Qidan Ling

A Λ-shaped donor–π–acceptor–π–donor molecule with AIEE and CIEE activity and sequential logic gate behaviour

A novel Λ-shaped donor–π–acceptor–π–donor molecule BCPMM with AIEE, CIEE and polymorphism-dependent fluorescence properties was developed. The emission of BCPMM in solid states could be tuned by an external stimulus, which was utilized to construct five simple logic gates and more than ten kinds of sequential combinational logic systems.

Polymorphism-dependent fluorescence of bisthienylmaleimide with different responses to mechanical crushing and grinding pressure

A herringbone structured compound, 3,4-bisthienylmaleimide (BTM), with reversible four-color and on/off switching upon external stimuli is reported here. Three kinds of BTM crystals with strong red (RC), orange (OC) and yellow (YC) fluorescence, as well as a brown solid (BS) with weak orange luminescence are obtained in the experiments. Heating, solvent vapor and pressure, including crushing and grinding, can reversibly switch BTMs emission between RC, OC, YC and BS. Base vapor (NEt3)-heating cycle treatment of BTM film in polystyrene can induce emission switching between bright/dark (on/off) states. The results of crystal structural analysis and photophysical property studies demonstrate that although OC and YC have the same crystal structure, they exhibit different fluorescent properties, due to their different surface structures. Heat induces metastable RC, with orderly π-stacking, to turn into stable OC or YC, with brick stone stacking. Crushing can damage the surface structure of OC and transform it into YC without altering the crystal structure. Grinding OC or YC destroys the orderly stacking to yield amorphous BS.

Diarylmaleic anhydrides: unusual organic luminescence, multi-stimuli response and photochromism

Diarylmaleic anhydride derivatives containing benzene (BPMA), thiophene (BTMA) and indole (BIMA) exhibit diverse and distinct fluorescence: aggregation-caused quenching (ACQ) of red emission of BIMA, blue aggregation-induced emission (AIE) of BPMA, and green dual-state emission (DSE) of BTMA in both solution and the solid state. Theoretical calculation and crystal structure analysis indicate that intramolecular and intermolecular interactions are responsible for their different emission behavior. A series of DSE-active molecules with full-color emission could be developed for the first time, through modification of the structures of BPMA and BIMA. Interestingly, BTMA and BPMA display multi-stimuli-responsive luminescence with a high-contrast (Δλem > 100 nm) and an unusual photochromic phenomenon in dichloromethane, which were utilized to construct rewritable data storage and mimic molecular logic operation (4-to-2 encoder and 1 : 2 demultiplexer), respectively.

A facile one-pot synthesis of hyper-branched carbazole-based polymer as a hole-transporting material for perovskite solar cells

A low-cost, hyper-branched, carbazole-based polymer (HB-Cz) was designed and synthesized by a facile “A3 + B2” one-pot Suzuki polycondensation reaction. Due to the hyper-branched structure and carbazole unit, HB-Cz is a promising candidate for a hole-transporting material, which was confirmed in perovskite solar cells (PVSCs) with a configuration of ITO/TiO2/MAPbI3/HB-Cz/Ag. The films of poly-(3-hexylthiophene) and linear poly[N-(1-octylnonyl)-9H-carbazole-2,7-diyl] were also used as hole-transporting layers (HTLs) in the reference devices. Time-resolved photoluminescence spectra indicate that HB-Cz has the fastest charge regeneration. Electrochemical impedance spectroscopy revealed that HB-Cz could reduce carrier recombination effectively, improving the open circuit voltage and fill factor of the PVSCs. A PCE of 14.07% obtained from the HB-Cz-based device was much higher than those of devices based on P3HT (9.05%) and PCz (6.60%), and this is attributed to the superior hole-transporting property and surface smoothing effect of the HB-Cz HTL.

White-light hydrotalcite-like compound emission from the incorporation of red-, green-, and blue-emitting metal complexes

A white-light hydrotalcite-like compound (Eu/Tb/Zn-HTlc) fabricated from Eu, Tb, and Zn complexes co-doped into magnesium-aluminum hydrotalcite (MgAl-LDH) was prepared by a simple one-pot chemical method. The structural and luminescent properties of Eu/Tb/Zn-HTlc were investigated. Excited by 370 nm UV light, the simultaneous emission bands of this single-matrix material are located in the red, green, and blue regions, combined to give a pure white emission (CIE x = 0.346 and y = 0.3339). This research represents a new strategy for designing layered organic-inorganic hybrid materials for LED-pumped white light.

Diarylmaleimide fluorophores: intensely emissive low-band-gap guest for single white polymers with highly efficient electroluminescence

A series of novel single white polymers, PFPMs and PFTMs, were designed and synthesized by introducing a green diphenylmaleimide (PM, λem = 500 nm) or yellow dithienylmaleimide (TM, λem = 557 nm) fluorophore guest into a blue polyfluorene (PF) host. By adjusting the feed ratio of the maleimide unit and fluorene unit, the resulting single white polymers exhibited a dual emission, including blue emission (415/439 nm) from PF and yellow (546 nm) or red (659 nm) emission from the PM or TM guest. The large red-shift in emission of the PM and TM in the backbone of the polymers originates from their conjugated structure being extended by the fluorene units. All the polymers show similar and high thermal stability and large solubility in common organic solvents. Their electroluminescent properties were investigated in single-emitting-layer devices fabricated by a solution process with the configuration of ITO/PEDOT:PSS/polymer/TPBI/LiF/Al. PFPM03, containing 0.3% PM, exhibited an excellent white electroluminescent performance for the effective and incomplete energy transfer from the PF host to the maleimide guest. The white device based on annealed PFPM03 at 140 °C for 30 min could be further improved to reach a maximal current efficiency of 8.14 cd A−1, power efficiency of 3.93 lm W−1, and external quantum efficiency of 3.78% with CIE coordinates of (0.34, 0.41).

Rylene diimide and dithienocyanovinylene copolymers for polymer solar cells

Two polymers containing (E-2,3-bis(thiophen-2-yl)acrylonitrile (CNTVT) as a donor unit, perylene diimide (PDI) or naphthalene diimide (NDI) as an acceptor unit, are synthesized by the Stille coupling copolymerization, and used as the electron acceptors in the solution-processed organic solar cells (OSCs). Both polymers exhibit broad absorption in the region of 300–850 nm. The LUMO energy levels of the resulted polymers are ca.–3.93 eV and the HOMO energy levels are–5.97 and–5.83 eV. In the binary blend OSCs with PTB7-Th as a donor, PDI polymer yields the power conversion efficiency (PCE) of up to 1.74%, while NDI polymer yields PCE of up to 3.80%.

Preparation of MgAl-EDTA-LDH based electrospun nanofiber membrane and its adsorption properties of copper(II) from wastewater

Adsorption is recognized as one of the most promising technologies applied to remove heavy metals from contaminated water. However, the adsorption efficiency often decreases because of the aggregation and loss of adsorbents. Herein, a novel adsorbent was synthesized by intercalation ethylenediaminetetraacetic acid (EDTA) into layered double hydroxides (LDH) and subsequent encapsulated into PAN polymer matrix using electrospinning. The synthesized electrospun nanofiber membrane (MgAl-EDTA-LDH@PAN) was found to combine the advantages of LDH@PAN nanofiber membrane (high surface area, easy to separate, free from aggregation and loss) and EDTA (powerful chelating agent). The adsorption performance of the MgAl-EDTA-LDH@PAN was evaluated using Cu(II) as target metals by varying experimental conditions such as pH, contact time, initial adsorbent dosage, and temperature. The maximum adsorption capacity of MgAl-EDTA-LDH@PAN was 120.77mg/g with the initial Cu(II) concentrations ranging from 0.6 to 40mg/L. MgAl-EDTA-LDH@PAN was also used in real industrial contaminated water treatment, and the final effluent was approximate to class-I criteria of the National Wastewater Discharge Standard of China. (GB 8978-1996). In addition, Cu K-edge XAS and XPS analyses were applied for unraveling the adsorptive performance of MgAl-EDTA-LDH@PAN by revealing the molecular-level mechanism of Cu(II) uptake.

Solvent-dependent and highly selective anion sensing and molecular logic application of bisindolylmaleimide derivatives

A series of bisindolylmaleimide dyes (IMs) with different N-substituents (IM-PFB, IM-TBA and IM-MB) and planarity (IMC-MB and IM-MB) were designed and synthesized to detect anions selectively and sensitively. The anion-sensing properties were investigated systematically by changing the N-substituents of maleimide, solvent type and molecular planarity. Results indicate that the anion recognition is significantly affected by the solvent type rather than the N-substituents. Different anion sensitivity in various solvents makes IMs selectively detect F− in ACN, H2PO4− in DCM and CN− in THF. Due to the fixed location of two NH groups, the dye IMC-MB with planar structure exhibits poor sensing selectivity in various solvents. The titration curves of anions show that the sensing mechanism of IMs in various solvents for anions is different. The further experimental and DFT/TDDFT calculation results demonstrate that the hydrogen bond interaction and deprotonation of one H atom take place in DCM and THF, respectively, and that the two interactions synchronously exist in ACN. Interestingly, the solvent-dependent anion recognition can make IM-PFB mimic the function of three kinds of decoders (1-to-2, 2-to-3 and 2-to-4), a 4-to-2 encoder and a 1 : 2 demultiplexer. It is really rare for one molecule to mimic so many logic operations.

Full-solution processed, flexible, top-emitting polymer light-emitting diodes based on printed Ag electrodes

Full-solution processed, flexible, top-emitting polymer light-emitting diodes (PLEDs) are fabricated by using low-cost and high-quality printed Ag electrodes. Employing a composite cathode (Ag/ZnO/PEI) and bi-layer anode of WO3/PH1000, the resulting devices exhibit quite comparable device performances to the conventional PLEDs, remarkable flexibility and great potential for large-area production.