Nano molar detection of Al3+ in aqueous medium and acidic soil using chromone based fluorescent organic nanoparticles (FONPs)

Abstract

Compounds 1 (1,2-bis[4-oxo-4H-1-benzopyran-3-ylmethylenamino]-ethanes) and 2 (3-((E)-(3-(dimethylamino) propylimino)methyl)-4H-chromen-4-one) were synthesized using a one pot condensation reaction between 3-formylchromone and ethylenediamine/N,N-dimethylpropylamine, respectively. Compounds 1 and 2 were purified and characterized using ¹H and ¹³C NMR, IR, mass and CHN analysis. Fluorescent organic nanoparticles (FONPs) were developed from the compounds 1 and 2 using a reprecipitation technique. The size and morphology of nano-aggregates 1 and 2 was analysed using DLS and TEM analysis. Nanoaggregates of 1 and 2 were further exploited for chemosensory applications in an aqueous medium. An efficient nanoaggregate of compound 1 has shown an excellent detection limit of 100 nM for Al³⁺ in an aqueous medium. The stoichiometry of the complex formation of 1 with Al³⁺ was found to be 1 : 1 using Job's plot method. The sensor 1 was further checked for its practical applications, e.g., soil and water analysis (drinking, tap and river water). Results of Al³⁺ determination in soil and water were well coordinated with the existing methods. Finally, the mechanism of fluorescence recognition is supported with DFT calculations, which shows the effective binding of Al³⁺ with chromone leading to the lowering in the energy and thus stability. The present approach is the first report on the fabrication and chemosensory applications of chromone-based FONPs for the nanomolar detection of Al³⁺ in an aqueous medium.