Photoisomerization Studies in Langmuir Films of Retinal Derivatives

Spectroscopy of Retinoic Acid at the Air–Water Interface

“…The maximum surface concentration and compression reached corresponded to 6 Å 2 / molecule; in between the 15 to 6 Å 2 /molecule, the surface pressure became noisy but stayed below 2 mN/m, and relaxation back to baseline happened rapidly once compression stopped. For comparison, de Melo and Mosquera-Sańchez 38 and Tenorio et al 39 were able to obtain π−A isotherms of pure ATRA at the air−water interface, but their π−A isotherms are not in agreement with each other with the former having liftoff at about 50 Å 2 /molecule and the latter, at 20 Å 2 /molecule. Additionally, de Melo and Mosquera-Sańchez 38 aggregation might be insignificant due to the generally lower concentration used, compared to our work.…”

“…Given that ATRA, an amphiphilic molecule, is nearly insoluble in water, it will be in excess at the air–water interface once released into an aqueous environment. − There is mounting evidence that the air–water interface can influence chemical processes compared to the aqueous bulk. − The surface partitioning of ATRA has been confirmed with π– A isotherms of ATRA Langmuir–Blodgett films. , The spectroscopic properties of ATRA are especially interesting as the compound is known to absorb light by the S 0 to S 1 electronic transition with a large absorption cross-section around wavelengths of 300–400 nm. , While ATRA’s spectra have been recorded in the bulk aqueous phase as well as a variety of organic solvents, to the best of our knowledge, spectra at the air–water interface have not been reported before. ,,− The fact that the S 0 to S 1 transition of ATRA is a strong absorber means it has the potential to act as a photosensitizer at the air–water interface in natural environments. ,,, …”

“…18−37 The surface partitioning of ATRA has been confirmed with π−A isotherms of ATRA Langmuir−Blodgett films. 38,39 The spectroscopic properties of ATRA are especially interesting as the compound is known to absorb light by the S 0 to S 1 electronic transition with a large absorption cross-section around wavelengths of 300−400 nm. 40,41 While ATRA's spectra have been recorded in the bulk aqueous phase as well as a variety of organic solvents, to the best of our knowledge, spectra at the air−water interface have not been reported before.…”