Red fluorescent and electrochemical detection of Hg2+ ions using perylene diimide dye: Analysis in soil, urine and water samples

Red (λem =620 nm) fluorescent and electrochemical detection of Hg2+ ions has been achieved in HEPES buffer/DMSO (9/1, v/v, pH = 7.4) using dimethylthiocarbamoyl (DMTC)-functionalized perylene diimide (PDI 2) dye. The self-assembly of PDI 2 showed formation of red-violet non-fluorescent aggregates having spherical microstructures at the interface in >50 % H2O/DMSO mixture supported by optical methods, dynamic light scattering (DLS) studies and atomic force microscopy. The aggregation induced emission (AIE) in PDI 2 transformed into aggregation induced quenching (ACQ) in >30 % H2O/DMSO. Linear correlation ranges for the detection of Hg2+ ions are 0–2 μM and 0–10 nM showed LOD of 8.1 nM and 7.4 nM by absorption and emission-based methods, respectively. The mechanism involves interaction of DMTC with Hg2+ ions however longer incubation time (>24 h) shows chemodosimeter mechanism wherein Hg2+ induced cleavage of DMTC moiety to release PDI-OH. These mechanisms have been supported by NMR/IR studies, model reaction and partially by electrochemical and DLS methods. PDI 2 has been applied for detection of Hg2+ in real water, soil and urine samples with excellent recovery.