Highly sensitive simultaneous electrochemical determination of myricetin and rutin via solid phase extraction on a ternary Pt@r-GO@MWCNTs nanocomposite

Tursynbolat, Satar; Bakytkarim, Yrysgul; Huang, Jianzhi; Wang, Lishi

Electrochemical cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pules voltammetry (DPV) measurements were performed using a CHI 660B electrochemical workstation (Chenhua Co. Ltd. Shanghai, China). A threeelectrode system consisting of a bare or modified GCE (3 mm in diameter) working electrode, platinum wire counter electrode, and saturated calomel reference electrode (SCE) was used. DPV scans from À0.1e0.8 V with an amplitude of 0.05 V, pulse width of 0.05 s, pulse period of 0.5 s, and increment of 0.004 V were performed. For CV, scan rate was 50 mV/s and sample interval was 0.001 V. EIS was obtained in a 5.0 mmol/dm 3 6 ] solution containing 0.1 M KCl under an open circuit potential at a frequency range from 0.1 Hz to 100 kHz and 5 mV amplitude. The surface morphology was characterized via field emission scanning electron microscopy (FE-SEM; Zeiss Ultra 55, Germany) and energy dispersive X-ray spectroscopy (EDS). Fig. 1 shows the SEM images at low and high magnifications of the ternary Pt@r-GO@MWCNTs nanocomposites. The MWCNTs and r-GO were clearly observed, and the Pt NPs were uniformly and densely distributed in the MWCNTs and r-GO. The Pt@r-GO@MWCNTs composite was also analyzed by EDS (Fig. 2) , showing that the main components were C, O and Pt at approximately 85.27, 12.5, and 2.23 wt%, respectively (Si was also observed because the Pt@r-GO@MWCNTs nanocomposite was dropped onto the silicon wafer for SEM sample preparation). The above results indicate the successful fabrication of the Pt@r-GO@MWCNTs nanocomposite. After modification with the Pt@r-GO@MWCNTs nanocomposite (curve b), the redox peak currents increased and a larger background current was observed due to the Pt@r-GO@MWCNTs nanocomposite dramatically increasing the electrode surface area and exhibiting good electrical conductivity [41, 42] . Fig. 3B shows the EIS plots of the bare GCE and Pt@r-GO@MWCNTs/GCE. The bare GCE (curve a) exhibited a small resistance, but when the Pt@r-GO@MWCNTs nanocomposite GCE was used (curve b), it displayed a significantly smaller resistance. Therefore, the CV and EIS diagrams further demonstrate the successful preparation of the Pt@r-GO@MWCNTs/GCE sensor.