Salah Kouass

By Salah Kouass, Amor Fadhalaoui, Hassouna Dhaouadi and Fathi Touati

Most of the work has been done on the optical properties of the rare earth doped CePO4, so there are few studies on the effect of metal ion doping on CePO4. The doping improves the properties of the compounds and can lead to new properties. It is the first time, that multi- ionic doping process is used in the CePO4matrix, in order to improve the ionic conductivity and the electrochemical stability. The low percentage of (Cd2+, Li+), Cr3+, Bi3+ dopant affect the structure showing a weak decrease in the lattice parameters compared to the CePO4. Impedance spectroscopy analysis was used to analyze the electrical behavior of samples as a function of frequency at different temperatures. The total electrical conductivity plots obtained from impedance spectra shows an increase of the total conductivity as Li, Cr-content increases. The determined energy gap values decrease with increasingly Li+, Cr3+ and Bi3+ doping content. Electrochemical tests showed an improved capacity when increasing the Li+, Cr3+ and Bi3+ content and a stable cycling performance.

Part of the book: Electrochemical Impedance Spectroscopy

By Salah Kouass, Hassouna Dhaouadi, Abdelhak Othmani and Fathi Touati

The Fe2O3/TiO2 nanocomposite was synthesized on FTO subtract via hydrothermal method. The crystal structure, morphology, band structure of the heterojunction, behaviors of charge carriers and the redox ability were characterized by XRD, HR-TEM, absorption spectra, PL, cyclic voltammetry and transient photocurrent spectra. The as-prepared Fe2O3/TiO2 photocatalysts with distinctive structure and great stability was characterized and investigated for the degradation of methylene blue (MB) dye in aqueous solution. The ability of the photocatalyst for generating reactive oxygen species, including O2− and.OH was investigated. It was revealed that the combination of the two oxides (Fe2O3 and TiO2) nano-heterojunction could enhance the visible response and separate photogenerated charge carriers effectively. Therefore, the remarkable photocatalytic activity of Fe2O3/TiO2 nanostructures for MB degradation was ascribed to the enhanced visible light absorption and efficient interfacial transfer of photogenerated electrons from to Fe2O3 to TiO2 due to the lower energy gap level of Fe2O3/TiO2 hybrid heterojunctions as evidenced by the UV–Vis and photoluminescence studies. The decrease of the energy gap level of Fe2O3/TiO2 resulted in the inhibition of electron–hole pair recombination for effective spatial charge separation, thus enhancing the photocatalytic reactions. Based on the obtained results, a possible mechanism for the improved photocatalytic performance associated with Fe2O3/TiO2 was proposed. The Fe2O3/TiO2 nanocomposite has a specific capacity of 82 F.g−1 and shows a higher capacitance than Fe2O3.

Part of the book: Electrocatalysis and Electrocatalysts for a Cleaner Environment

By Marouene Bejaoui, Haykel Galai, Fathi Touati and Salah Kouass

Polyvinylpyrrolidone (PVP) has proven to be a highly versatile material, as evidenced by its long history as multifunctional biomaterial with a wide range of high-performance applications (e.g., tissue engineering, drug delivery systems, and ophthalmologic applications). PVP was frequently used in medical and pharmaceutical field due to its several interesting properties (higher glass transition temperature, water solubility, biocompatibility, biodegradability, chemical stability, very good adhesive, and emulsifying agent). This chapter highlights the multifunctional roles of PVP in pharmaceutical formulations in solid state. In fact, PVP acted as a stabilizing agent for various amorphous drug molecules by minimizing their molecular mobility. Physical stabilization resulted from the reinforcement of intermolecular interactions in binary or ternary systems due to the synergetic effect of PVP. This made it possible to overcome several challenges for drug formulations (e.g., solubility and bioavailability weakness, physical instability under stress conditions, complexation efficiency of cyclodextrin molecules). In this chapter, the effect of PVP on the binary solid dispersion (indomethacin:kaolin) is discussed. We have shown that PVP enhanced physical stability of amorphous indomethacin under stress conditions (at RH: 75% and T = 40°C for three months), leading to the improvement of drug aqueous solubility by suppressing kaolin adsorption effect.

Part of the book: Dosage Forms