A molybdenum disulfide/nickel ferrite-modified voltammetric sensing platform for ultra-sensitive determination of clenbuterol under the presence of an external magnetic field.

The electrochemical behavior and sensing performance of an electrode modified with NiFe2O4 (NFO), MoS2, and MoS2-NFO were thoroughly investigated using CV, EIS, DPV, and CA measurements, respectively. MoS2-NFO/SPE provided a higher sensing performance towards the detection of clenbuterol (CLB) than other proposed electrodes. After optimization of pH and accumulation time, the current response recorded at MoS2-NFO/SPE linearly increased with an increase of CLB concentration in the range from 1 to 50 µM, corresponding to a LOD of 0.471 µM. In the presence of an external magnetic field, there were positive impacts not only on mass transfer, ionic/charge diffusion, and absorption capacity but also on the electrocatalytic ability for redox reactions of CLB. As a result, the linear range was widened to 0.5-50 µM and the LOD value was about 0.161 µM. Furthermore, stability, repeatability, and selectivity were assessed, emphasizing their high practical applicability.

Insight into the Influence of Analyte Molecular Structure Targeted on MoS2-GO-Coated Electrochemical Nanosensors.

MoS2-GO composites were fabricated by an ultrasonication method at room temperature. Raman spectra, emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM) images were used to study the structural characteristics, morphologies, and sizes of the synthesized materials. An MoS2-GO/SPE (screen-printed electrode) was prepared by a facile dropping method and acted as an effective electrochemical sensor toward clenbuterol (CLB) and 4-nitrophenol (4-NP) detection. Based on the obtained results, the influence of analyte molecular structure on the adsorption ability and electronic interoperability between the targeted analyte and electrode surface were investigated in detail and discussed as well, through some electrochemical kinetic parameters (electron/proton-transfer number, electron transfer rate constant (ks), charge transfer coefficient, and adsorption capacity (Γ)). In particular, it should be stressed that 4-NP molecules possess a simple molecular structure with many positive effects (electronic, conjugation, and small steric effects) and flexible functional groups, resulting in fast electron transport/charge diffusion and effective adsorption process as well as strong interactions with the electrode surface. Therefore, 4-NP molecules have been facilitated better in electrochemical reactions at the electrode surface and electrode-electrolyte interfaces, leading to improved current response and electrochemical sensing performance, compared with those of CLB.