ABSTRACT
A novel cobalt-doped two-dimensional molybdenum diselenide/polypyrrole hybrid-based carbon nanofiber (Co/MoSe2/PPy@CNF) was prepared using the hydrothermal method followed by electrospinning technique. The structural and morphological properties of the 2D-TMD@CNF-based hybrids were characterized through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and transmission electron microscopy (TEM). The Co-MoSe2/PPy@CNF exhibited large surface area, porous structure, and improved active sites due to the synergistic effect of the components. The electrochemical and electrocatalytic characteristics of the 2D-TMD@CNF-modified electrodes were also investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The Co/MoSe2/PPy@CNF electrode was used as an electrochemical sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) and showed enhanced catalytic activity and sensitivity. Using DPV measurements, the Co/MoSe2/PPy@CNF demonstrated wide linear ranges of 30-3212 µM for AA, 1.2-536 µM for DA, and 10-1071 µM for UA with low detection limits of 6.32, 0.45, and 0.81 µM, respectively. The developed sensor with the Co/MoSe2/PPy@CNF-modified electrode was also applied to a human urine sample and gave recoveries ranging from 94.0 to 105.5% (n = 3) for AA, DA, and UA. Furthermore, the Co/MoSe2/PPy@CNF-based sensor exhibited good selectivity and reproducibility for the detection of AA, DA, and UA.
ABSTRACT
In this study, surface acoustic wave (SAW) systems are described for the removal of molecules that are unbound to micromotors, thereby lowering the detection limit of the cancer-related biomarker miRNA-21. For this purpose, in the first step, mass production of the Au/Pt bimetallic tubular micromotor was performed with a simple membrane template electrodeposition. The motions of catalytic Au/Pt micromotors in peroxide fuel media were analyzed under the SAW field effect. The changes in the micromotor speed were investigated depending on the type and concentration of surfactants in the presence and absence of SAW streaming. Our detection strategy was based on immobilization of probe dye-labeled single-stranded probe DNA (6-carboxyfluorescein dye-labeled-single-stranded DNA) to Au/Pt micromotors that recognize target miRNA-21. Before/after hybridization of miRNA-21 (for both w/o SAW and SAW streaming conditions), the changes in the speed of micromotors and their fluorescence intensities were studied. The response of fluorescence intensities was observed to be linearly varied with the increase of the miRNA-21 concentration from 0.5 to 5 nM under both w/o SAW and with SAW. The resulting fluorescence sensor showed a limit of detection of 0.19 nM, more than 2 folds lower compared to w/o SAW conditions. Thus, the sensor and behaviors of Au/Pt tubular micromotors were improved by acoustic removal systems.
