Modeling,Structural, and Spectroscopic Studies of Cobalt-doped Lithium Phosphate Glasses and Effect of Gamma Irradiation

Undoped and cobalt oxide-doped lithium phosphate glasses were prepared by normal melt annealing technique. The structure and optical properties were investigated in order to understand the spectroscopic properties and state of cobalt in this host glass. The glass samples were characterized by combined UV-Visible and Fourier transform infrared absorption spectroscopic techniques. Ultraviolet and visible spectroscopy is used to determine the optical absorption spectra of the base undoped glass and that due to the cobalt ions in this host glass. Spectroscopic investigations were approved using the density functional theory calculations, which were employed to interpret both theoretical and experimental IR data of this glass system and to identify the main building structural groups present in these glasses. Experimental results indicate that divalent cobalt ions occupy more than one coordination state, namely, the octahedral and tetrahedral forms. The changes in the UV-Vis and infrared spectral data are discussed in relation to the change in the state of cobalt ions with glass composition or dopant concentration or structural evolution caused by the changes in glass constituents.     

Effect of gamma-irradiation on the structural,optical and electrical properties of PEO/starch blend containing different concentrations of gold nanoparticles

ABSTRACT

Blend of polyethylene oxide (PEO)/starch (70/30 wt.%) filled with different amounts of gold nanoparticles (AuNPs) were prepared using the casting technique. X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) techniques were used to investigate the structure of polymeric samples before and after exposing to gamma irradiation at different times. XRD showed a gradual decrease in intensity of crystalline peaks with increasing the gamma dose denotes a decrease in the amount of crystalline phase in the films, while the FTIR measurement shows induced changes in chemical structure assigned to the AuNPs amount and irradiation times. The optical energy gap values (E_g) for unirradiated and irradiated samples were calculated and interpreted. The differential scanning calorimetry (DSC) which showed the miscibility between the two components of the blend. The electrical conductivity (σ) measurement was showed increased in electrical conductivity after exposure to the gamma dose. The gold nanoparticles were used as nano?ller to improve the structural and electrical properties of polymeric samples. The results showed the Gamma irradiation significantly effect on the structural and electrical properties of PEO/starch blend.     

UV-visible and infrared absorption spectra of gamma irradiated V2O5-doped in sodium phosphate, lead phosphate, zinc phosphate glasses: A comparative study

Radiation-induced defects generated by successive gamma irradiation have been investigated in V₂O₅-doped phosphate glasses of three basic compositions, namely, sodium metaphosphate, lead metaphosphate and zinc metaphosphate. Glasses were prepared from chemically pure materials. Melting was carried at 900°-1100 °C for 1 h and with several stirrings of the melt to achieve homogeneity. The glassy samples were annealed at 200°-250 °C and left to cool to room temperature at a rate of 20 °C/h. Polished samples from undoped and V-doped samples of equal thickness. ~ 2 mm were measured in a double beam UV-visible spectrophotometer at 200-1000 nm before and after gamma irradiation. Induced defects were analyzed for these three phosphate glass systems. Infrared absorption spectra were measured for the prepared undoped and V-doped samples by the KBr technique before irradiation and after being subjected to a high dose of 7 M Rads (7 × 10⁴ Gy). The cumulative effects of gamma irradiation on the UV-visible spectra are correlated with the intrinsic and extrinsic defects within the various three glasses. Some shielding behavior for the various glasses towards successive gamma irradiation are observed and realized in relation to the different partner anions studied. The effect of gamma irradiation on IR spectra indicates the persistence of the main characteristic bands due to phosphate network and the minor changes are correlated with the possible changes in the bond lengths and/or bond angles of the building units during the irradiation process. The effect of V₂O₅ on the IR spectra is correlated with the depolymerization effect of the glass network.