3,5-tri(4-cyano-methylbenzene) benzene (CP) and 2,7-dibenzaldehyde-benthiadiazole (BT)/1,4-bis(4-aldehyde phenyl)benzene (TD). The luminescent behaviors of CP-(BTxTD100-x) COP could be precisely tuned by the ratio of CP, BT and TD as well as excitation wavelength. The CP-(BT33TD67) COP emitted white light (0.3012, 0.3207) when excited at 310 nm. A ratiometric fluorescence sensor was developed for detecting furacillin using CP-(BT33TD67) COP, showing a detection limit of 8.23 ng mL−1. Based on the excitation-depending behaviors of CP-(BT33TD67) COP, combined with CP-(BT100TD0) COP, a kind of security and information encryption image in the form of a quick response was designed. The discoveries provide a new idea for the design of dual-emission LCOPs by regulating the ratio of monomers and excitation wavelengths. The findings also extend the potential applications of dual-emission LCOPs.

Role of Passivation Ligand in Exciton Diffusion and Emission Mechanism of Metal Halide Perovskite Nanocrystal Solid

Shorter-ligand passivated metal halide perovskite nanocrystal (PNC) solids possess smaller inter-NC edge distance which can potentially activate shorter-range nonradiative routes of energy transfer. However, these PNCs are prone to develop surface defects due to ligand detachment and the photogenerated excitons also have high probability to undergo dissociation. It remains unclear how these factors influence the exciton diffusion and emission mechanism of PNC solids. Herein, we prepare two PNC solids passivated with alkylamine and alkylacid ligands of different chain lengths and investigate the exciton diffusion and emission properties by combining time-resolved photoluminescence (PL) and low temperature PL spectroscopy. Our results show that due to the easy ligand detachment and rich surface defects, no prominent exciton transfer occurs in PNC solid passivated with short ligands, despite of the shorter distance between adjacent PNCs. In comparison, the PNC solid passivated with long ligands shows significant occurrence of exciton diffusion from high energy sites towards low energy sites. Accordingly, the PL spectra of thick PNC solid passivated with different ligands show a strikingly different evolution trend with decreasing temperature: in short ligand passivated PNC solid, an intrinsic emission is observed along with a defect-related emission arising from carrier trapping and subsequent radiative recombination, and both emissions are enhanced at lower temperature; in long ligand passivated PNC solid, high energy emission quenches while low energy emission is strengthened due to enhanced exciton transfer at lower temperature. This work reveals that the exciton diffusion and emission properties of PNC solid is strongly mediated by the passivation ligands, providing important insights for their applications in optoelectronic devices.

Dynamics and emission properties of flux ropes from two-temperature GRMHD simulations with multiple magnetic loops

Flux ropes erupting in the vicinity of a black hole are thought to be a potential model for the flares observed in Sagittarius\,A$^*$. In this study, we examine the radiative properties of flux ropes that emerged in the vicinity of a black hole. We performed three-dimensional two-temperature general relativistic magnetohydrodynamic (GRMHD) simulations of magnetized accretion flows with alternating multiple magnetic loops and general relativistic radiation transfer (GRRT) calculations. In the GRMHD simulations, we implemented two different sizes of initial magnetic loops. In the small loop case, magnetic dissipation leads to a weaker excitement of magneto-rotational instability inside the torus, which generates a lower accretion rate compared to the large loop case. However, the small loop case generates more flux ropes due to frequent reconnection by magnetic loops with different polarities. By calculating the thermal synchrotron emission, we found that the variability of light curves and the emitting region are tightly related. At $230\ GHz$ and higher, the emission from the flux ropes is relatively stronger compared to the background, which is responsible for the filamentary structure in the images. At lower frequencies (e.g. $43\ GHz$), emission comes from more extended regions, which have a less filamentary structure in the image. Our study shows that self-consistent electron temperature models are essential for the calculation of thermal synchrotron radiation and the morphology of the GRRT images. Flux ropes contribute considerable emission at frequencies $ GHz$.

Programmable quantum emitter formation in silicon.

Silicon-based quantum emitters are candidates for large-scale qubit integration due to their single-photon emission properties and potential for spin-photon interfaces with long spin coherence times. Here, we demonstrate local writing and erasing of selected light-emitting defects using femtosecond laser pulses in combination with hydrogen-based defect activation and passivation at a single center level. By choosing forming gas (N2/H2) during thermal annealing of carbon-implanted silicon, we can select the formation of a series of hydrogen and carbon-related quantum emitters, including T and Ci centers while passivating the more common G-centers. The Ci center is a telecom S-band emitter with promising optical and spin properties that consists of a single interstitial carbon atom in the silicon lattice. Density functional theory calculations show that the Ci center brightness is enhanced by several orders of magnitude in the presence of hydrogen. Fs-laser pulses locally affect the passivation or activation of quantum emitters with hydrogen for programmable formation of selected quantum emitters.

Modulation of fluorescence and phosphorescence of organoboron compounds from ortho-substituted phenolic Schiff bases by structural modification.

Light emission from organoboron compounds of Schiff bases is found to depend strongly on their chemical structure. Two of these compounds (OB1 and OB2), which contain a benzene ring between the Schiff base moieties, exhibit weak fluorescence in methanol, with marked viscosity dependence. Fluorescence lifetimes of these compounds are in picosecond timescale, as determined by femtosecond optical gating (FOG). A significant enhancement in fluorescence intensity and lifetime is observed at 77 K, indicating the operation of an activated nonradiative process. Using fluorescence lifetime imaging microscopy (FLIM), OB1 and OB2 are shown to be potential membrane probes. The third (OB3), which is devoid of this benzene ring, exhibits relatively stronger fluorescence with nanosecond lifetimes at room temperature. No viscosity dependence is observed in this case. The emission spectrum at 77 K is markedly more intense and exhibits an additional red shifted structured feature, which persists for a few seconds. Hence, OB3 seems to have greater promise not only as fluorescent probe but also for light harvesting. The marked improvement of the light emission properties of OB3 compared with OB1 and OB2 is likely to serve as a pointer for the design of Schiff base-derived organoboron luminophores with diverse potential applications.

Formation of Diamond Films with Different Grain Sizes on TiO2 Nanotubes and Its Field Emission Properties

Diamond films with different grain sizes are deposited on TiO2 nanotube (TNT) arrays prepared by anodic oxidation using a microwave plasma chemical vapor deposition reactor. The scanning electron microscope, X‐Ray diffractometer, and Raman results indicate that the diamond film is successfully deposited and that the substrate undergoes a phase transition due to the diamond deposition temperature, resulting in the rutile phase becoming dominant with lower energy bandgap and work function. Notably, after 5 h of deposition, a relatively continuous microcrystalline film is formed on the TNTs, and the diamond grains change from spherical to pyramidal and show excellent electron field emission behavior, with a low turn‐on field of 0.5 V μm−1 and a current density of 85.9 μA cm−2. In addition, the deposition environment of the nanocrystalline diamond has a large impact on the substrate morphology, resulting in a blocked electron transport path, which reduces the overall field emission performance. The enhanced performance is attributed to the synergistic effect between the highly efficient 1D electron path of the TNTs, the negative electron affinity of the diamond surface, and the lower work function of rutile TiO2.

Impact of Surrounding Environment on Hot‐Exciton Based Organic Emitters for TADF Applications

AbstractUnderstanding thermally activated delayed fluorescence (TADF) in solid‐state environments is crucial for practical applications. However, limited research focuses on how the medium affects TADF properties of hot‐exciton‐based emitters. In our study, we calculated and compared reverse intersystem crossing, radiative, and non‐radiative decay rates of TADF emitters in gas, solvent, and solid phases. The designed emitters have a donor‐acceptor‐donor (D‐A‐D) structure, with donors such as triphenylamine (TPA) and diphenylamine thiophene (ThPA), combined with acceptors such as benzothiadiazole (BT), pyridine thiadiazole (PT) and thiadiazolobenzopyridine (NPT). We model the solvent and solid phases with the polarizable continuum model (PCM) and quantum mechanical/molecular mechanics (QM/MM) methods, respectively. Using density functional theory (DFT) and time‐dependent DFT, we analyze how TADF emitters′ geometrical, electronic, and excited‐state properties vary in these phases. Our results show that the solid‐state environment significantly influences the geometry and TADF properties of emitters. In the presence of solid medium, our study indicates that non‐radiative decay rates tend to be slower. On the other hand, radiative emission rates were found to be less influenced by the properties of the surrounding medium. Overall, our study connects emitter chemical structure and the surrounding environment‘s impact on excited‐state characteristics and photochemical properties.

Constructing Multi‐Functional Polymeric‐Termination Surface Enables High‐Performance Flexible Perovskite LEDs

AbstractFlexible perovskite light‐emitting diodes (f‐PeLEDs) have attracted increasing interest to realize true‐color, low‐cost, and light‐weight wearable optoelectronic and flexible display applications. However, their external quantum efficiency (EQE) and mechanical stability lag far behind because of the inherent surface and brittle issues of polycrystalline perovskite films. In this work, a multi‐functional polymeric‐termination surface of perovskite film is constructed for achieving efficient and mechanically stable f‐PeLEDs. It takes the roles to not only reduce defects through equipping coordination groups to improve emission properties, but also optimize film morphology and eliminate pinholes to solve the long‐standing issue of leakage current. Meanwhile, the polymeric‐termination surface with anchoring points and polymeric soft chains on perovskites demonstrates synergetic effects beyond the corresponding functional group‐only or polymer‐only strategies in reducing the Young's modulus and improving the mechanical flexibility. Ultimately, the record EQE of 22.1% and significantly enhanced mechanical stability of maintaining 82% of the initial performance after 2000 bending cycles with radius of 5 mm are achieved in pure‐green f‐PeLEDs. The work paves the way for the development of high‐performance flexible optoelectronic devices.

CHEX-MATE: A LOFAR pilot X-ray – radio study on five radio halo clusters

The connection between the thermal and non-thermal properties in galaxy clusters hosting radio halos seems fairly well established. However, a comprehensive analysis of such a connection has only been done for integrated quantities (e.g. LX − Pradio relation). In recent years, new-generation radio telescopes have enabled the unprecedented possibility to study the non-thermal properties of galaxy clusters on a spatially resolved basis. In this work, we performed a pilot study to investigate the mentioned properties on five targets by combining X-ray data from the CHEX-MATE project with the second data release from the LOFAR Two meter Sky survey. We find a strong correlation (rs ∼ 0.7) with a slope less than unity between the radio and X-ray surface brightness. We also report differences in the spatially resolved properties of the radio emission in clusters that show different levels of dynamical disturbance. In particular, less perturbed clusters (according to X-ray parameters) show peaked radio profiles in the centre, with a flattening in the outer regions, while the three dynamically disturbed clusters have steeper profiles in the outer regions. We fitted a model to the radio emission in the context of turbulent re-acceleration with a constant ratio between thermal and non-thermal particles’ energy densities and a magnetic field profile linked to the thermal gas density as B(r) ∝ nth0.5. We found that this simple model cannot reproduce the behaviour of the observed radio emission.

Influence of Quadrupolar Molecular Transitions within Plasmonic Cavities.

Optical nanocavities have revolutionized the manipulation of radiative properties of molecular and semiconductor emitters. Here, we investigate the amplified photoluminescence arising from exciting a dark transition of β-carotene molecules embedded within plasmonic nanocavities. Integrating a molecular monolayer into nanoparticle-on-mirror nanostructures unveils enhancements surpassing 4 orders of magnitude in the initially light-forbidden excitation. Such pronounced enhancements transcend conventional dipolar mechanisms, underscoring the presence of alternative enhancement pathways. Notably, Fourier-plane scattering spectroscopy shows that the photoluminescence excitation resonance aligns with a higher-order plasmonic cavity mode, which supports strong field gradients. Combining quantum chemistry calculations with electromagnetic simulations reveals an important interplay between the Franck-Condon quadrupole and Herzberg-Teller dipole contributions in governing the absorption characteristics of this dark transition. In contrast to free space, the quadrupole moment plays a significant role in photoluminescence enhancement within nanoparticle-on-mirror cavities. These findings provide an approach to access optically inactive transitions, promising advancements in spectroscopy and sensing applications.

A NIR-Fluorochrome for Live Cell Dual Emission and Lifetime Tracking from the First Plasma Membrane Interaction to Subcellular and Extracellular Locales

Molecular probes with the ability to differentiate between subcellular variations in acidity levels remain important for the investigation of dynamic cellular processes and functions. In this context, a series of cyclic peptide and PEG bio-conjugated dual near-infrared emissive BF2-azadipyrromethene fluorophores with maxima emissions at 720 nm (at pH > 6) and 790 nm (at pH < 5) have been developed and their aqueous solution photophysical properties determined. Their inter-converting emissions and fluorescence lifetime characteristics were exploited to track their spatial and temporal progression from first contact with the plasma membrane to subcellular locales to their release within extracellular vesicles. A pH-dependent reversible phenolate/phenol interconversion on the fluorophore controlled the dynamic changes in dual emission responses and corresponding lifetime changes. Live-cell confocal microscopy experiments in the metastatic breast cancer cell line MDA-MB-231 confirmed the usability of the dual emissive properties for imaging over prolonged periods. All three derivatives performed as probes capable of real-time continuous imaging of fundamental cellular processes such as plasma membrane interaction, tracking endocytosis, lysosomal/large acidic vesicle accumulation, and efflux within extracellular vesicles without perturbing cellular function. Furthermore, fluorescence lifetime imaging microscopy provided valuable insights regarding fluorophore progression through intracellular microenvironments over time. Overall, the unique photophysical properties of these fluorophores show excellent potential for their use as information-rich probes.

Reactivity-based detection of nitrite ion: Rapid colorimetric and fluorometric response down to nM level

Recent developments in our lab provided significant insight into the structure–reactivity relationship between electronic properties and the detection of nitrite ions. By fine-tuning electron-withdrawing and electron-donating power, the sulfonamide group on aniline moiety was found to be the fastest nitrite probe among the first generation of probe molecules. Based on our understanding of the detection mechanism, our attention was moved to additional modification by installing stronger electron-donating groups on the azo-coupling partner. Accordingly, the bis methoxy group version of the probe molecule was prepared. It showed clean conversion from the probe to the benzo[c]cinnoline product and excellent linear response to very low levels of nitrite ions. Proton NMR and high-resolution mass spectrometer captured the reaction between the probe molecule and nitrite ions. As the reaction with nitrite ion triggers diazonium intermediate formation followed by intramolecular cyclization, both absorption and emission property changes were monitored as the signal readout to assay nitrite ion. In this report, our design principle of a probe molecule and its performance in colorimetric and fluorimetric responses will be discussed. In addition, the low detection limit achieved by leveraging chromatographic separation and assaying by the mass detector will be discussed.

Evolutionary Map of the Universe (EMU): Observations of Filamentary Structures in the Abell S1136 Galaxy Cluster

Abstract We present radio observations of the galaxy cluster Abell S1136 at 888 MHz, using the Australian Square Kilometre Array Pathfinder radio telescope, as part of the Evolutionary Map of the Universe Early Science program. We compare these findings with data from the Murchison Widefield Array, XMM-Newton, theWide-field Infrared Survey Explorer, the Digitised Sky Survey, and the Australia Telescope Compact Array. Our analysis shows the X-ray and radio emission in Abell S1136 are closely aligned and centered on the BCG, while the X-ray temperature profile shows a relaxed cluster with no evidence of a cool core. We find that the diffuse radio emission in the centre of the cluster shows more structure than seen in previous low-resolution observations of this source, which appeared formerly as an amorphous radio blob, similar in appearance to a radio halo; our observations show the diffuse emission in the Abell S1136 galaxy cluster contains three narrow filamentary structures visible at 888 MHz, between ∼80 and 140 kpc in length; however the properties of the diffuse emission do not fully match that of a radio (mini-)halo or (fossil) tailed radio source.

Aggregation-Induced Emission (AIE) in Polymers: Effect of Polymer size on the Fluorescence of Low Molecular Weight PEG and PPG.

Aggregation-induced emission (AIE) is a fascinating phenomenon where specific molecules exhibit enhanced fluorescence upon aggregation. This unique property has revolutionized the design and development of new fluorescent materials for different applications, from biosensors and organic light-emitting diodes (OLEDs) to biomedical imaging and diagnostics. Researchers are creating sensitive and selective sensing platforms, opening new avenues in material science and engineering by harnessing the potential of AIE. To expand the knowledge in this field, this study explored the aggregation-induced emission (AIE) properties of two polymers, namely polyethylene glycol (PEG) and polypropylene glycol (PPG) of low molecular weight (MW) using fluorescence spectroscopy and absorbance (UV). PEG-300 and PPG-725 were the most fluorescent polymers at UV of the ten investigated. Interestingly, AIE did not correlate linearly with molecular weight (MW), and monobutyl ether substitution in PEG with a similar MW substantially altered its AIE. Furthermore, fluorescence precisely quantified low polymer concentrations in water, and non-aqueous solvents suppressed AIE, suggesting potential for AIE manipulation. These findings enhance our understanding of AIE in polymers, fostering the development of novel materials for applications such as biosensors.

Effect of blending L-lysine-modified montmorillonite into urea-formaldehyde resin on formaldehyde emission and physicomechanical properties of medium density fiberboard

Effect of blending L-lysine-modified montmorillonite into urea-formaldehyde resin on formaldehyde emission and physicomechanical properties of medium density fiberboard

Breakdown of steady-state superradiance in extended driven atomic arrays

Recent advances in generating well controlled dense arrangements of individual atoms in free space have generated interest in understanding how the extended nature of these systems influences superradiance phenomena. Here, we provide an in-depth analysis on how space-dependent light shifts and decay rates induced by dipole-dipole interactions modify the steady-state properties of coherently driven arrays of quantum emitters. We characterize the steady-state phase diagram, with particular focus on the radiative properties in the steady state. Interestingly, we find that diverging from the well-established Dicke paradigm of equal all-to-all interactions significantly modifies the emission properties. In particular, the prominent quadratic scaling of the radiated light intensity with particle number in the steady state—a hallmark of steady-state Dicke superradiance—is entirely suppressed, resulting in only linear scaling with particle number. We show that this breakdown of steady-state superradiance occurs due to the emergence of additional dissipation channels that populate not only superradiant states but also subradiant ones. The additional contribution of subradiant dark states in the dynamics leads to a divergence in the time scales needed to achieve steady states. Building on this, we further show that measurements taken at finite times for extended atom ensembles reveal properties closely mirroring the idealized Dicke scenario. Published by the American Physical Society 2024

Predicting combustion, performance, and emission characteristics of a compression ignition engine utilising coconut oil methyl ester and MoO3 nanoparticles

The present study used a blend of biofuel and nanoparticles to examine the effectiveness and emission properties of a four-stroke, single-cylinder, direct-injection diesel engine with an injection pressure of 250 bar. The use of MoO3 in biodiesel enhances its environmental sustainability and dependability, making it a promising substitute for traditional diesel fuel. The study emphasises the ecological advantages of using a combination of coconut oil and MoO3 to accomplish the production of renewable energy. MoO3 nanoparticles ultimately function as an oxidation catalyst, enhancing combustion. A study with MoO3 nanoparticles at 50 and 100 ppm concentrations was carried out. Utilising a photo spectrometer, stability was determined. The CI engine demonstrated improved thermal efficiency and reduced Fuel Consumption compared to diesel, both at full load conditions and at 64.5 bar pressure. The performance, combustion, and emission parameters were precisely forecasted using Design Expert, exhibiting a robust connection with the testing results. The Rb values for Brake Specific Fuel Consumption (BSFC), Brake Thermal Efficiency (BTE), Peak Cylinder Pressure (P-CA), Net Heat Release Rate (NHRR), Crankcase Heat Release Rate (CHRR), Carbon Monoxide (CO), Unburned Hydrocarbons (UHC), Nitrogen Oxides (NOX), and Smoke Opacity are 0.997, 0.9998, 0.8898, 0.979, 0.9838, 0.9815, 0.9917, 0.9958, and 0.9261 respectively.

Recent Progress of Advanced AIE Materials for Visualization of 3‐Level Latent Fingerprints

The 3‐level features of Latent fingerprints (LFPs) are pivotal in linking suspects with problematic or incomplete fingerprint data, constituting one of the most robust forms of evidence. Aggregation‐induced emission (AIE) materials, known for their heightened emissive properties in high aggregation states, provide a robust and powerful approach for developing techniques for 3‐level details of LFPs. So far, tremendous efforts have been devoted to solving high background fluorescence interference during the 3‐level LFPs visualization process. This review commences with an overview of 3‐level features and summarizes the interaction and mechanism of visualizing LFPs involving AIE materials and LFPs secretions. Moreover, it encompasses strategies to enhance the contrast and brightness of 3‐level LFPs images. We highlight the mechanism of AIE's physicochemical properties and their effects on the visualization of 3‐level LFPs. Additionally, we provide insights into potential challenges and opportunities in this emerging field.

Three-State Dielectric Switching within a Narrow Temperature Range in Isopropylammonium Lead Iodide, a One-Dimensional Perovskite with Polar Phase.

The phenomenon of dielectric switching has garnered considerable attention due to its potential applications in electronic and photonic devices. Typically, hybrid organic-inorganic perovskites, HOIPs, exhibit a binary (low-high) dielectric state transition, which, while useful, represents only the tip of the iceberg in terms of functional relevance. One way to boost the versatility of applications is the discovery of materials capable of nonbinary switching schemes, such as three-state dielectric switching. The ideal candidate for that task would exhibit a trio of attributes: two reversible, first-order phase transitions across three distinct crystal phases, minimal thermal hysteresis, and pronounced, step-like variations in dielectric permittivity, with a substantial change in its real part. Here, we demonstrate a one-dimensional lead halide perovskite with the formula (CH3)2C(H)NH3)PbI3, abbreviated as ISOPrPbI3, that fulfills these criteria and demonstrates three-state dielectric switching within a narrow temperature range of ca. 45 K. Studies on ISOPrPbI3 also revealed the polar nature of the low-temperature phase III below 266 K through pyrocurrent experiments, and the noncentrosymmetric character of the intermediate phase II and low-temperature phase III is confirmed via second harmonic generation measurements. Additionally, luminescence studies of ISOPrPbI3 have demonstrated combined broadband and narrow emission properties. The introduction of ISOPrPbI3 as a three-state dielectric switch not only addresses the limitations posed by the wide thermal gap between dielectric states in previous materials but also opens new avenues for the development of nonbinary dielectric switchable materials.

Polarization switching in a mid-infrared Er:YAlO3 laser

We report on a polarization-resolved study of mid-infrared emission properties of Er3+-doped orthorhombic yttrium aluminum perovskite YAlO3 single crystal. For the 4I11/2 → 4I13/2 Er3+ transition, the stimulated emission cross section is 0.20 × 10−20 cm2 at 2919 nm for light polarization E ‖ c. Pumped by an Yb-fiber laser at 976 nm, the 10 at.% Er:YAlO3 laser delivered 1.36 W at 2919 nm with a slope efficiency of 31.4%, very close to the Stokes limit, a laser threshold as low as 33 mW and a linear polarization. Pump-induced polarization switching between E || b and E || c eigen states was observed and explained by excited-state absorption from the terminal laser level.