Electrochemical sensor based on carbon nanohorns and hydrophobic deep eutectic solvent for the determination of serotonin in biological samples

Augusto, KKDL, Gomes-Junior, PC, Longatto, GP, Piccin, E, Cavalheiro, ÉTG, Bernalte, E, Banks, CE ORCID: https://orcid.org/0000-0002-0756-9764 and Fatibello-Filho, O (2025) Electrochemical sensor based on carbon nanohorns and hydrophobic deep eutectic solvent for the determination of serotonin in biological samples. Electrochimica Acta, 520. 145836. ISSN 0013-4686

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Abstract

A new electrochemical sensor was developed using a hydrophobic deep eutectic solvent (HDES) and carbon nanohorns (CNH) to modify a glassy carbon electrode (GCE). The HDES was based on decanoic acid (DecA) and tetrabutylammonium bromide (TBAB). The performance of the sensor was characterized and optimized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which allowed to determine the ideal amount of HDES in the electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to physically characterize the modified film on the GCE surface. The analytical performance for serotonin (5–HT) determination on the modified electrode (DecA:TBAB(5mg)-CNH/GCE) was evaluated using optimized square-wave voltammetry (SWV). The addition of HDES resulted in a more uniform surface, enabling enhanced electron transfer at the electrode interface and improving the performance for 5–HT detection. The sensor exhibited high sensitivity (0.20 µA L µmol−1) in the concentration range from 0.50 to 32.71 µmol L‒1 and a low limit of detection (LOD) (0.09 µmol L‒1) for 5–HT. Additionally, the sensor demonstrated excellent selectivity for detecting 5–HT in the presence of common interferents (concomitants) and displayed good repeatability, reproducibility, and stability. Finally, the sensor was successfully utilized for determining 5–HT in biological fluids, yielding good recovery results.