No abstract

In this work, new samples of PVA-TiO2/Cu nanocomposites were prepared via the casting method. The prepared samples were examined using different analytical methods. An XRD analysis showed the semi-crystalline nature of the PVA polymer, as well as showing a decrease in the degree of the crystallinity of the PVA structure as a result of the addition of the mixed nanoparticles. TEM images indicate the spherical shape of the Cu NPs, with a size ranging from 2 to 22 nm, and the rectangular shape of the TiO2 NPs, with a size ranging from 5 to 25 nm. It was evident via FTIR measurements that there were interactions between the functional groups of the PVA and the TiO2/Cu NPs. The optical properties of the PVA nanocomposites were improved with an increase in the content of the TiO2/Cu nanoparticles, as shown via a UV/Vis analysis. DSC curves showed an improvement in the thermal stability of the PVA-TiO2/Cu nanocomposites after the embedding of the TiO2/Cu nanoparticles. It was evident using impedance spectroscopy that the AC conductivity was improved by adding the TiO2 and Cu nanoparticles to the polymeric matrix. The maximum AC conductivity was found at 1.60 wt.% of TiO2/Cu nanoparticles in the PVA polymer, and this was 13.80 × 10−6 S/cm at room temperature. Relaxation occurred as a result of the charge carrier hopping between the localized state and the correlated barriers hopping model, describing the dominant mechanism, as presented in an electrical modulus analysis. These results indicate that the PVA-TiO2/Cu nanocomposite samples can be used in energy storage capacitor applications and in the alternative separator-rechargeable lithium-ion battery industry.

The diolefinic dye BQVB is an efficient fluorescer with φ f values as high as 0.82 in n-heptane. The dye exhibits low values of the excited state lifetimes of ca. 0.4 ns. Both electronic absorption and fluorescence spectra are sensitive to medium acidity, and in acidic media a strong fluorescence is obtained at 500 nm. The laser activity of BQVB has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 450 nm upon excitation by 337.1 nm nitrogen laser pulse. The excited state absorption S 2 r S 1 of BQVB has been measured using laser flash photolysis, and in DMF the S 2 r S 1 absorption occurs at ca. 762 nm. Energy transfer from BQVB to rhodamine 6G and to molecular oxygen has been studied. The quantum yields for the trans-cis photoisomerization (φ c ) of BQVB in different organic solvents are also reported.

No abstract

No abstract