Acid Treatment of a Carbon Nanotube@Ordered Mesoporous Carbon Composite via a Simple Sonication Procedure: Sensitive Determination of Bisoprolol in Biological and Pharmaceutical Samples

Based on the high specific surface area and electrical conductivity of carbon electrodes, in this work we have fabricated a carbon nanotube@ordered mesoporous carbon (CNT@CMK-3) composite by combining acid treatment and sonication. The CNT@CMK-3 composite after acid treatment retains a tubular and entangled framework. The CNT@CMK-3 nanostructure shows that CMK-3 is uniformly covered by CNTs. The acid-treated CNT@CMK-3 composites, due to the presence of –OH and –COOH groups on defects, show greatly increased hydrophilicity, solubility, tuning structure, real electrochemical active surface (of 0.22 cm²), and electron transfer kinetics. Furthermore, after 500 h, no precipitation is found for acid-treated CNT@CMK-3 dispersions, exhibiting excellent stability. Also, a sensitive electrochemical sensor based on CNT@CMK-3 was fabricated for bisoprolol (BIS) determination. Thin film of the acid-treated CNT@CMK-3 composite was cast on a carbon paste electrode (CPE), and selective and sensitive detection of BIS was studied at electro-oxidation potential of 998 mV, with a linear range of 0.1–35 μmol L⁻¹, limit of detection of 0.05 μmol L⁻¹, and sensitivity of 10.76 µA μmol⁻¹ L. The presence of functional groups due to acid treatment improved the sensitivity, demonstrating effective electron transfer between CNT@CMK-3 and BIS. Finally, the developed sensor was successfully used to detect BIS in human serum and urine samples and tablets.