Electrochemical response of carbon paste electrodes modified with carbon nanotubes: Effects of temperature of nitrogen doping and oxygen functionalization

Carbon paste electrodes (CPE) were modified with nitrogen-doped carbon nanotubes (N-CNTs) synthesized at 750 degrees C (N-CNT750) and 850 degrees C (N-CNT850), carboxyl functionalized carbon nanotubes (MWCNTCOOH), and pristine carbon nanotubes (MWCNT). Their electrochemical properties were investigated and compared towards a common redox probe, potassium ferricyanide (K3[Fe(CN)6]). The electrochemical responses were probed using cyclic voltammetry, and the results unveiled that modification with carbon nanotubes enhanced anodic peak currents (Ipa) for the electrodes CPE/MWCNTCOOH, CPE/N-CNT750 and CPE/N-CNT850 (Ipa, p < 0.05 in relation to pure CPE). In particular, CPE modified with N-CNTs synthesized at 850 degrees C (CPE/N-CNT850) exhibited better electrochemical response, with lower peak-to-peak potential separation (Delta Ep, p < 0.05 in relation to pure CPE). Complementary studies were conducted to investigate the electroactive area (A) and heterogeneous electron transfer kinetics (k0). CPE/N-CNT850 (0.034 +/- 0.005 cm2) and CPE/MWCNTCOOH (0.057 +/- 0.002 cm2) pre-sented more satisfactory results for the anodic and cathodic electroactive area (A), respectively. Kinetic studies revealed a higher k(0) (1.03 x 10(-3) cm.s(-1)) for the CPE/N-CNT850 electrode. Differential pulse voltammetry was employed for the electrochemical detection of Acetaminophen (AC). The response was linear for an AC con-centration range from 66.2 to 259.7 mu mol L-1, with the lowest detection limit (LOD) of 0.37 mu mol L-1 and the highest sensitivity of 0.244 +/- 0.002 mu A L mu mol(-1) for the respective electrodes CPE/N-CNT850 and CPE/ MWCNTCOOH. The CPE/N-CNT850 and CPE/MWCNTCOOH electrodes show the best correlation of results, the presence of polar groups on the surface of MWCNTCOOH and a higher amount of graphitic nitrogen bond of N-CNT850 suggest that these CNTs are particularly promising for applications in electrochemical fields.

Automated summary

This study investigated the electrochemical properties of carbon paste electrodes (CPE) modified with different types of carbon nanotubes (CNTs). The results showed that modification with carbon nanotubes enhanced the anodic peak currents for the electrodes, with the CPE/N-CNT850 electrode exhibiting the best electrochemical response. Additionally, the CPE/N-CNT850 and CPE/MWCNTCOOH electrodes had larger electroactive areas and higher heterogeneous electron transfer kinetics. Furthermore, the CPE/N-CNT850 and CPE/MWCNTCOOH electrodes showed the best correlation of results when detecting Acetaminophen (AC) using differential pulse voltammetry.