Studies on the covalent attachment of dyes onto the layer of silylated graphite oxide and their fluorescence properties

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Graphite oxide was successfully silylated by various silylating reagents. Pyrene chromophores were covalently attached onto the layer of graphite oxides silylated by alkyltrichlorosilanes with various alkyl chain lengths using a dye prepared from the reaction between 1-pyrenecarboxaldehyde and 3-aminopropyltriethoxysilane. The amount of attached pyrene was determined from the absorption of 1-pyrenecarboxaldehyde formed as the result of hydrolysis of the above materials and it reached 0.7 per 8 carbons of graphite oxide unit. The aggregation of pyrene chromophores occurred only when the alkyl chains in the layer of graphite oxide took bilayer orientation. This suggests that pyrene molecules attached on the same graphite oxide layer hardly aggregate. The maximum amount of monomeric pyrene in the layer of graphite oxide reached 0.45 per graphite oxide unit. Pyrene chromophores were also attached by the reaction between 1-pyrenebutannoic acid succimidyl ester and silylated graphite oxide containing amino groups. In this system, the fluorescence became stronger because C=N bonding causing self absorption was excluded. The substitution of alkyl chains by perfluoroalkyl chains with lower vibration energy also resulted in the increase of fluorescence since the radiationless transition from dyes decreased.