Graphene quantum dot /Ag-based metal-organic framework nanocomposite modified carbon paste electrode for simultaneous determination of diazepam, dopamine, clonazepam and adrenaline in real samples

Abstract

This research describes a nanocomposite comprising graphene quantum dot (GQD) and silver-based metal-organic framework (Ag-MOF), referred to as GQD-Ag-MOF, which was utilized as a modifier in order to introduce as an electrochemical sensor for the quantification of diazepam. The as-prepared nanocomposite was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The cyclic voltammetry (CV) results confirmed that the GQD-Ag-MOF modified CPE (GQD-Ag-MOF/CPE) exhibits well electrocatalytic activity toward the diazepam oxidation. Additionally, electron transfer coefficient (α) for the diazepam oxidation at the sensor surface was investigated using the CV technique. The diffusion coefficient of diazepam and the analytical performance of the proposed sensor were evaluated using chronoamperometry and electrochemical impedance spectroscopy techniques. By means of square wave voltammetry (SWV), a linear response range of 0.1-1300.0 μM for diazepam and a limit of detection of 0.03 μM were obtained. The introduced sensor was utilized to determine diazepam, dopamine, clonazepam, and adrenaline simultaneously, and the recorded SW voltammograms showed four well-separated anodic oxidation peaks at 202.7, 319.2, 466.2, and 689.2 mV, respectively. Furthermore, the linear ranges of 175.3-526.0 μM for diazepam, 16.0-48.0 μM for dopamine, 12.3-37.0 μM for clonazepam, and 4.1-15.1 μM for adrenaline were obtained. In conclusion, the introduced sensor was successfully utilized for the quantification of these drugs in medicinal and biological samples.