Sol-Gel Route for the Synthesis of CoFe2-x Er x O4 Nanocrystalline Ferrites and the Investigation of Structural and Magnetic Properties for Magnetic Device Applications.

This study reports the formation of Er-doped nanocrystalline cobalt ferrite with the formula CoFe2-x Er x O4 (0.0 ≤ x ≤ 0.10) from nontoxic metal precursors Co(NO3)2·6H2O, Fe(NO3)3·9H2O, and Er(NO3)3·5H2O through an easy and economical sol-gel route in which citric acid is served as the chelating agent. The as-prepared powder was annealed at 700 °C for 3 h in ambient air to get the required spinel structure. The annealed samples were subjected to structural and magnetic characterization. The X-ray diffraction (XRD) data of the samples confirmed the cubic spinel structure formation. The average crystallite size evaluated from XRD data increased from 21 to 34 nm with the substitution of Er due to the larger atomic size of Er3+ than Fe3+. Moreover, the crystallite size obtained from XRD data are well matched with the particle size measured from transmission electron microscopy images. The lattice parameters obtained from XRD data agree well with the values estimated from theoretical cation distribution and Rietveld refinement calculation. The hysteresis curve exhibits the particles are soft ferromagnetic and the coercivity increased from 54.7 to 76.6 kA/m with maximum saturation magnetization, M s = 61 emug-1 for 0.10 Er content. The squareness ratios were found to be less than 0.5, which indicates the single-domain nature of our particles. The blocking temperature measured from field cooled-zero field cooled curves is T B > 350 K for all the samples, which is much higher than the room temperature (300 K). The enhancement of saturation magnetization and coercivity has been explained based on the crystallite size, anisotropy constant, and cation distribution. Thus, the structural and magnetic properties of CoFe2O4 nanoparticles (NPs) can be tuned by Er incorporation and these NPs can be applied in different soft magnetic devices.

Evaluation of the Thermoelectric Properties and Thermal Conductivity of CH3NH3PbI3-x Cl x Thin Films Prepared by Chemical Routes.

The thermoelectric properties and thermal conductivity of mixed-phase CH3NH3PbI3-x Cl x thin films have been reported as a function of temperature, ranging from room temperature (RT) to 388 K. Thermoelectric study confirms that CH3NH3PbI3-x Cl x is a p-type material and the charge carrier transport in CH3NH3PbI3-x Cl x is governed by polarons and the thermal scattering process. The Peltier function and power factor are found to decrease initially up to ∼325 K, after which they increase with increasing temperature. The position of (E F - E V) of all samples drops down sharply to zero level around 325 K. The avalanches of thermoelectric properties at ∼325 K indicate the existence of tetragonal-cubic phase transition in CH3NH3PbI3-x Cl x . The calculated thermal conductivity is very low, as desired for thermoelectric materials, due to strong anharmonic interactions. Both the figure of merit (ZT) and device efficiency increase with increasing temperature. However, ZT remains small with temperature. Despite the limitations on the operating temperature range due to phase complexity and small ZT, CH3NH3PbI3-x Cl x exhibits reasonable thermoelectric power and low thermal conductivity. This signifies the possibility of CH3NH3PbI3-x Cl x as a prospective thermoelectric material.

Synthesis of 4-aryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinazoline-2-one/thione-5-one derivatives and evaluation as antibacterials.

A novel, ecofriendly, one pot solvent free method for the synthesis of 4-aryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinazoline-2-one/thione-5-one derivatives is described which devoids the use of any organic solvents and auxiliaries. All the synthesized compounds were screened for their in vitro antibacterial activity against standard strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa.

Aqua mediated synthesis of substituted 2-amino-4H-chromenes and in vitro study as antibacterial agents.

A simple, clean, environmentally benign route to the synthesis of 2-amino-chromenes is described using K2CO3 as a green catalyst in water under microwave irradiation. This implies a convenient route avoiding the usage of hazardous organic solvents and organic bases. This technique requires only water in both the reaction step and workup, thus rendering the whole procedure into a truly ecofriendly green protocol. All the synthesized compounds were shown to possess antibacterial activity as tested in vitro against standard strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.