A nickel nanoparticle/carbon nanotube-modified carbon fiber microelectrode for sensitive insulin detection

A nickel nanoparticle (NiNP)/carbon nanotube (CNT)-modified carbon fiber microelectrode (NiNPs/CNTs/CFME) was fabricated using a two-step electroless plating/chemical vapor deposition method. The morphology of the NiNPs/CNTs composite structure was characterized by scanning electron microscopy, and its elemental composition was characterized by an energy dispersive spectrometer. The electrochemical behavior of the NiNPs/CNTs/CFME in aqueous alkaline solutions of insulin was investigated by cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy in sequence. CV curves show that the NiNPs/CNTs/CFME displays a high oxidation peak current, a fast electron transfer rate, and good electrocatalytic activity towards insulin, compared to a bare CFME and a pure NiNP-modified CFME. In the chronoamperometry tests, the NiNPs/CNTs/CFME demonstrates an excellent analytical performance in detecting low concentrations of insulin, including good sensitivity (1.11 nA μM−1) and a low detection limit (270 nM). Moreover, this microelectrode exhibits great reproducibility in successive potential cycling and satisfactory long-term stability after storage at room temperature for approximately 8 weeks.