Solvatochromic probes in supercritical fluids

Abstract

Supercritical fluids (SCFs) have in recent years become favored solvents for chemical reactions and separations. In order to be used as solvents, their solvation properties should be known, and solvatochromic probes are effectively used for this purpose. They have been applied foremost for supercritical carbon dioxide (SCCD), which is by far the most widely employed SCFs, but also for supercritical water, fluorocarbons and other substances. The probes have also found use in mixtures involving SCF and a more polar additive that have better solvation properties for polar solutes and in solvents expanded by dissolving in them SCCD. Clustering of the molecules of the SCF around the probe molecule is a common feature of the systems studied and this may reflect on the employment of the probes as stand‐ins for other solutes. Copyright © 2004 John Wiley & Sons, Ltd.

Tunable solvents: Shades of green

“…Using supercritical fluids requires working at temperatures and pressures above ambient conditions in sealed apparatus, where the density of the supercritical fluid as well as its diffusivity and viscosity depends on the exact conditions [17,20]. Polarity is similarly affected [21]. After the process is complete, the supercritical fluids that can be depressurised to a gas (e.g.…”

Some Advances in Supercritical Fluid Extraction for Fuels, Bio-Materials and Purification

“…The chemical and physicochemical properties of the supercritical fluids that are relevant to extraction are their hydrogen bond donation and acceptance abilities, and their polarity and polarizability. These properties for room temperature solvents are generally obtained by solvatochromic probes, and for the supercritical fluids they are discussed in Reference [5], their applicability being much diminished. Hydrogen bonding and hydrogen bond donation and acceptance persist in supercritical water, methanol, and ethanol, but are absent in supercritical carbon dioxide that is non-polar but has an appreciable quadrupole moment.…”

Simulation and UV–visible spectra of organic dyes in subcritical and supercritical carbon dioxide

“…The effect of solvent on absorption and emission bands of chromophores in liquids and in supercritical fluids is a phenomenon of fundamental and practical importance [1][2][3][4]. In the last decades, electronic spectral shifts modelling in supercritical fluids by Monte Carlo (MC) or Molecular Dynamics (MD) simulations has been developed [5][6][7][8][9][10].…”