Targeted modification of graphene quantum dots for design and fabrication of chemical sensors for some pharmaceutical compounds such as: serotonin and levodopa

Abstract

In this thesis, the design of electrochemical sensors based on electrodes modified with graphene quantum dot nanostructures and its nanocomposites have been considered for the analysis of pharmaceutical samples. This thesis includes four studyis for electrochemical analysis pharmaceutical compounds with proposed electrodes. In the first study, graphene quantum dot was synthesized by using thermal pyrolysis method and its morphology was investigated by electron-transfer microscopy. The results showed that 4-5 nm nanosheets were well synthesized. In the next step, carbon paste electrodes modified by ionic liquid and graphene quantum dot were used as a sensitive sensor for determination of Levodopa and Serotonin. By using the square wave voltammetry technique, the detection limit of the modified electrode for Levodopa was obtained 10/0 nM with linear range 0.05 to 250 μM. Also the linear range for Serotonin with the proposed electrode was 0.5 to 500 μM and the detection limit was 0.1 μM. In the second study, the possibility of Methyldopa measurement was studied by using of carbon paste electrode modified by graphene quantum dot and 1-methyl-3-butylimidazolium hexafluoro phosphate. The proposed sensor showed a linear concentration range of 0.04-750 μM with a limit of detection 0.01 μM for the Methyldopa analysis. The proposed sensor was successfully used to determine methyldopa in tablet and serum products. In the third study, the synthesis of graphene quantum dot / perasidium oxide nanocomposite was carried out. The synthesis nanocomposite was characterized by nanomaterial identification techniques such as X-ray Diffraction (XRD), Energy Dispersive X-ray spectroscopy (EDX), and Transfer -Electron Microscopy (TEM). Then, this nanocomposite and ionic liquid were used as carbon paste electrode modifier to detect Tramadol. The linear range for Tramadol was determined 4 × 10-4 mM to 9.0 × 10 -9M and the detection limit was 3.0 nM. Finally, the proposed sensor was successfully used to determine Tramadol in real samples. In the fourth study, the possibility of simultaneous determination of Acetaminophen and Diclofenac by electrochemical methods was studied. For this purpose, the graphene quantum dot / iron oxide nanocomposite was initially synthesized and characterization. Then, by using of differential pulse voltammetry technique, the effect of pH was investigated and optimum pH=8 obtained. In the final stage, the linear range of the proposed sensor for electrochemical simultaneous determination of Acetaminophen and Diclofenac were calculated 0/1 to 300 and 0/15 to 330 μM and the detection limit were 0/04 and 0/053 μM respectively.