Fluorescent ‘turn-on’ porphyrin CQD nanoprobes for selective sensing of heavy metal ions

In this work, a one-step pyrolysis technique is employed to synthesize porphyrin based carbon quantum dots (Porp-CQDs). The as-synthesized Porp-CQDs permit fluorescence “on/off” strategies to detect heavy metal ions. The structural formation of the Porp-CQDs with optical properties is confirmed through characterization techniques like UV–visible, fluorescence spectroscopy, HR-TEM, AFM, X-ray diffraction, and FT-IR studies. Porp-CQDs have an average particle size of 2.4 nm and a spherical shape with a semi-crystalline appearance. The excitation wavelength appears at 434 nm corresponding to the π-π* electronic transition of the soret band between the HOMO and LUMO energy levels with emission at 670 nm. The CV curves of the modified Porp-CQDs/GCE at a scan rate of 10 mV s−1 and Porp-CQDs/GCE exhibits good oxidation and reduction peaks at 1.43 V and − 0.36 V, respectively. The metal ion sensing mechanism is driven through the structure of the porphyrin core which makes it easy to form transition complexes with various metal ions in the central cage of the system. Porphyrins tagged on CQDs have been used as active sensing components in this work. The Porp-CQDs effectively sensed the Zn2+ metal ions with a limit detection of 75 μM in bore well water analysis.