Latest ArticlesDeep-blue emitter with high photoluminescence efficiency (PLQY) is highly desirable in ultra-high definition displays and white solid-state lightings. In this work, two deep-blue phenanthro[9,10]imidazole derivatives, PPIS and PPPIS, with hot exciton property are successfully developed. Compared to PPIS, the embedded phenyl bridge in PPPIS is able to effectively increase the overlap of frontier molecular orbitals. In consequence, PPPIS shows higher oscillator strength and significantly enhanced PLQY. PPPIS also achieves better electroluminescence performance in non-doped device, showing deep-blue emission with Commission International de l'Eclairage (CIE) coordinates of (0.153, 0.087) and the maximum external quantum efficiency (EQEmax) of 8.5% with minuscule efficiency roll-off. Meanwhile, when PPPIS serves as the host for phosphor PO-01, high-efficiency orange phosphorescent device is obtained with high EQEmax of 29.8% and negligible efficiency roll-off at 1000 cd/m2. Further, efficient single-emissive-layer white device is assembled via utilizing PPPIS as a blue emitter as well as the host for PO-01 simultaneously, providing warm-white emission with CIE coordinates of (0.429, 0.433) at 1000 cd/m2, the forward-viewing EQEmax of 27.2% and maximum power efficiency (PEmax) of 80.1 lm/W, respectively. Our studies can establish a viable design strategy for deep-blue emitters in high-performance non-doped blue OLEDs and hybrid WOLEDs.
The adsorption of peroxymonosulfate (PMS) is crucial for PMS activation in the heterogeneous advanced oxidation processes. However, the investigation of PMS adsorption on the piezocatalysts still remains insufficient. In this work, bismuth oxychloride (BiOCl) nanosheets were prepared as the piezocatalysts for PMS activation under ultrasonic vibration to remove carbamazepine (CBZ) in aqueous solutions. Up to 92.5% of CBZ was degraded for 40 min in BiOCl piezo-activated PMS system with the reaction rate constant of 0.0741 min−1, being 1.63 times that of the sum of BiOCl piezocatalysis, BiOCl-activated PMS, and vibration-activated PMS. PMS adsorption on the surface of BiOCl was specifically studied by comparing the microscopic structure change of the fresh and used BiOCl. The results suggested that the piezoelectric field of BiOCl was able to promote the tight adsorption of PMS on the surface, thus facilitating the fast activation of PMS through electrons transfer to produce reactive species (HO•, SO4•−, O2•−, 1O2). This work presents an in-depth understanding for the role of piezoelectric effect on the adsorption and activation of PMS.
Silicon-based anodes including Si, SiOx and SiO2 could deliver ultra-large capacities, but degrade fast owing to huge volume change and low conductivity. Generally, large amounts of elastic binder and conductive additives were composited with nanosized silicon-based materials to yield reasonable cycling stability, which nevertheless not only decrease specific capacity but also induce inhomogeneous lithiation/delithiation as well as uneven stress variations. Artificial nanolattice has exhibited superior mechanical properties which could be ideal structure for silicon-based anodes, but yet faces challenges in integration of chemical reactivity, conductivity and mechanical stability. Herein, we fabricate artificial SiO2 honeycomb nanolattice consisting of numerous nanoscale SiO2 cells interconnected by through-holes, and conformal coating of highly graphitic carbon on the nanolattice is achieved through in situ catalytic graphitization. Moreover, the nanolattice is firmly bonded on Cu substrate through atomic interdiffusion irrespective of surface roughness. This unique structure allows fast charge transportation and homogeneous lithiation/delithiation throughout the micron-meter nanolattice, which results in excellent stability and large reversible capacity over 500 cycles at 1 A/g. The results highlight design and constructing artificial nanolattice can be an effective way to prevent chemo-mechanical degradation of silicon-based anode materials.
Oligo[n]rotaxanes are one of the most extensively studied categories of mechanically bonded macromolecules. In this study, a supramolecular oligo[2]rotaxane is successfully constructed driven by platinum(Ⅱ) metallacycle and pillar[5]arene-based host–guest interactions in an orthogonal way. The supramolecular oligo[2]rotaxane is further applied in fabricating a light harvesting system.
Triphenylamine (TPA)-containing 2-(2′-hydroxyphenyl)benzoxazoles (2a-2c) have been synthesized via a highly efficient rhodium-catalyzed C–H/C–H cross-coupling reaction. Compound 2a is a novel mechanofluorochromic material with blue-shifted mechanochromic properties. Compounds 2b and 2c presented opposite mechanochromic trends. For 2b, the enol-form emission enhanced, and the keto-form emission blue-shift after grinding. In contrast, 2c exhibited the weak enol-form emission disappeared and the keto-form emission slightly red-shift after grinding treatments. The estrone-containing 2b-based water-dispersed nanoparticles (NPs) exhibit apparent dual-emission and were applied for fluorescence images. In addition, bis(TPA)-containing 2c-based devices exhibit dual-emission with good performance and a singlet exciton yield of 92%, which breaks through the theoretical upper limit of 25% in conventional fluorescent OLEDs. This is one of the highest exciton utilization values recorded for the ESIPT molecules with a dual emission system.
The first example of metal Sn-fused perylene diimides (PDI) derivative (Sn-PDI) was designed, synthesized, and investigated. To obtain this type compound, a simple one-pot synthesis, named stannylative cycloaddition reaction, has been successfully developed via a palladium-based catalyst system. The novel mechanism exhibits that the reaction experiences oxidative addition, Pd-cyclization, stannylation, Pd-Sn-cyclization, and reductive elimination processes successively. This stannylative cycloaddition does realize unique σ-π hyperconjugation effect and therefore significantly influencing on the photophysical, electrochemical and excited state properties. Compared with those of PDI, both of the absorption and fluorescence spectra of Sn-PDI display large red-shifts over 20 nm. The electron energy levels of Sn-PDI have changed with an uncommon regulation. And Sn-PDI gives a considerably raised highest occupied molecular orbital (HOMO) level of -6.00 eV More importantly, the singlet excitons of Sn-PDI could efficiently intersystem cross (ISC) into triplet state with a long lifetime of 17.8 µs, which is far longer than that (4.4 ns) of PDI.
Sequential C-H bond addition with two different coupling partners is a powerful method for the rapid and modular construction of complex molecules based on simple starting materials. Herein, an efficient ruthenium-catalysed multicomponent long-range C-H functionalization of 2H-imidazoles was developed. This protocol showed good substrate suitability and yielded alkyl arylation products with potential biological activity.
The development of efficient and stable bifunctional overall water-splitting is a crucial goal for clean and renewable energy, which is a challenging task. Herein, we report an Mn-incorporated RuO2 (Mn-RuO2) catalyst for highly efficient electrocatalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in acid and alkaline media. Benefiting from a more electrochemical active area with the incorporation of Mn, the Mn-RuO2 required an overpotential of 200 mV to attain a current density of 10 mA/cm2 for OER in acid. DFT result indicates that the doping of Mn into RuO2 can enhance the OER activity. An acidic overall water-splitting electrolyzer with good stability constructed by bifunctional Mn-RuO2 only requires a cell voltage of 1.50 V to afford 10 mA/cm2 and can operate stably for 50 h at 50 mA/cm2, which is better than the state-of-the-art Ru-based catalyst. Additionally, the Mn-RuO2 exhibits excellent HER and OER activity in alkaline media, and it shows superior activity and durability for overall water-splitting, only needing a cell voltage of 1.49 V to attain 10 mA/cm2. The present work provides an efficient approach to designing and constructing efficient Ru-based electrocatalysts for overall water-splitting.
Trifluoroacetic acid (TFA) catalyzed condensation reaction between tetraaminooxacalix[4]arene and N-alkylcarbazole-3,6-dicarbaldehyde in CH2Cl2 afforded a single product in 87%–89% yield. Well-defined yet undissolvable 1H NMR spectra suggested formation of robust and discrete structures in solution. X-ray single crystal analysis further revealed a giant twisted double-layer chiral macrocycle in the solid state, which was formed from [4 + 8] condensation of the two reactants via 16 imine bonds. DFT calculations discovered that only the [4 + 8] twisted product is thermodynamically favorable, which accounts for its highly selective and efficient formation out of a library of many other combinations.
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