Graphene-porphyrin composite synthesis through graphite exfoliation: The electrochemical sensing of catechol

This paper reports for the first time a novel approach for the synthesis of graphene-porphyrin composite (EGr-TPyP) through the electrochemical exfoliation of graphite in the presence of 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP), in a neutral electrolyte (0.2 M KCl). No exfoliation was observed in the absence of TPyP molecules. The XRD investigation proves that the EGr-TPyP composite consists in a mixture of few-layer (FLG) and multi-layer (MLG) graphene. The mean crystallites size, calculated from the full-width at half-maximum (FWHM) of the corresponding diffraction peak, was found to be 0.73 nm in case of FLG and 6.33 nm in case of MLG. Moreover, the interlayer distance for MLG (0.337 nm) is similar with that of bulk graphite (0.335 nm) while for FLG this number is larger (0.397 nm) suggesting the presence of more wrinkled or disordered graphene sheets. UV-vis and XPS spectroscopy prove that TPyP molecules remained attached to graphene sheets at the end of the exfoliation process. The performances of the EGr-TPyP layer deposited on top of a glassy carbon (GC) electrode were evaluated during the catechol (CAT) detection. In case of EGr-TPyP/GC modified electrode, the CAT redox process is highly accelerated, so the peak currents are significantly higher than those obtained with bare GC substrate. The GC electrode has a low sensitivity towards CAT detection (0.185 AM−1·cm−2), a narrow linear range (one decade, 10−5 − 10−4 M) and a relatively high detection limit (LOD = 3.03 × 10−6 M). In contrast, the EGr-TPyP/GC electrode has a larger sensitivity (3.22 AM−1·cm−2), a considerably wider linear range (two decades, 10−6 − 10−4 M) and lower detection limit (LOD = 3.03 × 10−7 M).