Circularly polarized thermally activated delayed fluorescence (CP‐TADF) and multiple‐resonance thermally activated delayed fluorescence (MR‐TADF), which exhibit novel circularly polarized ...luminescence and excellent color fidelity, respectively, have gained immense popularity. In this study, integrated CP‐TADF and MR‐TADF (CPMR‐TADF) are prepared by strategic design and synthesis of asymmetrical peripherally locked enantiomers, which are separated and denoted as (P,P″,P″)‐/(M,M″,M″)‐BN4 and (P,P″,P″)‐/(M,M″,M″)‐BN5 and exhibit TADF and circularly polarized light (CPL) properties. As the entire molecular frame participates in the frontier molecular orbitals, the resulting helical chirality of (+)/(−)‐BN4‐ and (+)/(−)‐BN5‐based solution‐processed organic light‐emitting diodes (OLEDs) helps in achieving a narrow full width at half maximum (FWHM) of 49/49 and 48/48 nm and a high maximum external quantum efficiency (EQE) of 20.6%/19.0% and 22.0%/26.5%, respectively. Importantly, unambiguous circularly polarized electroluminescence signals with dissymmetry factors (gEL) of +3.7 × 10−3/−3.1 × 10−3 (BN4) and +1.9 × 10−3/−1.6 × 10−3 (BN5) are obtained. The results indicate successful exploitation of CPMR‐TADF‐emitter‐based OLEDs to exhibit three characteristics: high efficiency, color purity, and circularly polarized light.
Circularly polarized thermally activated delayed fluorescence (CP‐TADF) and multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) properties are integrated into a new advanced material, a CPMR‐TADF material. OLEDs based on these CPMR‐TADF emitters show excellent performance, attaining a three‐in‐one advantage: high efficiency, color purity, and circular polarized light simultaneously.
Research into organic light emitters employing multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) materials is presently attracting a great deal of attention due to the ...potential for efficient deep-blue emission. However, the origins and mechanisms of successful TADF are unclear, as many MR-TADF materials do not show TADF behaviour in solution, but only as particular pure solids. Here, an investigation into a well-known MR-TADF material, DABNA-1, together with other new MR materials (9H-quinolino3,2,1-klphenothiazin-9-one (QPO) and 9H-quinolino-3,2,1-kl-phenothiazin-9-one 5,5-dioxide (QP3O)), yields new insights regarding the origin of TADF. Although a material system may support the concept of MR, inefficiency in both forward and reverse intersystem crossings forbids TADF unless a suitable host material allows an exciplex-like host–emitter interaction that boosts TADF. This boosted-TADF mechanism can be generalized to any fluorescence dye that lacks TADF in the photoluminescence measurement but has a thermally accessible S1–T1 energy gap, opening the way to high-performance organic light-emitting diodes.This study reveals the importance of host–guest interactions for effective multiple-resonance thermally activated delayed fluorescence in organic light emitters.
Near‐infrared organic light‐emitting diodes (NIR OLEDs) enable many unique applications ranging from night‐vision displays and photodynamic therapies. However, the development of efficient NIR OLEDs ...with a low efficiency roll‐off is still challenging. Here, a series of new heteroleptic Pt(II) complexes (1–4) flanked by both pyridyl pyrimidinate and functional azolate chelates are synthesized. The reduced ππ* energy gap of the pyridyl pyrimidinate chelate, and strong intermolecular interaction and high crystallinity in vacuum‐deposited thin films engender strong intermolecular charge transfer transition including metal–metal‐to‐ligand charge transfer; thereby, exhibiting efficient photoluminescence within 776–832 nm and short radiative lifetimes of 0.52–0.79 µs. Consequently, nondoped NIR‐emitting OLEDs based on these Pt(II) complexes are fabricated, to which Pt(II) complexes 2 and 4 give record high maximum external quantum efficiency of 10.61% at 794 nm and 9.58% at 803 nm, respectively. Moreover, low efficiency roll‐off is also observed, among which the device efficiencies of 2 and 4 are at least four times higher than that of the best NIR‐emitting OLEDs recorded at current density of 100 mA cm−2.
Nondoped near‐infrared organic light‐emitting diodes based on pyrimidinate‐pyrazolate Pt(II) metal complexes 2 and 4 are fabricated, yielding a record high maximum external quantum efficiency of 10.61% at 794 nm and 9.58% at 803 nm, respectively.
In the emerging field of intramolecular charge transfer induced counterion migration, we report the new insights into photophysical features of luminescent donor–acceptor phosphonium dyes (D−π−)nA+X− ...(π=−(C6H4)x−). The unique connectivity of the phosphorus atom affords multipolar molecules with a variable number of arms and the electronic properties of the acceptor group. In the ion‐paired form, the transition from dipolar to quadrupolar configuration enhances the low energy migration‐induced band by providing the additional pathways for anion motion. The multipolar architecture, adjustable lengths of the π‐spacers and the nature of counterions allow for efficient tuning of the emission and achieving nearly pure white light with quantum yields around 30 %. The methyl substituent at the phosphorus atom reduces the rate of ion migration and suppresses the red shifted bands, simultaneously improving total emission intensity. The results unveil the harnessing of the multiple emission of phosphonium fluorophores by anion migration via structure and branching of donor–acceptor arms.
The photophysical properties of a series of multipolar donor–acceptor phosphonium fluorophores (D−π−)nA+X− have been investigated. These dyes exhibit steady‐state panchromatic luminescence attributed to the photoinduced counterion migration. The intra‐ion‐pair dynamics and the fluorescence response can be rationally tuned on the molecular level that might broaden the scope of functionalities and stimulate the development of new ionic systems.
Phosphonium‐based compounds gain attention as promising photofunctional materials. As a contribution to the emerging field, we present a series of donor‐acceptor ionic dyes, which were constructed by ...tailoring phosphonium (A) and extended π‐NR2 (D) fragments to an anthracene framework. The alteration of the π‐spacer of electron‐donating substituents in species with terminal −+PPh2Me groups exhibits a long absorption wavelength up to λabs=527 nm in dichloromethane and shifted the emission to the near‐infrared (NIR) region (λ=805 nm for thienyl aniline donor), although at low quantum yield (Φ<0.01). In turn, the introduction of a P‐heterocyclic acceptor substantially narrowed the optical bandgap and improved the efficiency of fluorescence. In particular, the phospha‐spiro moiety allowed to attain NIR emission (797 nm in dichloromethane) with fluorescence efficiency as high as Φ=0.12. The electron‐accepting property of the phospha‐spiro constituent outperformed that of the monocyclic and terminal phosphonium counterparts, illustrating a promising direction in the design of novel charge‐transfer chromophores.
Low energy absorption and emission were realized in a series of anthracene‐derived donor‐acceptor phosphonium dyes. The electron deficiency of the rare phospha‐spiro architecture allowed to achieve fluorescence at 797 nm in dichloromethane and at 860 nm in the solid state.
Red-bed argillaceous siltstone is one of main types of rocks composing unstable slopes on both banks of water diversion project from the Yangtze to Huaihe River and is prone to deterioration after ...subjected to drying-wetting cycle conditions during water diversion project operation. The study of the damage degradation and the constitutive relationship of rocks subjected to drying-wetting cycle process is therefore of critical scientific importance. In this paper, laboratory tests were conducted to investigate the effect of drying-wetting cycles on the mechanical properties and microstructural characteristics. The experimental results show that the microstructure of the sample surface is no longer dense and uniform and the porosity of tested samples significantly increases with drying-wetting cycles increasing. After subjected to cycles of drying-wetting, the compaction stage of the stress-strain curve becomes longer with more pronounced nonlinear features, while uniaxial compression strength (UCS) and elastic modulus drop obviously. Combined with the evolution characteristics of microstructure found as the porosity grew, UCS and elastic modulus gradually decline. Additionally, from the perspective of energy analysis, the input energy density and dissipated energy density gradually extended with the increasing strain, and the elastic energy density increased first and then declined. As the number of drying-wetting cycles increases, the energy density of samples all present linear fell. Based on the evolution of dissipated energy, a new damage model of red-bed argillaceous siltstone subjected to drying-wetting cycles was established by introducing compaction coefficient. The coefficients of determination (R2) of the constitutive model are always greater than 0.85, indicating that the proposed model is generally in good agreement with the experimental data under different drying-wetting cycles. This paper has specific research and reference value to understand the damage evolution characteristics of red-bed argillaceous siltstone under cyclic drying-wetting.
To understand and evaluate the thermomechanical property of Ti–6Al–4V alloy prepared by the 3D laser deposition technology, an uniaxial compression test was performed on cylindrical samples using an ...electronic universal testing machine and enhanced Hopkinson technique, over the range of strain rate from 0.001/s to 5000/s, and at initial temperatures from the room temperature to 1173K. The microstructure of the undeformed and deformed samples was examined through optical microscopy and the use of scanning electron microscope (SEM). The experimental results show the followings: (1) the anisotropy of the mechanical property of this alloy is not significant despite the visible stratification at the exterior surfaces; (2) initial defects, such as the initial voids and lack of fusion, are found in the microstructure and in the crack surfaces of the deformed samples, and they are considered as a major source of crack initiation and propagation; (3) adiabatic shear bands and shearing can easily develop at all selected temperatures for samples under compression; (4) the yield and ultimate strengths of this laser-deposited Ti–6Al–4V alloy are both lower than those of the Ti–6Al–4V alloy prepared by forging and electron beam melting, whereas both of its strengths are higher than those of a conventional grade Ti–6Al–4V alloy at high strain rate only. In addition to compression tests we also conducted tensile loading tests on the laser-deposited alloy at both low and high strain rates (0.1/s and 1000/s). There is significant tension/compression asymmetry in the mechanical response under high-strain-rate loading. It was found that the quasi-static tensile fracturing exhibits typical composite fracture characteristic with quasi-cleavages and dimples, while the high-strain-rate fracturing is characterized by ductile fracture behavior.
Fractions of waste polypropylene and polyethylene were pyrolyzed in a pyrolysis plant under different conditions. In this study, the influence of the reaction temperature (650–750
°C), the feed rate, ...and the kind of fluidizing medium on the product spectrum were investigated. Pyrolysis of the PP fraction produced oils up to 43
wt.
% of the product. With respect to the PE fraction, the maximum oil yield was above 60
wt.
% of the product. The target compound was BTX aromatics, whose amount in the oils reached 53
wt.% for the PP fraction and 32
wt.
% for the PE fraction. It was shown that the PE fraction yielded a higher liquid product compared to the PP fraction, and that the concentration of aromatics in the oil increased at higher reaction temperatures for both the PP and PE fractions. A higher feed rate and the use of a gas product as the fluidizing medium were favored for the production of oils for both the PP and PE fractions. The oils that were obtained in the experiments almost had no metal and chlorine contents. The maximum heating value of the gas obtained in the experiments was about 50
MJ/kg.
•A colorimetric sensor array was developed to classify different coffees.•The unique color profile for each coffee sample was obtained.•The samples were successfully distinguished according to their ...categories.•We demonstrated that the sensor array was useful for rapid discrimination of different coffees.
A method based on colorimetric sensor array (CSA) was used to classify different coffees. The array was fabricated by printing twelve sensing materials selective to key coffee aroma odorants on a hydrophobic membrane. The unique color profile for each coffee sample was obtained, resulting in facile differentiation by the naked eye without any statistical analysis. The color responses of CSA were evaluated by principal component analysis and hierarchical cluster analysis to identify classification patterns of ground roasted coffee, espresso coffee, and aero-press coffee samples, and the samples were successfully distinguished according to their categories such as variety and roast degree of coffee beans or brewing procedure. The results of hierarchical cluster analysis and linear discriminant analysis using the CSA data obtained from sixty coffee samples demonstrate that the CSA is a potentially promising methodology for rapid discrimination of different coffees.
In this study, the chromophore 3,4,9,10-perylenetetracarboxylic diimide (PDI) is anchored with phenyl substituents at the imide N site, followed by thionation, yielding a series of thione products ...1S-PDI-D, 2S-cis-PDI-D, 2S-trans-PDI-D, 3S-PDI-D, and 4S-PDI-D, respectively, with n = 1, 2, 3, and 4 thione. The photophysical properties are dependent on the number of anchored thiones, where the observed prominent lower-lying absorption is assigned to the S0 → S2(ππ*) transition and is red-shifted upon increasing the number of thiones; the lowest-lying excited state is ascribed to a transition-forbidden S1(nπ*) configuration. All nS-PDIs are non-emissive in solution but reveal an excellent two-photon absorption cross-section of >800 GM. Supported by the femtosecond transient absorption study, the S1(nπ*) → T1(ππ*) intersystem crossing (ISC) rate is > 1012 s–1, resulting in ∼100% triplet population. The lowest-lying T1(ππ*) energy is calculated to be in the order of 1S-PDI-D > 2S-cis-PDI-D ∼ 2S-trans-PDI-D > 3S-PDI-D > 4S-PDI-D, where the T1 energy of 1S-PDI-D (1.10 eV) is higher than that (0.97 eV) of the 1O2 1Δ g state. 1S-PDI-D is further modified by either conjugation with peptide FC131 on the two terminal sides, forming 1S-FC131, or linkage with peptide FC131 and cyanine5 dye on each terminal, yielding Cy5-1S-FC131. In vitro experiments show power of 1S-FC131 and Cy5-1S-FC131 in recognizing A549 cells out of other three lung normal cells and effective photodynamic therapy. In vivo, both molecular composites demonstrate outstanding antitumor ability in A549 xenografted tumor mice, where Cy5-1S-FC131 shows superiority of simultaneous fluorescence tracking and targeted photodynamic therapy.
PDF
