Smartphone assisted fluorescent-colorimetric probe for bismuth (III) ion and potential applications

A new dual fluorescent-colorimetric probe (E)-4-methyl-N'-((2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin9-yl)methylene)benzenesulfonohydrazide (L) was synthesized by condensation reaction of julolidine carboxaldehyde and p-toluene sulfonyl hydrazide to get the probe (L) for recognition of bismuth ions (Bi3+). The structural conformation of L was confirmed through 1H NMR, IR, and mass spectral analysis. The probe L showed visual color change and turn-on emission upon interaction with Bi3+ in H2O:CH3CN (7:3, v/v) media over other divalent and trivalent metal ions. The probe displays selective 'turn-on' emission for Bi3+ via chelation enhanced fluorescence (CHEF) and > C--N isomerization mechanism. The experimental analysis of Job's plot showed a 2:1 stoichiometric ratio of L-Bi3 thorn complex formation and this was further verified with theoretical studies. The detection limit by spectrophotometric and spectrofluorometric were found to be 170 nM and 6.39 nM, respectively. The binding mechanism was verified by 1H NMR, ESI-mass, and theoretical studies. Furthermore, the selective colour change of L with Bi3+ was integrated with a smartphone to monitor the change in the RGB tool and test paper kit. The turn-on response of the probe with Bi3+ was used to capture by the fluorescence imaging technique in live Human Bone Osteosarcoma cell line (HOS) cells. Overall, probe L demonstrates a promising potential for the detection of Bi3+ ions in the protic environment and this is the first report of a fluorescent probe used in HOS cell live imaging.

Automated summary

A new dual fluorescent-colorimetric probe (L) was synthesized for the recognition of bismuth ions (Bi3+). The probe showed visual color change and turn-on emission upon interaction with Bi3+ and demonstrated a promising potential for the detection of Bi3+ ions. The probe's selective color change with Bi3+ was integrated with a smartphone and used for fluorescence imaging in live Human Bone Osteosarcoma cell line (HOS) cells.