Label-free and sensitive determination of toxic Cd(II) in environmental waters using a Fe3O4-PEI-Au based electrochemical aptasensor

A novel electrochemical strategy was presented using gold nanoparticles decorated on polyethyleneimine-modified iron oxide nanoparticles (Fe3O4-PEI-Au) as a nanocomposite modifier for sensitive and selective detection of Cd(II). The aptasensor was fabricated by immobilizing a thiol-terminated Cd(II) aptamer onto a screen-printed carbon electrode modified with the Fe3O4-PEI-Au nanocomposite. This nanocomposite provided high surface area for enhanced aptamer loading, excellent biocompatibility, and good conductivity to promote the signal amplification at the sensing interface. Differential pulse voltammetry was used for quantitative measurement of Cd(II), demonstrating a dynamic linear detection range from 0.04 nM to 25 nM. The limit of detection was found to be 0.01 nM, which is lower than the safe limit in drinking water defined by the U.S. Environmental Protection Agency. The label-free aptasensor showed high selectivity, reproducibility, stability and reliability for real-time Cd(II) monitoring in environmental water samples. This work successfully demonstrates the development of a novel electrochemical aptasensor utilizing a Fe3O4-PEI-Au nanocomposite modifier for sensitive and selective detection of trace levels of Cd(II) in water resources

A simple approach for simultaneous detection of cadmium(II) and lead(II) based on glutathione coated magnetic nanoparticles as a highly selective electrochemical probe

We introduce the synthesis and electrochemical application of a glutathione functionalized magnetic nano composite (GSH@Fe3O4) for the development of a simple, stable and selective sensor for heavy metal ion detection in real-life samples for the first time. The monitoring method is based on electrochemical pre-concentration/reduction of metal ions onto a GSH@Fe3O4 modified magnetic glassy carbon electrode, followed by subsequent anodic stripping. This method allows the detection of Pb2+ and Cd2+ ions with high sensitivity (calculated detection limits of 0.182 mu gL(-1) and 0.172 mu gL(-1)), low cost, and great convenience in operation and was tested for different water samples. The results infer that the GSH@Fe3O4 nanocomposite can be an alternative candidate for practical applications in electrochemical detection of metal ions

A Voltammetric Sensor Based on NiO Nanoparticle-Modified Carbon-Paste Electrode for Determination of Cysteamine in the Presence of High Concentration of Tryptophan

A carbon-paste electrode modified with ferrocenecarboxaldehyde and NiO nanoparticle (NiO/NPs) was used for the sensitive and selective voltammetric determination of cysteamine in the presence of tryptophan. The oxidation of cysteamine at the modified electrode was investigated by cyclic voltammetry (CV), chronoamperometry, and square-wave voltammetry (SWV). The values of the catalytic rate constant () and diffusion coefficient () for cysteamine were calculated. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for cysteamine and tryptophan. At the optimum pH of 7.0 in a 0.1 M phosphate buffer solution, the SWV anodic peak currents showed a linear relationship versus cysteamine concentrations in the range of 0.09–300.0 µM and a detection limit of 0.06 µM. Finally, the proposed method was also examined as a selective, simple, and precise electrochemical sensor for the determination of cysteamine in real samples such as urine and capsule

Oxidative Aromatization of 1,3,5-trisubstituted 2-pyrazolines Using Oxalic Acid/Sodium Nitrite System

<p>Oxidative aromatization of 1,3,5-trisubstituted 2-pyrazolines by <i>in-situ</i> generation of NO⁺ from oxalic acid/sodium nitrite system has been described. The main advantages of this procedure are the use of an inexpensive and readily available catalyst, facile work-up, and improved yields in aqueous ethanol.</p

Antibacterial Evaporator Based on Wood-Reduced Graphene Oxide/Titanium Oxide Nanocomposite for Long-Term and Highly Efficient Solar-Driven Wastewater Treatment

Herein, we developed antifouling and highly efficient solar absorbers consisting of poplar wood coated with titanium dioxide (TiO2) and reduced graphene oxide (RGO) nanocomposites (with different weight ratio of TiO2 to RGO). The antibacterial activity of all prepared nanocomposites against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was investigated. The results showed that T2G1 (a nanocomposite in which the weight ratio of TiO2 to RGO is 2:1) has the highest antibacterial activity among all nanocomposites (MIC of 0.08 and 0.08 mg mL–1 and MBC of 0.6 and 0.8 mg mL–1 for E. coli and S. aureus, respectively). Therefore, it was considered to be the most efficient photothermal material for interfacial solar desalination and solar-driven treatment of wastewater. Because of the broad-band solar absorption by T2G1, the solar absorber composed of T2G1 and wood (denoted as T2G1-w) showed a high energy conversion efficiency of 90.12% under 1 sun (1 kW m–2). T2G1-w also had a high stability for long-term cycles. T2G1-w also showed great performance of freshwater production from contaminated water containing dye or heavy metals. The concentration of heavy metals of Zn2+, Pb2+, Fe2+, Ni2+, and Cr6+ reduced from 1000 mg L–1 to near zero in the presence of the prepared solar absorber, indicating its great potential application for sewage treatment

A novel detection method for organophosphorus insecticide fenamiphos: Molecularly imprinted electrochemical sensor based on core-shell Co3O4@MOF-74 nanocomposite

Organophosphorus insecticide fenamiphos (FEN) is utilized to control the detrimental nematode pests. In this report, a novel molecular imprinted electrochemical sensor for insecticide FEN detection was prepared. The molecular imprinted sensor was prepared based on Co3O4 nanowire and core-shell Co3O4@MOF-74 nanocomposite. Firstly, hydrothermal method followed by thermal annealing was applied for the preparation of Co3O4 nanowire. Then, solvothermal technique was used in no presence of metal salts to prepare core-shell Co3O4@MOF-74 nanocomposite. In addition, several solvothermal cycles were tried to optimally adjust the reaction efficiency. After the modification of the clean carbon electrode surfaces with Co3O4@MOF-74 nanocomposites, the molecular imprinted electrodes based on Co3O4@MOF-74 nanocomposites were prepared in presence of 100.0 mM pyrrole as monomer and 25.0 mM FEN as analyte molecule between +0.30 V and +1.50 V by cyclic voltammetry (CV). The prepared molecularly imprinted sensor based on Co3O4 nanowire and core-shell Co3O4@MOF-74 nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), x-ray diffraction (XRD) method, x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and CV. The quantification limit (LOQ) and the detection limit (LOD) were obtained as 1.0 × 10−11 M and 3.0 × 10−12 M, respectively, by using the developed sensor. Hence, the developed molecularly imprinting electrochemical sensor having high selectivity, stability and reproducibility was presented in this study for insecticide FEN detection. © 2021 Elsevier Inc