Tham khảo tài liệu 'biomedical engineering trends in materials science part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 352 Biomedical Engineering Trends in Materials Science surface area and encapsulation ability in hollow nanotubes these nanostructures are exceptionally promising in various fields such as confined catalysis biotechnology photonic devices and electrochemical cells Xu Asher 2004 Lou et. al. 2006 Wei et. al. 2008 . Although lanthanide oxides are excellent host lattices for the luminescence of various optically active lanthanide ions Mao et. al. 2009 Gd2O3 is a promising host matrix for down- and up conversion luminescence because of its good chemical durability thermal stability and low phonon energy Yang et. al. 2007 Jia et. al. 2009 . 3. Synthesis of Gd2Ũ3 Eu 3 nanostructures Gd2O3 doped with Eu3 nanostructures were synthesized by either sol-gel or coprecipitation wet chemical solution methods. Nanoparticles were synthesized by a sol-gel method from their acetate hydrate precursors which were dissolved in water. This solution was mixed with citric acid solution in 1 1 volume ratio ultrasonically for about 30 min. The mixture was heated in a water bath at 80 C until all water is evaporated yielding a yellowish transparent gel. The gel was further heated in an oven at 100 C which formed a foamy precursor. This precursor decomposed to give brown-colored flakes of extremely fine particle size on further heating at 400 C for 4 h. The flakes were ground and sintered at 800 C for duration of 2 h. Further heating in O2 ambient removed the carbon content. The nanoparticles of Eu Gd2O3 were coated by adopting a base-catalyzed sol-gel process. 100 mg of Eu Gd2O3 were dispersed in 20 ml of 2-propanol solution and sonicated for 30 min. 75 pl of tetraethoxysilane TEOS and 25 uL of 25 NH3H2O solution were injected into the above mixture and sonicated for 30 min at 60 C. By means of centrifugation the suspended silica capsulated Eu Gd2O3 were obtained. The coated particles were washed several times by using acetone and methanol in order to remove any excess unreacted chemicals. .
