Efficient synthesis of graphene–multiwalled carbon nanotubes nanocomposite and its application in electrochemical sensing of diethylstilbestrol

An electrochemical sensor for the voltammetric determination of artemisinin based on carbon materials and cobalt phthalocyanine

An electrochemical sensor for the determination of artemisinin has been developed based on a glassy carbon electrode modified with hybrid nanocomposites of cobalt phthalocyanine, graphene nanoplatelets, multi-walled carbon nanotubes and ionic liquids (IL). To improve the sensitivity and selectivity of the sensor, cobalt phthalocyanine (CoPc) was used as an effective redox mediator to promote and catalyze the artemisinin reduction. Furthermore, the graphene nanoplatelets and multi-walled carbon nanotubes were used as excellent conducting supporting materials to improve the sensitivity of the electrochemical sensor. Moreover, IL with a surface charge was also employed to prevent aggregation of the graphene nanoplatelets and multi-walled carbon nanotubes. The analytical signal was generated from the reduction of Co(III)Pc generated by artemisinin. The proposed electrochemical sensor was applied to the detection of artemisinin using differential pulse voltammetry and provided a signal with wide linearity ranging from 1.5-60 μM and 60-600 μM and a detection limit of 0.70 μM (3SD/m). Furthermore, the proposed sensor displayed good repeatability and reproducibility of 2.9-3.0 and 3.1-4.4% RSD, respectively. Applications of the sensor to drug and plant samples demonstrated accuracy in a range of 105-116% recoveries. In addition, the results were in good agreement with those obtained from the HPLC method as a reference technique. Thus, the proposed electrochemical sensor provides a new alternative platform for sensitive and selective determination of artemisinin in the analysis of pharmaceuticals with good precision and accuracy.

Molecularly imprinted ratiometric electrochemical sensor based on carbon nanotubes/cuprous oxide nanoparticles/titanium carbide MXene composite for diethylstilbestrol detection

Conventional molecularly imprinted polymers (MIP)-based electrochemical sensors are generally susceptible to the changes of personal operation, electrode surface, and solution conditions. Herein, a ratiometric strategy was employed through introducing Cu₂O nanoparticles (NPs) as inner reference probe to realize the reliable detection of diethylstilbestrol (DES). MIP film was prepared by electropolymerization of 1H-pyrrole-3-carboxylicacid in the presence of DES on carbon nanotubes/cuprous oxide/titanium carbide (CNT/Cu₂O NPs/Ti₃C₂T_x) modified electrodes. The Ti₃C₂T_x with accordion-like structure not only possessed good electrical conductivity, but also facilitated the immobilization of Cu₂O NPs, which contributed to stabilizing the signal. CNT was introduced to further improve the sensitivity of the sensor. Under optimum conditions, the MIP/CNT/Cu₂O NPs/Ti₃C₂T_x electrochemical sensors showed a broad linear response range of 0.01 to 70 μM, and a low detection limit of 6 nM (S/N = 3). Moreover, the sensor was applied to detect DES in real samples including lake water, milk, and pork, and the recoveries for spiked standard were 88-112%. Thus, this work provides a new way for reliable DES detection.

Nickel clusters grown on three-dimensional graphene oxide–multi-wall carbon nanotubes as an electrochemical sensing platform for luteolin at the picomolar level

This study focuses on enhancing the catalytic activity of metallic Ni by using 1D MWCNTs, 2D GO and GR, and 3D GO–MWCNTs as supporting matrixs for the fabrication of electrochemical sensor for detecting the flavonoid luteolin.