Sulfur vacancy-rich N-doped MoS ₂ nanoflowers act as highly effective electrochemical catalysts for efficient nitrogen reduction.

Here we report on a selective and sensitive graphene-oxide-based electrochemical sensor for the detection of naproxen. The effects of doping and oxygen content of various graphene oxide (GO)-based nanomaterials on their respective electrochemical behaviors were investigated and rationalized. The synthesized GO and GO-based nanomaterials were characterized using a field-emission scanning electron microscope, while the associated amounts of the dopant heteroatoms and oxygen were quantified using x-ray photoelectron spectroscopy. The electrochemical behaviors of the GO, fluorine-doped graphene oxide (F-GO), boron-doped partially reduced graphene oxide (B-rGO), nitrogen-doped partially reduced graphene oxide (N-rGO), and thermally reduced graphene oxide (TrGO) were studied and compared via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that GO exhibited the highest signal for the electrochemical detection of naproxen when compared with the other GO-based nanomaterials explored in the present study. This was primarily due to the presence of the additional oxygen content in the GO, which facilitated the catalytic oxidation of naproxen. The GO-based electrochemical sensor exhibited a wide linear range (10 µM–1 mM), a high sensitivity (0.60 µAµM⁻¹cm⁻²), high selectivity and a strong anti-interference capacity over potential interfering species that may exist in a biological system for the detection of naproxen. In addition, the proposed GO-based electrochemical sensor was tested using actual pharmaceutical naproxen tablets without pretreatments, further demonstrating excellent sensitivity and selectivity. Moreover, this study provided insights into the participatory catalytic roles of the oxygen functional groups of the GO-based nanomaterials toward the electrochemical oxidation and sensing of naproxen.

In the fields of medicine, environmental protection, and food safety, sensors are imperative for the detection of biomarkers, contaminants, and preservatives. The use of nanoporous gold (NPG) as a sensing platform may greatly enhance performance due to its stability, high surface area, and catalytic abilities. There are many methods reported in the literature for fabricating NPG, including chemical strategies and various electrochemical techniques. The primarily use of NPG in sensing applications may be classified into three categories: electrochemical, bioelectrochemical, and optical. Although both electrochemical and bioelectrochemical sensors are based on the electrical signal produced by a specific analyte, a biological recognition element is involved in the bioelectrochemical sensing process. On the other hand, optical sensors exploit NPG through unique surface plasmon resonance properties that can be monitored by UV-Vis, Raman, or fluorescence spectroscopy. For this review, the primary strategies for fabricating NPG, including dealloying, electrochemical, and dynamic hydrogen bubble template (DHBT), are discussed. In addition, advances made over the last decade towards the detection of biomarkers, pollutants, contaminants, and food additives are highlighted. The future development of NPG based sensors for medical, environmental, and food safety applications is discussed.

Transition metal chalcogenide MoS ₂ catalysts are highly selective for the electrochemical reduction of dinitrogen (N ₂ ) to ammonia (NH ₃ ) in aqueous electrolytes.

Hydrogen is a promising green fuel carrier that can replace fossil fuels; however, its storage is still a challenge. Carbon-based materials with metal catalysts have recently been the focus of research for solid-state hydrogen storage due to their efficacy and low cost. Here, we report on the exfoliation of expanded graphite (EG) through high shear mixing and probe tip sonication methods to form graphene-based nanomaterial ShEG and sEG, respectively. The exfoliation processes were optimized based on electrochemical capacitance measurements. The exfoliated EG was further functionalized with palladium nanoparticles (Pd-NP) for solid-state hydrogen storage. The prepared graphene-based nanomaterials (ShEG and sEG) and the nanocomposites (Pd-ShEG and Pd-sEG) were characterized with various traditional techniques (e.g., SEM, TEM, EDX, XPS, Raman, XRD) and the advanced high-resolution pair distribution function (HRPDF) analysis. Electrochemical hydrogen uptake and release (Q_H) were measured, showing that the sEG decorated with Pd-NP (Pd-sEG, 31.05 mC cm⁻²) and ShEG with Pd-NP (Pd-ShEG, 24.54 mC cm⁻²) had a notable improvement over Pd-NP (9.87 mC cm⁻²) and the composite of Pd-EG (14.7 mC cm⁻²). Q_H showed a strong linear relationship with an effective surface area to volume ratio, indicating nanoparticle size as a determining factor for hydrogen uptake and release. This work is a promising step toward the design of the high-performance solid-state hydrogen storage devices through mechanical exfoliation of the substrate EG to control nanoparticle size and dispersion.