There are many works on the interaction of surfactants with dyes. Titration of cationic surfactants with methylene blue in chloroform is used to determine the content of anionic surfactants. The change in the spectrum is explained by the change of the hydrophilic medium (water) on the hydrophobic medium (micelle), the interaction with the surfactant by electrostatic and hydrophobic interaction. There is still no consensus on the structure of micelles of ionic surfactants. Therefore, it is necessary to take into account subtle effects. Watch

Preprint Quantum entanglement in micellar solutions of ionic surfactants.

Dear Sachit,

I have recently done some work on the interaction of cationic dyes, like methylene blue, with anionic surfactants. I used toluidine blue and lauryl ether sulfates. Depending on the ratio between dye and surfactant there are three distinct structures possible. If you used anionic surfactant, then please have a look at my paper on this. Not wanting to push my paper, but it may help and has some good references on work by other authors that may be helpful. Article Toluidine blue-Sodium Lauryl Ether Sulfate complexes: Influe...

Kind regards, Leo

Dear Sachit Shah ,

Spectra are often explained by thinking in terms of 'energy levels'. When the so-called ground state is more polar than the excited state, a hydrophobic environment stabilizes the excited state more than the ground state.

So overall there is increase in the energy gap between excited and ground state. More energy means higher frequency (E = h. f) and thus lower wavelength (λ = c/f) thus resulting in blue shift.

This is the theoretical background behind this phenomenon. General it is an often seen thing: more hydrophobic environment means blue shift.

Hope this clarifies some of this ‘mystery’ to you.

Thank you all for your responses! They were very helpful!