Husheng Jia

Tunable white light emission of Eu,Tb,Zn-containing copolymers by RAFT polymerization

In this work, a novel copolymer PS–Eu–Tb–Zn, which can match a 365 nm UV chip, was synthesized by the RAFT polymerization of Tb(p-BBA)3UA, Eu(TTA)2(Phen)MAA, Zn(BTZ)UA and styrene. TG-DTG and PL analyses indicate that the copolymer PS–Eu–Tb–Zn displays favorable thermal stability and luminescence properties. When excited at 365 nm, the copolymer exhibits emission peaks at 421 nm (blue emission), 488, 543 nm (green emission), 589 and 615 nm (red emission). The white light of the copolymer can be obtained by tuning the ratios of the three complexes and excitation wavelengths. The CIE coordinates (0.352, 0.330) of the copolymer are optimal upon excitation at 365 nm. For the fabricated white LED using a 365 nm UV chip with the copolymer, the CCT is 5684 K, and the CRI is 83.1. All the results indicate that the copolymer can be applied as a phosphor for the fabrication of NUV-based white LEDs.

Synthesis, characteristic and intramolecular energy transfer mechanism of reactive terbium complex in white light emitting diode

Abstract A reactive Tb(III) complex with 2-aminobenzoic acid (2-ABAH) and acrylonitrile (AN) as ligands was synthesized. The structure of the complex was characterized by elemental analysis and Fourier transform infrared spectrometry (FT-IR). The results indicated that the ligands were coordinated with Tb(III) ion. Thermal gravity-derivative thermogravimetric (TG-DTG) analysis indicated that the complex kept stable up to 198 °C. Luminescence properties were investigated by UV-vis absorption spectra and fluorescence spectra. The results suggested that being excited at 361 nm, the complex exhibited characteristic emission of Tb(III) ion, revealing that the complex could be excited by 365 nm ultraviolet chip. The HOMO and LUMO, Δ E (HOMO–LUMO) , molecular frontier orbital, and the singlet state and triplet energy state levels of the ligands were calculated at the B3LYP/6-31+G (d) level. The results indicated that intramolecular energy transfer mechanism followed Dexter exchange energy transfer theory. Both the calculation for excited state of ligand and energy transfer mechanism could provide the theoretical basis for the design of high luminescent materials of rare earth complexes with organic ligands.

First principle study of cysteine molecule on intrinsic and Au-doped graphene surface as a chemosensor device

To search for a high sensitivity sensor for cysteine, we investigated the adsorption of cysteine on intrinsic and Au-doped graphene sheets using density functional theory calculations. Binding energy is primarily determined by the type of atom which is closer to the adsorbed sheet. Compared with intrinsic graphene, Au-doped graphene system has higher binding energy value and shorter connecting distance, in which strong Au-S, Au-N and Au-O chemical bond interaction play the key role for stability. Furthermore, the density of states results show orbital hybridization between cysteine and Au-doped graphene sheet, but slight hybridization between the cysteine molecule and intrinsic graphene sheet. Large charge transfers exist in Au-doped graphene-cysteine system. The results of DOS and charge transfer calculations suppose that the electronic properties of graphene can be tuned by the adsorption site of cysteine. Therefore, graphene and Au-doped graphene system both possess sensing ability, except that Au-doped graphene is a better sensor for cysteine than intrinsic graphene.

The study on properties of CdS photocatalyst with different ratios of zinc-blende and wurtzite structure

The mixtures of zinc blende and wurtzite CdS nanoparticles were prepared via a solvothermal method by controlling the precursor ratio (Cd/S molar ratio). The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible (UV-vis) spectroscopy. These results demonstrate that not only the morphology but also the phase composition of CdS nanostructures was sensitively altered by the precursor ratio (Cd/S molar ratio). Photocatalysis test results show that the photocatalytic activity was mainly dependent on the ratio between zinc blende and wurtzite phases in CdS samples. The product prepared with 1:2 Cd/S molar ratio exhibited higher photocatalytic activities in comparison with products prepared with other Cd/S molar ratios, which can be attributed to the improved charge separation at the zinc blende/wurtzite junction interface.

Shape-controlled synthesis of three-dimensional branched CdS nanostructure arrays: structural characteristics and formation mechanism

Through a combination of electrodeposition and subsequent solvothermal reaction, three-dimensional (3D) branched CdS nanostructure arrays were fabricated by nanowires self-assembly in ethanediamine solution containing thiourea and hexamethylenetetramine (HMTA) for the first time, where HMTA acted as a capping agent. In the absence of HMTA, only disordered CdS nanowires were obtained. The reaction conditions influencing the synthesis of 3D branched CdS nanostructure arrays, such as the concentration of HMTA and thiourea, reaction temperature and reaction time, were studied and optimized. The 3D branched CdS nanostructure arrays were characterized by X-ray diffraction, field emitting scanning electron microscopy and transmission electron microscopy. The results show that HMTA played an important role in the formation of 3D branched CdS nanostructure arrays. A growth process of HMTA-assisted gradual crystallization and subsequent oriented attachment was proposed as a plausible mechanistic interpretation for the formation of the 3D branched nanostructure arrays. In addition, the photoluminescence property of the novel 3D branched CdS nanostructure arrays was investigated.

Synthesis and luminescent properties of terbium complex containing 4-benzoylbenzoic acid for application in NUV-based LED

Abstract A novel Tb(III) ternary complex Tb(p-BBA) 3 MAA was synthesized with 4-benzoylbenzoic acid (p-BBA) and methacrylic acid (MAA) as ligands. The complex was characterized by IR, UV-visible, thermogravimetric analysis and fluorescence spectroscopy. Monitored at 544 nm, the complex displayed wide and strong excitation band at 300-400 nm, which matched well with the 365 nm-emitting UV chip. The complex exhibited excellent green emission at 544 nm ( 5 D 4 → 7 F 5 transition of Tb 3+ ) under an excitation at 365 nm. Besides, the complex showed high thermal stability. Its intramolecular energy transfer process was further discussed. Furthermore, the complex also had higher fluorescence lifetime (1.38 ms) and higher quantum yield (0.372). Finally, electroluminescent properties indicated that when used to fabricate LED with 365 nm UV chip (power efficiency is 18.6 lm/W), the complex remained its favorable optical performance. These results implied that Tb(p-BBA) 3 MAA could be used as a green phosphor for NUV-based white LED.

Morphological evolution of ZnO microspheres from Zn5(OH)8Ac2·2H2O by ultrasonic irradiation method

Monodispersed ZnO microspheres were synthesized through ultrasonic irradiation using zinc acetate as a Zn source and triethanolamine as the structure-directing and alkalinity control agent. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo-gravimetric analyses were used to describe the as-prepared products and understand the formation mechanism. The results indicate that the morphology of the products is strongly dependent on the precursor Zn5(OH)8Ac2·2H2O. As the reaction time increased, the precursor, Zn5(OH)8Ac2·2H2O, decomposed into ZnO nanoparticles and simultaneously, ZnO nanoparticles assembled into a spherical structure under ultrasonic irradiation until the precursor, Zn5(OH)8Ac2·2H2O, completely disappeared. UV-vis absorption measurements of the as-prepared products at different stages show that the absorption peaks became sharper and blue-shifted from 422 to 364 nm with the change of composition and morphology. Photoluminescence (PL) measurements show that the intensity of the UV emission increased and that the wavelength first red-shifted and then blue-shifted with the increase of the reaction time, which may be related to the size and crystallinity of the ZnO particles.

Preparation and properties of heat resistant polylactic acid (PLA)/Nano-SiO2 composite filament

In order to improve the thermal properties of polylactic acid (PLA) filament, nano-SiO2 was applied to mix with PLA, then they were spun as composite filament by melt-spinning. The dispersion of nano-SiO2 and the fracture surfaces of filaments were studied by scanning electron microscopy (SEM). The properties of composite filament, such as orientation degree, mechanical properties, and surface friction properties, were analyzed. The thermal performances of composite filament were analyzed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The results showed that the nano-SiO2 modified by 5% KH-550 could disperse evenly and loosely in nano-scale, and 1 wt% and 3 wt% nano-SiO2 dispersed throughout PLA evenly. As the quantity of nano-SiO2 increased, the properties of composite filament, such as orientation degree, friction coefficient, thermal decomposition temperature, and glass transition temperature, increased more or less. The breaking tenacity increased when 1 wt% SiO2 was added in PLA, but declined when 3 wt% SiO2 was added.

Functional porous carbons from waste cotton fabrics for dyeing wastewater purification

A new functional porous carbons (PC-WF) is prepared by activation-pyrolysis method use waste cotton fabrics (WF) as an abundant, cheap and available precursor for removal of Brilliant Crocein (BC-GR) and Cationic Red 2GL (CR-GL) from aqueous phase. The PC-WF was characterized by BET, FTIR, SEM, and XRD techniques, the surface area, total pore volume, average pore diameter was found as 1463.5 m2 g-1, 0.783 cm3 g-1 and 2.14 nm, respectively. The influences on BC-GR and CR-GL adsorption of various experimental factors such as initial concentration and temperature were investigated. Adsorption kinetics was found to be best represented by the pseudo-second order model. The adsorption capacity was 319.8 mg g-1 for BC-GR and 842.5 mg g-1 for CR-GL at 30 °C, respectively. The results indicate that for waste cotton fabrics in particular, the practical application of this process to the production of porous carbon would be possible.

Fabrication of In2O3/ZnO@Ag nanowire ternary composites with enhanced visible light photocatalytic activity

Herein, an In2O3/ZnO@Ag ternary photocatalyst was synthesized by a facile co-precipitation process. The results indicated that Ag nanowires were encapsulated by In2O3/ZnO compounds, and the obtained In2O3/ZnO@Ag photocatalyst showed strong absorption in the visible light region. The photoluminescence (PL) emission intensity gradually decreased for In2O3/ZnO@Ag as compared to that for the In2O3/ZnO composites and pure ZnO. The as-prepared In2O3/ZnO@Ag composites exhibited excellent visible light photocatalytic activities for degradation of organic contaminants (methyl orange and 4-nitrophenol). The enhancement of photocatalytic activity was ascribed to the extended visible light absorption region by Ag nanowires and the formation of close hetero-structure by the matched band structures of In2O3 and ZnO. Finally, a possible photocatalytic mechanism was proposed based on the matched energy band structure and active species trapping experiments.