Dielectric relaxation, diffuseness and conductivity behavior of transition metal-ion substituted SrBi2Nb2O9 synthesized by chemical route

Nanocrystalline Sr(0.5)A(0.5)Bi(2)Nb(2)O(9) powders (A = Co2+, Ni2+, Cu2+; abbreviated as SCoBN, SNiBN, SCuBN respectively) were synthesized by chemical route. Powder X-ray diffraction study confirmed the tetragonal phase when calcined at 650 A degrees C for 2 h. Average crystallite and particle size were calculated to be between 15 and 25 nm. The tetragonality was increased from Co2+ to Ni2+ to Cu2+-substituted SrBi2Nb2O9. SCuBN showed highest dielectric constant of 1344 and a loss in the order of 10(-2) when measured at 100 kHz. SNiBN and SCuBN showed relaxation behavior and maximum diffusivity of 1.88 was observed for the later composition. The activation energy was calculated from DC and AC conductivity. Hysteresis loops displayed by the ceramics giving rise to a remnant polarization (P-r) of 0.046 mu C/cm(2) and a coercive field (E-c) of 495 V/cm for SCuBN. Both SCuBN and SNiBN showed high fatigue endurance values with a fatigue free behavior up to 10(5) switching cycles

Investigation of density of states and electrical properties of Ba0.5Co0.5Bi2Nb2O9 nanoceramics prepared by chemical route

Barium-cobalt-bismuth-niobate, Ba0.5Co0.5Bi2Nb2O9 (BCoBN) nanocrystalline ferroelectric ceramic was prepared through chemical route. XRD analysis showed single phase layered perovskite structure of BCoBN when calcined at 650 A degrees C, 2 h. The average crystallite size was found to be 18 nm. The microstructure was studied through scanning electron microscopy. The dielectric and ferroelectric properties were investigated in the temperature range 50-500 A degrees C. The dielectric constant and dielectric loss plot with respect to temperature both indicated strong relaxor behavior. Frequency versus complex impedance plot also supported the relaxor properties of the material. The impedance spectroscopy study showed only grain conductivity. Variation of ac conductivity study exhibited Arrhenius type of electrical conductivity where the hopping frequency shifted towards higher frequency region with increasing temperature. The ac conductivity values were used to evaluate the density of state at the Fermi level. The minimum hopping distance was found to be decreased with increasing temperature

Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl3 center dot 6H(2)O at 120 degrees C in the presence of sodium acetate as an alkali source and 2,2'-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 +/- 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T-2 contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations

Biofunctionalized, phosphonate-grafted, ultrasmall iron oxide nanoparticles for combined targeted cancer therapy and multimodal

A novel, inexpensive biofunctionalization approach is adopted to develop a multimodal and theranostic nanoagent, which combines cancer-targeted magnetic resonance/optical imaging and pH-sensitive drug release into one system. This multifunctional nanosystem, based on an ultrasmall superparamagnetic iron oxide (USPIO) nanocore, is modified with a hydrophilic, biocompatible, and biodegradable coating of N-phosphonomethyl iminodiacetic acid (PMIDA). Using appropriate spacers, functional molecules, such as rhodamine B isothiocyanate, folic acid, and methotrexate, are coupled to the amine-derivatized USPIO-PMIDA support with the aim of endowing simultaneous targeting, imaging, and intracellular drug-delivering capability. For the first time, phosphonic acid chemistry is successfully exploited to develop a stealth, multifunctional nanoprobe that can selectively target, detect, and kill cancer cells overexpressing the folate receptor, while allowing real-time monitoring of tumor response to drug treatment through dual-modal fluorescence and magnetic resonance imaging

Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl3·6H2O at 120°C in the presence of sodium acetate as an alkali source and 2, 2'-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 ± 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T2 contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations