Turn-on/turn-off fluorescent hybrid silica nanoparticles. A new promising material for selective anions’ sensing

This work focused on the elaboration of a new fluorescent hybrid material based on spherical silica nanoparticle generated by sol–gel chemsitry (Stöber process). A fluorescent molecule (quaternized pyridinoindolizin) was introduced on the inorganic framework via an organosilane entities possessing hydrolysable group (methoxy group in the present case) to ensure the covalent linkage between the inorganic host and the organic substrate. The material obtained was fully characterized with FTIR, 29Si and 13C Solid state NMR, thermogravimetric and elemental analysis, Atomic force and scanning electron microscopy and the fluorescence properties of these nano-objects were determined with a home-made device. Finally, the influence of the counter-ion of the pyridinium fragment on the fluorescence emission was also investigated. In this case, a specific behavior (turn-on, exaltation of emission) was observed following exchange with perchlorate anions contrary to exchange with other anions such as acetate, chloride and nitrate which provoke a quenching of fluorescence.