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Magnetic nanoparticles and ionic liquid (IL, 1-hexyl-3-methyl-imidazolium bromide) based on graphene oxide (GO) composite provide unique physical and chemical properties in electrochemical sensors performance. Magnetic nanoparticles can cover active sites that increase chemical reactions with easy separation. IL increases the scan rate of electron transfer between the modified electrode and solution because it includes conductive adhesion properties. Also, IL in the next steps of design carbon paste electrodes (CPE) increases the cohesion. The study aims are to study the effects of magnetic nanoparticles and IL on the electrochemical detection of dopamine (DA). DA has a vital role in the mammalian central nervous system and change its value from the standard range leads broad mental diseases. But magnetic graphene oxide (MGO) may not exist capable of enhancing electrochemical signs alone. In this regard, after the synthesis of MGO, IL was established on composite. Then gold nanoparticles (AuNPs) and molecularly imprinted polymer (MIP) were modified MGO nanocomposite. MIP polymerization was continued by methacrylic acid (MAA) in the presence of DA as a template molecule. The developed sensor with modified nanocomposite studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The modified sensor based on nanocomposite with a broad concentration linear range, between 1×10-7 to 1×10-4 M and a limit of detection of 1×10-8 M (S/N=3) was used for the detection of DA in biological samples. Furthermore, these results prove that MGO was improved active sites of surface nanocomposite and IL was increased conductivity in the based electrochemical sensor for DA detection.

Metal nanoparticles trapped in a biopolymer composite due to electrical conductivity properties improve electrochemical sensors with biomedical and environmental applications. The study aims are to design a novel molecularly imprinted polymer (MIP) composite based on magnetic graphene oxide (Fe3O4@GO) modified silica (SiO2) and gold nanoparticles (AuNPs) to electrochemical detect serotonin (5-hydroxytryptamine, 5-HT). A suitable amount of 5-HT is effective on motivational functions and the environment because it is a serotonergic neurotransmitter. But the desired nanocomposite may have a relatively low recognition, therefore must be in choosing the type of functional monomer be careful. In this regard, the design of the electrochemical sensor began by synthesis of Fe3O4@GO-SiO2@AuNPs nanocomposite. Then, MIP electropolymerization was carried out by using p-aminothiophenol (PATP)-functionalized Fe3O4@GO-SiO2@AuNPs nanocomposite in the presence of 5HT as a template molecule. Electrochemical polymerization of MIP nanocomposite was developed using cyclic voltammetry (CV) and the electrochemical properties of 5-HT were studied use differential pulse voltammetry (DPV) technology in the 5HT solution. After optimization of preparation and measurement conditions on the designed sensor, the 5HT concentration range is 0.1 μM to 10 μM linearly, and the detection limit was 1 × 10-5 μM (S / N = 3). The wide concentration range and low detection limit were presented metal nanoparticles functionalized MIP with appropriate functional monomer have a great effect on the performance of the sensor. Furthermore, PATP-functionalized metal nanoparticles increase the conductivity and recognition of the prepared MIP electrochemical sensor to the quantification of 5-HT in biological samples with high selectivity and recovery.