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Chromium (Cr) and the emission of its compounds into the environment have caused long-term environmental contamination. In this study, the modes of occurrence of Cr in low-rank coal and their thermal stability in pyrolysis were investigated by sequential chemical extraction (SCE), single-component samples (SCS) pyrolysis, and thermochemical equilibrium simulation. The results showed that organic matter, aluminosilicate, and carbonate were the dominant modes of occurrence of Cr in low-rank coal. The modes of occurrence and chlorine (Cl) content affected the volatilization of Cr in coal. The characteristic release temperature range of Cr bounded to aluminosilicate was >600 °C and 400–600 °C for Cr bounded to a disulfide. Cr bounded to organic matter almost released completely before 600 °C. Cl enhanced the volatility of Cr and reduced its release temperature in Cr bounded to aluminosilicate. The simulation showed the content of gas products was very low, mainly chlorides. While the content of solid products, sulfides, and oxides, was much higher than gas products, showing their high thermal stability. The sulfides and oxides in chars were closely related to the carbonate and aluminosilicate bound form of Cr. The results of the equilibrium simulation were consistent with the experimental results.

Novel smart materials that can achieve a diverse range of practical applications with simple molecular structures and green synthesis routes are still in great demand. Herein, by a green photo-oxidation reaction, two simple aggregation-induced emission luminogens (AIEgens) CZ-PYZ and p-CZ-BYZ were developed, with the difference of linking type between the donor group (carbazole) and the acceptor group (a benzoylimino derivative). These two analogues exhibited different luminescence behaviors in the aggregation state. The molecule p-CZ-BYZ showed mechanochromic luminescence and room-temperature phosphorescence simultaneously, while none of the similar phenomena was observed in the case of CZ-PYZ. According to photophysical property tests, single crystal structural analyses and theoretical calculations, we found that this difference was induced by their different stacking manners. It was believed that the present results may provide us with a better understanding of structure–property relationship and offer an important guideline for multifunctional molecular design.

High performance solution processable thermally activated delayed fluorescence (TADF) emitters are of huge importance in the development of organic light-emitting diodes (OLEDs). In this article, two solution processable D3–A star-shaped TADF emitters, namely TATC-TRZ and TATP-TRZ, with different flexible alkyl and rigid phenyl side chains are developed. Both emitters show similar photophysical properties and obvious TADF characteristics with a sub-micro second delayed lifetime of 0.6 μs for TATC-TRZ and 0.4 μs for TATP-TRZ while the flexible alkyl chain ensures TATC-TRZ with superior film forming ability and morphological stability compared to TATP-TRZ. Owing to such advantages, solution processed non-doped OLEDs based on TATC-TRZ secure a high maximum external quantum efficiency (EQEmax) of 7.5% and current efficiency (CEmax) of 19.9 cd A−1, respectively, which is much higher than that of TATP-TRZ with EQEmax of 2.8% and CEmax of 7.4 cd A−1. This work demonstrates the effectiveness of a flexible alkyl tail on the performance of solution-processed devices.

Developing highly efficient red thermally activated delayed fluorescence (TADF) emitters remains a formidable challenge due to strict molecular design principles. In this contribution, two red emitters PXZ-AQPy and PXZ-AQPhPy with high structural rigidity and linear configurations are designed and synthesized based on phenoxazine (PXZ) as a donor and acenaphtho[1,2-b]quinoxaline (AQ) as an acceptor. Both molecules with horizontal orientation are endowed with TADF and aggregation-induced emission (AIE) properties. By elongating the acceptor segment via phenyl decoration, PXZ-AQPhPy exhibits higher horizontal ratios of the emitting dipole orientation (Θ‖ = 85%), while the emission characteristics are almost unaltered. Consequently, the PXZ-AQPhPy based device achieves a high external quantum efficiency of 19.6% with an emission peak at 610 nm. This work provides a simple and effective design strategy to selectively promote the horizontal orientation of red TADF emitters.

Thermally activated delayed fluorescent (TADF) emitters have been extensively investigated in the past decade. Compared to the prosperous development of the donor unit, the development of an effici...

A tri-armed arylsulfone-based acceptor (SF) linked by triphenylbenzene (TPB) has been developed to construct solution-processable thermally activated delayed fluorescence (TADF) materials with large band gaps. The acceptor suffered limited conjugation due to the tetrahedral geometry of sulfonyl groups, as well as a meta-linkage at the central TPB moiety. By simple conjugation of the SF with appropriate donor units, luminophores SF–DMAC and SF–PXZ capable of producing efficient blue/green emissions were obtained, with peak efficiencies of 11.3% (19.0 cd A−1 and 10.0 lm W−1) and 12.4% (35.6 cd A−1 and 17.8 lm W−1) in the corresponding wet-processed OLEDs. Decent resistance to roll-off at high brightness was noticed in the device based on SF–PXZ, ascribing to reduced intermolecular interactions due to its star-shaped architecture and an efficient reverse intersystem crossing (RISC) process.

Photoluminescence quantum yield (PLQY) and the reverse intersystem crossing (RISC) process are critical for next-generation highly efficient organic light-emitting diodes (OLEDs). However, it is not easy to simultaneously obtain high PLQY and fast RISC, especially in TADF emitters with twisted donor–acceptor structures due to their conflicting requirements for wave function overlapping. Herein, based on a rigid planar dibenzo[a,c]phenazine (DPPZ) unit as an acceptor, four emitters (isomers of DMAC-11-DPPZ and DMAC-10-DPPZ, and isomers of PXZ-11-DPPZ and PXZ-10-DPPZ) with 9,9-dimethylacridine (DMAC) and 10H-phenoxazine (PXZ) as donors substituted via 11- and 10-positions were designed and synthesized to balance the wave function overlapping and explore the relationship between their structures and luminescence properties. Photophysical characterization and theoretical calculations suggest small energy gaps (ΔEST) featuring fast RISC rates in all these compounds. Meanwhile, DMAC-11-DPPZ and PXZ-11-DPPZ achieve higher PLQYs due to the largely suppressed non-radiative transition as revealed by the decreased Huang–Rhys factors. As a result, high external quantum efficiencies (EQEmax) of 23.8% for DMAC-11-DPPZ and 13.7% for PXZ-11-DPPZ are obtained. This work provides a promising strategy to improve the PLQY of TADF materials by adjusting the substituted site, and also shows the potential of phenazine derivatives for OLED applications.

Herein, we report a new pyrene (PY)-based derivative, 1-(4-(phenylsulfonyl)phenyl)pyrene (1-DPS-PY), whose two crystals (crystal-B and crystal-G) exhibit sky-blue and green excimer fluorescence, respectively. Crystal-B and crystal-G have a similar dimeric π–π PY stacking in the crystals, but with a different single-molecule conformation. The experimental and theoretical investigations demonstrate that the substituent orientation of 4-(phenylsulfonyl)phenyl (DPS) plays a crucial role in modulating the excited-state properties of the PY excimer. The small twist angle (Φ) between DPS and PY facilitates the larger overlap between two PY planes in the excited state, resulting in more red-shifted excimer emission, and vice versa. Moreover, crystal-B shows a photoluminescence (PL) efficiency (ηPL) as high as 77% due to the better discreteness of PY dimer stacking, in contrast to ηPL = 60% of crystal-G with the non-discrete PY dimer stacking. Organic light-emitting diodes (OLEDs) were fabricated with doped and non-doped device structures. The devices showed a gradual emission change from deep blue to sky blue with increasing doping concentration, corresponding to the emission species transformation from a monomer to an excimer. A non-doped device exhibited the best performance with an external quantum efficiency (EQE) of nearly 4.5% and a maximum luminance of 13 733 cd m−2. These results provide us with a new understanding of the mechanism of the PY excimer, and a new strategy to design the polymorphic PY dimers for high-efficiency excimer fluorescence with tunable emission color.

A photochemical reaction in which the imidazole ring is opened under UV irradiation to generate highly luminescent benzoylimino group by O2 has been discovered. This photochemical reaction displays great potential for applications that use a fluorescent probe as a oxygen sensor; it has a lowest detectable volume ratio of ∼0.2% and photo storage area.

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

Luminescent coinage metal complexes have shown promising applications as electroluminescent emitters, photocatalysts/photosensitizers, and bioimaging/theranostic agents, rendering them attractive alternatives to transition metal complexes based on iridium, ruthenium, and platinum that have extremely low earth abundance. In comparison to the widely studied Au(I) and Cu(I) complexes, Ag(I) complexes have seldom been explored in this field because of their inferior emission properties. Herein, we report a novel series of [Ag(N^N)(P^P)]PF6 complexes exhibiting highly efficient thermally activated delayed fluorescence by using easily accessible neutral diamine ligands and commercially available ancillary diphosphine chelates. The photoluminescence quantum yields (PLQYs) of the Ag(I) emitters are ≤0.62 in doped films. The high PLQY with a large delayed fluorescence ratio enabled the fabrication of solution-processed organic light-emitting diodes (OLEDs) with a high maximum external quantum efficiency of 8.76%, among the highest values for Ag(I) emitter-based OLEDs. With superior emission properties and an excited state lifetime in the microsecond regime, together with its potent cytotoxicity, the selected Ag(I) complex has been used for simultaneous cell imaging and anticancer treatment in human liver carcinoma HepG2 cells, revealing the potential of luminescent Ag(I) complexes for biological applications such as theranostics.

A novel electron donor, namely, TMDBP is designed by angularly fusing two acridine moieties. The DMAC subunits in TMDBP exhibit a dominant quasi-equatorial conformation due to steric H-H repulsion. The new TADF emitters render excellent OLED performances with EQE up to 24.2% and small efficiency roll-off.

Excited-state properties (characteristics and composition) play a crucial role in luminescence properties of the new-generation organic light-emitting materials. As a special excited species, the hybridized local and charge-transfer (HLCT) state is composed of locally excited (LE) state and charge-transfer (CT) state, which can harvest simultaneous high photoluminescence (PL) efficiency and high exciton utilization in organic light-emitting diodes. In this work, we designed and synthesized three donor (D)–acceptor (A) compounds with different donor units and a typical electron-deficient unit acridine as the acceptor unit to investigate the different hybridization statuses among them. As is revealed by the molecular design, the three compounds precisely show the different hybridization statuses: LE-dominated hybridization (CZP-1AC), quasi-equivalent HLCT (qHLCT, TPA-1AC), and CT-dominated hybridization (PTZ-1AC). As a result, TPA-1AC exhibits the highest PL efficiency and multifold device performance, meri...

To develop colorless and soluble polyimide films, a novel dianhydride containing 1,4:3,6-dianhydro-D-mannitol unit, 2,5-bis(3,4-dicarboxyphenoxy)-1,4:3,6-dianhydromannitol dianhydride (IMDA) was synthesized. And two series of polyimides were prepared via a two-step thermal imidization, PI−(1–4) were obtained from IMDA and four kinds of aromatic diamines while PI−(5–7) from IMDA and three kinds of semiaromatic diamines. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough and colorless films with transparency up to 89% at 450 nm. Especially, polyimides simultaneously containing 1,4:3,6-dianhydrohexitol units in diamine and dianhydride exhibited comparable optical and soluble performance with the alicyclic fluorinated ones. Meanwhile, it was certified that 1,4:3,6-dianhydrohexitol fragment in dianhydride was more determinant in solubility and transmittance of polyimides than that in diamine. An overall investigation of these polyimides on thermal, mechanical, morphological, soluble, optical and dielectric properties was presented, and their structure-property relationships were discussed in detail.

Charge-transfer (CT) state is becoming a useful excited state to design next-generation luminescence materials for high-performance organic light-emitting diode (OLED). However, strong CT state usually causes serious decrease in photoluminescence (PL) efficiency due to the small overlap between HOMO and LUMO. In order to harvest both high exciton utilization and high PL efficiency in fluorescent OLEDs, figuring out the strategy of fine modification of CT component in excited state through structural modulation is important. In this work, four donor–acceptor structure triphenylamine (TPA) - acridine (AC) isomers (TPA-9AC, TPA-1AC, TPA-2AC and TPA-3AC) were designed and synthesized to investigate structure-property relationship between isomerization effect and excited state properties. Density functional theory (DFT) calculations and solvatochromic absorption, emission and photoluminescence decay spectra are carried out for the deep understanding of their emissive state character. The four isomers exhibit gradually increased PL efficiency from low-polarity hexane to medium-polarity tetrahydrofuran (THF), which could be assigned to the formation of hybridized local and charge-transfer (HLCT) states and effectively suppressed non-radiative transition arised from acridine in medium-polarity solvents. Among four isomers, TPA-3AC achieved the best EL performance, due to the proper LE and CT compositions in the emissive state, demonstrating that isomerization of donor and acceptor functional moieties is an effective approach for structural modification for high-efficiency fluorescent OLED emitters.

Polyaromatic compounds are significant members of leading candidates for organic semiconductors and optical materials. However, a thorny problem of polyaromatic materials is that their good emissive abilities in solutions are seriously weakened in solids due to strong π–π interactions between aromatics. As a typical case, the intermolecular π–π interaction tends to form excimers for polyaromatic system, which were always considered to quench fluorescence and decrease luminous efficiency in the past decades. Herein, anthracene is modified by meta-substituted bromobenzene to facilitate the formation of discrete dimeric stack in solids, leading to the enhanced anthracene excimer fluorescence. Particularly, instead of excimer quenching fluorescence, the more anthracene dimers in solids, the higher fluorescence efficiency, namely, excimer-induced enhanced solid-state emission. This work not only provides a meta-substituted strategy for molecular design to form excimer in solids but also demonstrates that high-...

Simple and fast detection of chemical warfare agents vapor is necessary and urgent to fight against uncertain terrorist attacks and wars. In this contribution, inspired by the design of the hybrid locally excited and charge transfer (HLCT) excited state, two fast and highly sensitive visualization and fluorescence probes for DCP detection with relative small interstate coupling (J) TPA-2AC and TPA-9AC are reported. Upon exposure to saturated DCP vapor, the TPA-9AC test strips exhibited a rapid fluorescent response in no more than 1 s, accompanied by a change of the color from green to red. The detection limit of the test strips can be estimated as sensitive as 0.15 ppb, which is far superior to the "harmless" level (7 ppb) of human response to acute sarin exposure. More impressively, the fluorescent intensity of the test strips can be quickly restored when exposed to ammonia vapor for cyclic utilization, demonstrating an application prospect in the real-time detection of chemical warfare agents.

Advanced adenomas are of higher risk to progress to colorectal cancer (CRC), the third leading cause of cancerous death worldwide. Endoscopy-based adenoma removal greatly contributes to arresting the progression of adenoma to CRC. Precise diagnosis, post-polypectomy surveillance and the follow-up clinical decisions predominantly depend on histopathologic inspection of the resected tissues. The common artificial histological inspection is not fully reliable and is only compatible with the en bloc removed tissues. An alternative measure ensuring more objective tissue malignance appraisal, which is applicable to various endoscopically acquired sample types are highly appreciated. In this study, we firstly employed capillary electrophoresis-mass spectrometry-based untargeted metabolomic technique to analyze CRC and corresponding paracancerous tissues to narrow the scope of malignancy-related metabolite changes. The primary results implied the most perturbated metabolites by CRC onset were amino acids. Subsequently, a targeted amino acid analysis by ultra-performance liquid chromatography-mass spectrometry indicated 9 amino acids were of different content between advanced adenoma and CRC tissues. Finally, regression analysis of the 9 differential amino acids exhibited that methionine, tyrosine, valine and isoleucine could be used to differentiate CRC from advanced adenomas with good sensitivity and specificity (p

Based on novel phenanthro[9,10-d]imidazole (PI) chromophore, three deep-blue luminescent donor-acceptor molecules with different molecular configurations at the triphenylamine (TPA) core were designed and synthesized, the linear TPA-1PI, the V-shaped TPA-2PI and the star-shaped TPA-3PI. All three molecules displayed the hybridized local and charge-transfer (HLCT) excited state character, and highly efficient deep blue emissions were observed in their solution state, but only those of linear TPA-1PI and V-shaped TPA-2PI molecule were maintained in the solid state. Meanwhile, the V-shaped TPA-2PI and star-shaped TPA-3PI showed the much better thermal properties. Thus the molecular configurations of HLCT materials significantly influence their solid-state, and the V-shaped TPA-2PI molecule was highlighted because of its both deep-blue emission and good thermal stability. A double-layer device by using TPA-2PI as the emitter showed a highly efficient deep-blue electroluminescence with a very good CIE coordinate of (0.14, 0.08) and high current efficiency of 2.7 cd A−1, which suggest that it might be a promising candidate for emission-layer materials for high-performance deep-blue OLEDs.

The reverse intersystem crossing (RISC) process plays a decisive role in next-generation organic light-emitting diodes (OLEDs), which depends on the energy gap and spin-orbit coupling (SOC) between singlet state and triplet state. To investigate the excited state structure-property relationship and the SOC effect in electro-fluorescent donor-acceptor (D-A) materials, herein, we constructed four quinoxaline derivatives based donor-acceptor (D-A) materials and investigated their excited state properties with a theoretical combined experimental research. The four materials are of different hybridized local and charge-transfer (HLCT) characters. Among them, the most hybridized TPA-DPPZ achieved a higher quantum efficiency over 90% for the effective suppression of non-radiative transition, and it exhibited a higher exciton utilization of 42.8% in non-doped OLED due to a “hot-exciton” channel facilitated with sizeable SOC.

ZnGa2O4 octahedral crystallites have been prepared via a hydrothermal method assisted with cetyltrimethyl ammonium bromide (CTAB). It was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The results indicated the hydrothermal temperature and CTAB play an important role in the formation of ZnGa2O4 octahedral crystallite and its self-assembled three-dimensional rodlike structure. The photocatalytic degradation test using rhodamine B as a model pollutant showed that the photocatalytic activity of the ZnGa2O4 crystallites assisted with CTAB can be significantly decreased with temperature increasing and the best photodegradation efficiency was the sample prepared at 160 °C, of which the degradation efficiency was 97.6% in 60 min.

The efficiency of water flooding in heavy oil reservoirs would be improved by increasing the viscosity of the displacing phase, but the sweep efficiency is not of significance due to the low mobility of the vicious oil. On the basis of mobility control theory, increasing the residual resistance factor not only reduces the water-oil mobility ratio but also decreases the requirement for viscosity enhancement of the polymer solution. The residual resistance factor caused by hydrophobic associating polymer solution is higher than that caused by polyacrylamide solution in brine containing high concentrations of calcium and magnesium ions. The results of numerical simulations show that the polymer flooding efficiency improved by increasing the residual resistance factor is far better than that by only increasing solution viscosity. The recovery factor of heavy oil reservoirs (70 mPa·s) can be enhanced by hydrophobic associating polymer solution of high residual resistance factor (more than 3) and high effective viscosity (24 mPa·s). Therefore, increasing the residual resistance factor of the polymer solution not only decreases the requirement for the viscosity of polymer solution injected into heavy oil reservoirs but also is favorable to enhanced oil recovery during polymer flooding.

Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids (PynPMo10V2O40, n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were detected by FT-IR. Among various catalysts, Py3PMo10V2O40 exhibits the highest catalytic activity (yield of phenol, 11.5%), without observing the formation of catechol, hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent, oxidant and reducing reagent, respectively. Influences of reaction temperature, reaction time, oxygen pressure, amount of ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H5PMo10V2O40), mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and dramatically modify the redox properties, at the same time, pyridine adsorbed on heteropoly acids can promote the effect of “pseudo-liquid phase”, thus accounting for the enhancement of phenol yield.

The hybrid catalysts, pyridine (Py) modified molybdovanadophosphates with Keggin structure Pyn–PMo(12−m)VmO40 (n = 1–3, m = 1–3), were prepared and characterized by FT-IR. Among various catalysts, Py1–PMo10V2O40 exhibited the highest yield of phenol (20.5%) with the selectivity of phenol of 98.0% at 353 K for 5 h in the direct hydroxylation of benzene to phenol with H2O2 in the acetic acid and acetonitrile (volume ratio 1:1) mixed solvent. Pyridine plays an important role in the promotion of the catalytic activities, mostly due to the electronic interaction between pyridine and heteropolyacid together with the more remarkable pseudo-liquid-phase behavior. The influences of the reaction temperature, the amount of H2O2, the amount of Py1–PMo10V2O40 and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.

Pyridine(Py)-modified Keggin-type mono-vanadium-substituted heteropoly acids (PynPMo11V, n = 1–4) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were characterized by FT-IR. Among various catalysts, Py4PMo11V exhibited the highest catalytic activity (yield of phenol 9.0%) with the high selectivity for phenol, without observing the formation of catechol, hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent, oxidant and reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H4PMo11VO40), mostly because the organic π electrons in the hydrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and thus dramatically modify the redox properties.

Cyclodextrins (CyDs) complexes with vanadium-substituted heteropoly acids (PMoV n -β-CyDs, n = 1, 2) were prepared by simple mixing and their structures were characterized by FT-IR. Among various catalysts, PMoV1-β-CyDs, an efficient phase transfer catalyst, exhibited the highest yield (13.1%) of phenol without observing the formation of catechol, hydroquinone and benzoquinone in direct hydroxylation of benzene to phenol in 80 vol% aqueous acetic acid with molecular oxygen and ascorbic acid used as the oxidant and the reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.

Organic-inorganic hybrid catalysts were prepared by combining laurylamine (or octadecylamine) and molybdovanadophosphoric acid, and their catalytic performance for the hydroxylation of benzene to phenol was evaluated using molecular oxygen as the oxidant in a pressured batch reactor. The laurylamine-modified heteropolyacid catalyst with a 4:1 molar ratio for the two moieties exhibited a much higher yield of phenol (11.5%) than that of the neat heteropolyacid H5PMo10V2O40 (3.9%). We discuss the promotional effect of the long chain aliphatic amines with regards to the interaction between the amine and the heteropolyacid framework, and we also discuss the “pseudo-liquid phase” behavior of the heteropolyacid.