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

Abstract

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.