Hui-Min Zhang

Sol–gel synthesis and photoluminescent properties of LaPO4:A (A = Eu3+, Ce3+, Tb3+) nanocrystalline thin films

Rare-earth ion (Eu3+, Tb3+, Ce3+)-doped LaPO4 nanocrystalline thin films and their patterning were fabricated by a Pechini sol–gel process combined with soft lithography on silicon and silica glass substrates. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), scanning electron microcopy (SEM), optical microscopy, absorption and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicate that the films begin to crystallize at 700 °C and the crystallinity increases with increasing annealing temperature. The morphology of the thin film depends on the annealing temperature and the number of coating layers. The 1000 °C annealed single layer film is transparent to the naked eye, uniform and crack-free with a thickness of about 200 nm and an average grain size of 100 nm. Patterned thin films with different strip widths (5–50 µm) were obtained by micromolding in capillaries (soft lithography). The doped rare earth ions show their characteristic emission in the nanocrystalline LaPO4 films, i.e., Eu3+5D0–7FJ (J = 1, 2, 3, 4), Tb3+5D3,4–7FJ (J = 6, 5, 4, 3, 2) and Ce3+ 5d–4f transition emissions, respectively. Both the lifetimes and the PL intensities of Eu3+ and Tb3+ increase with increasing annealing temperature, and the optimum concentrations for them were determined to be 5 mol% and 16 mol% of La3+ in LaPO4 thin films, respectively. An energy transfer phenomenon from Ce3+ to Tb3+ has been observed in LaPO4 nanocrystalline thin films, and the energy transfer efficiency depends on the doping concentration of Tb3+ if the concentration of Ce3+ is fixed.

Luminescence properties of rare-earth (Eu3+ and Tb3+) complexes with paraaminobenzoic acid and 1,10-phenanthroline incorporated into a silica matrix by sol-gel method

Ternary complexes of europium and terbium with paraaminobenzoic acid and 1,10-phenanthroline (Eu(p-ABA)(3). phen . 2H(2)O and Tb(p-ABA)(3). phen . 2H(2)O, where p-HABA = paraaminobenzoic acid and phen = 1,10-phenanthroline) were introduced into a silica matrix by sol-gel method. The luminescence behavior of the complexes in silica gels was studied in comparison with the. corresponding solid-state complexes by means of emission, excitation spectra, and Lifetimes. Within the range of effective dopant concentrations, the luminescence intensities of rare-earth complexes in silica gel increase with the increasing of their dopant concentration. The lifetimes of rare-earth ions (Eu3+ and-Tb3+) in silica gel doped with europium and terbium complexes become longer than those in pure complexes. Very small amounts of rare-earth complexes doped in silica gel matrix can exhibit excellent luminescence properties, (C) 1998 Elsevier Science Ltd.

Scanning tunneling microscopy of the formation, transformation, and property of oligothiophene self-organizations on graphite and gold surfaces.

Two alkyl-substituted dual oligothiophenes, quarterthiophene (4T)-trimethylene (tm)-octithiophene (8T) and 4T-tm-4T, were used to fabricate molecular structures on highly oriented pyrolytic graphite and Au(111) surfaces. The resulted structures were investigated by scanning tunneling microscopy. The 4T-tm-8T and 4T-tm-4T molecules self-organize into long-range ordered structures with linear and/or quasi-hexagonal patterns on highly oriented pyrolytic graphite at ambient temperature. Thermal annealing induced a phase transformation from quasi-hexagonal to linear in 4T-tm-8T adlayer. The molecules adsorbed on Au(111) surface in randomly folded and linear conformation. Based on scanning tunneling microscopy results, the structural models for different self-organizations were proposed. Scanning tunneling spectroscopy measurement showed the electronic property of individual molecules in the patterns. These results are significant in understanding the chemistry of molecular structure, including its formation, transformation, and electronic properties. They also help to fabricate oligothiophene assemblies with desired structures for future molecular devices.

Luminescence properties of the rare earth (Eu3+ and Tb3+) complexes with 1,10-Phenanthroline incorporated in silica matrix by a sol-gel method

Europium and terbium complexes with 1,10-phenanthroline were introduced into silica gel by the sol-gel method. The luminescence behavior of the complexes in silica gels was studied compared with the corresponding solid state complexes by means of emission, excitation spectra and lifetimes

Controllable AuPt bimetallic hollow nanostructures

We describe a facile procedure for one step, large-scale synthesis of AuPt bimetallic hollow tube-like 1-D nanomaterials and hollow nanospheres, which can be easily manipulated by merely changing the concentration of citric acid.

Electroluminescent devices based on monohexadecyl phthalate terbium

Electroluminescent devices with PVK film doped with monohexadecyl phthalate terbium and PBD were fabricated. The device structure of glass substrate/ITO/PPV/PVK:Tb(MHP)(3):PBD/Alq(3)/Al was employed. The emissive layer was formed by a spin-casting technique. The EL cells exhibited characteristic emission of terbium ions with a maximum luminance of 74 cd/m(2) at 18 V

Effect of the bridge alkylene chain on adlayer structure and property of functional oligothiophenes studied with scanning tunneling microscopy and spectroscopy.

Five dual-quinquethiophene self-assemblies are prepared on a highly oriented pyrolytic graphite (HOPG) surface. The dual-quinquethiophenes are quinquethiophenes (5T)-di to hexamethylene (n, 2-6)-quinquethiophenes (5T), abbreviated as 5T-n-5T (n = 2-6). The effect of the bridge alkylene chains on the structure and property of the five assemblies are investigated by scanning tunneling microscopy (STM). It is found that all 5T-n-5T molecules form ordered adlayers on a HOPG surface with stripe feature. The alkylene bridge part in a molecule appears in a dark contrast in an STM image. Intriguingly, the thiophene backbones of individual molecules in the adlayer always keep an angle with the direction of molecular stripes. With alkylene bridge length increasing, different structures are found in 5T-5-5T and 5T-6-5T assemblies. To understand the effect of bridge chains on single molecular property, scanning tunneling spectroscopy is used to probe the electronic property of the different adlayers. The results will be important in surface engineering by self-assembly and molecular device fabrication with oligothiophenes.

Preparation and optical characterization of an organoeuropium-doped sol-gel transparent luminescence thin film

Binary and ternary europium complexes with dibenzplymethane (DBM) and 1,10-phenanthroline (phen) were synthesized and doped into a sol-gel luminescence thin film and polyvinylbutyral (PVB) film. The luminescent spectra and lifetime of the films were measured. The final results showed that Eu(III) characteristic emission bands were observed in the spectra of all the doped films. Longer lifetimes and a higher photo-stability were observed in SiO2:Eu(III) complex luminescent thin films than in PVB:Eu(III) complex films that contained a corresponding amount of pure complexes. Heat-stability tests showed that SiO2:Eu(III) complex thin films still showed certain fluorescence after heat-treatment at a temperature of 130 degreesC, while little fluorescence could be observed in PVB:Eu(III) complex films under a UV lamp

Fabrication, characterization and electrochemical behaviors of the orientated film of a C60 derivative

Abstract The ability of a C60 derivative (1) to form Langmuir monolayer at air/water interface was investigated by using surface pressure vs. molecular area isotherm and Brewster angle microscopy (BAM). The monolayers were transferred on quartz, mica and ITO substrates with LB technique, respectively, and characterized using atomic force microscopy (AFM) and UV–vis spectra. These LB films were studied employing cyclic voltammetry in aqueous solutions of Fe(CN)63−. The results show that a true monolayer of compound 1 is formed in the spreading process and that no three-dimensional aggregates are formed. The cyclic voltammetric behaviors show that the LB film of the C60 derivative may exhibit some ionic charge-selective electron-transfer phenomena, implying that LB film of C60 derivative bearing appropriate group may be used as electrode modifier.

Novel electrocatalytic activity in layered Ni–Cu nanowire arrays

By using template synthesis method, well-defined composite Ni-Cu nanowire electrode arrays (CNNEAs) were prepared. Homogeneous nanoparticles of Ni in CNNEAs show extraordinary high catalytic activity, which was discussed in terms of the size effect of Ni nanoparticles.