A multiwalled carbon nanotube/tetra-β-isoheptyloxyphthalocyanine cobalt(ii) composite with high dispersibility for electrochemical detection of ascorbic acid.

A sensitive electrochemical sensor for ascorbic acid (AA) is designed and synthesized via the following steps. The novel tetra-β-isoheptyloxyphthalocyanine cobalt(ii) (PcCo) spontaneously adsorbs on the surface of acid-treated multi-walled carbon nanotubes (aMWCNTs). Then, the aMWCNT/PcCo composite was immobilized on the glassy carbon electrode (GCE). The results of UV-vis, FT-IR, TG, XPS, SEM and TEM revealed the successful self-assembly between PcCo and aMWCNTs via the π-π stacking interaction, and the aMWCNT/PcCo composite appears to have a uniform network-like structure on the GCE surface due to the four peripheral isoheptyl substituents of PcCo. Such a structure can effectively increase the electrode area, facilitate the mass transport of analytes and provide continuous conducting pathways for the transportation of electrons. Synchronously, benefitting from the synergistic effect between PcCo and aMWCNTs, the obtained electrochemical sensor has a high current and low potential for the oxidation of AA. The linear range for the AA detection is from 10 μM to 1.2 mM and the detection limit is as low as 4.0 μM. The developed biosensor exhibited good reproducibility and acceptable stability, providing a simple method for the analysis of AA.