Ahmed H. Hammad

The Effects of Bi2O3 on Optical, FTIR and Thermal Properties of SrO-B2O3 Glasses

Combined optical and FTIR were measured for binary bismuth borate glass together with samples containing 2.5 – 15 mol % Bi2O3 glasses to justify the role of bismuth (Bi3+) ions on the spectral properties. The density and molar volume values were calculated to obtain some insight on the compactness and structural arrangement in the network. DTA measurements were carried out to calculate the thermal transition parameters of the studied glasses and to justify their stability. Optical spectra reveal three strong UV-near visible absorption bands at 250, 275 and 310 nm due to collective absorption of trace iron (Fe3+) ions impurities together with absorption from Bi3+ ions at 360 nm. The absorption edges reveal an obvious increase with the Bi2O3 content. FTIR spectra reveal vibrational bands characteristic for triangular borate groups at 1200- 1600 cm−1, tetrahedral borate groups at 800 – 1200 cm−1 together with interference of Bi-O vibrations upon the introduction of Bi2O3. The observed bands at about 429, 465, and 595 cm−1 are related to BiO6 and the band at 879 cm−1 is related to BiO3 in the host sample 15 % Bi2O3. Thermal properties are found to depend on the Bi2O3 content depending on the specific role of the formed groups (BiO6, BO3) and their function as modifier or former together with the formation of nonbridging oxygens.

Thermal, Structural, and Morphological Investigations of Modified Bismuth Silicate Glass-Ceramics

Glass-ceramics were prepared based on the basic glass composition in mole fraction 0.65 Bi2O3 -0.35 SiO2 with replacements of 0.05 SiO2 by equivalent of one of the oxides: MoO3, WO3, SrO, BaO or CdO. The glass transition temperature of the parent glass is 465 ∘C which is observed to decrease when doped with Mo, W, Sr, Ba, or Cd oxides. A eulytite phase is formed through controlled crystallization of the parent glass-ceramic and the samples doped with Mo or W, while a Bi2O2SiO3 phase is detected for the samples doped with Sr and Cd. Orthorhombic bismuth silicate crystals were observed only in the sample doped with Ba. SEM images show that all samples have elongated particles with few rectangular or spherical crystals. BiO6 and BiO3 units are assumed to be formed in all samples within the characteristic IR silicate absorption bands.

The role of V2O5 on the Structural and Optical Properties of MgO-ZnO-CdO-P2O5 Glasses and the Impact of Gamma Irradiation

The quaternary glasses of mixed divalent oxides including ZnO, MgO, CdO within a phosphate network former were prepared. Vanadium pentoxide was introduced as a dopant in the range from 0.5 to 3%. Optical and infrared absorption studies for all glass samples were carried out. The optical spectra reveal the presence of both V3+ and V4+ ions in the studied host mixed divalent oxides phosphate glass. Fourier transform infrared absorption spectral analysis indicates the appearance of distinct vibrational bands due to the presence of characteristic phosphate groups depending on the glass composition and the ratio of V2O5 content. The optical band gap and Urbach energy were calculated and discussed in relation to the effect of V2O5 content. Finally, the glasses were optically and structurally examined affter gamma irradiation with a dose of 80 KGy.

Size controlled ultrafine CeO 2 nanoparticles produced by the microwave assisted route and their antimicrobial activity

Cerium oxide (CeO2) nanoparticles (NPs) have a wide range of biological and biomedical applications. This work describes a new methodology for producing ultrafine, highly uniform NPs with controlled sizes using the chemical microwave assisted route. The size of CeO2-NPs decreased from 10 to 5 nm by increasing the molar ratio of cerium nitrate Ce(NO3)3.(6H2O) to that of hexamethylenetetramine (C6H12N) from 1:20 to 20:20. Detailed information about their structural characterization was obtained from the XRD, UV-visible, photoluminescence, Raman spectroscopy, SEM, TEM and AFM. These CeO2-NPs were tested as antimicrobial agent against Gram-negative (Escherichia.coli), Gram-positive (Bacillus.subtilis) bacteria and yeast (Saccharomyces cerevisiae). The obtained results showed significant inhibition of these strain even at low concentration of CeO2-NPs. The CeO2-NPs with the molar ratio 5:20 had the most effective inhibition against E.coli (~70%) at a concentration of 20 µL. The CeO2-NPs with the ratio 12:20 were found to be the most effective against B.subtilis (inhibition ~68%). On the other hand, CeO2-NPs synthesized with the 20:20 molar ratio caused the highest inhibition for S. cerevisiae (~60%). It is observed that at higher NPs concentration (i.e., >20 µL) the inhibition of these strains decreased. The antimicrobial activity may be attributed to the penetrating power of CeO2-NPs size beside the generated oxygen species radicals that caused inhibition of bacterial growth.Graphical abstract