Adsorption-Controlled Electrochemical Behavior of Acetaminophen at Carbon Nanotube–Chitosan Modified Glassy Carbon Electrodes

Abstract

Carbon nanotube–polymer interfaces provide a versatile platform for controlling molecular adsorption and charge-transfer processes at electrochemical surfaces. In this work, multi-walled carbon nanotubes (MWCNTs) dispersed in chitosan were used to modify glassy carbon electrodes, and their interfacial electrochemical behavior toward acetaminophen was investigated. The MWCNT composition and ultrasonication conditions were optimized using cyclic voltammetry, with a 3:1 MWCNT ratio and 15 min of ultrasonication providing the highest electrochemical response. The interaction of acetaminophen with the modified surface was subsequently investigated as a function of accumulation time, analyte concentration, applied potential, and scan rate. The anodic peak current progressively increased with accumulation time and approached surface saturation after approximately 40 min. Increasing acetaminophen concentration resulted in earlier saturation of the modified surface, further supporting an adsorption-mediated interaction. Scan-rate experiments between 0.025 and 0.15 V s⁻¹ showed a linear dependence of anodic peak current on scan rate (R² = 0.9861), consistent with a surface-controlled electrochemical process. Under optimized conditions, open-circuit accumulation produced the highest anodic response. The resulting MWCNT–chitosan interface enabled electrochemical detection of acetaminophen with a detection limit of 1.3 × 10⁻⁶ M and a quantification limit of 3.7 × 10⁻⁶ M. These results demonstrate that the electrochemical response is strongly governed by adsorption at the carbon nanotube–chitosan interface, highlighting the role of interfacial interactions in controlling the electrochemical behavior of acetaminophen.

Keywords: Carbon nanotubes; Chitosan; Acetaminophen adsorption