Synthesis and Optical Properties of Ce-doped ZnO

ZnO nanorods were synthesized using the sol-gel method, and the effects of annealing temperature and Ce doping on the morphologies and optical properties of ZnO nanostructures were investigated in detail. The XRD measurements showed that the as-synthesized ZnO nanostructures had a hexagonal wurtzite structure. SEM images showed that uniform nanorods formed at 900 °C. Photoluminescence measurements showed an ultraviolet emission peak and a relatively broad visible light emission peak for the samples sintered at different temperatures. The UV emission peak bathochromically shifted when the annealing temperature rose from 850 to 1000 °C. Ce doping decreased the synthesized temperature of the ZnO nanorods to 500 °C, and the UV peaks hypsochromically shifted.     

MOLECULAR DESIGN OF LIGHT EMITTING POLYMERS

Fluorene-based alternating and statistical copolymers were synthesized by employing reaction methods of Wittig,Heck and Suzuki. The copolymers were classified into three groups with the photoluminescence (PL) emission maxima at420, 475 and 500 nm, respectively. Statistical copolymers with two chromophores having PL emission maxima at 420 and475 nm emitted light with the emission maximum at 475 nm on photoexcitation at 365 nm and improved the quantumefficiency by the energy transfer. However, the intramolecular energy transfer was inefficient compared to the intermolecularenergy transfer when the two chromophores were apart from each other in the range of the Forster critical distance. Fluorene-pyridinedivinylene alternating copolymer was synthesized by the Wittig reaction and found to have physical, electronic andelectrochemical properties of the individual units intact. The double-layered light emitting diode (LED) with the statisticalcopolymer as an emitting layer and the pyridine-containing copolymer as an electron transporting-hole blocking layer, whichwere sandwiched between ITO and Al, displayed a quantum efficiency of 0.1%.     

纳米ZnO的制备及发光特性研究

The samples of nano-size ZnO were prepared by precipitation, hydrolysis, sol-gel method and characterized by X-ray diffraction, Uv-Vis diffuse reflection spectrum, and time resolved luminescent spectrum. The results showed that the crystallite dimensions of all ZnO samples were coarsening with increasing annealing temperature and the grain sizes prepared by sol-gel method were obviously smaller than the others prepared by precipitation and hy-drolysis method. Under excitation of monochromatic light of wavelength 300nm, a strong and broad photolumines-cence (PL) emissions were observed in the wavelength range of 420～780nm. As the grain size decreased, the PL peak positions moved to shorter wavelengths. And as the annealing temperature increased, the peak intensity de-creased. The photoluminescence decay profile of ZnO was well described by three decay components of 46ns, 330ns and 1630ns.     

Preparation, characterization and photocatalytic performance of Mo-doped ZnO photocatalysts

A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grinding-calcination method.The structure of these photocatalysts was characterized by a variety of methods,including N 2 physical adsorption,X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared(FT-IR) spectroscopy,photoluminescence(PL) emission spectroscopy,and UV-vis diffuse reflectance spectroscopy(DRS).It was found that Mo 6+ could enter into the crystal lattice of ZnO due to the radius of Mo 6+(0.065 nm) being smaller than that of Zn 2+(0.083 nm).XRD results indicated that Mo 6+ suppressed the growth of ZnO crystals.The FT-IR spectroscopy results showed that the ZnO with 2 wt.% Mo-doping has a higher level of surface hydroxyl groups than pure ZnO.PL spectroscopy indicated that ZnO with 2 wt.% Mo-doping also exhibited the largest reduction in the intensity of the emission peak at 390 nm caused by the recombination of photogenerated hole-electron pairs.The activities of the Mo-doped ZnO photocatalysts were investigated in the photocatalytic degradation of acid orange II under UV light(λ = 365 nm) irradiation.It was found that ZnO with 2 wt.% Mo-doping showed much higher photocatalytic activity and stability than pure ZnO.The high photocatalytic performance of the Mo-doped ZnO can be attributed to a great improvement in the surface properties of ZnO,higher crystallinity and lower recombination rate of photogenerated hole-electron(e-/h+) pairs.Moreover,the undoped Mo species may exist in the form of MoO3 and form MoO3 /ZnO heterojunctions which further favors the separation of e-/h+ pairs.     

A novel terbium complex using oxadiazole derivative as a neutral ligand： Synthesis and properties

A novel terbium complex using 1,3,4-oxadiazole derivative as a neutral ligand was synthesized and characterized. Its thermal stability and photoluminescent properties were studied. The strong emission peaked at 546 nm with a full width at half maximum of 5 nm was observed in the pure terbium complex film under excitation of 328 nm light, which is attributed to the characteristic emission of terbium ion. The good thermal stability and intense sharp emission of this terbium complex display its potential application in electroluminescence devices.     

Optical and gas sensing properties of mesoporous hollow ZnO microspheres fabricated via a solvothermal method

Mesoporous,hollow Zn O microspheres were synthesized via a hydrothermal method,using glycerol and zinc acetate as the starting materials.XRD and FESEM analysis showed that the surface morphology of the spheres with a Wurtzite structure could be reasonably adjusted by varying the weight ratio(Rw) of Zn(CH3COO)2 2H2O:H2O:C3H8O3.The responses of the gas sensor based on the spheres to 100 ppm ethanol and 100 ppm acetone are 18.9 and 10.4,respectively.The response and recovery times of the sensor to ethanol and acetone are 2 s and 3 s,3 s and 5 s,respectively.The hollow spheres show an intense UV emission at 392 nm and a broad blue-green emission at 488 nm.Interestingly,a light trapping phenomenon is revealed by UV emission and scattering measurements on the microspheres,which can be attributed to the mesoporous shell and hollow structure of the microsphere.     

Electrospinning Synthesis and Photoluminescence Properties of SnO2：xEu3＋ Nanofibers

NnO2：xEu3＋（x=O, 1%, 3%, 5%, molar fraction） fibers were synthesized by electrospinning technology. The size of the as-prepared fibers is relatively uniform and the average diameter is about 200 nm with a large draw ratio. The as-prepared Eu3＋ doped SnO2 nanofibers have a rutile structure and consist of crystallitc grains with an average size of about 10 nm. A slight red shift of the A1gand Bag vibration modes and an additional peak at 288 nm were observed in the Raman spectra of the nanofibers. The energies of bandgaps of the SnO2 nanofiber with Eu doping of 1% and 3% are 2.64 eV, and the energy of bandgap is 2.94 eV with Eu doping of 5%（molar fraction）. There is only orange emission（5D0→7F1 magnetic dipole transition） for Eu doped SnO2 nanofibers, and no red emission could be observed. The orange emission upon indirect excitation splits into three peaks and the peak intensity at the excitation wavelength of 275 nm is higher than that at the excitation wavelength of 488 nm.     

Fabrication,Characterization and Optical Properties of TiO2 Nanotube Arrays on Boron-doped Diamond Film Through Liquid Phase Deposition

TiO2 nanotube（TiNT） arrays were deposited on boron-doped diamond films by a liquid-phase deposition method with ZnO nanorod arrays as the template.The different morphologies of TiNTs have been obtained by controlling the morphology of ZnO template.The X-ray diffraction and energy-dispersive X-ray analysis show that the ZnO nanorod array template has been removed in the TiNTs formation process.The crystalline quality of the TiNTs is improved by increasing the annealing temperature.The band gap of the TiNTs is about 3.25 eV estimated by the UV-Vis absorption spectroscopy,which is close to the value of bulk TiO2.In the photoluminescence spectrum,a broad visible emission in a range of ca.550-750 nm appears due to the surface oxygen vacancies and defects.     

ZnO nanopowders and their excellent solar light/UV photocatalytic activity on degradation of dye in wastewater

Low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O nanopowders(NPs)would determine their practical application in purifying wastewater.In this contribution,ZnO NPs were scalably synthesized via the simple reaction of Zn powder with H_2O vapor in autoclave.The structural,morphological and optical properties of the samples were systematically characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectra,transmission electron microscopy,Micro-Raman,photoluminescence,and ultraviolet-visible spectroscopy.The as-prepared Zn O NPs are composed of nanoparticles with 100–150 nm in diameter,and have a small Brunauer-Emmett-Teller surface area of 6.85 m~2/g.The formation of Zn O nanoparticles is relative to the peeling of H_2 release.Furthermore,the product has big strain-stress leading to the red-shift in the band gap of product,and shows a strong green emission centered at 515 nm revealing enough atomic defects in Zn O NPs.As a comparison with P25,the obtained dust gray Zn O NPs have a strong absorbance in the region of 200–700 nm,suggesting the wide wave-band utilization in sunlight.Based on the traits above,the Zn O NPs show excellent photocatalytic activity on the degradation of rhodamine B(Rh-B)under solar light irradiation,close to that under UV irradiation.Importantly,the Zn O NPs could be well recycled in water due to the quick sedimentation in themselves in solution.The low-cost and scalable preparation,high photocatalytic activity,and convenient recycle of Zn O NPs endow themselves with promising application in purifying wastewater.     

纳米氧化锌的制备与发光性能的研究

Nanocrystalline ZnO Powders were prepared by sol-gel process from Zn(Ac)₂·2H₂O and 2-methoxyethanol solutions containing monoethanolamine. It was found that the photoluminescence (PL) spectra of samples (calcined at 250, 350 and 500 ℃, respectively) had two emission bands in UV region (at ～378 nm) and visible region (at ～502 nm) . The intensity of UV emission bands decreased with the increase of the calcination temperature, and the opposite was true for the visible emission band. TEM, TG-DTG, DTA, XRD, FTIR and surface photovoltage spectra (SPS) were used to investigate this competitive phenomenon. The results indicate that the adsorption of organies on the surface of nanoparticles is the key factor responsible for the relative PL intensity of the two emission bands.