High Photoluminescence Efficiency Research Articles

High-Resolution X-ray Image from Copper-Based Perovskite Hybrid Polymer.

Cs3Cu2I5 nanocrystals (NCs) are considered to be promising materials due to their high photoluminescence efficiency, lack of lead toxicity, and X-ray responsiveness. However, during the crystallization process, NCs are prone to agglomeration and exhibit uneven size distribution, resulting in several light scattering that severely affect their imaging resolution. Herein, we successfully developed a high-resolution scintillator film by growing copper-based perovskite NCs within a hybrid polymer matrix. By leveraging the ingenious integration of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA), the size and distribution uniformity of Cs3Cu2I5 NCs can be effectively controlled. Consequently, a high spatial resolution of 14.3 lp mm-1 and a low detection limit of 105 nGy s-1 are achieved, and the scintillator film has excellent flexibility and stability. These results highlight the promising application of Cs3Cu2I5 scintillator films in low-cost, flexible, and high-performance medical imaging.

Constructing ZnTe Spherical Quantum Well for Efficient Light Emission.

ZnTe colloidal semiconductor nanocrystals (NCs) have shown promise for light-emitting diodes (LEDs) and displays, because they are free from toxic heavy metals (Cd). However, so far, their low photoluminescence (PL) efficiency (∼30%) has hindered their applications. Herein, we devised a novel structure of ZnTe NCs with the configuration of ZnSe (core)/ZnTe (spherical quantum well, SQW)/ZnSe (shell). The inner layer ZnTe was grown at the surface of ZnSe core with avoiding using highly active and high-risk Zn sources. Due to the formation of coherently strained heterostructure which reduced the lattice mismatch, and the thermodynamic growth of ZnTe, the surface or interface defects were suppressed. A high PL efficiency of >60% was obtained for the green light-emitting ZnSe/ZnTe/ZnSe SQWs after ZnS outer layer passivation, which is the highest value for colloidal ZnTe-based NCs. This work paves the way for the development of novel semiconductor NCs for luminescent and display applications.

Performance-improved narrowband near-ultraviolet emission from a simple butyl and cyanogen substituted indolocarbazole

High-efficiency narrowband near-ultraviolet (NUV) organic light-emitting diodes with high color purity have currently encountered great challenges. Here, using butyl (Bu) and cyanogen (CN) substituted strategy in the simplest polycyclic aromatic hydrocarbons of indolocarbazole (ICz), two simple emitters of BuICz and BuICzCN were demonstrated. This simple strategy was observed to enable both emitters to realize NUV emission at 380–381 nm with a small full width at half maximum (FWHM) of 21–23 nm and high photoluminescent quantum efficiency of 50%–59% in toluene solution. Furthermore, the BuICzCN doped devices exhibited a slightly blueshifted narrowband NUV electroluminescence at 388 nm with a small FWHM of 32.3 nm but a higher external quantum efficiency of 3.92% in comparison with the BuICz doped devices. This work provides a path to realize high-performance narrow-band NUV emission.

Efficient and bright broadband electroluminescence based on environment-friendly metal halide nanoclusters

Broadband electroluminescence based on environment-friendly emitters is promising for healthy lighting yet remains an unprecedented challenge to progress. The copper halide-based emitters are competitive candidates for broadband emission, but their high-performance electroluminescence shows inadequate broad emission bandwidth of less than 90 nm. Here, we demonstrate efficient ultra-broadband electroluminescence from a copper halide (CuI) nanocluster single emitter prepared by a one-step solution synthesis-deposition process, through dedicated design of ligands and subtle selection of solvents. The CuI nanocluster exhibits high rigidity in the excitation state as well as dual-emissive modes of phosphorescence and temperature-activated delayed fluorescence, enabling the uniform cluster-composed film to show excellent stability and high photoluminescent efficiency. In consequence, ultra-broadband light-emitting diodes (LEDs) present nearly identical performance in an inert or air atmosphere without encapsulation and outstanding high-temperature operation performance, reaching an emission full width at half maximum (FWHM) of ~120 nm, a peak external quantum efficiency of 13%, a record maximum luminance of ~50,000 cd m−2, and an operating half-lifetime of 137 h at 100 cd m−2. The results highlight the potential of copper halide nanoclusters for next-generation healthy lighting.

Microwave-assisted Green Synthetic Approach towards Water Dispersible Luminescent PVP-coated Tb3+ and Ce3+/Tb3+ -doped KZnF3 Nanocrystals

Background: Perovskite fluoride nanomaterials are an interesting research topic in material science due to their exciting properties like high-temperature superconductivity, magnetic behaviour, piezoelectric behaviour, etc. Doping of lanthanide ions into the perovskite fluoride nanomaterials makes them more promising as they have applications from biological labelling to multicolor optical devices. Objective: This study aimed to carry out the synthesis of perovskite KZnF3 nanocrystals in an ecofriendly environment with the help of a microwave-assisted route in a shorter reaction time and at low temperatures. Moreover, it aimed to make the nanocrystals water dispersible, illuminating brighter photoluminescence, which was achieved by coating nanocrystals surface with poly(N-vinyl-2-pyrrolidone) and doping of different lanthanide ions (Ln= Tb3+ and Ce3+/Tb3+) respectively, into the KZnF3 nanocrystals matrix. Methods: The synthesis of nanocrystals was performed in an environment-friendly microwave-assisted way and under green conditions. For example, in the preparation of Tb3+(5mol%)-doped KZnF3 nanocrystals, 0.95 mmol of Zn(NO3)2 and 0.05 mmol of Tb(NO3)3 were dissolved in 8 mL of distilled water. Then, an 8 mL aqueous solution of KF (3 mmol) was added to it. The entire mixture was stirred well for 15 minutes. About 60 mg of PVP was added to the mixture and stirred for another 15 minutes. Then, a microwave reaction vessel was made by transferring the final reaction mixture into it and kept under microwave irradiation at 90°C temperature for 15 minutes. Finally, the product was cooled to room temperature and collected by centrifugation. Results: Both Tb3+(5mol%)-doped and Ce3+(15mol%)/Tb3+(5mol%) co-doped KZnF3 nanocrystals exhibit very strong green photoluminescence. The structural and optical properties of as-obtained nanocrystals were characterized by PXRD, field emission scanning electron microscopy, Fourier infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, and photoluminescence spectra. Conclusion: The nanocrystals with uniform cubical morphology having ~60 nm sizes were successfully synthesized. The high photoluminescence efficiency, together with the water dispersibility of the nanocrystals, makes the material useful in many fields of optical devices and offers several biological applications. Moreover, this method could be used to make other lanthanide-doped perovskite fluoride nanocrystals

Red-emissive silicon nanodots with highly biocompatible for mitochondrial dynamic tracking and blood-brain barrier penetration imaging

As one of the most indispensable organelles in eukaryotic cells, mitochondria are the primary site of cellular energy acquisition. Visual monitoring of mitochondria is an important way to understand mitochondrial morphology and cellular activities. However, it is difficult to achieve long-term localization and tracking due to the poor photostability of commercial mitochondria-targeted dyes. In this work, red-emissive silicon nanodots (R-SiNDs) with a highly mitochondrial-targeting and optimal emission peak at 614 nm were designed. The absolute quantum yield (QY) was up to 22.68%, while Pearson’s correlation coefficient in co-localization analysis was as high as 0.94. Subsequently, the long-term dynamic processes of mitochondrial fusion, division and interaction with lipid droplets were clear visualization in living cells based on good photostability and high photoluminescence efficiency. More interestingly, R-SiNDs without any other modification exhibited wonderful blood-brain barrier (BBB) penetration capacity and were accumulated in the central canal of the spinal cord of zebrafish. Therefore, the as-prepared R-SiNDs can not only be used to study mitochondrial dynamics, but also provide a reliable basis for diagnosing mitochondria-related brain diseases, which is of great value in biomedical applications.

Polymer-Surface-Mediated Mechanochemical Reaction for Rapid and Scalable Manufacture of Perovskite QD Phosphors.

Perovskite quantum dots (QDs) have been considered new-generation emitters for lighting and displays due to their high photoluminescence (PL) efficiency, and pure color. However, their commercialization process is currently hindered by the challenge of mass production in a quick and environmentally friendly manner. In this study, a polymer-surface-mediated mechanochemical reaction (PMR) is proposed to prepare perovskite QDs using a high-speed multifunction grinder for the first time. PMR possesses two distinctive features: i) The ultra-high rotating speed (>15 000rpm) of the grinder facilitates the rapid conversion of the precursor to perovskite; ii) The surface-rich polymer particulate ensures QDs with high dispersity, avoiding QD aggregation-induced PL quenching. Therefore, PMR can successfully manufacture green perovskite QDs with a high PL quantum yield (PLQY) exceeding 90% in a highly material- (100% yield), time- (1kgmin-1), and effort- (solvent-free) efficient manner. Moreover, the PMR demonstrates remarkable versatility, including synthesizing by various polymers and producing diverse colored and Pb-free phosphors. Importantly, these phosphors featuring a combination of polymer and perovskite, are facilely processed into various solid emitters. The proposed rapid, green, and scalable approach has great potential to accelerate the commercialization of perovskite QDs.

Growth of Medium-Sized InP Quantum Dots with High Photoluminescence Efficiency and Enhanced Stability

This study introduces medium-sized core/shell InP quantum dots (QDs) with high photoluminescence (PL) efficiency and remarkable material stability. The incorporation of a ZnSe interlayer between the core and the thicker outer ZnS shell enhances both the optical performance and material stability. When further increasing the S/Se ratio to synthesize larger QDs with a thicker ZnS layer, optical performance significantly declines despite the improvement in stability. To achieve QDs with superior optical performance and stability, we controlled the S/Se ratio variation during shell growth and examined its impact on the structure, morphology, and size of InP QDs. Our approach resulted in medium-sized InP/ZnSe/ZnS QDs with tunable wavelengths (606-630 nm), PL quantum yields (PLQY) > 90%, full width at half maximum (FWHM) values < 40 nm, and enhanced material stability.Keywords: indium phosphide (InP), quantum dots (QDs), high efficiency and stability, S/Se ratio of shell, medium-size quantum dots, stainless steel reactor Figure 1

Centimeter-Sized Single Crystals of Tetrahedral Manganese (II) Halide Hybrids for Wide-Color Gamut Backlighting Displays.

Phosphors with narrow-band green emissions and high photoluminescent quantum efficiency (PLQY) are significantly required for backlighting displays with wider color gamut. In this work, two centimeter-sized manganese (II) halide single crystals TMG2MnCl4 and TMG2MnBr4 (TMG = 1,1,3,3-tetramethylguanidine) are synthesized, exhibiting bright narrow-band green emissions with high PLQYs up to 62% and 90%, respectively. The narrow-band green light emission is located at 520nm with a full-width at half-maximum (FWHM) of only 57nm. The photoluminescence mechanisms of two single crystals are elaborated. Two white-light-emitting diodes for backlighting displays (BD-WLEDs) based on them are fabricated, exhibiting the widest color gamut of 122% National Television Standards Committee (NTSC), and a luminous efficacy reached ≈93lmW-1 with excellent luminescence stability at high temperatures. These properties indicate the potential applications of tetrahedral manganese (II) hybrids in wide-color gamut backlighting displays.

Antimony Doping Enabled Photoluminescence Quantum Yield Enhancement in 0D Inorganic Bismuth Halide Crystals.

Owing to the exterior self-trapped excitons (STEs) with adjustable fluorescence beams, low-dimensional ns2-metal halides have recently received considerable attention in solid-state light-emitting applications. However, the photoluminescence (PL) mechanism in metal halides remains a major challenge in achieving high efficiency and controllable PL properties because the excited-state energy of ns2 conformational ions varies inhomogeneously with their coordination environments. Here, a novel zero-dimensional (0D) lead-free bismuth-based Rb3BiCl6·0.5H2O crystal was reported as a pristine crystal to modulate the optical properties. By doping Sb3+ ions with 5s2 electrons into Rb3BiCl6·0.5H2O crystals, bright orange emission at room temperature was obtained with a photoluminescence quantum yield of 39.7%. Optical characterizations and theoretical studies show that the Sb3+ doping can suppress the strong exciton-phonon coupling, optimize the electronic energy band structure, improve the thermal activation energy, soften the structural lattice of the host crystals, deepen the STE states, and ultimately lead to strong photoluminescence. This work manifests a fruitful manipulation in ripening bismuth-based halides with high-efficiency PL properties, and the PL enhancement mechanisms will guide future research in the exploration of emerging luminescent materials.

Zero-Dimensional Hybrid Antimony Chloride with Near-Unity Broad-Band Orange-Red Emission toward Solid-State Lighting.

Zero-dimensional (0D) hybrid metal halides are attractive owing to their distinctive structure as well as photoluminescence (PL) characteristics. To discover 0D hybrid metal halides with high photoluminescence quantum yield and good stability is of great significance for white light-emitting diodes (LEDs). Herein, a novel hybrid antimony chloride (CTP)2SbCl5 is synthesized, which shows a bright broad-band orange-red emission peaking at 620 nm under the low energy excitation (365 nm), achieving an excellent photoluminescence quantum yield of 96.8%. In addition, (CTP)2SbCl5 shows an additional emission peaking at 470 nm when excited at high energy (323 nm). PL spectra and density functional theory results demonstrate that the observed dual-band emission originates from the singlet and triplet self-trapped excitons confined in isolated [SbCl5]2- square pyramids. Moreover, (CTP)2SbCl5 presents relatively superior air stability, and the PL intensity still maintains 78% of the initial PL intensity when exposed to the air for above 2 weeks. Benefiting from high-efficiency PL emission and good stability of (CTP)2SbCl5, a stable warm white LED device with a 92.3% color rendering index was prepared by coating blue phosphor BaMgAl10O17:Eu2+, green (Sr,Ba)2SiO4:Eu2+, and orange-red (CTP)2SbCl5 on a 365 nm LED chip. This work provides an efficient luminescent material and also demonstrates the potential application of 0D hybrid antimony chloride in solid-state lighting.

Insights into the β‐phase of polyfluorene: characterization, regulation, and mechanism

AbstractDue to the unique blue‐light properties, wide excited emission interval and so on, polyfluorenes (PFs) are among the most promising blue‐light polymers that are widely used in organic lasers and organic light‐emitting diodes. Usually, PFs exhibit two different phases: α‐phase and β‐phase, and the β‐phase has higher photoluminescence efficiency and carrier mobility than the one of α‐phase. Hence, improving the content of β‐phase is very important to enhance the device performance. In this paper, we introduce the methods for characterizing the β‐phase in PFs and summarize the recent research progress in regulating the β‐phase content. Firstly, the differences between the α‐phase and the β‐phase of PFs in terms of structure, aggregation behavior, and optoelectronic properties are summarized. Then, the characterization for the β‐phase, including ultraviolet–visible absorption spectrum (UV–vis), photoluminescence spectrum (PL), and Raman spectrum, transmission electron microscope (TEM), and X‐ray diffraction (XRD) are introduced, and the calculating rules for the content of β‐phase is also introduced. Furthermore, the methods to increase the content of β‐phase are reviewed. Finally, a brief outlook on the challenges and future development prospects of β‐phase in PFs are discussed.

A chiral spirofluorene‐embedded multiple‐resonance thermally activated delayed fluorescence emitter for efficient pure‐green circularly polarized electroluminescence

AbstractThe simultaneous achievement of chiral multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters with narrowband and circularly polarized electroluminescence (CPEL) poses a challenge. Herein, a MR‐TADF emitter, Spiro‐BNCz, embedding spirofluorene structure was developed and chiral separated, whose emission peaks at 528 nm in toluene with Commission Internationale de L'Eclairage coordinates of (0.26, 0.69). The conjugation extension caused by embedding sulfur substituted spirofluorene on B/N framework shortens the singlet‐triplet energy gap and increases spin‐orbital coupling matrix element. Therefore, a fast reverse intersystem crossing rate constant of 2.8 × 106 s−1 and a high photoluminescence efficiency of 92% in film were achieved. The organic light‐emitting diode (OLED) exhibits a maximum external quantum efficiency of 32.3%. Particularly, the circularly polarized OLEDs based on Spiro‐BNCz enantiomers show symmetric CPEL with dissymmetry factors (|gEL|) ≈ 10−3.

White light emitting devices with high color rendering index and electrically adjustable color temperature

Herein, we report a rare earth-free white light emitting composite for applications in solid-state lighting, which is made up of carbon nitride (CN) and Mn2+-doped perovskite quantum dots (PQDs). The correlated color temperature (CCT) is adjustable from 18 088 to 2926 K by varying the ratio of the two components. When the PQDs content is 2.88%, the white light emitting diode (W-LED) based on the CN/PQDs composite shows a competitive color rendering index of 88, a CCT of 5737 K, and a chromaticity coordinate of (0.327, 0.33), which is close to the standard white light. The light conversion efficiency of the composite is around 10%, which is attributed to the high photoluminescence efficiencies of the two components and weak photon reabsorption between them. Moreover, the CCT can be tuned from 4750 to 7315 K by changing the repetition frequency of the electrical input.

Synthesis, characterization, and photophysical properties of dicyanoarylamine‐based semi‐aromatic polymers

AbstractIntroductionFluorescent high‐performance polymers have been extensively used in designing optoelectronic devices due to their low cost, excellent thermal stability, high mechanical strength, low flammability, good chemical and radiation resistance, and good electronic properties. While conventional organic luminophores fluoresce strongly in dilute solutions, they suffer from undesirable aggregation‐caused quenching in concentrated solutions and in the solid state due to extensive π‐π stacking interactions and formation of delocalized excitons or excimers. This phenomenon leads to non‐radiative decay thus, decreased fluorescence emission of the material in the solid film state, which significantly limits their real‐world application as solid light‐emitting materials.ObjectivesTo develop new high‐performance polymers with high photo luminescent efficiency, good processability, film‐forming properties, which could potentially be used in the fabrication of optoelectronic devices.MethodsThe preparation of the polyimide DiCN‐PI was carried out by a one‐step, high‐temperature solution imidization method. In this procedure, 1,2,4,5‐cyclohexanetetracarboxylic dianhydride and the diamine were polymerized in 1‐methyl‐2‐pyrrolidinone and γ‐butyrolactone co‐solvent at 180°C for 15 hours in the presence of isoquinoline as catalyst. On the other hand, polyamide DiCN‐PA was synthesized according to the direct phosphorylation polycondensation technique described by Yamazaki from diamine and trans‐1,4‐cyclohexanedicarboxylic acid using triphenyl phosphite and pyridine as condensing agents.Results and DiscussionBoth polymers were soluble in several polar aprotic solvents and exhibited useful levels of thermal stability. The polymers were emissive with PL emission bands around 555 (bluish‐green) and 498 (cyan) nm in dilute 1‐methyl‐2‐pyrrolidinone solutions for polyimide and polyamide, respectively. In the solid film state, the polymers emit light green and yellow colors, which simulate the PL behavior of their aggregated states, thereby demonstrating aggregation‐induced fluorescence changes.ConclusionsThese results indicate that the incorporation of bulky dicyanoarylamine moiety and alicyclic monomer units into the rigid polymer backbones effectively disrupted the planarity of the chain packing which resulted to the fluorescent high‐performance polymers with desired properties for potential optoelectronic applications.

Synthesis, crystal structure, and characterizations of Eu3+-activated Ca2LnHf2(AlO4)3 (ln = Lu, Y and Gd) red-emitting phosphors for phosphors-converted white LEDs

High-brightness red-emitting Ca2LnHf2Al3O12:Eu3+ (Ln = Lu, Y and Gd) garnet phosphors with high photoluminescence efficiency are demonstrated for application in white light-emitting diodes (LEDs), and they have been successfully prepared using a high-temperature solid-state method. X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence excitation and photoluminescence spectra, decay lifetimes, photoluminescence quantum yield and temperature-dependent emission spectra have been used to characterize these samples. Under near-ultraviolet excitation into the 7F0→5L6 transition of Eu3+ at 394 nm, the Ca2LnHf2Al3O12:Eu3+ (Ln = Lu, Y and Gd) samples produce the characteristic red emissions of Eu3+ ions with peaks around 591, 611, 656, and 709 nm, corresponding to the 5D0→7F1, 5D0→7F2, 5D0→7F3, and 5D0→7F4 transitions. These samples exhibit significant concentration-dependent luminescence behaviors, and the highest emission intensity is achieved at 50 mol% Eu3+ doping concentration owing to the concentration quenching effect caused by the dipole-dipole interaction between neighboring Eu3+ activators. The CIE color coordinates of these optimal Ca2LnHf2Al3O12:50%Eu3+ (Ln = Lu, Y and Gd) phosphors are (0.6339, 0.3654), (0.6341, 0.3653), and (0.6343, 0.3651), along with respective color purity of 92.4%, 92.6%, and 92.6%. The photoluminescence quantum yields of Ca2LnHf2Al3O12:50%Eu3+ are determined to be 39.2%, 56.6%, and 53.3% for Ln = Lu, Y, Gd, respectively. A white LED device has been fabricated through utilizing the Ca2YHf2Al3O12:50%Eu3+ phosphor as red-emitting color converter, which generates bright warm-white light with high color rendering index (80.8), low correlated color temperature (3920 K), CIE chromaticity coordinates (0.3827, 0.3742), and high luminous efficacy (11.56 lmW−1) under 40 mA driving current.

Rational design of hybridized local and charge-transfer (HLCT) emitters towards blue OLEDs with high luminance and low efficiency roll-off

Organic blue emitters have been get more and more attention by scientists and industries in the field of organic light-emitting diodes (OLEDs). The design of efficient blue emitters, especially deep-blue ones, is still a challenge because of their intrinsic wide band-gaps and unbalanced carrier mobilities. Herein, two donor‒π‒acceptor (D‒π‒A) type molecules with phenanthro[9,10-d]imidazole (PI) as A and pyridinyl as π-bridge were designed and synthesized by fine-turning the D moieties, namely mPTPA and mP3PCZ, respectively. Theoretical calculation and single-crystal analysis showed that there exist intramolecular hydrogen bond (IHB) interactions inducing small torsion angles between pyridinyl and adjacent phenyls. The rigid 9-phenyl-9H-carbazole (PCZ) and IHB interactions makes mP3PCZ exhibiting planar configuration along the long-axis of the molecule, which could increase the orbital overlap and oscillator strength (fos). The solvatochromic effect manifested that both two emitters have hybridized local and charge-transfer (HLCT) characteristics, and the excited state of mP3PCZ exhibited LE-dominated HLCT state which is beneficial for high photoluminescence efficiency. Ultimately, the non-doped devices based on mPTPA and mP3PCZ achieved maximum luminance larger than 12000 cd m−2. Furthermore, the doped device based on mP3PCZ exhibited maximum external quantum efficiency of 5.14% with low efficiency roll-off, and with the corresponding deep-blue Commission international de l’éclairage (CIE) coordinate of (0.166, 0.085).

1,8-diphenyl-carbazole-based boron, sulfur-containing multi-resonance emitters with suppressed aggregation emission for narrowband OLEDs

Multi-resonance emitters are attractive for organic light-emitting diode (OLED) applications because of their narrowband emissions and high photoluminescent efficiencies. Nevertheless, their tendency to aggregation by intermolecular interactions could cause doping sensitivity and reduce color purity at high concentrations. Here, we report a novel boron, sulfur (B, S)-containing multi-resonance emitter (BSS-Ph-TBCz) consisting of 1,8-diphenyl-carbazole substituent at para-position of boron atom of B, S-doped polycyclic aromatic skeleton. Different from control compound (BSS-TBCz) containing conventional carbazole substituents showing aggregation-caused spectral broadening, BSS-Ph-TBCz with 1,8-diphenyl-carbazole group exhibits weak intermolecular aggregation behavior owing to the large twist angle between polycyclic skeleton and carbazole plane caused by two steric phenyl groups on carbazole group, leading to nearly unchanged emissions with small full width at half-maximum of 30–31 nm at doping concentration ranging from 1 to 100 wt%. OLEDs employing BSS-Ph-TBCz as emitter reveal blue electroluminescence at 468 nm and maximum external quantum efficiency of 21.4% at 5 wt% doping concentration, which remains at 20.1% at high doping concentration of 25 wt%.

Luminescent Bimetallic Two-Coordinate Gold(I) Complexes Utilizing Janus Carbenes.

A series of bimetallic carbene-metal-amide (cMa) complexes have been prepared with bridging biscarbene ligands to serve as a model for the design of luminescent materials with large oscillator strengths and small energy differences between the singlet and triplet states (ΔEST). The complexes have a general structure (R2N)Au(:carbene─carbene:)Au(NR2). The bimetallic complexes show solvation-dependent absorption and emission that is analyzed in detail. It is found that the molar absorptivity of the bimetallic complexes is correlated with the energy barrier to rotation of the metal-ligand bond. The bimetallic cMa complexes also exhibit short emission lifetimes (τ = 200-300 ns) with high photoluminescence efficiencies (ΦPL > 95%). The radiative rates of bimetallic cMa complexes are 3-4 times faster than that of the corresponding monometallic complexes. Analysis of temperature-dependent luminescence data indicates that the lifetime for the singlet state (τS1) of bimetallic cMa complexes is near 12 ns with a ΔEST of 40-50 meV. The presented compounds provide a general design for cMa complexes to achieve small values for ΔEST while retaining high radiative rates. Solution-processed organic light-emitting devices (OLEDs) made using two of the complexes as luminescent dopants show high efficiency and low roll-off at high luminance.

Shedding Novel Photophysical Insights Toward Discriminative Detection of Three Toxic Heavy Metal Ions and a hazard class 1 nitro-explosive By Using a Simple AIEE Active Luminogen.

In this work, we introduced a simple aggregation-induced emission enhancement (AIEE) sensor (PHCS) which can selectively detect and discriminate three environmentally and biologically imperative heavy metal ions (Cu2+, Co2+ and Hg2+) and a hazard class 1 categorized nitro-explosive picric acid (PA) in differential media. By virtue of its weak fluorescence attributes in pure organic medium owing to the synergistic operation of multiple photophysical quenching mechanisms, the molecular probe showcased highly selective 'TURN ON' fluorogenic response towards hazardous Hg2+ with a limit of detection (LOD) as low as 97nM. Comprehensive investigation of binding mechanism throws light on the cumulative effect of probe-metal complexation induced chelation enhanced fluorescence (CHEF) effect and subsequent AIEE activation within the formed probe-metal adducts. Noteworthily, the probe (PHCS) can be readily used in real water samples for the quantitative determination of Hg2+ in a wide concentration range. In addition, the probe displayed modest colorimetric recognition performances to selectively detect and discriminate two essential heavy metal ions (Cu2+ and Co2+) with a LOD of 96nM and 65nM for Cu2+ and Co2+ respectively, in semi-aqueous medium. Intriguingly, based on high photoluminescence efficiency, the AIEE active nano-aggregated PHCS displayed a remarkable propensity to be used as a selective and ultra-sensitive 'TURN-OFF' fluorogenic chemosensor towards PA with LOD of 34.4ppb in aqueous medium. Finally, we specifically shed light on the interaction of PHCS hydrosol towards PA using some unprecedented techniques, which helped uncover new photophysical insights of probe-explosive molecule interaction.