Sub PPM Detection of NO2 Using Strontium Doped Bismuth Ferrite Nanostructures

The present work investigates the NO₂ sensing properties of acceptor-doped ferrite perovskite nanostructures. The Sr-doped BiFeO₃ nanostructures were synthesized by a salt precursor-based modified pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The synthesized materials were drop coated to fabricate chemoresistive gas sensors, delivering a maximum sensitivity of 5.2 towards 2 ppm NO₂ at 260 °C. The recorded values of response and recovery time are 95 s and 280 s, respectively. The sensor based on Bi_0.8Sr_0.2FeO_3-δ (BSFO) that was operated was shown to have a LOD (limit of detection) as low as 200 ppb. The sensor proved to be promising for repeatability and selectivity measurements, indicating that the Sr doping Bismuth ferrite could be a potentially competitive material for sensing applications. A relevant gas-sensing mechanism is also proposed based on the surface adsorption and reaction behavior of the material.

Widening of the electroactivity potential range by composite formation - capacitive properties of TiO2/BiVO4/PEDOT:PSS electrodes in contact with an aqueous electrolyte

Composites based on the titania nanotubes were tested in aqueous electrolyte as a potential electrode material for energy storage devices. The nanotubular morphology of TiO2 was obtained by Ti anodization. TiO2 nanotubes were covered by a thin layer of bismuth vanadate using pulsed laser deposition. The formation of the TiO2/BiVO4 junction leads to enhancement of pseudocapacitance in the cathodic potential range. The third component, the conjugated polymer PEDOT:PSS, was electrodeposited from an electrolyte containing the monomer EDOT and NaPSS as a source of counter ions. Each stage of modification and deposition affected the overall capacitance and allowed for an expansion of the potential range of electroactivity. Multiple charge/discharge cycles were performed to characterize the electrochemical stability of the inorganic-organic hybrid electrode. Capacitance values higher than 10 mF·cm-2 were maintained even after 10000 galvanostatic cycles (i c = i a = 0.5 mA·cm-2).

Photocatalytic activity of V doped ZnO nanoparticles thin films for the removal of 2- chlorophenol from the aquatic environment under natural sunlight exposure

Vanadium doped ZnO powders were used as precursors to deposit thin films of V(5+) incorporated ZnO nanoparticles on glass substrates by the pulsed laser deposition technique. The observed variations in Raman signals, visible region shift in the diffuse reflectance spectra along with a small shift in the (101) reflections of the X-ray diffraction (XRD) confirmed the insertion of V(5+) ions in ZnO lattice. No other additional reflection in the XRD results other than ZnO further endorsed the occupation of lattice positions by V entities rather than independent oxide formation. The asymmetric XPS peaks of Zn2p and V2p core levels confirmed the existence of both in the vicinity. The existence of minimal proportion of V(3+) along with V(5+) states varied the alteration of the oxidation states V in the synthetic route. The SEM images at various resolutions displayed the uniform distribution identical nanoparticles without the presence of additional phases in the deposited films. The SEM cross-section measurements revealed the uniform thickness of ∼90 nm of each film, whereas the surface studies of the films were performed by AFM. The as-synthesized films were tested for photocatalytic activity in sunlight illumination for the removal of 2-chlorophenol. The unique feature of the study was the estimation of the photocatalytic activity 20 ppm of 2-chlorophenol by exposing the low exposed area. The degradation of the substrate was measured by liquid phase UV-vis spectroscopy, whereas total organic carbon measurement revealed the mineralization of the substrate. The released Cl(-) ions were also measured by ion chromatography. The estimated flatband potentials and pHzpc values of the V doped materials, by Mott-Schottky analysis and zeta potential measurements respectively, were correlated with the photocatalytic activity. The kinetics of the photocatalytic degradation/mineralization process was estimated and results were correlated with the plausible mechanism.