Background: The traditional methods for the detection and quantification of Cu2+ and Fe3+
heavy metal ions are usually troublesome in terms of high-cost, non-portable, time-consuming, specialized
personnel and complicated tools, so their applications in practical analyses is limited. Therefore,
the development of cheap, fast and simple-use techniques/instruments with high sensitivity/selectivity
for the detection of heavy metal ions is highly demanded and studied.
Methods: In this study, a fluorene-based fluorescent ''turn-off'' sensor, methyl 2-(2-((((9H-fluoren-9-
yl)methoxy)carbonyl)amino)-3- phenylpropanamido) acetate (probe FLPG) was synthesized via onepot
reaction and characterized by 1H-NMR, 13C-APT-NMR, HETCOR, ATR-FTIR and elemental
analysis in detailed. All emission spectral studies of the probe FLPG have been performed in
CH3CN/HEPES (9/1, v/v, pH=7.4) media at rt. The quantum (Φ) yield of probe FLPG decreased considerably
in the presence of Cu2+ and Fe3+. The theoretical computation of probe FLPG and its complexes
were also performed using density functional theory (DFT). Furthermore, bio-imaging experiments
of the probe FLPG was successfully carried out for Cu2+ and Fe3+ monitoring in living-cells.
Results: The probe FLPG could sense Cu2+ and Fe3+ with high selectivity and sensitivity, and quantitative
correlations (R2>0.9000) between the Cu2+/Fe3+ concentrations (0.0−10.0 equiv). The limits of detection
for Cu2+ and Fe3+ were found as 25.07 nM and 37.80 nM, respectively. The fluorescence
quenching in the sensor is managed by ligand-to-metal charge transfer (LMCT) mechanism. Job’s plot
was used to determine the binding stoichiometry (1:2) of the probe FLPG towards Cu2+ and Fe3+. The
binding constants with strongly interacting Cu2+ and Fe3+ were determined as 4.56×108 M-2 and
2.02×1010 M-2, respectively, via the fluorescence titration experiments. The outcomes of the computational
study supported the fluorescence data. Moreover, the practical application of the probe FLPG
was successfully performed for living cells.
Conclusion: This simple chemosensor system offers a highly selective and sensitive sensing platform
for the routine detection of Cu2+ and Fe3+, and it keeps away from the usage of costly and sophisticated