Exploration of sorption properties of sonochemically synthesized BaMoO<SUB>4</SUB> nanoparticles for hazardous cationic dye removal

We report the synthesis of barium molybdate (BaMoO4) nanoparticles via a simple sonochemical technique. The nanoparticles have been characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM. The surface area of the nanoparticles has been determined using Brunauer-Emmett-Teller (BET) analysis. The as-prepared spherical BaMoO4 nanostructures demonstrate excellent adsorbent properties to remove harmful organic dyes like Rhodamine B (RhB), Malachite green (MG) and Methylene blue (MB). The effect of pH, concentration of dye and loading of sorbent on the process of adsorption has been evaluated. Kinetic study on the adsorption process has been discussed using Langmuir and Freundlich models. Regeneration of the sorbents is easily possible through simple thermal treatment and similar adsorption efficiency upto five consecutive cycles has been demonstrated. The dye adsorbed on BaMoO4 samples have also been tested for photocatalytic degradation. In principle, these BaMoO4 nanostructures with higher adsorption abilities could be very promising adsorbents for treatment of cationic dye effluent from various industries

Nanostructured PdO Thin Film from Langmuir–Blodgett Precursor for Room-Temperature H₂ Gas Sensing

Nanoparticulate thin films of PdO were prepared using the Langmuir–Blodgett (LB) technique by thermal decomposition of a multilayer film of octadecylamine (ODA)–chloropalladate complex. The stable complex formation of ODA with chloropalladate ions (present in subphase) at the air–water interface was confirmed by the surface pressure–area isotherm and Brewster angle microscopy. The formation of nanocrystalline PdO thin film after thermal decomposition of as-deposited LB film was confirmed by X-ray diffraction and Raman spectroscopy. Nanocrystalline PdO thin films were further characterized by using UV–vis and X-ray photoelectron spectroscopic (XPS) measurements. The XPS study revealed the presence of prominent Pd²⁺ with a small quantity (18%) of reduced PdO (Pd⁰) in nanocrystalline PdO thin film. From the absorption spectroscopic measurement, the band gap energy of PdO was estimated to be 2 eV, which was very close to that obtained from specular reflectance measurements. Surface morphology studies of these films using atomic force microscopy and field-emission scanning electron microscopy indicated formation of nanoparticles of size 20–30 nm. These PdO film when employed as a chemiresistive sensor showed H₂ sensitivity in the range of 30–4000 ppm at room temperature. In addition, PdO films showed photosensitivity with increase in current upon shining of visible light