Determination of Optimum Temperature and Time for Electrodeposition of Gold Nanoparticles to Measure Serotonin Neurotransmitter

Serotonin (5-hydroxytryptamine, 5-HT) that is a monoamine neurotransmitter has an important role in various biological systems, pharmacological and psychological functions [1]. For this reason, its precise determination in biological samples can help the diagnosis of various psychological and clinical disorders [2]. So far, some methods have been developed to determine the concentration of 5-HT [1]. In this work, a simple, fast, cost-effective, rapid monitoring and sensitive electrochemical biosensor made for measurement of serum 5-HT concentration. To make biosensor, gold nanoparticle immobilized at the surface of glassy carbon electrode using electrodeposition method. Since the best procedure of electrodeposition was very important for correct performance of fabricated biosensor, for this reason, the optimum time and temperature of electrodeposition determined and the results presented in this report. At first, the glassy carbon electrode polished by alumina slurry. Then, the gold nanoparticles (chloroauric acid; AuNPs) electrodeposited at the glassy carbon surface using constant potential electrolysis. This process performed in a deaerated NaNO3 solution containing chloroauric acid; 14th Annual Electrochemistry Seminar of Iran Materials and Energy Research Center (MERC), 12- 13 Dec, 2018 67 HAuCl4 and called AuNPs-GC. Then AuNPs-GC activated in a deaerated 0.5M H2SO4 solution by running 30 scans between 0.2 V and 1.6 V at a scan rate of 100 mVs−1. All the electrochemical measurements (in presence or absence of serotonin) carried out in buffer phosphate solution using a Galvanostat/Potentiostat system (Dropsens, 400 μStat, Spain). The measurements performed using three electrode system in which an Ag/AgCl, platinum and modified glassy carbon were used as reference, counter electrode and working electrode, respectively and the cyclic voltammograms considered as biosensor responses. For determination of optimum electrodeposition time, the constant potential applied to glassy carbon for 60s, 120s and 240s. Additionally, in order to evaluation of temperature effect, the electrodeposition at fixed time (240s) carried out in 20ºC, 30 ºC, 37 ºC, 40 ºC, 50 ºC and 60 ºC. The results showed that the 240s and 37 ºC were the best time and the best temperature for electrodeposition of gold nanoparticles at the surface of glassy carbon electrode, respectively.