Fluorescent organic nanoparticles (FONs) for the selective recognition of Zn2+: Applications to multi-vitamin formulations in aqueous medium

Abstract

The ligand N,N′-bis(pyridyl-2yl-methyl)ethylenediimine (PMEDI) was synthesized and then transformed into organic nanoparticles (ONPs) which were characterized by analytical methods. The ONPs were employed for the specific recognition of Zn2+ in an aqueous medium by measuring the fluorescence intensity that increased with the concentration of Zn2+ in the PMEDI solution. This proves that PMEDI-ONPs act as a chemo-sensor in detecting Zn2+ at low concentration in aqueous medium. This chemo-sensor (ONPs) is able to determine the concentration of Zn2+ ion in multi-vitamin formulations, and does so selectively for Zn2+ in the presence of other nutrient metal ions. Apparently, photo induced electron transfer (PET) works in the PMEDI-ONPs when the fluorophore is excited. For [PMEDI-Zn]2+ system, the PET is inhibited considerably by lowering the receptor HOMO energy due to the formation of a bond between the metal ion and the ligand. Due to inhibition of PET phenomenon the enhancement in the fluorescence emission of PMEDI-ONPs takes place. This is consistent with the theoretical study that the energy of the HOMO of the ligand is lowered when the [PMEDI-Zn]2+ complex is formed.