Zhenjun Si

Injection, transport, absorption and phosphorescence properties of a series of blue-emitting Ir(III) emitters in OLEDs: a DFT and time-dependent DFT study.

Quantum-chemistry methods were explored to investigate the electronic structures, injection and transport properties, absorption and phosphorescence mechanism of a series of blue-emitting Ir(III) complexes {[(F(2)-ppy)(2)Ir(pta -X/pyN4)], where F(2)-ppy = (2,4-difluoro)phenylpyridine; pta = pyridine-1,2,4-triazole; X = phenyl(1); p-tolyl (2); 2,6-difluororophenyl (3); -CF(3) (4), and pyN4 = pyridine-1,2,4-tetrazolate (5)}, which are used as emitters in organic light-emitting diodes (OLEDs). The mobility of hole and electron were studied computationally based on the Marcus theory. Calculations of Ionization potentials (IPs) and electron affinities (EAs) were used to evaluate the injection abilities of holes and electrons into these complexes. The reasons for the lower EL efficiency and phosphorescence quantum yields in 3-5 than in 1and 2 have been investigated. These new structure-property relationships can guide an improved design and optimization of OLED devices based on blue-emitting phosphorescent Ir(III) complexes.

Hierarchically structured Fe3O4 microspheres: morphology control and their application in wastewater treatment

Novel three-dimensional (3D) flower-like Fe3O4 microspheres were synthesized by a facile precursor-templated conversion method. The precursor was prepared by an ultrasound-assisted hydrothermal method without the help of any surfactant. The possible formation mechanism of the precursor was proposed, and it was found that the synthetic parameters for the precursor such as the time of ultrasonic pretreatment and NH4Ac concentration are crucial for the formation of the flower-like hierarchical precursor structure. The flower-like Fe3O4 microspheres obtained by calcining the precursor in N2 exhibit superparamagnetic behaviour and show relative high saturation magnetization at room temperature. Furthermore, the as-obtained product, with high BET surface area, has been used as an absorbent in wastewater treatment and exhibit a strong capability to remove organic pollutants.

Multi-ring aromatic carbonyl compounds enabling high capacity and stable performance of sodium-organic batteries

Herein we report that organic compounds comprising planar C6 ring structures and carboxylate groups can function as an excellent anode material for sodium-organic batteries. Systematic comparisons of different electrode materials including the multi-ring aromatic compounds with or without carboxylate groups are carried out, the Na insertion mechanism is proposed, and the factors determining the capacity and potential plateaus are also elucidated by experimental and theoretical analyses.

Direct hydrothermal synthesis of single-crystalline triangular Fe3O4 nanoprisms

Single-crystalline Fe3O4 triangular nanoprisms (TNPs) were fabricated by a facile hydrothermal route in the presence of 1,3-propanediamine (PDA). It was found that the EG to PDA volume ratio played an important role in the formation of the TNP structures and greatly affected the morphology of the magnetites.

Nitrogen-doped graphene-supported Co/CoNx nanohybrid as a highly efficient electrocatalyst for oxygen reduction reaction in an alkaline medium

In this work, we utilize a one-step pyrolysis method to thermally synthesize a non-precious cobalt-based nitrogen-doped graphene (Co-NG) using graphene oxide (GO) and guanidine hydrochloride (GuHCl) with a small amount of CoCl2 precursor as a low-cost and highly efficient catalyst for the oxygen reduction reaction (ORR). The synthesized cobalt-based nitrogen-doped graphene (Co-NG) was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of the Co-NG composite towards the ORR was evaluated using linear sweep voltammetry method. Electrochemical measurements reveal that the obtained Co-NG 850 composite has excellent catalytic activity towards the ORR in an alkaline electrolyte, including a large kinetic-limiting current density and good stability, as well as it exhibits the desirable four-electron pathway for the formation of water. These superior properties make the Co-NG 850 a promising cathode catalyst for alkaline fuel cells.

A three-dimensional metal–organic framework based on a triazine derivative: syntheses, structure analysis, and sorption studies

A novel metal–organic framework [Cu3(m-TATB)2Py(CH3OH)2] (1) constructed of a triazine-based trigonal-planar ligand, 3,3′,3″-s-triazine-2,4,6-triyltribenzoate (m-H3TATB), has been synthesized and structurally characterized. Compound 1 features three-dimensional (3D) channels and cavities together, and exhibits high carbon dioxide sorption at normal pressure.

Ultraviolet light-emitting CdII complexes: synthesis and property studies

Four ultraviolet light-emitting CdII complexes, [CdL1(H2O)]n (1), [CdL1(bpy)(H2O)2]n (2), [CdL2(H2O)]n (3), and [CdL2(bpy)(H2O)2]n (4), where L1 = 3,3′-(4-phenyl-4H-1,2,4-triazole-3,5-diyl)dibenzoate, L2 = 3,3′-(4-(4-fluorophenyl)-4H-1,2,4triazole-3,5-diyl)dibenzoate, and bpy = 2,2′-bipyridine, were hydrothermally synthesized and characterized by single-crystal X-ray diffraction, powder scattering spectra, and infrared spectra. 1–4 possess excellent thermal stability with decomposition temperature of ca. 340 °C. Their powder samples mainly give luminescent spectra at 350, 339, 351, and 339 nm, respectively, which should be attributed to the ligand-centered π* → π transfer transitions. Additionally, 1–4 have weak emission bands at 400–500 nm, which are tentatively attributed to the triplet ligand to ligand charge transfer transitions. Graphical abstract Four ultraviolet light-emitting CdII complexes were hydrothermally prepared and their single-crystal structures and luminescent properties were fully studied. It is found that the addition of 2,2′-bipyridine not only changes the single-crystal structures, but also the luminescence spectra.

Novel 1D Mn(II) complexes containing aromatic dicarboxylic acids

Three Mn(II) complexes of [MnL(Bipy)(H2O)]n (I), [Mn3(Phen)2(HL)2(L)2]n (II), and [Mn(Phen)2(HL)(OH)] (III), where L = 4,4′-(2-acetylpropane-1,3-diyl)dibenzoic acid, Bipy = 2,2′-bipyridine, and Phen = 1,10-phenanthroline, were hydrothermally synthesized and characterized by single crystal X-ray diffractions, infrared spectroscopy, thermogravimetric analyses, and magnetic analyses. Complexes I and II are one dimensional (1D) coordination polymers which can form the supramolecules with the help of the intermolecular hydrogen bond interactions. Finally, the landé factors are simulated by magentochemical analysis to be 2.15 and 1.80 for I and II with S = 5/2, respectively.

MnII Complexes with a Novel Triacid as Ligand: Synthesis and Characterization

A novel aromatic tricarboxylic acid of 4,4′-(2-carboxypropane-1,3-diyl)dibenzoic acid (H3L) was used to prepare two MnII complexes of [Mn3(L)2(bpy)2]n (1) and [Mn3(L)2(phen)2]n (2), where bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline. The single crystal structures, thermal stability, and the magnetism of 1 and 2 were measured and discussed in this article. According to the magnetism measurements, the Curie constants and the Weiss constants should be 12.29 K·cm3·mol−1 (g = 1.94, S = 5/2) and −9.80 K for 1 and 11.11 K·cm3·mol−1 (g = 1.83, S = 5/2) and −9.26 K for 2, respectively.