Nanomaterials and Their Recent Applications in Impedimetric Biosensing.

Impedimetric biosensors measure changes in the electrical impedance due to a biochemical process, typically the binding of a biomolecule to a bioreceptor on the sensor surface. Nanomaterials can be employed to modify the biosensor's surface to increase the surface area available for biorecognition events, thereby improving the sensitivity and detection limits of the biosensor. Various nanomaterials, such as carbon nanotubes, carbon nanofibers, quantum dots, metal nanoparticles, and graphene oxide nanoparticles, have been investigated for impedimetric biosensors. These nanomaterials have yielded promising results in improving sensitivity, selectivity, and overall biosensor performance. Hence, they offer a wide range of possibilities for developing advanced biosensing platforms that can be employed in various fields, including healthcare, environmental monitoring, and food safety. This review focuses on the recent developments in nanoparticle-functionalized electrochemical-impedimetric biosensors.

Flower-like Superhydrophobic Surfaces Fabricated on Stainless Steel as a Barrier against Corrosion in Simulated Acid Rain.

Functionalisation of the metal surface of low-carbon ferritic stainless steel (from hydrophilic to hydrophobic properties) was achieved by flower-like hierarchical structures on a steel substrate prepared by a low-cost immersion method. The flower-like structured hydrophobic layers on the steel substrate were obtained by immersing the samples in an ethanolic solution of stearic acid with the addition of various concentrations of expired vitamin E ((+)α-tocopherol). The stability and corrosion-inhibiting effect of the hierarchically structured (such as natural cornflower) hydrophobic layers were studied systematically during short and long immersion tests, 120 h (five days) in an acidic environment (pH = 3) using potentiodynamic measurements, electrochemical impedance spectroscopy and chronopotentiometry. The surfaces of the samples, their wettability, surface morphology and chemical composition were characterised by contact angle measurements, SEM, ATR-FTIR and EDAX. After 120 h of immersion, the inhibition efficiency of the flower-like structured hydrophobic layers on the steel substrate in the selected corrosion medium remained above 99%, and the hierarchical structure (flower-like structure) was also retained on the surface.

The Use of Yeast Saccharomyces Cerevisiae as a Biorecognition element in the Development of a Model Impedimetric Biosensor for Caffeine Detection.

In the present study, an electrochemical-impedimetric biosensor using Saccharomyces cerevisiae as an effective biorecognition element was designed to detect caffeine. The presented biosensor consists of a previously developed stainless steel electrochemical cell constructed as a three-electrode system in the RCW side-by-side configuration. The electrochemical stability of the sensing electrode was evaluated by measuring the open circuit potential (OCP), and electrochemical impedance spectroscopy (EIS) was applied to determine the impedimetric response of the biosensor with Saccharomyces cerevisiae cells attached to the working electrode (WE) in the absence (0.9% NaCl) and presence (10 mg/mL in 0.9% NaCl) of caffeine. Moreover, the limit of detection (LOD) was determined. In this way, a new approach in biosensor development has been established, which involves assembling a low-cost and disposable electrochemical system to detect alkaloids such as caffeine. The developed biosensor represents a good candidate for detecting caffeine in beverages, foods, and drugs with the merits of time-saving, robustness, low cost, and low detection limit.

Sage Extract as a Natural Source of Corrosion Inhibitor for Tinplate in 3.0% NaCl.

RESEARCH BACKGROUND: Due to the growing interest and attention of the world towards environmental problems and protection of environment, the worldwide demand for biodegradable and effective corrosion inhibitors for tinplate has grown. Considering the diversity of the structures of polyphenols that are present in sage extract, it represents a promising potential source of low-cost and effective biodegradable green corrosion inhibitor for tinplate in 3.0% sodium chloride solution which is evaluated in this study. EXPERIMENTAL APPROACH: Tafel polarisation and electrochemical impedance spectroscopy (EIS) at 25 °C have been used to evaluate the inhibitory activity of sage (Salvia officinalis L.) extract as a green inhibitor for the protection of tinplate from corrosion in 3.0% sodium chloride solution. RESULTS AND CONCLUSIONS: We used electrochemical impedance spectroscopy to show that sage extract could serve as an effective inhibitor (94.1%) of the corrosion of tinplate in 3.0% NaCl at a mass concentration of 0.2 mg/L and temperature of 25 °C. The results obtained from potentiodynamic polarisation reveal that the sage extract acts as a mixed type inhibitor, with inhibition efficiency up to 82.5%, and the inhibition efficiencies calculated from EIS are in close agreement with these results. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) results indicated that the inhibitory effect of the sage extract is due to the presence of a passivation layer on the tinplate surface, which consists of organic compounds such as polyphenols. These results confirm that the sage extract is more efficient in inhibiting the corrosion of tinplate at a concentration of 0.2 mg/L than at higher concentrations. Also, it shows good inhibition of tinplate in 3.0% sodium chloride solution. NOVELTY AND SCIENTIFIC CONTRIBUTIONS: The exceptional corrosion inhibition potential of sage extract opens a door for its use and revalorization as a green corrosion inhibitor in the food industry.

Electrochemical impedance spectroscopy as a tool in the plate making process optimization.

The structure of the porous aluminium-oxide layer, which builds non-image areas, has the most significant influence on the quality of final graphical product. This paper presents the results of the application of EIS in the characterisation and detection of changes on the aluminium-oxide layer caused by chemical processing in highly alkaline solution. The Al2O3 layer was characterised using SEM, fractal dimension and surface free energy calculation and EIS analysis. The results of the investigation showed that chemical processing has a significant influence on the structure of aluminium-oxide which could lead to a decrease in the quality of the printing plate. EIS enables the detection of changes on the aluminium-oxide layer. The two equivalent circuits are proposed. Based on modelling with the obtained EIS spectra, precise evaluation of developing time in which complete removal of the photoactive layer is achieved. This makes EIS a powerful tool in optimizing chemical processing of lithographic printing plates.