Abstract
Photoacoustic spectroscopy was used to study thermal (dark) paths of excited state deactivation of β-carotene in ionic liquids. The dark paths of excited state deactivation of all-trans and 15-cis β-carotene isomers are very important in photosynthesis and medicine. The photoacoustic measurements of β-carotene in traditional solvents are difficult due to fast evaporation of the solvent which leads to concentration fluctuation. Room temperature ionic liquids are good medium for temperature study due to their high thermal stability and low volatility. Dark deactivation of both β-carotene isomers in ionic liquids occurs in a similar way except for an additional path of deactivation of excited state 11A +g (‘cis’ peak). The thermal-excited state deactivation of all-trans and 15-cis β-carotene isomers is not sensitive to the ionic liquid structure, in contrast to the radiative path.
Highlights
Carotenoids are natural pigments which play an important role in multiple vital processes
The photoacoustic spectra of b-carotene in nhexane are broader and shifted towards longer wavelength in comparison to the absorption spectrum. This effect is due to the crystallization of the samples measured in n-hexane and is not observed in the samples solubilized in ionic liquids
Ionic liquids are thermally stable within a wide range of temperature that allows to perform the photoacoustic measurements in a liquid phase
Summary
Carotenoids are natural pigments which play an important role in multiple vital processes. One of the most studied carotenoids is b-carotene. It can be found in mono-cis configuration in photosynthetic reaction centres, where is it responsible for the photo-protection of the photosynthetic apparatus [1–3]. A theoretical description of b-carotene (polyenes)excited states was proposed by Tavan and Schulten [7] in 1987. The first excited singlet state is labelled 21Ag- (S1) and has the same symmetry as a ground singlet state-11Ag(S0). The transition between these two states is optically forbidden. Strong transition in the blue-green region, from ground state to the second excited state 11Ag- (S0) ? In case of mono-cis isomers (15-cis b-carotene), the transition from 11Ag- (S0) to 11Ag? Excited state is optically allowed, the so-called ‘cis’ peak [8] In case of mono-cis isomers (15-cis b-carotene), the transition from 11Ag- (S0) to 11Ag? excited state is optically allowed, the so-called ‘cis’ peak [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
