Carotenoids in Sol−Gels:  Incorporation, Stability, and Sensitivity to Oxidant and Acid

It is shown in this paper that carotenoids can be incorporated into sol−gels and can be evenly distributed by using appropriate amounts of organic solvents (e.g., EtOH and acetone). Some carotenoids (e.g., 8‘-apo-β-caroten-8‘-al) are relatively stable in sol−gels. The studied sol−gel matrix has no obvious effect on the stability of carotenoids. Carotenoids in sol−gels can still react with an oxidant and acid (FeCl 3 and H 2 SO 4, respectively, in our experiments) that are present in the contacting aqueous solutions. This observation suggests that one may take advantage of the visible absorption of carotenoids and the solid and transparent character of sol−gels to build sensors for oxidants and acids using the carotenoid-containing sol−gels.