Molybdenum metallic nanoparticle detection via differential pulse voltammetry

Electrochemical detection of ornidazole in commercial milk and water samples using an electrode based on green synthesis of silver nanoparticles using cellulose separated from Phoenix dactylifera seed

The widespread use of antibiotics has contributed to the control of disease and the nutritional well-being of livestock. Antibiotics reach the environment via excretions (urine and feces) from human and domestic animals, through non proper disposal or handling of unused drugs. The present study describes a green method for the synthesis of silver nanoparticle (AgNPs) using cellulose extracted from Phoenix dactylifera seed powder via mechanical stirrer method for the electroanalytical determination of ornidazole (ODZ) in milk and water samples. The cellulose extract is used as the reducing and stabilizer agent for the synthesis of AgNPs. The obtained AgNPs were characterized by UV-Vis, SEM and EDX, presenting a spherical shape and an average size of 48.6 nm. The electrochemical sensor (AgNPs/CPE) was fabricated by dipping a carbon paste electrode (CPE) in the AgNPs colloidal solution. The sensor shows acceptable linearity with ODZ concentration in the linear range from 1.0 × 10^-5 to 1.0 × 10^-3 M with a limit of detection (LOD =3S/P) and quantification (LOQ =10S/P) of 7.58 × 10^-7 M and 2.08 × 10^-6 M respectively.

Stability analysis of silver nanoparticle suspensions by cyclic voltammetry

We report the application of cyclic voltammetry and absorption spectroscopy to the characterization and study of the stability of silver colloids in water. The samples are prepared via chemical reduction and the reactions are catalyzed by irradiation with white light. The electrochemical response is related to the characteristic sample surface plasmon resonance (SPR) in the UV-visible absorption spectra. Cyclic voltammetry shows a characteristic reduction peak whose position is specific to each analyzed sample. Optical analysis of a colloid precursor during a 12 h time span, under low-power white-light irradiation, shows that nanoparticles undergo change in size and surface state (absorption bands splitting and inversion) to attain the "stable" colloidal form. While the absorption spectrum bands of the precursor return almost periodically to similar positions, the cyclic voltammogram characteristic reduction peak is displaced as a function of time. Finally, we follow the SPR changes of one "stable" colloid being subjected to electrolysis, heating, and sunlight irradiation, for environmental remediation purposes. Sunlight exposure produces the most significant SPR intensity drop, but the electrochemical technique shows itself promising as well.

A core-shell molybdenum nanoparticles entrapped f-MWCNTs hybrid nanostructured material based non-enzymatic biosensor for electrochemical detection of dopamine neurotransmitter in biological samples

Dopamine (DA) is a critical neurotransmitter and has been known to be liable for several neurological diseases. Hence, its sensitive and selective detection is essential for the early diagnosis of diseases related to abnormal levels of DA. In this study, we reported novel molybdenum nanoparticles self-supported functionalized multiwalled carbon nanotubes (Mo NPs@f-MWCNTs) based core-shell hybrid nanomaterial with an average diameter of 40–45 nm was found to be the best for electrochemical DA detection. The Mo NPs@f-MWCNTs hybrid material possesses tremendous superiority in the DA sensing is mainly due to the large surface area and numerous electroactive sites. The morphological and structural characteristics of the as-synthesized hybrid nanomaterial were examined by XRD, Raman, FE-SEM, HR-TEM, EDX. The electrochemical characteristics and catalytic behavior of the as-prepared Mo NPs@f-MWCNTs modified screen-printed carbon electrode for the determination of DA were systematically investigated via electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The results demonstrate that the developed DA biosensor exhibit a low detection limit of 1.26 nM, excellent linear response of 0.01 µM to 1609 µM with good sensitivity of 4.925 µA µM⁻¹ cm⁻². We proposed outstanding appreciable stability sensor was expressed to the real-time detection of DA in the real sample analysis of rat brain, human blood serum, and DA hydrochloride injection.

Anodic stripping voltammetry of silver nanoparticles: aggregation leads to incomplete stripping

The influence of nanoparticle aggregation on anodic stripping voltammetry is reported. Dopamine-capped silver nanoparticles were chosen as a model system, and melamine was used to induce aggregation in the nanoparticles. Through the anodic stripping of the silver nanoparticles that were aggregated to different extents, it was found that the peak area of the oxidative signal corresponding to the stripping of silver to silver(I) ions decreases with increasing aggregation. Aggregation causes incomplete stripping of the silver nanoparticles. Two possible mechanisms of 'partial oxidation' and 'inactivation' of the nanoparticles are proposed to account for this finding. Aggregation effects must be considered when anodic stripping voltammetry is used for nanoparticle detection and quantification. Hence, drop casting, which is known to lead to aggregation, is not encouraged for preparing electrodes for analytical purposes.

Carbons and electrolytes for advanced supercapacitors

Electrical energy storage (EES) is one of the most critical areas of technological research around the world. Storing and efficiently using electricity generated by intermittent sources and the transition of our transportation fleet to electric drive depend fundamentally on the development of EES systems with high energy and power densities. Supercapacitors are promising devices for highly efficient energy storage and power management, yet they still suffer from moderate energy densities compared to batteries. To establish a detailed understanding of the science and technology of carbon/carbon supercapacitors, this review discusses the basic principles of the electrical double-layer (EDL), especially regarding the correlation between ion size/ion solvation and the pore size of porous carbon electrodes. We summarize the key aspects of various carbon materials synthesized for use in supercapacitors. With the objective of improving the energy density, the last two sections are dedicated to strategies to increase the capacitance by either introducing pseudocapacitive materials or by using novel electrolytes that allow to increasing the cell voltage. In particular, advances in ionic liquids, but also in the field of organic electrolytes, are discussed and electrode mass balancing is expanded because of its importance to create higher performance asymmetric electrochemical capacitors.