A novel deep blue-emitting Zn II complex Zn(L c ) 2 (L c -) 2-(1-(6-(9H-carbazol-9-yl)hexyl)-1H-benzo [d]imidazol-2-yl)phenolate) based on a carbazole-functionalized N^O ligand was synthesized by a modified method. Other two Zn II complexes (Znwere also prepared for comparison. The remarkable substitution effect on the photoluminescent and thermal properties of the complexes was studied. The investigation indicated an unexpected amplifying hypsochromic effect of the substituents on the emission of the complex in the solid state: the larger substituent corresponded to the larger blue shift of the emission of the complex (Zn(L c ) 2 has the shortest emission wavelength of 422 nm as the deep blue emission among these three complexes). The stronger steric effect induced by the bulky substitutions should be one of the most important factors. Among the three Zn II complexes, the temperature of decomposition of Zn(L c ) 2 is the highest at 427 °C. Cyclic voltammetry (CV) of the complexes showed that the carbazole moieties remarkably improved the hole injection ability of Zn(L c ) 2 with the HOMO energy level 0.6 eV higher than those of Zn(L a ) 2 and Zn(L b ) 2 . The good hole injection and transporting ability of Zn(L c ) 2 was further proved by its three-layer devices, in which the electroluminescent (EL) emission mainly originated from the electron-transporting Alq 3 layer. Through the four-layer devices with the hole-blocking layer, the pure blue emission of Zn(L c ) 2 at 452 nm was demonstrated. Zn(L c ) 2 seems favorable among the blue-emitting Zn II complexes with a brightness more than 2000 cd m -2 , a high efficiency stability, and an excellent EL spectra stability.

Ultrafine Y2O3:Eu3+ phosphors were prepared by a modified solution combustion method. The as-prepared samples with sizes of 17.6–80 nm (nanophosphors) and 300 nm (submicron phosphors) were characterized by x-ray diffraction, transmission electron microscope, scanning electron microscopy, selected area electron diffraction, and energy dispersive x-ray spectroscopy. The emission spectra of the samples are unchanged in comparison with that of standard material. The excitation spectra show a redshift in the charge-transfer-state band and a blueshift in the host gap band. In relation to commercial sample, the relative luminescence intensities of nano- and submicron phosphors are increased sufficiently to 64.4% and 93.6%, respectively. Higher quenching concentration of the activator Eu3+ ion was observed in the nanophosphor than that in the phosphor synthesized by solid state reaction.

Photocatalytic water splitting into H 2 is the most economic and environmentally friendly strategy for H 2 production, and rationally constructing a heterojunction retains enormous influence on a photocatalytic system. Herein, 2D/2D covalent organic framework/graphitic carbon nitride (COF/CN) van der Waals heterojunctions were readily prepared via an ultrasonic method for high-efficiency visible-light photocatalytic H 2 production. The photocatalytic H 2 production performance of optimized COF/CN composites can reach up to 449.64 μmol•h −1 , which is approximately 5 times that of pure CN (89.08 μmol•h −1 ). The characterization and experimental studies reveal that the synergistic effect between COF and CN contributes to promoting the interfacial migration and spatial separation of photoinduced e − −h + pairs, further boosting the photocatalytic hydrogen production activity. This work may open a new window to design and fabricate effective heterojunction photocatalysts for photocatalytic energy conversion.

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