Jingying Zhang

Efficient single-layer electroluminescent device based on a bipolar emitting boron-containing material

A novel multifunctional 1,6-bis(2-hydroxyphenyl)pyridine boron bis(4-n-butyl-phenyl)phenyleneamine compound in which the hole-transporting (HT), electron-transporting (ET), and emitting (EM) components are integrated into a single molecule was synthesized and used as an emitting material to fabricate an efficient single-layer electroluminescent device.

Phenanthroimidazole-derivative semiconductors as functional layer in high performance OLEDs

Four phenanthroimidazole derivatives (a: 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole; b: 2-phenyl-1-p-tolyl-1H-phenanthro[9,10-d]imidazole; c: 1-phenyl-2-p-tolyl-1H-phenanthro[9,10-d]imidazole; d: 1,2-di-p-tolyl-1H-phenanthro[9,10-d]imidazole) were synthesized and their single crystal structures, photophysical, electrochemical and mobility properties were carefully studied. Taking advantage of the thermal stability and the hole transporting (HT) ability, the highly efficient Alq3-based organic light-emitting diodes (OLEDs) have been achieved by employing the compounds a–d as a functional layer between NPB (4,4-bis(N-(1-naphthyl)-N-phenylamino)biphenyl) and Alq3 (tris(8-hydroxyquinoline)aluminium) layers. For the device of [ITO/NPB/d/Alq3/LiF/Al], a maximum luminous efficiency (LE) of 8.1 cd A−1 was obtained with a maximum brightness of 65130 cd m−2, which exhibited much higher efficiency compared to the device with structure of [ITO/NPB/Alq3/LiF/Al]. The results demonstrated not only an alternative idea to design novel HT materials, but also a convenient way to improve the performance of the NPB/Alq3-based devices by introduction of a suitable organic buffer layer.

Construction of 2-D lanthanide coordination frameworks: syntheses, structures and luminescent property

A series of layered lanthanide coordination frameworks [Ln4(NIPH)6(H2O)4]·(4,4′-bipy) [Ln = La (1), Pr (2)], [La(NIPH)2(H2O)2]·0.5(4,4′-H2bipy) (3), Ln(NIPH)2(H2O)2]·0.5(4,4′-H2bipy)·2H2O [Ln =Pr (4), Nd (5)], and [Ln(NIPH)2]·0.5(4,4′-H2bipy) [Ln = Sm (6), Eu (7), Tb (8), Ho (9), Yb (10)] (NIPH = 5-nitroisophthalate and 4,4′-bipy = 4,4′-bipyridine) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. All the coordination frameworks display identical crystal system (triclinic) and space group (P). Compounds 1 and 2 are isostructural, their coordination sheets are constructed by polynuclear helical-like chains. Compounds 3–5 are extremely similar in structure, in which Ln atoms are bridged into rod-shaped chains by carboxylate groups. For compounds 6–10, the coordination layers are built up from 1-D zig-zag chains. The 3-D supramolecular frameworks of 1–10 are finally formed through the alternate stack of Ln coordination layers and 4,4′-bipy layers based on hydrogen bonding interactions. Compound 7 displays luminescent property.

Efficient deep-blue OLEDs based on phenanthro[9,10-d]imidazole-containing emitters with AIE and bipolar transporting properties

Highly efficient deep-blue emitters, especially those matching the NTSC (National Television Standards Committee) blue standard CIE (Commission Internationale de L’Eclairage) coordinate of (0.14, 0.08), are crucial for full-colour displays and white lighting. However, deep-blue emitters with excellent electroluminescence performance are rare. According to the strategy of developing highly luminescent solids by constructing aggregation-induced emission (AIE) systems, two AIE-type blue emitters, mTPE-PPI and mTPE-DPI, have been synthesized by integrating a triphenylethylene (TPE) group with one or two phenanthro[9,10-d]imidazole (PI) groups. The adoption of the PI unit with a large optical bandgap, the meta-linkage of the PI and the TPE units on a benzene ring, and the twisted molecular conformations of present AIE systems endow these compounds with bright blue emission in the solid state. In addition, these compounds are capable of transporting both electrons and holes and possess appropriate HOMO and LUMO levels for carrier injections. These features enable them to serve as excellent blue-emitting materials in OLEDs. A non-doped OLED based on mTPE-PPI displayed deep-blue light with the CIE coordinate of (0.15, 0.09) and a maximum external quantum efficiency (EQEmax) of 2.30%. An analogous device with mTPE-DPI as the emitting layer emitted blue light (CIE: 0.15, 0.14) with a high EQEmax of 3.69% and low efficiency roll-off. Further improvement of device performance has been achieved by the doping technique. The doped device of mTPE-DPI was able to realize deep-blue emission (CIE: 0.15, 0.10) matching well the blue standard, meanwhile reaching a EQEmax of 5.52% that represents the highest value reported for deep-blue OLEDs based on AIE compounds.

Pentaphenylphenyl substituted quinacridone exhibiting intensive emission in both solution and solid state

Pentaphenylphenyl substituted quinacridone (QA) derivative BPP–QA with two propeller-like substituted groups was synthesized and showed intense emission in both solution and solid state.

Polymorphs and luminescent properties of a cetyl substituted quinacridone derivative

The crystallization of N,N-di(n-cetyl)quinacridone (DCQA) gives two crystalline polymorphs A and B. It is found that crystalline polymorphs A and B adopt remarkable different packing structures. The form A crystal is characterized by the strong intermolecular π⋯π interaction and C–H⋯O interaction. The form B crystal displays an intermolecular C–H⋯π interaction and hydrogen bonding interaction feature. In form B, every quinacridone core is sandwiched by two alkyl chains from two adjacent DCQA molecules. The photoluminescent (PL) spectra of two polymorphs in solution and in the solid state were reported. The PL spectra of DCQA in solution exhibit concentration-dependent property. The emission spectrum of form A displayed an obvious red shift compared to that of form B. The studies of the single-crystal structures and the solid-state emission spectra of the two polymorphs demonstrated that the molecular packing is the critical element determining the solid-state emission.

Polymorph, assembly, luminescence and semiconductor properties of a quinacridone derivative with extended π-conjugated framework

The structures and properties of an indole-ring-fused quinacridone derivative 5,8,15,18-tetraoctyl-5,8,15,18-tetrahydroindolo[3,2-a]indole[3′,2′ : 5,6]quinacridone (IDQA), which was synthesized by an improved procedure, have been carefully investigated and compared with its parent compound N,N′-di(n-octyl)quinacridone (C8-QA). Concentration-dependent 1H NMR spectra revealed that the strong aggregations of IDQA existed in solution because of the flat and extended π-conjugation. Two polymorphs of IDQA with and without π⋯π interactions exhibited red and non emissions, respectively. One-dimensional micromaterials with different morphologies constructed by IDQA molecules were fabricated by a reprecipitation approach and they displayed different emission properties due to the different molecular packing. The nine-ring fused flat skeleton endowed this material with several elegant properties, including a high photoluminescent quantum yield in solution, and a high thermal and electrochemical stability. Therefore, the efficient doped organic light emitting device (OLED) with IDQA as the emitter was fabricated. Moreover, the large π-conjugation system endowed the IDQA thin film with ordered molecular packing and good hole transport properties (hole mobility μh = 0.047 cm2 V−1 s−1).

Extraction of steroid saponins from Paris polyphylla Sm. var. yunnanensis using novel ultrahigh pressure extraction technology

A new method of ultrahigh pressure extraction (UPE) was used to extract steroid saponins from Paris polyphylla SM. var. yunnanensis (chonglou) at room temperature. The microstructure of the drug before and after the extraction was studied by scanning electron microscopy (SEM). The mechanism of UPE is discussed and demonstrated based on the results of SEM investigation. The influence of several factors, including solvent type, solvent concentration, UPE pressure, UPE time, and liquid-to-solid ratio, has been studied in order to optimize the extraction process. The optimum extraction takes place with an ethanol concentration of 90%, a pressure of 400 MPa, an extraction time of 2 min, and a liquid-to-solid ratio of 40: 1. In comparison with usual room-temperature extraction at normal pressure, ultrasound-assisted extraction, microwave-assisted extraction, and Sohxlet extraction, the UPE method shows higher efficiency at room temperature.

Chemical composition and antioxidant activity of essential oil from berries of Schisandra chinensis (Turcz.) Baill

Essential oils of Schisandra chinensis seeds and berries without seeds were separately extracted. A total of 55 compounds were identified in the essential oil of berries without seeds (EOB), representing 85.75% of the total content. A total of 52 compounds were identified in the essential oil of seeds (EOS), representing 89.74% of the total content. For EOB, the top three content compounds were α-cis-bergamotene (10.79%), 4,11-selinadiene (5.28%) and α-cadinol (5.19%), while the top three content compounds of EOS were ylangene (10.16%), β-himachalene (9.46%) and di-epi-α-cedrene (8.92%). The antioxidant activity of the essential oil was tested using the DPPH radical-scavenging method. The antioxidant activity of EOB was higher than EOS. The IC50 values of EOB and EOS were 8.4 and 15.8 mg/mL, respectively. This study concluded that EOB and EOS were not only different in extraction yield but also in chemical composition and antioxidant activity.

Basket-shaped quinacridone cyclophanes: synthesis, solid-state structures, and properties

A series of basket-shaped quinacridone (QA) cyclophanes 1–6 has been synthesized and characterized. Single-crystal X-ray analysis of 5 shows no infinite π–π aggregation between QA cores, reflecting a significant isolated effect of the bridging tethers. Photophysical properties have been carefully investigated. All cyclophanes show much higher quantum yields in concentrated solutions compared to the non-bridged QA analogue 7. Further application of 1 as a green dopant in EL devices exhibits current efficiencies of 11.2 and 7.2 cd A−1 with doping concentrations of 0.5 and 3 wt%, respectively. QA cyclophanes maintain a high luminescent yield in both concentrated solution and high doping concentration EL devices, verifying that the basket-shaped functionalization is an ideal strategy for depressing fluorescence quenching of QA dyes in the condensed phase.