Composite films based on copper nanoparticles and nickel phthalocyanine as electrochemical sensors for serotonin detection

Electrochemical sensors for detecting neurotransmitters have been extensively explored owing to the versatility and low cost of electrochemical techniques. Although serotonin (5-HT) is a very important neurotransmitter, very few studies have investigated its electrochemical detection. Herein, the use of layer-by-layer (LbL) films, containing layers of copper nanoparticles alternating with nickel phthalocyanine in indium-doped tin-oxide electrodes, for electrochemically detecting 5-HT is proposed. Copper nanoparticles were synthesized and characterized based on size, zeta potential, and spectroscopic behavior in the ultraviolet–visible (UV–Vis) region. Subsequently, the films were produced and characterized by UV–Vis spectroscopy and cyclic voltammetry. The electrochemical response of the films was evaluated as a function of the supporting electrolyte, number of adsorbed layers, material adsorption sequence, stability, electrochemical mechanism, and other parameters. In the electrochemical detection of serotonin, the developed material exhibited high sensitivity and specificity for 5-HT compared to some interferents such as ascorbic acid, hydrogen peroxide, cysteine, sulfamethoxazole, and aspartic acid. The results showed a 400% increase in the current densities of the film in the presence of 20 µmol•L−1 of 5-HT. The electrochemical signal recorded for 5-HT was unaffected even in the presence of ascorbic acid at the same concentration. The sensor exhibited a linear response over a wide concentration range (0.35–135 µmol•L−1) and a low detection limit (0.13 µmol•L−1) for 5-HT. Furthermore, the developed electrode enables successive 5-HT analyses without requiring new films. The material reported herein is promising for 5-HT electrochemical analysis in biological samples.