Synthesis of nanocrystalline Ba(CoxZn1-x)(2)Fe16O27 by sol-gel auto-combustion method

The synthesis of nanocrystalline W-type hexaferrites Ba(CoxZn1-x)(2)Fe16O27 powders by sol-gel auto-combustion method has been investigated. The thermal decomposition process of dried gel was studied by thermogravimetry (TG), differential thermal analysis (DTA) and infrared spectra (IR). The structural and magnetic properties of resultant particles were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). The results reveal that the dried gel exhibits auto-combustion behavior. After combustion, pure nanocrystalline W-type hexaferrite phase starts to appear at the calcination temperature of 800 degrees C. The crystallinity and the grain size increase at higher temperature. The saturation magnetization and coercivity clearly depend on calcination temperature and Co content X.

Structure and properties of the ordered double perovskites Sr2MWO6 (M = Co, Ni) by sol-gel route

The single-phase double perovskites Sr2MWO6 (M=Co, Ni) were prepared by sol-gel method. Crystal Structure, magnetic properties and the morphology of Sr2CoWO6 and Sr2NiWO6 were investigated. X-ray powder diffraction (XRD) analysis shows single phase structure for Sr2MWO6 (M=Co, Ni) without any traces of impurities and the crystal structure of all the samples belongs to the tetragonal I4/m space group. SEM image for Sr2MWO6 (M=Co, Ni) indicate that the grains are homogeneous and connect each other very well. The Neel temperature for Sr2CoWO6 and Sr2NiWO6 are 23 K and 59 K, respectively. Magnetic measurements showed that the magnetic moment in these double perovskites originates mainly from the interactions between Ni ions and Co ions.

Preparation and properties of ternary polyimide/SiO2/polydiphenyisiloxane composite films

A series of novel ternary polyimide/SiO2/polydiphenylsiloxane (PI/SiO2/PDPhS) composite films were prepared through co-hydrolysis and condensation between tetramethoxysilane, diphenyldimethoxysilane (DDS) and aminopropyltriethoxysilane-terminated polyamic acid, using an in situ sol-gel method. The composite films exhibited good optical transparency up to 30 wt% of total content of DDS and SiO2. SEM analysis showed that the PDPhS and SiO2 were well dispersed in the PI matrix without macroscopic separation of the composite films. TGA analysis indicated that the introduction of SiO2 could improve the thermal stability of the composite films. Dynamic mechanical thermal analysis showed that the composite films with low DDS content (5 wt%) had a higher glass transition temperature (T-g) than pure PI matrix. When the content of DDS was above 10 wt%, the T-g of the composite decreased slightly due to the plasticizing effect of flexible PDPhS linkages on the rigid PI chains. The composite films with high SiO2 content exhibited higher values of storage modulus. Tensile measurements also showed that the modulus and tensile strength of the composite films increased with increasing SiO2 content, and the composite films still retained a high elongation at break due the introduction of DDS.

Photoluminescent properties of sol-gel derived (La, Gd)MgB5O10 : Ce3+/Tb3+ nanocrystalline thin films

Ce3+ and/or Tb3+-doped (La,Gd)MgB5O10 nanocrystalline thin films were deposited on silica glass substrates by a sol-gel dip-coating process using triethyl borate B(OC2H5)(3) as the boron source. The results of XRD indicated that the films have fully crystallized after annealing at 800 degrees C. The films are transparent, uniform and crack free with a thickness of about 300 nm, consisting of particles with an average grain size of 50 nm. The luminescence and energy transfer properties of Ce3+ and Tb3+ have been studied in the films. It is confirmed that the excitation energy of Ce3+ transfers to the Gd3+, migrates over the Gd3+ sublattices, trapped by the Tb3+ and resulted in its characteristic green emission (D-5(4)-F-7(5) at 543 nm) in GdMgB5O10 nanocrystalline films as in the powder phosphors.

Microstructure and properties of new polyimide/polysiloxane composite films

A series of novel polyimide/polydiphenylsiloxane) (PI/PDDS) composite films with different contents of DDS were prepared using sol-gel method. The noncrosslinked PI-DDS and crosslinked PIS-DDS were synthesized through cohydrolysis and condensation between DDS and polyamic acid (PAA) or aminopropyltriethoxysilane(APTES)-terminated polyamic acid (PAAS). All the composite films have high thermal stability near pure PI. Field emission scanning electron microscopy (FE-SEM) study shows that the polysiloxane from hydrolyzed DDS well dispersed in polyimide matrix, without macroscopic separation for the composite films with low content of DDS, while large domain of polysiloxane was formed in films with high DDS content. The microstructure of composite films is in accordance with the transparency of corresponding films. X-ray study shows the PDDS is amorphous in PI matrix. The introduction of DDS into PI can improve the elongation at break and at the same time, the composite films still remained with higher modulus and tensile strength. The density and water absorption of the composite films decreased with the increasing DDS content. The composite films with DDS content below 10 wt % exhibit good solvent resistance.

Medicated wound dressings based on poly(vinyl alcohol)/poly(N-vinyl pyrrolidone)/chitosan hydrogels

Poly(vinyl alcohol) /poly(N-vinyl pyrrolidone) (PVP)/chitosan hydrogels were prepared by a low-temperature treatment and subsequent Co-60 -gamma-ray irradiation and then were medicated with ciprofloxacin lactate (an antibiotic) and chitosan oligomer (molecular weight = 3000 g/mol). The gel content, swelling ratio, tensile strength, and crystallinity of the hydrogels were determined. The effects of the chitosan molecular weight, the low-temperature treatment procedure, and the radiation dosage on the hydrogel properties were examined. The molecular weight of chitosan was lowered by the irradiation, but its basic polysaccharide structure was not destroyed. Repeating the low-temperature treatment and gamma-ray irradiation caused effective physical crosslinking and chemical crosslinking, respectively, and contributed to the mechanical strength of the final hydrogels. The incorporation of PVP and chitosan resulted in a significant improvement in the equilibrium swelling ratio. and elongation ratio of the prepared hydrogels. The ciprofloxacin lactate and chitosan oligomer were soaked into the hydrogels. Their in vitro release behaviors were examined, and they were found to follow diffusion-controlled kinetics.

Fabrication and luminescence properties of Y2SiWO8 : Dy3+ phosphors via sol-gel process

(YSiWO8)-Si-2:Dy3+ phosphors were prepared through a sol-gel process. XRD and photoluminespectra were used to characterize the resulting phosphors. The results indicated that the phosphors crystallized completely at 1000 degrees C. In Y2SiWO8:Dy3+ phosphors, the Dy3+ showed its characteristic yellow emission at 483nm (F-4(9/2)-H-6(5/2)) and 575nm (F-4(9/2)-H-6(13/2)) upon excitation into 275nm.

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 degreesC 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 degreesC 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 mm) 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+ D-5(0)-F-7(J) (J = 1, 2, 3, 4), Tb3+ D-5(3,4) - F-7(J) ( 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.

Sol-gel fabrication, patterning and photoluminescent properties of LaPO4 : Ce3+, Tb3+ nanocrystalline thin films

Ce3+ and/or Tb3+-doped LaPO4 nanocrystalline thin films and their patterning were fabricated by a sol-gel process combined with soft lithography on silicon and quartz glass substrates. The results of XRD indicated that the films began to crystallize at 700 degreesC. The 1000 degreesC annealed single layer films are transparent by eyes, uniform and crack-free with a thickness of about 200 nm and an average grain size of 100 nm. Patterned thin film with different band widths (5-50 mum) were obtained by micro-molding in capillaries technique. The luminescence and energy transfer properties of Ce3+ and Tb3+ were studied in LaPO4 films.

Preparation, patterning and luminescent properties of oxyapatite La-9.33(SiO6)(4)O-2 : A (A = Eu3+, Tb3+, Ce3+) phosphor films by sol-gel soft lithography

Silicate oxyapatite La-9.33 (SiO6)(4)O-2:A (A = Eu3+, Tb3+ and/or Ce3+) phosphor films and their patterning were fabricated by a sol-gel process combined with soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, atomic force microscopy, optical microscopy and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 800degreesC and the crystallinity increased with the increase in annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of rodlike grains with a size between 150 and 210 nm. Patterned thin films with different bandwidths (20, 50 mum) were obtained by the micromoulding in capillaries technique. The doped rare earth ions (Eu3+, Tb3+ and Ce3+) showed their characteristic emission in crystalline La-9.33(SiO6)(4)O-2 phosphor films, i.e. Eu3+ D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4), Tb3+ D-5(3,4)-F-7(J) (J = 3, 4, 5, 6) and Ce3+ 5d (D-2)-4f (F-2(2/5), F-2(2/7)) emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ions increased with increasing annealing temperature from 800 to 1100 degreesC, and the optimum concentrations for Eu3+, Tb3+ were determined to be 9 and 7 mol% of La3+ in La-9.33(SiO6)(4)O-2 films, respectively. An energy transfer from Ce3+ to Tb3+ was observed in the La-9.33(SiO6)(4)O-2:Ce, Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+ concentration.

Luminescent properties of rare-earth-doped CaWO4 phosphor films prepared by the Pechini sol-gel process

CaWO4 phosphor films doped with rare-earth ions (Eu3+, Dy-,(3+) Sm3+, Er3+) were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis, atomic force microscopy, and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting powders and films. The results of the XRD analysis indicated that the films began to crystallize at 400degreesC and that the crystallinity increased with elevation of the annealing temperature. The doped rare-earth ions showed their characteristic emissions in crystalline CaWO4 phosphor films due to energy transfer from WO42- groups to them. Both the lifetimes and PL intensities of the doped rare-earth ions increased with increasing annealing temperature, from 500 to 900degreesC, and the optimum concentrations for Eu3+, Dy3+, Sm3+, Er3+ were determined as 30, 1.5, 1.5, 0.5 at.% of Ca2+ in CaWO4 films annealed at 900degreesC, respectively.

Luminescence properties of RP1-xVxO4: A (R=Y, Gd, La; A=Sm3+Er3+ x=0, 0.5, 1) thin films prepared by pechini sol-gel process

Thin film phosphors with compositions of RP1-xVxO4: A (R = Y, Gd, La; A = Sm3+, Et3+; x = 0, 0.5, 1) have been prepared by a Pechini sol-gel process. X-Ray diffraction, atomic force microscopy (AFM), photoluminescence excitation and emission spectra were utilized to characterize the thin film phosphors. The results of XRD showed that a solid solution formed in YVxP1-xO4: A film series from x = 0 to x = 1 with zircon structure, which also held for GdVO4: A film. However, LaVO4: A film crystallized with a different structure, monazite. AFM study revealed that the phosphor films consisted of homogeneous particles ranging from 90 to 400 nm depending on the compositions. Upon short ultraviolet excitation, the films exhibit the characteristic Sm(3+ 4)G(5/2)-H-6(J) (J=5/2, 7/2, 9/2) emission in the red region and Er3+ H-2(11/2), S-4(3/2)-I-4(15/2) emission in the green region, respectively With the increase of x values in YVxP1-xO4: SM3+ (Er3+) films, the emission intensity Of SM3+ (Er3+) increases due to the increase of energy transfer probability from VO43- to Sm3+ (Er3+). Due to the structural effects, the Sm3+ (Er3+) shows similar spectral properties in YVO4 and GdVO4 films, which are much different from those in LaVO4 film.

Patterning and luminescent properties of nanocrystallineY(2)O(3): Eu3+ phosphor films by sol-gel soft lithography

Nanocrystalline Y2O3:Eu3+ phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained, which mainly consisted of grains with an average size of 70 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped Eu3+ showed its characteristic emission in crystalline Y2O3 phosphor films due to an efficient energy transfer from Y2O3 host to them. Both the lifetimes and PL intensity of the Eu3+ increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+ were determined to be 5 mol%.

Preparation, patterning and luminescent properties of nanocrystalline Gd2O3 : A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films via Pechini sol-gel soft lithography

Nanocrystalline Gd2O3:A (A = Eu3+, Dy3+, Sm3+, Er3+) phosphor films and their patterning were fabricated by a Pechini sol-gel process combined with a soft lithography. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy, UV/vis transmission and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 500 degreesC and that the crystallinity increased with the elevation of annealing temperatures. Uniform and crack free non-patterned phosphor films were obtained by optimizing the composition of the coating sol, which mainly consisted of grains with an average size of 70 nm and a thickness of 550 nm. Using micro-molding in capillaries technique, we obtained homogeneous and defects-free patterned gel and crystalline phosphor films with different stripe widths (5, 10, 20 and 50 mum). Significant shrinkage (50%) was observed in the patterned films during the heat treatment process. The doped rare earth ions (A) showed their characteristic emission in crystalline Gd2O3 phosphor films due to an efficient energy transfer from Gd2O3 host to them. Both the lifetimes and PL intensity of the rare earth ions increased with increasing the annealing temperature from 500 to 900 degreesC, and the optimum concentrations for Eu3+, Dy3+, sm(3+), Er3+ were determined to be 5, 0.25, 1 and 1.5 mol% of Gd3+ in Gd2O3 films, respectively.

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.