A Porphyrin-based NIR Fluorescent Probe for Bi³⁺ and Potential Applications

Area of Science:

• Analytical Chemistry
• Materials Science
• Biochemistry

Background:

• Selective and sensitive detection of metal ions is crucial in environmental monitoring and biological studies.
• Bismuth ions (Bi³⁺) play roles in various industrial applications and biological processes, necessitating reliable detection methods.
• Existing methods for Bi³⁺ detection often lack selectivity or sensitivity, driving the need for novel probes.

Purpose of the Study:

• To develop and characterize a new porphyrin-based probe (P) for the selective and sensitive detection of Bi³⁺ ions.
• To investigate the photophysical properties and binding mechanism of probe P with Bi³⁺.
• To evaluate the applicability of probe P for quantitative Bi³⁺ determination in real-world samples and assess its biocompatibility.

Main Methods:

• Synthesis and characterization of 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (P) using NMR, IR, and ESI-MS.
• Spectrophotometric and spectrofluorometric studies in DMSO:H₂O (8:2, v/v) media to assess photophysical properties and selectivity.
• Job's plot analysis, Stern-Volmer quenching studies, and DFT calculations to elucidate binding stoichiometry and mechanism.

Main Results:

• Probe P exhibited selective red fluorescence quenching in the presence of Bi³⁺ ions, with no significant response to other metal ions.
• A 1:1 stoichiometric binding ratio between probe P and Bi³⁺ was determined, with an association constant of 3.4 ×10⁵ M^-1.
• The probe achieved a detection limit of 27 nM for Bi³⁺ and demonstrated successful quantitative determination in water samples with good biocompatibility.

Conclusions:

• The synthesized porphyrin probe P is highly selective and sensitive for Bi³⁺ detection in semi-aqueous media.
• Probe P represents the first reported colorimetric and fluorogenic probe for Bi³⁺ detection.
• The probe's promising performance and biocompatibility suggest its potential for practical applications in environmental and biological monitoring.