Phenol Blue as a solvent polarity indicator for binary aprotic solvents

Solvatochromic characterization of the liquid phase in liquid—supercritical CO2 mixtures

“…The reproducibility of A, , is typically less than f0.3 nm. The data for the pure solvents are consistent with values reported earlier (Figueras, 1971; Kolling and Goodnight, 1973;Phillips and Brennecke, 19931, but differ slightly from the published values because of the higher ttemperatures used in this study. When the pure solvent nieasurements are repeated at 25"C, the data obtained are in complete agreement with the literature values.…”

“…These interactions are apparently enough to offset the lower polarity of these solvents. Similarly, the known interactions between methanol and Phenol Blue (Kolling and Goodnight, 1973;Figueras, 1971;Kim and Johnston, 1987a) produce a significantly larger local composition enhancement for this system. At first glance the behavior of cyclohexane is fairly surprising.…”

“…The methanol data, on the other hand, gives a curve that is parallel to the acetone data but at wavelengths that are about 25 nm longer. Phenol Blue is known to be subject to specific interactions with alcohols, however, so this behavior is not unexpected (Kolling and Goodnight, 1973;Kim and Johnston, 1987a).…”

Predicting solvatochromic shifts and colours of a solvated organic dye: The example of nile red

“…Using perturbation theory and making a number of limiting approximations (such as assuming that the solvent forms a spherical cavity around the solute and neglecting any direct solventsolute interactions through, for example, hydrogen bonding) it is possible to derive a simple expression relating the solvatochromic shift of a dye to only the relative static permittivity 0 and the relative optical permittivity opt of the solvent [30,37]:…”

“…Studies with both TDDFT [28] and higher order quantum chemistry methods [29] have shown that rotation around the C-N bond is a key feature influencing the dye's absorption and fluorescence spectra. Nile red is very stable in alkaline aqueous environments [25] compared to other dyes like phenol blue [30] and its fluorescent properties have proven to be useful in a number of biological applications, for example as a stain for the detection of intracellular lipid droplets [31]. For this reason, the absorption and emission properties of nile red are well characterised experimentally in a large number of different solvent environments [25,32].…”