Papers by Keyword: UV-Shielding

Abstract: In present work, the structure, absorption and energy gap of films prepared from biodegradable polymer doped ZrO₂-SiC NPs for UV-shielding, biomedical fields and optoelectronics approaches were investigated. The nanocomposites films were fabricated by casting method. The absorption spectra was measured in range (200-800) nm. Results indicated to enhance in absorption and energy gap of biopolymer by adding of ZrO₂-SiC NPs ratios, this behavior make it suitable for various applications like antibacterial films, anti-UV light, diodes, solar cell, transistors and other fields. Keywords: biodegradable polymer, UV-shielding, absorption, energy gap, ZrO₂.

Abstract: Thin UV-blocking films of poly(methyl methacrylate) and CdSe quantum dots (QDs) (CdSe@PMMA) are built up by CdSe-azo initiator through surface-initiated free-radical polymerization. CdSe@PMMA nanocomposite film possesses excellent transparency and ultraviolet (UV)-shielding properties. The average size of CdSe QDs is found to be less than 5 nm and well dispersed in the PMMA matrices without any significant agglomeration by the transmission electron microscopy (TEM) measurement. At the same time, excellent fluorescence (FL) spectra of the nanocomposite indicate that the luminescent properties of CdSe QDs remain effective after the polymerization. Such the transparent and luminescence CdSe@PMMA nanocomposite film exhibits prominent UV-absorbing capability and the high optical transparency in the visible-wavelength region, thus make it to be a promising material for the large scale fabrication of diverse optical devices.

Abstract: Transparent poly(methyl methacrylate) (PMMA)/TiO₂ nanocomposites have been prepared by solution mixing PMMA with organically soluble titania xerogel. The organically soluble titania xerogel in the form of amorphous phase has been synthesized via a simple sol-gel method, involving hydrolysis of tetrabutyl titanate (TBT) in trifluoroacetic acid (TFA) and gelation. The obtained PMMA/TiO₂ nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), thermogravimetry (TG) and ultraviolet-visible (UV-vis) absorption spectroscopy. The results showed that the interaction between titania nanoparticles and PMMA macromolecular chains led to a homogeneous dispersion of TiO₂ in PMMA matrix. The resulting PMMA/TiO₂ nanocomposites showed improved thermal stability, high transparency and high UV-shielding efficiency with a small amount of titania xerogel (£3.0 wt%). The present work is of interest for developing a series of transparent UV-shielding nanocomposites.

Abstract: The hybrid materials consisting of plate-like potassium lithium titanate (K0.81Li0.27Ti1.73O4) micro particles coated with calcia-doped ceria (Ce0.8Ca0.2O1.8) nano particles were prepared by the co-precipitation method and sol-gel method. Broad-spectrum UV-shielding composite materials with good comfort and low oxidation catalytic activity were successfully synthesized. The comfort when applied on skin and UV-shielding ability of the composites prepared by the sol-gel method were superior to those by the co-precipitation method.

Abstract: White nanoparticles of calcia-doped ceria were prepared from the precipitate by reacting CeCl3-CaCl2 mixed solution with NaOH solution at pH 12 and the oxidation with hydrogen peroxide solution at 40oC, followed by the calcination at 700oC for 1 h. The sample before calcination contained significant amount of OH- in the lattice and was yellow, but the powders calcined above 700oC were white, indicating that cationic defect formed by replacing O2- with OH- played as the color center. Calcia-doped ceria particles were coated with amorphous silica by means of seeded polymerization technique using hydrolysis of tetraethylorthosilicate (TEOS) or acid hydrolysis of sodium silicate. The silica coating by seeded polymerization with TEOS was much more efficient for the reduction of catalytic activity of ceria for the oxidation of organic materials than that by acid hydrolysis of sodium silicate. It is confirmed that ceria particles caused far less damage to the DNA plasmids upon UV illumination than either the titania or the zinc oxide reference pigments.

Abstract: Calcia-doped ceria is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of its excellent UV light absorption property and low catalytic ability for the oxidation of organic materials superior to undoped ceria. The performance of calcia doped ceria needs more enhancement through further control of its oxidation catalytic activity and improvement of its covering ability. In order to reduce the oxidation catalytic activity further, calcia-doped ceria was coated with amorphous silica by means of seeded polymerization technique. Generally, nanoparticles of calcia doped ceria do not provide a good coverage for human skin because of the agglomeration of the nanoparticles. The platy particles are required to enhance the covering ability of calcia doped ceria. This can be accomplished by synthesis of calcia-doped ceria/plate-like material (e.g., potassium lithium titanate (K0.8Li0.27Ti1.73O4) and mica) nanocomposite with subsequent silica coating. Calcia-doped ceria/plate-like material was prepared by soft chemical method followed by silica coating via seeded polymerization technique. Silica coated calcia-doped ceria/plate-like material nanocomposite was characterized by X-ray diffraction, SEM, TEM, XPS and FT-IR.