Synergistic Effect of 3D/2D Vanadium Diselenide/Tungsten Diselenide Hybrid Materials: Electrochemical Detection of 5-Nitroquinoline a Hazard to the Aquatic Environment.

The development of multidimensional structured electrode materials with simple synthetic methods and their electrochemical sensing ability against environmental pollution is still a challenge. In this article, we propose a hybrid formed using multidimensional (3D/2D) vanadium diselenide microspheres and tungsten diselenide nanosheets (VSe2/WSe2) for the electrochemical detection of 5-nitroquinoline (5-NQ), a highly toxic and hazardous substance that is polluting aquatic life due to increasing industrial activities. The 3D/2D VSe2/WSe2 hybrids were prepared by a simple solvothermal method and their morphological and structural analysis was confirmed by various spectroscopy and analytical techniques such as powder X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The proposed 3D/2D architecture showed a strong synergistic effect between the two components as well as high electrical conductivity. As a result, an increased peak current for the reduction and detection of 5-NQ was achieved compared to other modified and unmodified disposable screen-printed electrodes (SPE), such as bare SPE, VSe2/SPE, and WSe2/SPE. Under the optimized electrochemical conditions, VSe2/WSe2/SPE showed large linear response ranges (0.012-1053, 1183-3474 µM), a low detection limit (0.002 µM), good sensitivity along with good selectivity, and repeatability for the detection of 5-NQ. With this prominent electrochemical behavior, the VSe2/WSe2 electrode has clear potential to produce high-performance sensor devices.

Temperature-Induced Conversion of 2D Vanadium-Doped MoSe2 Nanosheets to 1D V2MoO8 Rods: Enhanced Performance in Electrochemical Antibiotic Detection in Biological and Environmental Samples.

In this work, new strategies were developed to prepare 1D-V2MoO8 (VMO) rods from 2D V-doped MoSe2 nanosheets (VMoSe2) with good control over morphology and crystallinity by a facile hydrothermal and calcination process. The morphological changes from 2D to 1D rods were controlled by changing the calcination temperature from 300 to 600 °C. The elimination of Se and the incorporation of O into the V-Mo structure were evaluated by TGA, p-XRD, Raman, FE-SEM, EDAX, FE-TEM, and XPS analyses. These results prove that the optimization of the physical parameters leads to changes in the crystal phase and textural properties of the prepared material. The VMoSe2 and its calcined products were investigated as electrochemical sensors for the detection of the antibacterial drug nitrofurantoin (NFT). At a calcination temperature of 500 °C, the modified screen-printed carbon electrodes (SPCE) proved to be an excellent electrochemical sensor for the detection of NFT in neutral media. Under the optimized conditions, VMO-500 °C/SPCE exhibits low detection limit (LOD) (0.015 µM), wide linear ranges (0.1-31, 47-1802 µM), good sensitivity, and selectivity. The proposed sensor was successfully used for the analysis of NFT in real samples with good recovery results. Moreover, the reduction potential of NFT agreed well with the theoretical analysis using quantum chemical calculations, with the B3LYP with 6-31G(d,p) basis set predicting an E0 value of -0.45 V. The interaction between the electrode surface and NFT via the LUMO diagram and the electrostatic potential surface is also discussed.

Design and synthesis of nickel-doped cobalt molybdate microrods: An effective electrocatalyst for the determination of antibiotic drug ronidazole.

Ronidazole (RDZ) is a veterinary antibiotic drug that has been used in animal husbandry as feed. However, improper disposal and illegal use of pharmaceuticals have severely polluted water resources. Doping/substitution of metal ions is an effective strategy to change the material's crystal phase, morphology, and electrocatalytic activity. In this work, nickel (Ni2+)-doped cobalt molybdate microrods (NCMO MRs) were prepared for the electrochemical detection of RDZ. The catalyst was prepared by reflux method followed by calcination at 500 °C. The prepared catalyst was confirmed by various spectroscopic and microscopic analyses. XRD and Raman spectroscopy demonstrated that the phase transition from ß-CoMoO4 to α-CoMoO4 was achieved by Ni2+ doping. The SEM analysis showed that cobalt molybdate (CMO) microrods were self-assembled during Ni2+ doping and formed an urchin-like structure, and the average diameter of the MRs was ±50 nm. The electrocatalytic activity of the catalysts was analyzed using the CV technique. The NCMO MRs/GCE exhibited the higher current response than the pristine CMO. The electron transfer coefficient (α = 0.56) and heterogeneous rate constant (ks = 0.32 s-1) of NCMO MRs/GCE were evaluated by kinetic studies. In addition, the diffusion coefficient of RDZ was determined to be 2.32 × 10-5 cm2/s. Moreover, NCMO MRs/GCE exhibits a low detection limit for RDZ (15 nM) as well as a higher sensitivity (1.57 µA µM-1 cm-2). The fabricated RDZ sensor was successfully applied to analysis of lake and tap water samples. Based on the results, we believe that the as-prepared NCMO MRs/GCE is a viable electrode material for RDZ sensors in environmental monitoring.

Effect of bismuth doping on zircon-type gadolinium vanadate: Effective electrocatalyst for determination of hazardous herbicide mesotrione.

Pesticides are used to promote the growth of plants and crops by killing weeds and other pests. On the other hand, overused and unused pesticides can leach into groundwater and agricultural lands, easily contaminating water, air, and soil resources. Doping with metal ions is an effective method to improve the catalytic activity of potential electrode materials. In the present study, an electrochemical sensor based on Bi3+-doped gadolinium vanadate nanoparticles (GVB NPs) was fabricated for sensitive and selective detection of harmful pesticide mesotrione (MST). The crystalline nature, functional groups, and elemental composition of the prepared electrocatalysts were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Field-emission scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) showed that the undoped gadolinium vanadate had a rice-like nanostructure and was designated as GV NRs, while GVB had the morphology of nanoparticles. The fabricated electrode exhibited a well-resolved MST reduction peak in cyclic voltammetry and linear sweep voltammetry (LSV). Bismuth doping effectively enhanced the MST reduction and produced a stronger cathodic current response than bare and GV NRs-modified GCE. Moreover, GVB NPs/GCE show a nanomolar detection limit of 45 nM with a sensitivity of 0.43 µA µM-1 cm-2. The proposed sensor showed good repeatability, reproducibility, and stability in LSV analysis. The fabricated MST sensor was successfully applied to the analysis of real samples (river water and corn) with good recovery results.