Sangeeta Kale

We report on comparison of zinc oxide nanoparticles with bulk powders as candidates for decolorisation of organic dyes in the textile industry. X-ray diffraction showed pure phase catalysts; while ultraviolet-visible (UV-vis) spectroscopy showed larger absorbance in a wide visible range of spectrum for bulk, compared to nanopowders. Two dyes, Methylene Blue (MB) and Methyl Orange (MO) were treated with these catalysts in solar light. UV-vis studies showed ZnO bulk to completely decolorise both the dyes in < 20 min; as against its nano form. When decolorised components were evaluated it was found that the treated components were much in the safety regime as prescribed by WHO standards and were found to be Na, Zn, S, SO4 2-, NO2 and NO3 -. Cell line studies performed on these treated samples showed the cell viability of ~ 100% on SiHa and B16F10 cell lines as well as on mouse primary fibroblasts, giving evidence of non-toxicity of the catalyst, as well as the byproducts upon treatm...

Monodispersed, superparamagnetic nickel cobaltite (NCO) nanoparticles were functionalized using mercaptopropionic acid (MPA). MPA conjugates with NCO forming a metal-carboxylate linkage, with the MPA-MPA interaction occurring via formation of disulfide bonds, leaving another carboxyl end free for additional conjugation. The cytotoxicity studies on NCO-MPA show cell viability of ∼100% up to a dosage of 40 μg/mL on SiHa, MCF7, and B16F10 cell lines, and on mouse primary fibroblasts. Time-dependent cell viability studies done for a duration of 72 hours showed the cell lines' viability up to 80% for dosages as high as 80 μg/mL. Negligible leaching (<5 ppm) of ionic Co or Ni was noted into the delivery medium. Upon subjecting the NCO-MPA dispersion (0.1 mg/mL) to radiofrequency absorption, the nanoparticles were heated to 75°C within 2 minutes, suggesting its promise as a magnetic hyperthermia agent. Furthermore, the amino acid lysine and the drug cephalexin were successfully adducted to the NCO system, suggesting its potential for drug delivery. NCO-MPA nanopartciles were found to be promising magnetic hyperthermia agents, suggesting potential future clinical applications.

ABSTRACT The perovskite manganite systems have been the materials of tremendous interest due to their strong correlation between structure, transport and magnetism. These materials in their single-crystal form show colossal magneto-resistance (CMR), but the applied fields are very high (∼1–5 T). The polycrystalline samples do show high low-field magneto-resistance (LFMR), but good amount of control over particle sizes and grain-boundary distribution is required, which is well known but less realized in practical approaches. In this context, we report on synthesis and manipulation of polycrystalline La0.7Ba0.3MnO3 (LBMO) submicron powders using citric acid chelation. The Citrate-gel route is used to synthesize poly-dispersed LBMO powders which are subjected to citrate chelation for a duration of 0 (LB0) to 4 h(LB4) . The samples show improved ordering in X-ray diffraction patterns. Raman spectroscopy scans indicate changed mode signatures due to the probable chelating process, which alters the surface morphology. X-ray photoelectron microscopy shows an evidence of fine citrate layer on the grain boundaries. Low temperature B–H curves exhibit fine hysteresis loops for all samples, while room temperature B–H curves shows paramagnetic response. Scanning electron microscopy images showed the formation of well arranged, connected, mono-dispersed grains of LB4 sample, as against polydispered LB0. The magneto-resistance (at H=100 kOe) is seen to enhance for LB4 at its transition temperature (75%, as compared to LB0, where it is 60%), which can be attributed to the well-controlled inter-grain tunneling phenomenon and thin insulating regions in between, created due to citrate chelation, which probably enhances the scattering phenomenon and its susceptibility to applied fields. As citric acid is known to chelate Mn ions, it probably chelates the smaller LB particulate structure and leaves behind citrate-connected submicron grains of LBMO, which are seen to be well engineered.

We will present measurements on the temperature dependence of the microwave loss (P_L) and the d.c. resistivity (rho) in (La_1-xPr_x)_0.7Ca_0.3MnO_3. As expected, both sets of data exhibit maxima. However, as x (tolerance factor) is increased (reduced) a large discrepancy develops between the peak in (rho) and that in (P_L), the latter lying lower by several tens of degree. Surprisingly, the microwave data also exhibit a more pronounced thermal hysteresis than found in (rho). Most likely, these crystallographically single phase materials undergo a first order transition to a state composed of several coexisting phases upon cooling, thereby yielding vastly different d.c. and a.c. conductivities. Work supported in part by MRSEC grant # DMR-00-80008.