The first fluorescent sensor for medium-chain fatty acids in water: design, synthesis and sensing properties of an organic–inorganic hybrid material

This paper reports the first fluorescent sensor for medium-chain fatty acids in water. The hybrid sensing material (S2) was prepared by the reaction of a rationally designed “recognition center”, N-butyl-4-piperazin-1,8-naphthalimide, with a 3-glycidoxypropyl group which is pre-grafted on the interior of a mesoporous solid (MCM-41). The organo-functionalization of the mesoporous solid (MCM-41) was confirmed by FT-IR, 29Si MAS NMR and elemental analysis. The results of XRD, N2 physical adsorption–desorption, SEM and TEM studies proved that the organized structure of the nanoscopic porous solid is preserved after the reactions. The fatty acid-selective signaling behavior of S2 was investigated in water at pH = 5.80/7.16/8.00. This material displays much stronger fluorescence enhancement with C8–C12 fatty acids than with the shorter and longer chains in aqueous media, both in the absence and in the presence of aromatic acids.