The g-C(3)N(4)-ZnO composite photocatalysts with various weight percents of ZnO were synthsized by a simple calcination process. The photocatalysts were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV-vis diffuse reflection spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The PXRD and HR-TEM results show that the composite materials consist of hexagonal wurzite phase ZnO and g-C(3)N(4). The solid-state UV-vis diffuse reflection spectra show that the absorption edge of the composite materials shifts toward the lower energy region and to longer wavelengths in comparison with pure ZnO and g-C(3)N(4). Remarkably, the photocatalytic activity of g-C(3)N(4)-ZnO composites has been demonstrated, via photodegradation of Methyl Orange (MO) and p-nitrophenol experiments. The photocatalytic activity of g-C(3)N(4)-ZnO for photodegradation of Methyl Orange and p-nitrophenol under visible light irradiation was increased by over 3 and 6 times, respectively, to be much higher than that of single-phase g-C(3)N(4), clearly demonstrating a synergistic effect between ZnO and g-C(3)N(4). The concentrations of Zn(2+) in g-C(3)N(4)-ZnO system after a photocatalytic reaction at various reaction times were found to be much lower than those for a ZnO system under the same reaction conditions, indicating that the g-C(3)N(4)-ZnO composite possesses excellent long-term stability for a photocatalytic reaction in aqueous solutions. Furthermore, a synergistic photocatalysis mechanism between ZnO and g-C(3)N(4) was proposed based on the photodegradation results. Such obviously improved performance of g-C(3)N(4)-ZnO can be ascribed mainly to the enhancement of electron-hole separations at the interface of ZnO and g-C(3)N(4).

Nonemissive tetraphenylethene ͑TPE͒ 1 and its diphenylated derivative 2 were induced to emit intensely by aggregate formation. Crystalline aggregates of the dyes emitted bluer lights than their amorphous counterparts. The emissions of the TPE dyes could be switched off and on continuously and reversibly by wetting and dewetting with solvent vapors, respectively, manifesting their ability to optically sense volatile organic compounds. The light-emitting diodes fabricated from 1 and 2 were turned on at ϳ2.9 and ϳ5 V and emitted blue lights with maximum luminance of ϳ1800 and ϳ11 000 cd/ m 2 , respectively.

Propeller-shaped molecules diphenyldibenzofulvene (1) and (4-methoxyphenyl)phenyldibenzofulvene (2) were nonemissive when dissolved in good solvents but became luminescent when aggregated in poor solvents or in the solid state, showing a novel phenomenon of aggregation-induced emission (AIE). 8-Phenylbenzo[e]-acephenanthrylene (3), a ring-closed form of 1 with one of its phenyl blades locked, was emissive in the solutions, suggesting that the AIE effects of 1 and 2 are caused by the restrictions of intramolecular rotations of their aromatic blades in the aggregation state. The crystals of 1 and 2 emitted stronger, bluer lights than their amorphous powders, possibly due to the structural rigidification and conformational twisting of the dye molecules in the crystalline phase. The light-emitting diodes with a device configuration of ITO/NPB/dye/ BCP/Alq 3 /LiF/Al were fabricated, which emitted bluish-green and yellow lights with maximum luminance and current efficiency up to 5000 Cd/m 2 and 1.90 Cd/A, respectively.

No abstract