Seasonal Variations in the Occurrence of Retinal Vein Occlusion: A Five-Year Nationwide Population-Based Study from Taiwan

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• 作者：Jau-Der Ho ; Ching-Yao Tsai ; Shiow-Wen Liou ; Ray Jui-Fang Tsai ; Herng-Ching Lin
• 关键词：Hybrid material ; Mesoporous ; Adsorption ; Thermodynamic ; Acid-base
• 刊名：American Journal of Ophthalmology
• 出版年：2008
• 期刊代码：7_00029394
• 类别：med
• 出版时间：April 2008
• 卷：145
• 期：4
• 页码：722-728.e3
• 文件大小：853 K

摘要

The inorganic–organic hybrid material was synthesized by co-condensation of tetraethylorthosilicate and the organosilane N-[3-(trimethoxysilyl)propyl]diethylenetriamine. Spectroscopic analysis of the hybrid material by FTIR showed bands at 2937 and 2839 cm⁻¹ related to ν(CH); ²⁹Si NMR spectrum gave signals at −108, −99, −68 and −59 ppm, Q⁴, Q³, T⁴ and T² species related to the silica backbone structure. The well-defined peaks obtained in the ¹³C NMR spectrum in the 10–58 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous silica. Particle morphology evaluated by a scanning electron microscopic (SEM) study showed the formation of spherical particles in the nanometer range. The X-ray diffraction pattern showed a peak at a 2θ of 2.3°, demonstrating the mesoporous characteristic of the synthesized material. Adsorption evaluated by batch equilibrium processes gave the maximum adsorption of 2.2 and 2.8 mmol g⁻¹ for copper and nickel, respectively. From these values a stoichiometry of 2:1 for cation/ligand was established, considering the amount of 1.2 mmol of pendant groups per gram of the hybrid material. Thermodynamic parameters related to the adsorption of metal ions, evaluated using the calorimetric titration technique presented a negative Gibbs free energy value, in agreement with the spontaneity of cation removal on the basic center in the mesoporous silica at the solid/liquid interface.