Tailoring aqueous solubility of functionalized single-wall carbon nanotubes over a wide pH range through substituent chain length.

Carboxylic acid-functionalized SWNTs prepared via the reaction of an amino acid, NH2(CH2)nCO2H, with fluoronanotubes show similar levels of sidewall functionalization; however, the solubility in water is controlled by the length of the hydrocarbon side chain (i.e., n). The 6-aminohexanoic acid derivative is soluble in aqueous solution (0.5 mg mL(-1)) between pH 4 and 11, whereas the glysine and 11-aminoundecanoic acid derivatives are insoluble across all pH values.