Synthesis and Optical Properties of a Novel Hybrid Nanosystem Based on Covalently Modified nSiO 2 Nanoparticles with a Curcuminoid Molecule.

A new curcuminoid molecule ( 3 ) has been designed and synthesized, containing a central -(CH 2 ) 2 -COOH chain at the α carbon of the keto-enol moiety in the structure. The carboxylic acid group is added to react with exposed amino groups on silica oxide nanoparticles (nSiO 2 ), forming an amide bond to attach the curcuminoid moiety to the nSiO 2 covalently. The Kaiser test quantifies the functionalization degree, yielding 222 μmol of curcuminoid per gram of nanoparticles. The synthesized hybrid nanosystem, nSiO 2 -NHCO-CCM, displays significant emission properties, with a maximum emission at 538 nm in dichloromethane, similar to curcuminoid 1 (without the central chain), which emits at 565 nm in the same solvent. Solvent-induced spectral effects on the absorption and emission bands of the new hybrid nanosystem are confirmed, similar to those observed for the free curcuminoid ( 1 ). The new nanosystem is evaluated in the presence of kerosene in water, showing an emission band at 525 nm as a detection response. The ability of nSiO 2 -NHCO-CCM to change its fluorescence when interacting with kerosene in water is notable, as it overcomes the limitation caused by the insolubility of free curcuminoid 1 in water, allowing for the exploitation of its properties when connected to the water-stable nanosystem for future detection studies.