Wet Chemical Feasible Synthesis of PPy-Nickel Oxide nanocomposites and their photocatalytic effects on Methylene Blue

In this paper, we report, the synthesis of conducting polymer nanocomposites of nickel oxide polypyrrole (NiO-PPy) doped with dodecyl benzene sulphonic acid for its application as a photocatalyst. In-situ polymerization of the pyrrole technique was employed along with oxidant ammonium persulphate and dodecyl benzene sulphonic acid as a dopant. The nanostructures were synthesized at different concentrations of NiO nanoparticles viz. 0.05 wt.%, 0.1 wt.%, 0.2 wt.% and 0.3 wt.%. The development of nanostructures was explored by Fourier Transform Infrared Spectrophotometer, Field Emission Scanning Electron Microscope, X-ray diffraction spectrometer, and electrical conductivity measurements. FTIR studies revealed a shift in the absorption band when pure PPy and NiO-PPy nanocomposites were studied, exhibiting the substantial interaction between the PPy network and the NiO. FE-SEM analysis demonstrated the consistent distribution of NiO with globular-shaped metal oxide materials in the PPy host template. The XRD studies for pure PPy revealed its amorphous nature while nanocomposites indicated the prominent NiO peaks arising from (111), (200) and (220) planes. The nanocomposites' direct electrical conductivity at room temperature was much higher than pure PPy. It was observed that the electrical conductivity for pure PPy was 0.409×10-5 S/cm while it substantially increased to 4.2×10-5 (S/cm) for 0.3% nanocomposite. The electrical studies revealed that the electrical conductivity goes on increasing with increased NiO concentration and then after a saturation point more PPy encapsulates the NiO and in turn reduces the electrical conductivity. With 50 mg of 0.3% nanocomposite, the photocatalytic degradation of the Methylene-Blue dye was 84.98%

Aluminium doped ZnO nanostructures for efficient photodegradation of indigo carmine and azo carmine G in solar irradiation

Aluminium doped zinc oxide (AZO) nanomaterials (AlxZn1-xO) with x fraction varying as 0.02 and 0.04 were synthesized using the auto-combustion method using glycine as a fuel. The synthesized catalysts were characterized with X-ray diffraction (XRD), UV–Visible Spectroscopy (UV–Vis), Raman spectroscopy, Photoluminescence (PL) spectroscopy, and High Resolution Transmission Electron Microscopy (HR-TEM). XRD results showed that synthesized materials possessed good crystallinity, while UV–VIS was employed to find the band gaps of synthesized materials. Raman was used to determine the vibrational modes in the synthesized nanoparticles, while TEM analysis was performed to study the morphology of the samples. Industrial effluents such as indigo carmine and azo carmine G were used to test the photodegradation ability of synthesised catalysts. Parameters such as the effect of catalyst loading, dye concentration and pH were studied. The reduction in crystallite size, band gap and increased lattice strain for the 4% AZO was the primary reason for the degradation in visible irradiation, degrading 97 and 99% equimolar concentrations of indigo carmine and azo carmine G in 140 min. The Al doped ZnO was found to be effective in faster degradation of dyes as compared to pure ZnO in presence of natural sunlight.This work was supported by an NPRP grant from the Qatar National Research Fund under NPRP12S-0131–190030

Enhanced thermoelectric performance in spark plasma textured bulk n -type BiTe 2.7 Se 0.3 and p-type Bi 0.5 Sb 1.5 Te 3

International audienceBulk p and n-type bismuth tellurides were prepared using spark plasma texturization method. The texture development along the uniaxial load in the 001 direction is confirmed from both x-ray diffraction analysis and electron backscattering diffraction measurements. Interestingly, those textured samples outperform the samples prepared by conventional spark plasma sintering (SPS) leading to a reduced thermal conductivity in the ab-plane. The textured samples of n-type BiTe2.7Se0.3 and p-type Bi0.5Sb1.5Te3 showed a 42% and 33% enhancement in figure of merit at room temperature, respectively, as compared to their SPS counterparts, opening the route for applications

Synthesis of In2-xGexO3 nanopowders for thermoelectric applications

Bulk ceramics In2-xGexO3 have been synthesized in air by using citrate gel process. Nanoparticles of less than 20 nm have been synthesized through an accurate control of the processing parameters. X-ray diffraction and scanning electron microscopy studies confirmed that the solubility limit of Ge in In2O3 (xℓ) is very small and that additions of more than about 0.5 at.% Ge lead to the presence of In2Ge2O7 inclusions. Thanks to a high interdispersion of metal ions and homogeneity in elemental composition of the nanopowders obtained by citrate gel process, well-dispersed In2Ge2O7 secondary phases can be formed in the Ge-doped In2O3 matrix. An abrupt increase in the electrical conductivity and in the carrier concentration with x is observed in the monophasic region (x , xℓ), whereas in the biphasic region (x . xℓ), these values do not vary significantly. Similarly, the thermopower |S| value is correlated to this variation decreasing as x increases for x , xℓ. Above the solubility limit, the decrease in the lattice thermal conductivity is shown to be dependent on the presence of well-dispersed In2Ge207 secondary phases. The dimensionless figure of merit value is increased up to 0.3, thanks to electron doping and phonon scattering

Enhanced thermoelectric performance in spark plasma textured bulk n -type BiTe 2.7 Se 0.3 and p-type Bi 0.5 Sb 1.5 Te 3

International audienc