Fabrication and optimization of polypyrrole/cerium oxide/glassy carbon sensing platform for the electrochemical detection of flupirtine

Effect of Nanoceria Suspension Addition on the Physicochemical and Mechanical Properties of Hybrid Organic-Inorganic Hydroxyapatite Composite Scaffolds

In the current study, the synthesis of hydroxyapatite-ceria (HAP-CeO2) scaffolds is attempted through a bioinspired chemical approach. The utilized colloidal CeO2 suspension presents antifungal activity against the Aspergillus flavus and Aspergillus fumigatus species at concentrations higher than 86.1 ppm. Three different series of the composite HAP-CeO2 suspensions are produced, which are differentiated based on the precursor suspension to which the CeO2 suspension is added and by whether this addition takes place before or after the formation of the hydroxyapatite phase. Each of the series consists of three suspensions, in which the pure ceria weight reaches 4, 5, and 10% (by mass) of the produced hydroxyapatite, respectively. The characterization showed that the 2S series's specimens present the greater alteration towards their viscoelastic properties. Furthermore, the 2S series's sample with 4% CeO2 presents the best mechanical response. This is due to the growth of needle-like HAP crystals during lyophilization, which-when oriented perpendicular to the direction of stress application-enhance the resistance of the sample to deformation. The 2S series's scaffolds had an average pore size equal to 100 μm and minimum open porosity 89.5% while simultaneously presented the lowest dissolution rate in phosphate buffered saline.

Fabrication of Reproducible and Selective Ammonia Vapor Sensor-Pellet of Polypyrrole/Cerium Oxide Nanocomposite for Prompt Detection at Room Temperature

Polypyrrole (PPy) and polypyrrole/cerium oxide nanocomposite (PPy/CeO₂) were prepared by the chemical oxidative method in an aqueous medium using anhydrous ferric chloride (FeCl₃) as an oxidant. The successful formulation of materials was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmittance electron microscopy (TEM). A four-in-line probe device was used for studying DC electrical conductivity and ammonia vapor sensing properties of PPy and PPy/CeO₂. The significant improvement in both the conductivity and sensing parameters of PPy/CeO₂ compared to pristine PPy reveals some synergistic/electronic interaction between PPy and cerium oxide nanoparticles (CeO₂ NPs) working at molecular levels. The initial conductivity (i.e., conductivity at room temperature) was found to be 0.152 Scm^-1 and 1.295 Scm^-1 for PPy and PPy/CeO₂, respectively. Also, PPy/CeO₂ showed much better conductivity retention than pristine PPy under both the isothermal and cyclic ageing conditions. Ammonia vapor sensing was carried out at different concentration (0.01, 0.03, 0.05, 0.1, 0.2, 0.3, 0.4, and 0.5 vol %). The sensing response of PPy/CeO₂ varied with varying concentrations. At 0.5 vol % ammonia concentration, the % sensing response of PPy and PPy/CeO₂ sensor was found to be 39.1% and 93.4%, respectively. The sensing efficiency of the PPy/CeO₂ sensor was also evaluated at 0.4. 0.3, 0.2, 0.1, 0.05, 0.03, and 0.01 vol % ammonia concentration in terms of % sensing response, response/recovery time, reversibility, selectivity as well as stability at room temperature.

Effective and reliable platform for nonenzymatic nanomolar-range quinol detection in water samples using ceria doped polypyrrole nanocomposite embedded on graphitic carbon nitride nanosheets

A glassy carbon electrode modification by a novel ternary nanocomposite of advantageously united ceria, polypyrrole, and graphitic carbon nitride (CeO₂/Ppy@g-C₃N₄) is reported here. It can be used to tailor the sensor surface for the electrochemical detection of nanomolar-level quinol (Qnl), a chemical widely used as a developing agent in photography and lithography, as a cosmetic, and as an antioxidant in rubber and food industries. The occupational exposure of Qnl may occur by inhalation or dermal contact, leading to lot of health hazards. The synthesized nanocomposite was characterized by various analytical techniques such as UV-Vis, Fourier transformed infrared (FTIR), X-ray powder diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, selected area electron diffraction, and elemental mapping analyses. The oxidation current of Qnl is linear to its concentration in the range of 0.01-260 μM and the lowest detection and quantification limit are found to be 1.5 nM and 0.004 μM, respectively, with a sensitivity of 283.33 μA mM^-1 cm^-2. The performance of the modified electrode was compared with those of high-performance liquid chromatography, which indicates that the proposed sensor can be used as an effective and reliable platform for nano-molar detection of Qnl in various environmental and biological fluids.