Interfacial Solvation within n-Alkane Monolayers in Contact with Supercritical CO₂

Abstract

We report on the rotational reorientation dynamics of a fluorescent reporter molecule, BODIPY 494/503, within n-alkyl (n = 1−18) monolayers formed on quartz in contact with pure supercritical carbon dioxide (scCO 2 ) at 313 K (reduced temperature, T r = 1.03) between a reduced CO 2 density (ρ r = ρ exp /ρ c ) of 0 and 1.8. The BODIPY 494/504 rotational dynamics are described by free (n ≥ 4) and hindered rotor (n ≤ 6) models. As the CO 2 density increases, hindered rotation shifts toward free rotation, and the local viscosity in the cybotactic region surrounding the BODIPY 494/504 reporter within the monolayer decreases. These results are interpreted in terms of n-and density-dependent scCO 2 alkyl chain solvation.

Unexpected efficiency boosting in CO2-microemulsions: a cyclohexane depletion zone near the fluorinated surfactants evidenced by a systematic SANS contrast variation study

“…The scattered neutrons were detected using a quadratic and two-dimensional 3 He multi-detector with 128 Â 128 detector pixels with a size of 7.5 Â 7.5 mm. A beam stop was positioned in front of the detector to prevent damage of the detector.…”

“…1 As its critical point is easily accessible (31 1C and 73 bar), the solvent power can be influenced via density and thus via pressure and temperature. These tunable solvents 2,3 can be applied in various fields like for example enzymatic catalysis 4 or the synthesis of nanoparticles. 5,6 In many industrial processes CO 2 is already used routinely, 7 the perhaps best known process being the decaffeination of coffee.…”