Shape-selective oriented cerium oxide nanocrystals permit assessment of the effect of the exposed facets on catalytic activity and oxygen storage capacity.

The catalytic performance of a range of nanocrystalline CeO2 samples, prepared to have different morphologies, was measured using two accepted indicators; oxygen storage and diesel soot combustion. The same powders were characterized in detail by HR-TEM, XRD, XPS, and Raman methods. The study demonstrates that activity is determined by the relative fraction of the active crystallographic planes, not by the specific surface area of the powders. The physical study is a step toward quantitative evaluation of the relative contribution to activity of the different facets. The synthetic protocol permits fabrication of CeO2 nanostructures with preferentially grown active planes, and therefore has potential in developing catalytic applications and in nanocompositing.

Mg-Al layered double hydroxide-methotrexate nanohybrid drug delivery system: evaluation of efficacy.

Mg-Al layered double hydroxide nanoparticles were synthesized by one-pot co-precipitation method and anticancerous drug methotrexate was incorporated into it by in-situ ion exchange. The LDH-MTX nanohybrid produced moderately stable suspension in water, as predicted by zeta potential measurement. X-ray diffraction revealed that the basal spacing increased to nearly twice the same for pristine LDH on MTX intercalation. Thermogravimetric analyses confirmed an increase in thermal stability of the intercalated drug in the LDH framework. A striking enhancement in efficacy/sensitivity of MTX on the HCT-116 cells was obtained when intercalated within the LDH layers, as revealed by the attainment of half maximal inhibitory concentration of LDH-MTX nanohybrid by 48 h, whereas, bare MTX required 72 h for the same. The MTX release from MgAl-LDH-MTX hybrids in phosphate buffer saline at pH7.4 followed a relatively slow, first order kinetics and was complete within 8 days following diffusion and crystal dissolution mechanism.

One-pot synthesis of ultra-small cerium oxide nanodots exhibiting multi-colored fluorescence.

CeO(2) nanodots of diameter 2nm have been synthesized by the thermolysis of cerium acetate in diphenylether in the presence of an oleic acid surfactant. The surfactant coating enabled them to be easily dispersible in nonpolar solvents. The CeO(2) dots exhibited size dependant optical properties such as a red shift in absorption and band gap. As a result, the surfactant coated CeO(2) nanocrystals emit photons in the visible region with broad photoluminescence spectra resulting in multi-colored fluorescence, which originates from defects associated with CeO(2) nanocrystals approaching molecular dimensions.

Photocatalytic activity enhancement in doped titanium dioxide by crystal defects.

Visible light sensitive Fe(3+) and Ce(4+) co-doped nano TiO(2) photocatalyst has been prepared by a modified aqueous sol-gel method and the activity has been measured in terms of degradation of MB dye. Both dopants shifted the absorption profile of TiO(2) to the visible region and improved activity. Fe(3+) ions trapped the charge carriers due to the stable electronic configuration and improved their separation. Ce(4+) ions, which were mainly located at the grain boundaries, cause dislocations by bending the valence and conduction bands of TiO(2) and prevent the recombination of photoexcited electrons and holes. The co-doped TiO(2) compositions exhibited higher photocatalytic activity than that of pure titania and commercially available Degussa P25 under visible light by utilising the individual and synergistic contributions of Fe(3+) and Ce(4+) dopants, respectively.

NMR studies into colloidal stability and magnetic order in fatty acid stabilised aqueous magnetic fluids.

We report the physico-chemical characterisation of fatty acid stabilised aqueous magnetic fluids, which are ideal systems for studying the influence of nanoparticle aggregation on the emergent magnetic resonance properties of the suspensions. Stable colloids of superparamagnetic magnetite, Fe(3)O(4), nanoparticle clusters in the 80 to 100 nm size range were produced by in situ nanoparticle growth and stabilisation, and by suspending pre-formed nanoparticles. NMR relaxation analysis shows that the magnetic resonance properties of the two types of suspension differ substantially and provides new insights into how the relaxation mechanisms are determined by the organisation of the nanoparticles within the clusters.

Preparation and characterization of guar gum nanoparticles.

The preparation of guar gum nanoparticles by nanoprecipitation and cross-linking method is reported here. Nanoparticles act as potential carries for several classes of drugs and cosmetics. It has been found that the formation of nanoparticles depends upon the molecular mass of the galactomannan, solvent, surfactant, cross-linker and agitation. The galactomannan nanoparticles functionalized with lipase and crystal violet as model drugs were used for release study. The sizes of the particles in suspension have been measured by light scattering technique. The size and the morphology of the particles have been determined by electron microscopy studies. Optimized method produced spherical nanoparticles of size approximately 20-50 nm with a polydispersity index in the range 0.1-0.4.

Nonaqueous magnetic nanoparticle suspensions with controlled particle size and nuclear magnetic resonance properties.

We report the preparation of monodisperse maghemite (gamma-Fe2O3) nanoparticle suspensions in heptane, by thermal decomposition of iron(III) acetylacetonate in the presence of oleic acid and oleylamine surfactants. By varying the surfactant/Fe precursor mole ratio during synthesis, control was exerted both over the nanocrystal core size, in the range from 3 to 6 nm, and over the magnetic properties of the resulting nanoparticle dispersions. We report field-cycling 1H NMR relaxation analysis of the superparamagnetic relaxation rate enhancement of nonaqueous suspensions for the first time. This approach permits measurement of the relaxivity and provides information on the saturation magnetization and magnetic anisotropy energy of the suspended particles. The saturation magnetization was found to be in the expected range for maghemite particles of this size. The anisotropy energy was found to increase significantly with decreasing particle size, which we attribute to increased shape anisotropy. This study can be used as a guide for the synthesis of maghemite nanoparticles with selected magnetic properties for a given application.

Magnetic-fluorescent nanocomposites for biomedical multitasking.

Fluorescent magnetite nanocomposites based on magnetic nanoparticles, a polyhedral octaaminopropylsilsesquioxane and a porphyrin derivative have been prepared. The intracellular uptake of the nanocomposites by macrophage and bone osteoblast cells, and their potential as MRI contrast agents, has been demonstrated.

Magnetic nanoparticle assemblies on denatured DNA show unusual magnetic relaxivity and potential applications for MRI.

Denatured (substantially single-stranded) herring sperm DNA acts as a template for the preparation of magnetic nanowires, forming stable aqueous suspensions, which exhibit unprecedentedly high relaxivity at low field, suggesting that the material may be a potentially useful reagent for MRI.