Nickel -doped iron oxide nanoparticle-conjugated porphyrin interface (porphyrin/FeO@Ni) for the non-enzymatic detection of dopamine from lacrimal fluid.

Herein, we synthesized nickel (Ni)-doped iron oxide nanoparticles (FeO). The presence of the dopant afforded anchoring sites for the porphyrinic hetero cavity of 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin to produce the porphyrin/FeO@Ni composite. The crystalline structure and morphology of porphyrin/FeO@Ni were assessed using various tools including Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. Porphyrin/FeO@Ni has proven to be an excellent dopamine (DA) probe material with good selectivity, reproducibility, stability and reliability owing to its clever morphology, which induces numerous active sites along with good active surface area. It consequently provides good accessibility to DA and allows for the smooth tunneling of electrons between the analyte and sensing interface. Meanwhile, the porphyrin molecules provide good carbon-based resilient support, inhibit the leaching of the electrode matrix and enhance electron shuttling, resulting in the robust oxidation of DA with amplified transduction signals. The designed porphyrin/FeO@Ni interface showed a low detection limit (1.2 nm) with good sensitivity (1.2 nM) in the linear bounds of 10 μM to 3500 μM. Additionally, the interface was employed successfully to analyze DA from lacrimal fluid with good percentage recoveries (99.8% to 100.1%). We anticipate that such a design will simplify the screening of DA in rarely studied tear samples with sensitivity and selectivity.