Synthesis of Fullerene-Containing Sol-Gel Glasses

Macroscopically homogeneous and visually transparent fullerene-containing glasses are fabricated from sol-gel mixtures of aminated C60 derivatives and tetraethyl orthosilicate (TEOS) through physical blending and chemical reaction. The aminated fullerenes are synthesized by the amination reactions of C60 with 6-amino-1-hexanol, cyclohexylamine, 2-(2-aminoethoxy)ethanol, and 3-aminopropyltriethoxysilane at 100°C under nitrogen. The amination products are purified by filtration, precipitation, and column chromatography and are isolated in good to excellent yields (32–82%). Characterization by NMR, MS, and TGA analyses reveals that the aminated fullerenes possess molecular structures HxC60[NH(CH2)6OH]x\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$(1;{\bar x = 7)}$$ \end{document}, HxC60(NH-cyclo-C6H11)x\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$(2;{\bar x = 11)}$$ \end{document}, HxC60[NH(CH2CH2O)2H]x\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$(3;{\bar x = 11)}$$ \end{document}, and HxC60[NH(CH2)3Si(OCH2CH3)3]x\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$(4;{\bar x = 4)}$$ \end{document}. All the aminated fullerenes except 2 are completely soluble in aqueous alcoholic solutions of TEOS and can be incorporated into silica gel networks by sol-gel process in the absence or presence of drying-control chemical additives, giving crack-free monoliths of large sizes (up to ∼60 mm). Electronic absorption spectrum of the fullerene glass continuously red shifts with an increase in the C60 content, suggesting the formation of fullerene nanoclusters in the sol-gel process. The fullerene glasses are thermally and optically stable, resisting continuous attack of strong laser pulses of 532 nm for a prolonged period of time without losing their optical limiting power.