An electrochemical omeprazole sensor based on shortened multi-walled carbon nanotubes-Fe3O4 nanoparticles and poly(2, 6-pyridinedicarboxylic acid)

Three types of shortened and acidified multi-walled carbon nanotubes (S-MWCNTs) were synthesized by ultrasonication of the raw long carbon nanotubes in H 2 SO 4 /HNO 3 mixed acids. A comparative electrochemical investigation was performed in 5   μM omeprazole (OMZ) solution. It demonstrated that S-MWCNTs with specific length and acidity showed higher electrocatalysis to the oxidation of OMZ. Magnetite nanoparticles Fe 3 O 4 were hybridized with S-MWCNTs to form a nanohybrid (S-MWCNTs-Fe 3 O 4 ) through a simple, effective and reproducible chemical co-precipitation method. The nanohybrid was characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), thermogravimetric analyses (TGA), and field emission scanning electron microscopy (FESEM). The electrochemical response characteristic of S-MWCNTs-Fe 3 O 4 modified GCE toward OMZ was investigated by cyclic voltammetry. It showed that the nanohybrid enhanced the electrocatalytic oxidation to OMZ. Linear sweep voltametry (LSV) was applied to determine low concentrations of OMZ on S-MWCNTs-Fe 3 O 4 /poly (2,6-pyridinedicarboxylic acid) modified electrode. A linear relationship was found between peak currents ( i p,a ) and the concentration of OMZ within 0.05–9.0   μM with an estimated detection limit of 15   nM.