Fluorescence quenching of photoluminescent organic polymer nanofilms by ferric ions

Abstract There are considerable reports on fluorescent detection of ferric ions, which were universally simplified as Fe3+, by using carbon dots-based sensors. Although several mechanisms have been proposed for the fluorescence quenching of the host, it deserves deep understanding on this topic because the hydrolysis of Fe3+ has not been considered in previous reports. In this contribution, we report on fluorescent detection of ferric ions in mixed metal-ion solution and in real water with organic polymer nanofilms (PNFs)-based sensor. The limit of detection of PNFs towards ferric ions is 44 nM. In particular, we focus on demonstration of the fluorescence quenching mechanisms through instrumental analysis and theoretical computations. The electron transfer from the LUMO level of PNFs to the LUMO level of Fe2(OH)24+ and the HOMO levels of Fe(OH)2+ is suggested to be responsible for the impressive fluorescence quenching of PNFs by ferric ions with concentration lower than 80 µM.