Synthesis and luminescent properties of europium (III) schiff base complexes covalently bonded to silica xerogels

A new kind of luminescent organic-inorganic hydrid material consisting of Eu(III)-schiff base complex covalently bonded to silica xerogel was synthesized via the sol-gel method using a Eu (N-propylene salicylimine ligand) complex modified with pendant triethoxysilane groups (Eu(III)(salenHSi)). The Eu(III)(salenHSi) complex is characterized by Fourier transform infrared (FT-IR) spectroscopy. Luminescent properties of the complex and the resulted hybrid silica xerogels have been investigated at room temperature.

Facile transformation of hydrophilic cellulose into superhydrophobic cellulose

Superhydrophobic cellulose-based materials coupled with transparent, stable and nanoscale polymethylsiloxane coating have been successfully achieved by a simple process via chemical vapor deposition, followed by hydrolyzation and polymerization.

Bifunctional magnetic-optical nanocomposites: Grafting lanthanide complex onto core-shell magnetic silica nanoarchitecture

Anew class of bifunctional architecture combining the useful functions of superparamagnetism and terbium complex luminescence into one material has been prepared via two main steps by a modified Stober method and the layer-by-layer (LbL) assembly technique. The obtained bifunctional nanocomposites exhibit superparamagnetic behavior, high fluorescence intensity, and color purity. The architecture has been characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-vis absorption and emission spectroscopy, X-ray diffraction, and superconducting quantum interference device (SQUID) magnetometry.

Deposition of GdVO4 : Eu3+ nanoparticles on silica nanospheres by a simple sol-gel method

The deposition and coating of GdVO4: Eu3+ nanoparticles on spherical silica was carried out using a simple sol - gel method at low temperature. The GdVO4: Eu3+-coated silica composites obtained were characterized by differential thermal analysis (DTA), thermogravimetric (TG) analysis, x-ray diffraction (XRD), Fourier-transform IR spectroscopy (FT-IR), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), photoluminescence spectra, and kinetic decay. It is found that the similar to 5 nm GdVO4: Eu3+ nanoparticles coating the silica spheres are crystal in the as-prepared samples and the crystallinity increases with increasing annealing temperature. The composites obtained are spherical in shape with an average size of 100 nm. The GdVO4: Eu3+ nanoparticles are linked with silica cores by a chemical bond. The photoluminescence spectra of the obtained GdVO4: Eu3+-coated silica composites are similar to those of the bulk GdVO4: Eu3+ phosphors. The strongest peak is near 617 nm, which indicates that Eu3+ is located in the low symmetry site with non-inversion centre.

Conductive hybrid film from polyaniline and polyurethane-silica

In order to improve the mechanical performance and water resistance of water-borne conducting polyaniline film, conducting polyaniline/polyurethane-silica hybrid film was prepared in aqueous solution employing silanol-terminated polyurethane and methyltriethoxysilane as sol-gel precursors. The hybrid film showed surface resistivity of 10(8) Omega even though the conducting polyaniline loading was only 10 wt% (or 1.5 wt% of polyaniline), and the mechanical performance as well as water resistance was significantly improved, making it suitable for antistatic application. Therefore, a practical route to water-borne processing of conducting polyaniline is disclosed.

Silica-coated Y2O3 : Eu nanoparticles and their luminescence properties

Crystalline Y2O3:Eu is of paramount significance in rare earth materials and research on luminescence spectra. In this work, the nanocrystalline Y2O3:Eu was coated with silica by a facile solid state reaction method at room temperature. The transmission electron microscope (TEM) photographs showed that the prepared Y2O3:Eu particle is polycrystalline with the size of 20 nm, the size of silica-coated particle is about 25 nm. The XPS spectra indicated that the silica layer is likely to interact with Y2O3:Eu by a Si-O-Y chemical bond. The luminescence spectra showed that the intensity of ground samples is lower than that of unground ones, the intensity of silica-coated phosphors is higher than that of the ground samples, while almost the same as that of the unground ones. Therefore, the silica coating decreases the surface defects of nanoparticles of the nanocrystalline Y2O3:Eu, thus increasing their luminescent intensity.

Non-isothermal crystallisation kinetics of polyamide 6/mesoporous silica nanocomposites

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA6) crystallites.

Shape-gradient composite surfaces: Water droplets move uphill

The approach of water droplets self-running horizontally and uphill without any other forces was proposed by patterning the shape-gradient hydrophilic material (i.e., mica) to the hydrophobic matrix (i.e., wax or low-density polyethylene (LDPE)). The shape-gradient composite surface is the best one to drive water droplet self-running both at the high velocity and the maximal distance among four different geometrical mica/wax composite surfaces. The driving force for the water droplets self-running includes: (1) the great difference in wettability of surface materials, (2) the low contact angle hysteresis of surface materials, and (3) the space limitation of the shape-gradient transportation area. Furthermore, the average velocity and the maximal distance of the self-running were mainly determined by the gradient angle (alpha), the droplet volume, and the difference of the contact angle hysteresis. Theoretical analysis is in agreement with the experimental results.

A reversibly tunable colloidal photonic crystal via the infiltrated solvent liquid-solid phase transition

A reversibly tunable colloidal photonic crystal between two stop bands was realized by a liquid-solid phase transition of liquid infiltrated into the air voids of silica opals. The difference of the peak wavelengths of the two stop bands was dependent on the diameter of the silica opals and the difference of the refractive index of the filled solvent between the solid and liquid state. The reversibly tunable photonic crystals have good stability and reproducibility.

Colloidal photonic crystals with a graded lattice-constant distribution

In this work, a gradient polystyrene colloidal photonic crystal was fabricated by annealing in a graded temperature field. The lattice constant of the gradient crystal gradually varied along the temperature-gradient direction. The positional bandgap wavelength as well as the attenuation of the bandgap wavelength could be tuned dependent on the position of the gradient colloidal crystal along the gradient direction because of the lattice-constant variation.

Structural characteristics and thermal properties of plasticized poly(L-lactide)-silica nanocomposites synthesized by sol-gel method

Plasticized poly(L-lactide)-silica nanocomposite materials have been successfully synthesized by sol-gel process. The resultant nanocomposites were characterized by infrared spectra (IR), X-ray diffraction (XRD), thermogravimetry (TG), Tensile testing and scanning electron microscope (SEM). IR measurements show that vibration of C-O-C group is confined by silica network. Also the crystallization of poly (L-lactide) is partly confined by silica network. The presence of even small amount of silica largely improves the tensile strength of the samples, TGA results reveal that the thermal stability of samples is improved with silica loading.

Surface-grafted silica linked with L-lactic acid oligomer: A novel nanofiller to improve the performance of biodegradable poly(L-lactide)

A new surface modification method by grafting L-lactic acid oligomer onto the surface silanol groups of silica nanoparticles has been developed. The surface-grafting reaction is confirmed by IR and Si-29 MAS NMR analyses. TEM and SEM results show that grafted SiO2 (g-SiO2) nanoparticles can be comparatively uniformly dispersed in chloroform or PLLA matrix, while the unmodified SiO2 nanoparticles tend to aggregate. The loading of g-SiO2 nanoparticles in poly(L-lactide) (PLLA) matrix greatly improves the toughness and tensile strength of this material. In contrast, the incorporation of un-grafted SiO2 nanoparticles into PLLA leads to the deterioration of its mechanical properties. DSC analysis shows that g-SiO2 nanoparticles can serve as a nucleating agent for the crystallization of PLLA in the composites. SEM characterization shows the tough characteristics and great interfacial combination strength for g-SiO2 (5wt%)/PLLA nanocomposites.

Interfacial supramolecular self-assembled monolayers of C-60 by thiolated beta-cyclodextrin on gold surfaces via monoanionic C-60

The supramolecular self-assembled monolayers (SAMs) of C-60 by thiolated beta-cyclodextrin (CD) on gold surfaces were constructed for the first time using C-60 monoanion. The results indicate that monoanionic C-60 plays a crucial role in the formation of the C-60-containing self-assembled monolayers. The generation of C-60 monoanion and the formation process of C-60 SAMs were monitored in-situ by UV-visible and near-IR spectroscopy. The resulting C-60 SAMs were fully characterized by spectroscopic ellipsometry (SE), cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and water contact angle measurements. After the immobilization of C-60 by the SAMs of thiolated beta-CD, the film thickness increased by approximately 1 nm from 0.8 to 1.8 nm as determined by SE, demonstrating the formation of the supramolecular self-assembled monolayers of thiolated beta-CD/C-60. The new C-60 SAMs exhibited one quasi-reversible redox couple at half wave potential of -0.57 V vs SCE in aqueous solution containing 0.1 M KCl. The surface coverage of C-60 on the gold surfaces was estimated to be 1.1 x 10(-10) mol cm(-2). The XPS showed the assembly of C-60 over the thiolated beta-CD SAMs.

In situ synthesis of silica gel nanowire/Na+-montmorillonite nanocomposites by the sol-gel route

Silica-gel nanowire/Na+-montmorillonite (Na+-MMT) nanocomposites were prepared by the in situ sol-gel process of tetraethyl orthosilicate (TEOS) in the presence of Na+-MMT and ammonia as catalyst. Microstructure characterization of the nanocomposites was done by SEM, , EDX, XRD and FTIR. It was found that a lot of silica-gel nanowires grew along the edges of Na+-MMT. The combination between the nanowires and Na+-MMT was accomplished via polycondensation of the hydrolyzed TEOS and the edge-OH groups of Na+-MMT.