Synthesis and luminescence properties of europium doped silica thin film

Mixture of europium oxide (Eu₂O₃) nanoparticles and spin-on glass (SOG) solution without annealing exhibited a strong room temperature photoluminescence (PL) at 610 nm. We developed a one-step synthesis to incorporate europium ions in silica thin film by mixing the Eu₂O₃ nanoparticles with the SOG solution and found that the weight ratio of the nanoparticles and the SOG solution was 1:5 for maximum PL. We also studied the temperature effect on the light emission of the europium doped thin film by time-of-flight secondary ion mass spectrometry (SIMS). The PL intensity of the thin film doubled after annealing. SIMS study confirmed the reduction of hydroxyl groups and explained the PL enhancement in the annealed europium doped silica thin film.     

Synthesis of Ag modified vanadium oxide nanotubes and their antibacterial properties

Vanadium oxide nanotubes (VO_x-NTs) modified by highly dispersed Ag nanoparticles have been synthesized via a facile silver-mirror reaction. The crucial factors that affected the preparation of the Ag modified vanadium oxide nanotubes (Ag/VO_x-NTs) have been also studied. The dispersion and structure of Ag nanoparticles in the obtained materials were characterized by transmission electron microscopy (TEM), electron diffraction (ED) and X-ray diffraction (XRD). The results showed the distribution and size of the formed Ag particles were greatly influenced by the concentration of AgNO₃ solution. Typically, Ag nanoparticles were well dispersed on the VO_x-NTs with the size range from 3 to 10 nm. The corresponding antibacterial tests demonstrated the as-synthesized Ag/VO_x-NTs exhibited strong antibacterial activity against Escherichia coli (E. coli).     

Preparation and luminescence properties of sol-gel hybrid materials incorporated with europium complexes

Microporous silica gel has been prepared by the sol-gel method utilizing the hydrolysis and polycondensation of tetraethylorthosilicate (TEOS). The gel has been doped with the luminescent ternary europium complex Eu(TTA)₃·phen: where HTTA = 1-(2-thenoyl)-3,3,3-trifluoracetone and phen = 1,10-phenanthroline. By contrast to the weak f-f electron absorption bands of Eu³⁺, the complex organic ligand exhibits intense near ultraviolet absorption. Energy transfer from the ligand to Eu³⁺ enables the production of efficient, sharp visible luminescence from this material. Utilizing the polymerization of methyl methacrylate or ethyl methacrylate, the inorganic/polymer hybrid materials containing Eu(TTA)₃·phen have also been obtained. SEM micrographs show uniformly dispersed particles in the nanometre range. The characteristic luminescence spectral features of europium ions are present in the emission spectra of the hybrid material doped with Eu(TTA)₃·phen.     

Preparation and thermoluminescence properties of aluminium oxide doped with europium

There is little information concerning the use of rare earths as dopants of Al2O3. This paper presents the preparation method and the results of studying the thermoluminescence characteristics of Al2O3:Eu exposed to ultraviolet light. Phosphor powder was obtained by the evaporation method. Optimum dopant concentration was 10% at an evaporation temperature of 700 degrees C. The powder obtained was submitted to thermal treatments at high temperatures in order to stabilise the traps. Diffraction patterns showed amorphous powder up to 500 degrees C; as the temperature was raised crystalline phases of Al2O3 appeared. The photoluminescence spectrum induced by 250 nm UV light exhibited four well defined peaks characteristic of the Eu3+ ion. The glow curve exhibited two peaks at 180 and 350 degrees C. The sensitivity of Al2O3:Eu was 10 times lower than Al2O3:C. The thermoluminescence response was linear from 2.4 to 3000 microJ.cm(-2) of spectral irradiance, and the fading 2% in a month. From these results it can be concluded that Al2O3:Eu has potential as an UV dosemeter.     

A facile solution-phase approach to the synthesis of luminescent europium methacrylate nanowires and their thermal conversion into europium oxide nanotubes

Novel one-dimensional (1D) nanostructures of rare earth complexes (europium methacrylate (Eu(MA)(3))) have been prepared from the precursor of irregularly shaped Eu(MA)(3) powder in ethanol solvent without the assistance of an added surfactant, catalyst, or template. These hexagonal-shaped complex nanowires have diameters of about 100-300?nm and lengths ranging from tens to hundreds of micrometers. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) studies and thermogravimetric analysis (TGA) show that the precursor powder and the resulting nanowires have identical compositions. Under UV light excitation, strong red fluorescence can be clearly seen throughout the whole wires. This good luminescence characteristic of the complex nanowires is further confirmed by the fluorescence spectrum where strong and narrow emission can be seen. These rare earth complex nanowires provide a useful source for 1D rare earth oxide materials, as the europium ions are distributed uniformly in the Eu(MA)(3) nanowires. Through calcination, the Eu(MA)(3) nanowires are successfully converted into Eu(2)O(3) nanotubes. X-ray investigation confirms that the Eu(2)O(3) nanotubes have a cubic body-centered structure. FTIR measurements and TGA analysis are used to follow the calcination process. A plausible mechanism responsible for the formation of Eu(2)O(3) nanotubes is presented.     

Synthesis and optical properties of photochromic perinaphthothioindigo

(1,2-naphtho)(1,8-naphtho)thioindigo (PNT) has been synthesized following a simple Friedel–Crafts route and its photochemical properties in toluene and polymethylmethacrylate (PMMA) have been characterized. PNT is a photochromic molecule capable of reversible photoisomerization between a yellow form (cis-PNT, λ_max = 484 nm) and a purple form (trans-PNT, λ_max = 595 nm). The stable purple form converts to the yellow form with a trans-PNT to cis-PNT conversion quantum yield of 0.027 in toluene and 0.062 in PMMA. The unstable yellow form exhibits a cis-PNT to trans-PNT quantum efficiency of conversion of 0.27–0.85 in toluene and 0.17–0.68 PMMA, with highest conversion efficiency occurring in the vicinity of its λ_max of 484 nm. trans-PNT has a strong fluorescence quantum yield, 0.14 (toluene) and 0.16 (PMMA). For samples prepared photochemically in the cis-PNT form, slow thermal relaxation to the trans form occurs in the dark, with a half life of about 17 h in toluene (25 °C) and even slower, 168 h, in PMMA. The property of photoswitching between fluorescent and non-fluorescent forms makes this material a candidate for many applications in imaging and data storage.     

Dispersion of functionalized multi-walled carbon nanotubes in multi-walled carbon nanotubes/liquid crystal nanocomposites and their thermal properties

A novel liquid crystal functionalized multi-walled carbon nanotubes (LC-MWNTs)/2-methyl-N,N′-bis(4′-methoxy benzoyloxy)-terephthalamide liquid crystal (LC) nanocomposite (LC-MWNTs/LC) was prepared via solution blend. The dispersion and thermal property of the nanocomposites with different loadings of LC-MWNTs (0.1-1 wt.%) were investigated using SEM, TGA and DSC. The results show that the dispersion of LC-MWNTs in LC matrix is more homogeneous than purified MWNTs. The decomposition temperature of nanocomposites exhibits obvious decrease at first and then increase with increasing concentration of LC-MWNTs, which is lower than that of LC for 0.1-0.4 wt.% LC-MWNT loadings and higher than that of LC for 0.5-1 wt.% LC-MWNT loadings. The addition of LC-MWNTs has little effects on the texture of smectic mesophase. These results illustrate the LC-MWNTs/LC nanocomposites, which have lower melting point and higher decomposition temperature than those of LC by adding adequate amount of LC-MWNTs, show a wide temperature range of mesophase and high thermostability. The increased mesophase temperature region of LC materials will be beneficial to their practical applications.     

Preparation and properties of polyarylene ether nitrites/multi-walled carbon nanotubes composites

Polyarylene ether nitriles (PEN)/multi-walled carbon nanotube (MWNT) composites have been successfully fabricated via PEN solution mixing MWNT and then solution-casting. The cast nanocomposite films were characterized by SEM, thermal properties and mechanical properties. The Young's modulus of PEN/MWNT composites was greatly increased with the increase of MWNT concentration. The crystalline behaviors of nanocomposites increased with the increase of MWNT concentration. Thermogravimetric analysis (TGA) measurement showed that MWNT could stabilize PEN when its weight content was greater than 2.0%, and a high char yield in N₂ could be obtained for PEN/MWNT composite at 600 °C.     

Investigation of the microwave-absorbing properties of Fe-filled carbon nanotubes

Carbon nanotubes encapsulated Fe nanowire composites were synthesized via pyrolyzing of ferrocene. The reflection loss (R.L.), matching frequency (f_m) and matching thickness (d_m) were calculated using the theory of the absorbing wall. The electromagnetic properties and microwave-absorbing characteristic effects by the encapsulation of metal Fe were investigated in a frequency range of 8-18 GHz. With matching thickness of 3.5 mm, the maximum reflection loss is about − 22.73 dB for the absorber. The bandwidth corresponding to the reflection loss below − 10 dB is more than 4.22 GHz. With increasing thickness, the peak value of the reflection loss shifts to a lower frequency.     

Studies on preparation and properties of the multi-walled carbon nanotubes (MWNTs)/epoxy nanocomposites

The MWNTs were coated with polyaniline (PANI) by in situ chemical oxidation polymerization method. FTIR spectroscopy, scanning electron microscope (SEM) and X-ray diffraction (XRD) indicated that the MWNTs were coated with PANI. The MWNTs/epoxy nanocomposites were fabricated by using the solution blending method. Differential scanning calorimetry (DSC), tensile testing, HP 4294A impedance analyzer and SEM were used to investigate the properties of the nanocomposites. The results showed that the modified carbon nanotubes were well dispersed in the polymer matrix. The nanocomposites have enhancements in mechanical, thermal and dielectric properties compare with the neat epoxy resin. The nanocomposites were proven to be a good polymer dielectric material.     

Synthesis and luminescence properties of water-dispersible ZnSe nanocrystals

Water-dispersible ZnSe nanocrystals were synthesized by a green and simple route. Growth of the nanocrystals was performed under water-bath temperature, using selenium powder and zinc acetate as precursors, upon addition of mercaptoacetic acid as a stabilizer. Products were characterized by X-ray photoelectron spectra (XPS), X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), absorption and fluorescence spectra. Photoluminescence (PL) properties of ZnSe nanocrystals in evolution are discussed. PL is the contribution of both excitonic and defect emission. The excitonic emission peak can be tuned by changing the refluxing time and pH value. Mercaptoacetic acid is available in controlling the ratio of excitonic emission to defect emission. All desired properties of nanocrystals prepared here imply the possibility of high quality ZnSe nanocrystals developed under a mild condition.     

YVO_4纳米棒的合成及其光致发光性能研究

以Na2EDTA为模板剂,采用水热法合成了纯净的四方锆石结构的单晶YVO4纳米晶体和YVO4∶Eu纳米晶体。通过XRD、TEM、HRTEM和荧光光谱仪等测试手段对产物的结构和光致发光性能进行了表征和测试。研究发现,模板剂和生长溶液的pH值决定着YVO4和YVO4∶Eu纳米晶体的结构与形貌。由于一维晶体的各向异性,导致了YVO4纳米棒的光致发光性能有所增强,而Eu的掺杂则显著改善了YVO4纳米棒的光致发光性能。     

Microstructure, crystallinity, and properties of low-pressure MOCVD-grown europium oxide films

A study of growth, structure, and properties of Eu₂O₃ thin films were carried out. Films were grown at 500–600 °C temperature range on Si(1 0 0) and fused quartz from the complex of Eu(acac)₃·Phen by low pressure metalorganic chemical vapor deposition technique which has been rarely used for Eu₂O₃ deposition. These films were polycrystalline. Depending on growth conditions and substrates employed, these films had also possessed a parasitic phase. This phase can be removed by post-deposition annealing in oxidizing ambient. Morphology of the films was characterized by well-packed spherical mounds. Optical measurements exhibited that the bandgap of pure Eu₂O₃ phase was 4.4 eV. High frequency 1 MHz capacitance–voltage (C–V) measurements showed that the dielectric constant of pure Eu₂O₃ film was about 12. Possible effects of cation and oxygen deficiency and parasitic phase on the optical and electrical properties of Eu₂O₃ films have been briefly discussed.     

W doped vanadium oxide nanotubes: Synthesis and characterization

W doped vanadium oxide nanotubes (VONTs) were prepared via a rheological phase reaction followed by self-assembling process. The nanotubes were characterized by elemental analysis, IR, XRD, SEM, TEM, HRTEM, SAED and XPS. Elemental analysis, IR, XRD, SAED and XPS could confirm the crystalline characteristic of the W doped VONTs, while the SEM, TEM, and HRTEM confirmed their morphology and microstructure.     

Synthesis temperature dependence of morphologies and properties of cobalt oxide and silicon nanocrystals

Cobalt and cobalt oxide nanocrystals were synthesized on Si substrates from aqueous cobalt nitrate [Co(NO₃)₂·6H₂O] powder via chemical vapor deposition method. Scanning electron microscope, field emission scanning electron microscope, and transmission electron microscope observations show different morphologies, such as continuous films, nano-bars, nano-dices, and nano-strings, depending on the synthesis temperature. The crystal structure characterization was conducted using X-ray diffraction methods. Furthermore, the properties of the samples were characterized using Raman spectroscopic analysis and vibrating sample magnetometer. The morpholo- gy change was discussed in terms of synthesis environments and chemical interactions between cobalt, oxygen, and silicon.     

Fe3O4纳米粒子修饰碳纳米管的制备及其磁学性能（英文）

通过FeCl2.4H2O和FeCl3.6H2O混合共沉淀,合成平均粒径为6 nm和10 nm的Fe3O4纳米粒子。然后将两种Fe3O4纳米粒子分别与经HNO3氧化处理的多壁碳纳米管(MWCNTs)置于乙醇水溶液(水和乙醇的体积比为1∶1)中,在超声波作用下制备Fe3O4/MWCNT复合材料。用高分辨透射电子显微镜、X-射线光电子能谱、振动样品磁强计、X射线衍射仪、热重分析仪对所制备的Fe3O4/MWCNT复合材料进行表征。结果表明:由6 nm和10 nm Fe3O4纳米粒子所制备的Fe3O4/MWCNT复合材料中,Fe3O4的质量分数分别为26.65%和29.3%,相应的磁饱和强度分别为16.5 emug-1和7.5 emug-1。     

Synthesis and cathode luminescence properties of ZnO multipod nanoneedles

Zinc oxide (ZnO) multipod nanoneedles over a large area have been synthesized on silicon substrate by thermally oxidizing zinc foil at 650 °C. These nanoneedles have sharp tails with diameter down to less than 100 nm, with length of 10 μm, growing from the surface of the silicon substrate and legs connected at a common base. X-ray diffraction (XRD) confirmed the sample as pure ZnO nanostructures with growth direction of [002]. The cathode luminescence behaviors at different regions of an individual nanoneedle of these multipod ZnO nanostructures were characterized. It is shown the whole nanostructures are luminescent, while the tips have relative higher visible emission than the bottom. The cathode luminescence mechanisms were also discussed.     

Lanthanides-clay nanocomposites: Synthesis, characterization and optical properties

Complexes of Europium(III) and Terbium(III) with 2,2-bipyridine and 1,10-phenanthroline were inserted into Na-bentonite by ion exchange reactions at room temperature. The products display interlaminar distances and stoichiometries in agreement with the ion exchange capacity and the interlayer space available in the clay. The optical properties of the intercalates, being qualitatively similar to those of the free complexes, are additionally improved with respect to exchange processes with the medium, especially in a moist environment. The protection again hydrolysis, together with the intensity of the optical transition ⁵D₀-⁵F₂ observed in the nanocomposite, makes these products promising for the development of novel optical materials.     

Preparation and electrochemical performance of manganese oxide/carbon nanotubes composite as a cathode for rechargeable lithium battery with high power density

Manganese oxide/carbon nanotubes (MO/CNTs) composite was prepared by hydrothermally reducing KMnO₄ with CNTs, where the used CNTs are of dual role, i.e., they serve as reductant during reaction and the remaining CNTs act as conducting agent in the composite. This composite was characterized by X-ray diffraction and scanning electron microscopy techniques. In addition, the electrochemical performances of the composite were investigated, which suggested an excellent rate-capability of this material; e.g., it delivered a high discharge capacity as 131 mAh g^− 1 at a high current density of 4 A g^− 1 (20 C), and high capacity at low discharge current density, e.g., about 209 mAh g^− 1 at 0.2 C rate. Therefore, such a MO/CNTs composite is promising in high power application of lithium battery and electrochemical capacitor.