Journal of Solid State Electrochemistry最新文献

An unprecedented electrochemical sensor based on low-cost films combining carbon black (CB) and green-synthesized silver nanoparticles (AgNPs) is proposed for the voltammetric determination of ciprofloxacin, an antibiotic widely used in the treatment of infectious diseases. AgNPs were biosynthesized by using an aqueous plant extract of Camellia sinensis (black tea) in which the metabolites worked as reducing and stabilizing agents. The AgNPs and CB nanoparticles were incorporated within a crosslinked chitosan (Ch) film over the surface of a glassy carbon electrode (GCE). The nanomaterials were characterized by scanning electron microscopy (SEM), ultraviolet–visible molecular absorption spectrophotometry (UV–Vis), dynamic light scattering (DLS), zeta potential, and cyclic voltammetry (CV). The sensor modified with both nanomaterials (AgNPs-CB-Ch/GCE) showed a significatively enhanced analytical signal for the ciprofloxacin irreversible oxidation peak. Using square-wave voltammetry (SWV) under the optimized working conditions and the proposed AgNPs-CB-Ch/GCE sensor, the analytical curve displayed two linear concentration ranges of 3.1 to 24.8 µmol L⁻¹ and of 36.9 to 130.3 µmol L⁻¹, with a limit of detection of 0.48 µmol L⁻¹. The proposed electrochemical sensor presented good precision as shown from repeatability tests, as well as it was successfully applied in the quantification of ciprofloxacin in the synthetic urine sample, with recovery results close to 100% for both linear concentration ranges. The presented AgNPs synthetic method and CIP electrochemical detection are found to be simple and efficient compared to the conventional methods commonly reported.

On March 11, 2020, the World Health Organization declared the coronavirus disease pandemic, caused by the SARS-CoV-2 virus. This declaration propelled the drug hydroxychloroquine into the global spotlight, as it was identified as a potential early treatment for the disease. Consequently, there was a surge in its consumption worldwide, particularly in Brazil. This increased usage has raised concerns about the potential contamination of natural water sources. In response to this concern, the present study proposes an electroanalytical method for detecting hydroxychloroquine in pharmaceutical and drinking water samples. The method aims to study the effects of modifying the sensor with carbon black Super P for HCQ detection, as well as improving the reproducibility and repeatability of the SPCB/GCE. The detection method and sensor modification have been thoroughly optimized for hydroxychloroquine detection. The optimal analysis conditions were established with a concentration of 5.0 mg mL⁻¹ of SPCB, a pH of 7.00, and a preconcentration time of 2 min. The detection and quantification limits were determined to be 0.0093 µmol L⁻¹ and 0.0312 µmol L⁻¹, respectively, with a linear range between 0.10 and 10.0 µmol L⁻¹. Analyses conducted on fortified samples indicated recovery responses of 110% for tap water and 100.5% for drug samples, demonstrating the method’s high accuracy, particularly for pharmaceutical samples.

Fast charging (~ 6 C rate) of Li-ion batteries (LIBs) is a key requirement to practically realize the growth of the electric vehicles (EVs) market. According to the US Department of Energy (DOE), the fast charge goal is an average of 20 mi min⁻¹ (miles added per minute) or more. However, current state-of-art battery technologies are still far away from the requirements. Ni-rich layered oxide materials are promising cathode materials for the long run due to their high practically achievable capacity of 200 mAh g⁻¹ at an average voltage of 3.8 V vs. Li⁺ /Li. Under fast charging, Ni-rich cathodes undergo anisotropic volume change followed by microcracks formation. As the Ni content increases, the particle crack formation becomes more severe under fast charging. This review article presents a mechanistic insight into the degradation of Ni-rich cathode materials during fast charging, bulk and surface structural evolution during delithiation-lithiation, lithium-ion diffusion kinetics, an overview of the mitigation strategy, and the practical reality of Ni-rich layered oxide cathode materials for fast charging applications.

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Herein, we prepared poly(heptazine imide) (PHI), a layered structure of carbon nitride material containing sodium cations that were later exchanged, allowing us to obtain single-atom catalyst (SAC) sites of nickel, cobalt, and iron. In addition, combinations among these metals (NiCo, NiFe, and CoFe) were evaluated as dual single-atom catalysts (DSAC). The samples containing transition metal presented a photocurrent response far superior to the unmodified Na-PHI. The maximum photocurrent obtained was for the sample NiCo-PHI in alkaline media, being ~ 70 µA cm⁻² at 1.2 V vs. RHE; this value was higher than both Ni-PHI and Co-PHI combined, indicative of a cooperative effect in the DSAC sample. Lastly, all samples containing transition metal, when studied in acidic media, presented both cathodic and anodic photocurrent indicating a bifunctionality potential for application in both reduction and oxidation of water.

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Contact angles of liquid, spherical cap droplets immobilised on an electrode surface and bathed by a fluid are important, quantifiable measures of the liquid/fluid interfacial tension. Optical goniometry, even if computer assisted, suffers when the contact angle is 10° or less. In this work, an alternative method of measurement is considered: electrochemical techniques (voltammetry and chronoamperometry), which rely on the transport of material from within the droplet to the conductive surface. As a result of the reactions that take place at the triple phase boundary, these are demonstrated to provide information on the size and the shape of the droplet, including its contact angle, for the cases when the droplets have a redox analyte and either have a supporting electrolyte, or not. The voltammetric behaviour is seen to change from exhaustive, thin film characteristics, to quasi-steady-state signals as the droplet becomes bigger, or the scan rate becomes larger, or diffusion of the redox material inside the droplet becomes slower. One of the surprising outcomes is that there is a zone of planar diffusion only in the case of the supported droplets, with both the droplet size and its contact angle determining whether this is seen at conventional combinations of scan rates and diffusion coefficients. Experimental data are provided which emphasize key features pertaining to the nature of the redox system and illustrate the facile nature of the contact angle estimation process, albeit to within 10% uncertainty.