Nitrogen-doped carbon nanotubes towards electrochemical sensing: Effect of synthesis temperature

Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized at various temperatures ranging from 650 to 950 degrees C, at 100 degrees C intervals, by chemical vapor deposition technique (CVD). The synthesized N-CNTs were employed as modifiers of glassy carbon paste electrodes (GCPE), which were further used as electrochemical sensors for the determination of dopamine (DA) and epinephrine (EP), two important catecholamines that display biological roles as neurotransmitters and hormones. The results revealed that electrodes modified with the N-CNTs synthesized at 650 degrees C (GCPE/N-CNT650) and 950 degrees C (GCPE/N-CNT950) presented better electrocatalytic activities and sensing capabilities than the others (GCPE/N-CNT750 and GCPE/N-CNT850). N-CNT950 had the highest graphitization and the highest powder conductivity, whereas N-CNT650 had the lowest graphitization and the lowest powder conductivity. However, both N-CNT950 and N-CNT650 had the highest nitrogen contents, 3.5 and 3.8 at.%, respectively, which probably enhanced their number of electroactive sites to interact with DA and EP molecules. This result is of high significance, because the use of the lowest temperature (650 degrees C) in the CVD process, yielded N-CNTs with improved electrocatalytic activity and less energy consumption during CVD.