Development of a Cr(III) ion selective fluorescence probe using organic nanoparticles and its real time applicability

The use of fluorescent organic nanoparticles for the determination of metal ions is highly significant. Among other analytical techniques, fluorescence spectroscopy finds significance due to high sensitivity, selectivity and ease of operation. A ligand 1 was synthesized using 1,8-naphthalic anhydride and triethylenetetramine and it was further processed into organic nanoparticles that displayed excellent sensing properties for selective detection of Cr3+ ion in aqueous medium using fluorescence spectroscopy. The sensor for Cr3+ ion showed competitive binding as no other metal ions caused interference in detection of Cr3+ ion. To check the efficacy of the sensor, titrations were performed with addition of Cr3+ ion in small aliquots and it efficiently detects Cr3+ ion with a detection limit of 64 nM. The mechanism behind the Cr3+ ion detection was studied using DFT calculations, which showed that chromium gets electrons from the nitrogen part of triethylenetetramine which resulted in inhibition of photoinduced electron transfer (PET) that led to an increase in the fluorescence profile.