Patterning and optical properties rhodamine B-doped organic-inorganic silica films fabricated by sol-gel soft lithography

Rhodamine B (RB)-doped organic-inorganic silica films and their patterning were fabricated by a sol-gel process combined with a soft lithography. The resulted film samples were characterized by atomic force microscope (AFM), optical microscope and UV/Vis absorption and photoluminescence excitation and emission spectra. The effects of the concentration of the RB dye and heat treatment temperature on the optical properties of the hybrid silica films have been studied. Four kinds of patterning structures with film line widths of 5, 10, 20 and 50 mum have been obtained by micromolding in capillaries by a soft lithography technique. The RB-doped hybrid silica films present a red color, with an excitation and emission bands around 564 and 585 mum, respectively. With increasing the RB concentration, the emission intensity of the RB-doped hybrid silica films increases and the emission maximum presents a red shift. The emission intensity of the films decreases with increasing the heat treatment temperatures.

Sol-gel derived silicate oxyapatite phosphor films doped with rare earth ions

Rare-earth (Eu3+, Tb3+)-doped Ca2Y8(SiO4)(6)O-2 luminescent thin films were dip-coated on silicon and quartz glass substrates through a sol-gel route. X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resultant films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC, and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM micrographs, where particles with various shape and average size of 250 nm can be resolved. The Eu3+ and Tb3+ ions show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4)-F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime of Eu-3divided by increases with the heat treatment temperature front 700 to 1100 degreesC.

Multi-color long-lasting phosphorescence in Mn2+-doped ZnO-B2O3-SiO2 glass-ceramics

Multi-color LLP phenomenon was observed in Mn2+-doped ZnO-B2O3-SiO2 glassceramics after the irradiation of a UV lamp at room temperature. Transparent ZnO-B2O3-SiO2 glass emitted reddish LLP while opaque glass-ceramics prepared by the glass sample after heat treatment emitted yellowish or greenish LLP. The change of the phosphorescence is due to the alteration of co-ordination state of Mn2+. The phosphorescence of the samples was seen in the dark with naked eyes even 12 h after the irradiation with a UV lamp (lambda(max) = 254 nm) for 30 min. Based on the approximative t(-1) decay law of the phosphorescence, we suggest that the LLP is attributed to the thermally assisted electron-hole recombination.

Annealing of nylon-1010 under high pressure

Full Paper: A study has been made on the annealing of nylon-1010 under high pressures. Heat treatment of melt-crystallized nylon-1010 was performed at 250degreesC for 30 min in the pressure range 0.7 similar to 2.5 GPa. It was found that the triclinic crystals of virgin nylon-1010 were retained at pressures less than 1.0 GPa or larger than 1.2 GPa. The X-ray diffraction intensity of (100) planes decreased with increasing pressure. The diffraction peaks shifted slightly to higher angles (2theta) relative to the virgin nylon-1010, indicating dense packing of polymer chains at high pressures. The highest melting temperature was 208degreesC for the sample annealed at 1.5 GPa. No extended-chain crystals were formed under the experimental conditions. Crosslinking occurred in the pressure range 1.0 similar to 1.2 GPa. The structure of the crosslinked samples was characterized by means of infrared spectroscopy and X-ray photoelectron spectroscopy. It is concluded that a mechanism of crosslinking via carbodiimide can explain the nature of crosslinking of nylon-1010 annealed at high pressures. The remarkable changes of the structure of annealed nylon-1010 are also discussed in this article.

Photoluminescence of organic-inorganic hybrid SiO2 xerogels

Organic-inorganic hybrid SiO2 xerogels were prepared by the sol-gel method under various preparation conditions and compositions by using tetraethoxysilane (TEOS), (3-aminopropyl) triethoxysilane (A-PS), (3-glycidoxypropyl) trimethoxysilane (GPS), organic acid (CH3COOH) and inorganic acids (HCl, HNO3, H2SO4) as the main precursors. Luminescence and FT-IR spectra were used to characterize the resulted hybrid SiO2 xerogels. The result of FT-IR spectrum shows that the xerogels are composed of non-crystalline -Si-O-Si- networks containing some organic groups such as -NH, -CH and -OH. Under the excitation of 365 nm, all the hybrid xerogels exhibit strong luminescence in the blue region, but the emission intensity and position depend on the starting precursor compositions to a large extent. Suitable amount of polyethylene glycol (PEG500 and PEG10000) in the hybrid xerogels can enhance the emission intensity. Additionally, the emission intensity of the hybrid xerogels increases with heat treatment temperature in the range of ambient to 200degreesC, and vacuum condition is also able to enhance the emission intensity.

Fabrication, patterning, and optical properties of nanocrystalline YVO4 : A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films via sol-gel soft lithography

Nanocrystalline YVO4:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM) and optical microscopy, UV/vis transmission and absorption spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 400 degreesC and the crystallinity increased with the increase of annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of grains with an average size of 90 nm. Patterned gel and crystalline phosphor film bands with different widths (5-60 mum) were obtained. Significant shrinkage and a few defects were observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline YVO4 phosphor films because of an efficient energy transfer from vanadate groups to them. The Sm3+ and Er3+ ions also showed upconversion luminescence in a YVO4 film host. Both the lifetimes and PL intensity of the rare earth ions increased with increasing annealing temperature from 400 to 800 degreesC, and the optimum concentration for Eu3+ was determined to be 7 mol % and those for Dy3+, Sm3-, and Er3+ were 2 Mol % of Y3- in YVO4 films, respectively.

Preparation and characterization of novel luminescent sol-gel films containing a RE3+ carboxylic acid complex

RE3+ (Eu3+, Tb3+) complexes with carboxylic acid (salicylic acid and benzoic acid) were introduced into the sol, which was prepared by the hydrolysis of tetraethoxysilane (TEOS). A sol-gel luminescent thin film (SG-LTF) was then prepared by dispersing the sol onto a silica substrate by a spin coating method. Multi-layer luminescent thin films were prepared by repeating the same process. The luminescent spectra, fluorescence lifetime and thermal stability of the SG-LTFs were investigated. For the reason of comparison polyvinylbutyral (PVB) was added into a N,N-dimethylformamide (DMF) solution in which the comparative RE3+ carboxylic acid complexes were previously dissolved to form the DMF/PVB solution and the PVB luminescent thin film (PVB-LTF) was prepared. The results show that a broad excitation band indicates the formation of RE complexes in the solid SG-LTFs. RE ions, which are restrained in the silica matrix, present longer lifetimes and higher thermal stability than that in the PVB-LTF containing the corresponding pure complexes. The different doping concentration of RE (III) complexes in the SG-LTFs and the different change of the emission intensities with the heat treatment temperature in the sol-gel thin film and the sol-gel bulk gel were also discussed in this paper.

Tunable photoluminescence in sol-gel derived silica xerogels

Silica xerogels prepared by sol-gel method show blue emission under UV excitation with a smaller Stokes shift. The luminescent properties have been investigated under various preparation conditions and compositions. The silica xerogels show similar luminescent properties when using C2H5OH and N,N-dimethylformamide (DMF) as solvents, which are very different from those when using dimethylsulfoxide (DMSO) as solvent, i.e., a red shift of excitation and emission has been observed in the latter case. The emission intensity of the silica xerogels also depends on the water content and pH of the starting reaction solution. The introduction of organic group (-CH3) in the silica xerogel modifies the network structure and further changes their luminescence properties. Heat treatment results in the decomposition of the organic (-SiCH3) groups, which eliminates the old luminescent centers and produces new luminescent centers in longer wavelength simultaneously. (C) 2000 Elsevier Science B.V. All rights reserved.

Sol-gel deposition of calcium silicate red-emitting luminescent films doped with Eu3+

Eu3+-activated calcium silicate (CaO-SiO2:Eu3+) luminescent films were prepared by the sol-gel method. The structural evolution of the film was studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the luminescence properties of the phosphor films were investigated as a function of heat treatment temperature. The XRD study indicates that a kilchoanite phase forms in the film sintered at 800 degreesC, which is different from that in gel powder treated under the same conditions. The SEM results show that the film thickness decreases and the particles in the film become smaller with increasing heat treatment temperature. The CaO-SiO2:Eu film shows the characteristic emission of Eu3+ under UV excitation, with the Eu3+ D-5(0)-->F-7(2) band (616 nm) being the most prominent. A large difference in the Eu3+ lifetime is observed between the film samples treated at 500 and 700 degreesC (or above). Concentration quenching occurs when the Eu3+ doping concentration is above 6 mol% of Ca2+ in the film.

Photosensitization of TiO2 nanoparticulate thin film electrodes by CdS nanoparticles

Surface photovoltage spectra (SPS) measurements of TiO2 show that a large surface state density is present on the TiO2 nanoparticles and these surface states can be efficiently decreased by sensitization using US nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO2 thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films, The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO2 nanoparticulate thin film sensitized using US nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response.

Mechanical properties of poly(beta-hydroxybutyrate)/poly(ethylene oxide) blends

Tensile properties of poly (P-hydroxybutyrate)/poly (ethylene oxide) (PHB/PEO) blends were reported in this paper. It was found that the blends of PHB with different molecular-weight PEO exhibited different mechanical properties. The mechanical properties of the blends of PHB and PEO3 (M-w=0.3x10(6)) were very poor. However, the blends of PHB and PEO5 (M-w=5x10(6)) showed compatible in mechanical properties. Excellent synergism was observed not only in tensile stress and tensile elongation but also in modulus. Moreover, the ductility of the blends could be improved further under proper heat-treatment.

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. (C) 2001 Elsevier Science B.V. All rights reserved.

Structural changes of TiO2 gel using Eu3+ ion as the fluorescence probe

Because of the extremely sensitivity to the local environment of the D-5(0) --> F-7(2) transition of Eu3+ ion, the fluorescence of Eu3+ ions was Studied by introducing Eu3+ ions to TiO2 gel by the sol-gel method, from which the structural changes of TiO2 gel were characterized. The results showed that the intensity of D-5(0) --> F-7(2) transition increased with the increasement of heat treatment temperature, which indicated the evaporation of molecular water and the completeness of the condensation reaction. Because of the quenching of the fluorescence induced by the cluster of Eu3+ ions, the addition of Al3+ ions greatly enhanced the emission intensity of Eu3+ ion.

Exploration of post radiation effects on polyamide-1010

Irradiated polyamide-1010 (PA1010) with and without heat treatment after gamma-ray irradiation was compared by wide angle x-ray diffraction (WAXD), differential scanning calorimeter (DSC) and the determination of gel fractions. The results indicate that post radiation effects due to post radiation crosslinking and scissions affect physical properties. Post radiation effects restrain the formation and perfection of the planes (010), and make the crystals imperfect. Post radiation effects change the crystalline structures of polyamide-1010.

IN-SITU COMPOSITE - PHENOLPHTHALEIN POLYETHERSULFONE-THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Phase behavior, thermal, theological and mechanical properties plus morphology have been studied for a binary polymer blend. The blend is phenolphthalein polyethersulfone (PES-C) with a thermotropic liquid crystalline polymer (LCP), a condensation copolymer of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET). It was found that these two polymers form optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separation during heat treatment. However, melt mixed PES-C/PHB-PET blends were heterogeneous based upon DSC and DMA analysis and SEM examination. Addition of LCP in PES-C resulted in a marked reduction of melt viscosity and thus improved processability. Compared to pure PES-C, the charpy impact strength of the blend containing 2.5% LCP increased 2.5 times. Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils were found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processing conditions.