title: Substrate-Mediated Cooperative Adsorption of Sodium Cholate on (6,5) Single-Wall Carbon Nanotubes.
abstract: The interaction of sodium cholate (NaC) with (6,5) single-wall carbon nanotubes (SWNTs) is investigated using photoluminescence spectroscopy. Dilution of SWNT-NaC suspensions is accompanied by changes in the exciton PL quantum yield and peak emission energy. An abrupt change of the exciton emission peak energy at NaC concentrations between 10 and 14 mM indicates strongly cooperative formation of a micellar phase on (6,5) SWNT surfaces with a Hill coefficient of nH = 65 ± 6. This is in contrast to the formation of free NaC micelles with aggregation numbers of only about 4 and suggests that the cooperativity of NaC micelle formation on nanotube surfaces is strongly substrate-enhanced. The temperature dependence of this previously unobserved transition is used for a determination of ΔmicG(⊖)/(1 + β) = -(11.4 ± 0.2) kJ·mol(-1) which, for typical Na(+) counterion binding with β ≈ 0.2, yields a free SWNT-NaC micellization enthalpy ΔmicG(⊖) of -13.7 kJ·mol(-1).
authors: Institute of Physical and Theoretical Chemistry and ‡Röntgen Research Center for Complex Material Systems, Julius-Maximilian University Würzburg , 97070 Würzburg, Germany.
authors: Felix F
authors: FF
authors: Bergler
authors: Institute of Physical and Theoretical Chemistry and ‡Röntgen Research Center for Complex Material Systems, Julius-Maximilian University Würzburg , 97070 Würzburg, Germany.
authors: Sabine
authors: S
authors: Stahl
authors: Institute of Physical and Theoretical Chemistry and ‡Röntgen Research Center for Complex Material Systems, Julius-Maximilian University Würzburg , 97070 Würzburg, Germany.
authors: Annika
authors: A
authors: Goy
authors: Institute of Physical and Theoretical Chemistry and ‡Röntgen Research Center for Complex Material Systems, Julius-Maximilian University Würzburg , 97070 Würzburg, Germany.
authors: Friedrich
authors: F
authors: Schöppler
authors: Institute of Physical and Theoretical Chemistry and ‡Röntgen Research Center for Complex Material Systems, Julius-Maximilian University Würzburg , 97070 Würzburg, Germany.
authors: Tobias
authors: T
authors: Hertel