Spectroscopic Tools in the Study of Micelles and Membranes

Zachariasse, Klaas A.

doi:10.1007/978-1-4615-7984-7_5

Cited by 2 publications

(1 citation statement)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In discussing the solvent shear viscosity influence on intramolecular excimer formation, ,,− ,,,− we will restrict ourselves to molecules M( n )M and MC( n )MC with Py end groups in pure solvents. Such a solvent viscosity dependence was first observed with 1Py(3)1Py, employing photostationary and time-resolved fluorescence in n -alkanes, tetrahydrofuran, and n -alcohols. , The overall excimer-to-monomer fluorescence intensity ratio I ′(exc)/ I (mon) I ′/ I strongly decreases with increasing solvent viscosity in a series of n -alcohol solvents, different from a report on the absence of a marked viscosity dependence for 1Py(3)1Py and 1Py(10)1Py.…”

Section: Resultsmentioning

confidence: 99%

Viscosity Dependence of Intramolecular Excimer Formation with 1,5-Bis(1-pyrenylcarboxy)pentane in Alkane Solvents as a Function of Temperature

Maçanita

Zachariasse

2011

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

Intramolecular excimer formation with 1,5-bis(1-pyrenylcarboxy)pentane, (1PC(5)1PC) is studied as a function of temperature in a series of alkane solvents and in toluene, covering a wide range of solvent viscosities η, from 0.2 to 125 cP. The rate constant k(a) of the monomer → excimer reaction is determined from the effectively single exponential monomer fluorescence decays. For the viscosity dependence of k(a) in n-alkanes, the Stokes-Einstein relation k(a) ∼ η(-1.0) does not hold. Instead, k(a) is proportional to η(-α), with α increasing upon cooling, from 0.56 at 85 °C to 0.86 at -30 °C. The activation energy E(a) of excimer formation with 1PC(5)1PC, always larger than the activation energy E(T/η) of solvent viscous flow, decreases when the solvent viscosity becomes smaller, from 20.7 kJ/mol in n-hexadecane to 11.8 kJ/mol in n-butane, approaching a value of 11-12 kJ/mol for the low viscosity solvents. As the excimer formation process depends on the restricted diffusion of the 1PC end groups as well as on the C-O and C-C rotations in the -O(CH(2))(5)O- chain, the limiting barrier of 11-12 kJ/mol is attributed to the activation energy E(c) of the multiple bond rotations. This fractional viscosity dependence (α < 1.0) is caused by the multidimensional character of the barrier crossing in the excimer formation process. This multidimensional character should also be taken into account in investigations of polymers and biological media employing excimer formation.

show abstract

Section: Resultsmentioning

confidence: 99%

Viscosity Dependence of Intramolecular Excimer Formation with 1,5-Bis(1-pyrenylcarboxy)pentane in Alkane Solvents as a Function of Temperature

Maçanita

Zachariasse

2011

J. Phys. Chem. A

Self Cite

View full text Add to dashboard Cite

show abstract

Salt Effects on Solute Exchange and Micelle Fission in Sodium Dodecyl Sulfate Micelles below the Micelle-to-Rod Transition

Rharbi

Winnik

2003

J. Phys. Chem. B

View full text Add to dashboard Cite

This paper describes micelle exchange kinetics of hydrophobic pyrene derivatives between SDS micelles in the presence of moderate concentrations of sodium counterions ([Na + ] < 150 mM). The kinetics were followed by fluorescence time-scan measurements in which the disappearance of excimer over time was monitored. The exchange rate constant k obs is highly sensitive to the counterion concentration and increases as a power law against [Na + ] with an exponent of 4, from a value of almost 0 in the absence of salt to 10 -2 s -1 for [Na + ] )100 mM. The exchange rate is not very sensitive to the concentration of SDS micelles, except as the SDS concentration affects the ionic strength, which indicates that the kinetics are dominated by a first-order process. This process is attributed to a fission-growth mechanism in which the fission rate is rate-limiting. Although fission can yield any size micelles, the use of hydrophobic probes restricts the observation to the events yielding two micelles large enough to bear the probe molecules. We propose that the barrier to fission is the creation of surface instabilities, which are enhanced in the proximity of the micelle-to-rod transition. Over the range of counterion concentrations investigated here, micelle fusion is inhibited by electrostatic repulsion.

show abstract

Spectroscopic Tools in the Study of Micelles and Membranes

Cited by 2 publications

References 62 publications

Viscosity Dependence of Intramolecular Excimer Formation with 1,5-Bis(1-pyrenylcarboxy)pentane in Alkane Solvents as a Function of Temperature

Viscosity Dependence of Intramolecular Excimer Formation with 1,5-Bis(1-pyrenylcarboxy)pentane in Alkane Solvents as a Function of Temperature

Salt Effects on Solute Exchange and Micelle Fission in Sodium Dodecyl Sulfate Micelles below the Micelle-to-Rod Transition

Contact Info

Product

Resources

About