期刊
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY
卷 60, 期 3, 页码 260-265出版社
SPRINGER
DOI: 10.1007/s10971-011-2484-x
关键词
Silica spheres; Functionalization; Co-condensation; Bronsted acidic groups
Silica spheres with uniform size of 230-250 nm were functionalized with sulfonic groups and bi-functionalized with carboxylic and sulfonic groups via a co-condensation route, by adding the organosilanes (3-(triethoxysilyl)mercaptopropyl and 4-(triethoxysilyl)butyronitrile) to a pre-hydrolized TEOS solution. The conversion of mercapto and cyano groups to, respectively, sulfonic and carboxylic groups was carried out by treating both the samples with nitric acid solution. The presence of alkyl-SO3H and alkyl-COOH species at the silica surface in an approximate molar ratio of 1:1 was assessed by TG and NMR. FT-IR spectroscopy showed that both Bronsted acidic groups are accessible and give proton-transfer reaction to ammonia with the formation of ammonium ion. Sulfonic groups react irreversibly with ammonia at room temperature at variance with carboxylic groups which give a reversible proton-transfer, in agreement with the stronger Bronsted acidity of the former.
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