| Single-walled carbon nanotubes (SWNTs) dispersed in sodium dodecyl sulfate (SOS) suspensions exhibit diameter-dependent oxidative quenching of their E11 fluorescence. This behavior can be substantially changed to become a near diameter independent quenching phenomenon in the presence of electron-withdrawing nitroaromatic compounds. This change is measured as a function of pH and concentration of oxidizing agents for SWNTs suspended either in SDS or in Nafion. Benzene, toluene, phenol, and nitromethane do not show such change. This suggests the possibility of forming an electron donor-acceptor (EDA) complex, where the SWNT is the electron donor and nitroaromatic compounds are the acceptor, and the resulting supramolecular complex exhibits different redox behavior than the uncomplexed SWNT.;Next, the dispersion of SWNTs in Nafion aqueous system is sustainable in ethanol and in salt solutions for observing well-resolved NIR fluorescence peaks of SWNTs. The optical property of the SWNT/Nafion suspension is studied by means of reversible oxidative quenching behavior with different oxidants including H2O2 and I2. Additionally, a simple and rapid one-step method for encapsulating SWNT/Nafion suspension into silica for fluorescence studies is also described. The redox reactions of fluorescent SWNT/silica composite with H2O2 and I2, either in water or in air, are studied with respect to time. Under this condition, the fluorescence of SWNT/silica composite shows the exponential decay and the dependence on the thickness of the silica composite.;Furthermore, solvent effect on the fluorescence properties of the surfactant-dispersed SWNT in the aqueous solution is investigated by addition of DMSO, DMF, and THF, respectively. By mixing with certain amount of water soluble organic solvents, the fluorescence intensity of Nafion-dispersed SWNTs shows significant enhancement because the conformational change of fluorinated backbone of Nafion can improve the dispersion of SWNTs in the aqueous solution. This conformational change also leads the formation of the fluorescent small nanotube bundles to affect the pattern of the relative intensities of different SWNT chiralities compared to the initial fluorescence spectra because of excition energy transfer. Compared to the Nafion system, the fluorescence intensity of SWNT dispersed in SDS and sodium dodecylbenzene sulfonate (SDBS) aqueous solutions do not show any enhancement upon addition of the same three organic solvents, respectively. Additionally, the Nafion fluorinated backbone shows strong hydrophobic interaction with SWNT surface to reduce the solvent effect on fluorescence quenching and spectral shift compared with SDS and SDBS surfactants. |
