Abstract:
Organic nanoparticles (ONPs) of N,N0
-ethylenebis(salicylimine) (salen) were synthesized and applied for
specific recognition of Zn2+ and Al3+ ions in an aqueous medium. The results show that fluorescence
intensity rises with the increasing concentration of Zn2+ in salen solution, proving that salen-ONPs detect
Zn2+ efficiently in the aqueous medium as chemo-sensor. Furthermore, the salen-ONPs/Zn2+ system performs
as an ON–OFF switch between pH 6.0 and 4.0. Amusingly, although salen-ONPs/Al3+ does not show
any significant effect in the fluorescence spectra, highest fluorescence intensity was observed when Al3+
ion was added to salen-ONPs/Zn2+ in a sequential order (addition of Zn2+ to salen-ONPs, followed by Al3+).
This system can be applied as a novel three inputs logic gate supported by the fluorescence for the detection
of Zn2+ and Al3+ in biological and environmental samples. It appears that photo induced electron
transfer (PET) occurs in the salen-ONPs when the fluorophore is excited. For salen/Zn2+ system, the
PET is being inhibited considerably by lowering the receptor HOMO energy due to the formation of a
bond between the metal ion and ligand, enhancing the fluorescence emission. This is consistent with
the theoretical study that the energy of HOMO of the ligand is lower than that of Zn(salen)2+ complex
