Browsing by Author "Wunderlich, W"

Now showing 1 - 5 of 5
  • Item
    An aqueous method for the controlled manganese (Mn2+) substitution in superparamagnetic iron oxide nanoparticles for contrast enhancement in MRI
    (PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 2015) Beeran, AE; Nazeer, SS; Fernandez, FB; Muvvala, KS; Wunderlich, W; Anil, S; Vellappally, S; Rao, MSR; John, A; Jayasree, RS; Varma, PRH
    Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential. In this context, an in situ substitution of Mn2+ was performed in SPION and a series of ferrite particles, MnxFe1-xFe2O4 with a varying molar ratio of Mn2+ : Fe2+ where 'x' varies from 0-0.75. The ferrite particles obtained were further studied in MRI contrast applications and showed appreciable enhancement in their MRI contrast properties. Manganese substituted ferrite nanocrystals (MnIOs) were synthesized using a novel, one-step aqueous co-precipitation method based on the use of a combination of sodium hydroxide and trisodium citrate (TSC). This approach yielded the formation of highly crystalline, superparamagnetic MnIOs with good control over their size and bivalent Mn ion crystal substitution. The presence of a TSC hydrophilic layer on the surface facilitated easy dispersion of the materials in an aqueous media. Primary characterizations such as structural, chemical and magnetic properties demonstrated the successful formation of manganese substituted ferrite. More significantly, the MRI relaxivity of the MnIOs improved fourfold when compared to SPION crystals imparting high potential for use as an MRI contrast agent. Further, the cytocompatibility and blood compatibility evaluations demonstrated excellent cell morphological integrity even at high concentrations of nanoparticles supporting the non-toxic nature of nanoparticles. These results open new horizons for the design of biocompatible water dispersible ferrite nanoparticles with good relaxivity properties via a versatile and easily scalable co-precipitation route.
  • Item
    An aqueous method for the controlled manganese (Mn2+) substitution in superparamagnetic iron oxide nanoparticle for contrast enhancement in MRI
    (Physical Chemistry Chemical Physics., 2015-01) Beerana, AE; Nazeerb, SS; Fernandezc, FB; Muvvala, KS; Wunderlich, W; Anil, S; Vellappally, S; Rao, R; John A, A; Jayasree, RS; Varma, HK
    Despite the success in the use of superparamagnetic iron oxide nanoparticles (SPION) for various scientific applications, its potential in biomedical fields has not been exploited to its full potential. In this context, an in situ substitution of Mn2+ was performed in SPION and a series of ferrite particles, MnxFe1−xFe2O4 with a varying molar ratio of Mn2+ : Fe2+ where ‘x’ varies from 0–0.75. The ferrite particles obtained were further studied in MRI contrast applications and showed appreciable enhancement in their MRI contrast properties. Manganese substituted ferrite nanocrystals (MnIOs) were synthesized using a novel, one-step aqueous co-precipitation method based on the use of a combination of sodium hydroxide and trisodium citrate (TSC). This approach yielded the formation of highly crystalline, superparamagnetic MnIOs with good control over their size and bivalent Mn ion crystal substitution. The presence of a TSC hydrophilic layer on the surface facilitated easy dispersion of the materials in an aqueous media. Primary characterizations such as structural, chemical and magnetic properties demonstrated the successful formation of manganese substituted ferrite. More significantly, the MRI relaxivity of the MnIOs improved fourfold when compared to SPION crystals imparting high potential for use as an MRI contrast agent. Further, the cytocompatibility and blood compatibility evaluations demonstrated excellent cell morphological integrity even at high concentrations of nanoparticles supporting the non-toxic nature of nanoparticles. These results open new horizons for the design of biocompatible water dispersible ferrite nanoparticles with good relaxivity properties via a versatile and easily scalable co-precipitation route.
  • Item
    High surface area sol-gel alumina-titania nanocatalyst
    (JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2009) Padmaja, P; Warrier, KGK; Padmanabhan, M; Wunderlich, W
    Alumina-titania mixed oxide nanocatalysts with molar ratios = 1:0.5, 1:1, 1:2, 1:5 have been synthesized by adopting a hybrid sol-gel route using boehmite sol as the precursor for alumina and titanium isopropoxide as the precursor for titania. The thermal properties, XRD phase analysis, specific surface area, adsorption isotherms and pore size details along with temperature programmed desorption of ammonia are presented. A specific surface area as high as 291 m(2)/g is observed for 1:5 Al(2)O(3)/TiO(2) composition calcined at 400 A degrees C, but the same composition when calcined at 1,000 A degrees C, resulted in a surface area of 4 m(2)/g, while 1:0.5 composition shows a specific surface area of 41 m(2)/g at 1,000 A degrees C. Temperature programmed desorption (of ammonia) results show more acidic nature for the titania rich mixed oxide compositions. Transmission electron microscopy of low and high titania content samples calcined at 400 A degrees C, shows homogeneous distribution of phases in the nano range. In the mixed oxide, the particle size ranges between 10-20 nm depending on titania content. The detailed porosity data analysis contributes very much in designing alumina-titania mixed oxide nanocatalysts.
  • Item
    High-Surface-Area Alumina-Silica Nanocatalysts Prepared by a Hybrid Sol-Gel Route Using a Boehmite Precursor
    (JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2010) Nampi, PP; Moothetty, P; Wunderlich, W; Berry, FJ; Mortimer, M; Creamer, NJ; Warrier, KG
    High-surface-area alumina-silica mixed oxide (Al(2)O(3):SiO(2)) nanocatalysts have been prepared by a hybrid sol-gel method using boehmite (synthesized from aluminum nitrate) as the source of alumina and tetraethyl orthosilicate as the source of silica. The gels, after calcination at 400 degrees C, result in mixed oxides with specific surface areas of 287 m2/g (Al(2)O(3):SiO(2)=3:1) and 262 m2/g (Al(2)O(3):SiO(2)=3:4). Further heating to 600 degrees C produces materials with specific surface areas of 237 and 205 m2/g, respectively. The larger specific surface areas characteristic of the 3Al(2)O(3):SiO(2) samples are attributed, via transmission electron micrograph investigations, to the presence of similar to 10 nm size, needle-like particles having an aspect ratio of 1:50. Further addition of silica leads to the formation of larger needles of 20-75 nm size. Calcination at 600 degrees C induced an approximately 5% decrease in the total pore volume for the 3Al(2)O(3):SiO(2) sample. In contrast, the material with Al(2)O(3):SiO(2)=3:4 showed an approximately 12% increase in pore volume when heated at 600 degrees C. The pore-size distribution was in the range 1-3.5 nm with r(max) at similar to 2 and similar to 2.5 nm at 600 degrees and 800 degrees C, respectively. Adsorption isotherms and pore-size distribution analyses are discussed in some detail for the aluminosilicates at different calcination temperatures. This discussion is supported by structural information determined from FTIR and 27Al MAS NMR studies. Relatively high acidity values (0.234 mmol/g for Al(2)O(3): SiO(2)=3:4) are observed for silica-rich compositions consistent with their application as efficient acid catalysts.
  • Item
    Synthesis and Characterization of Iron Oxide Embedded Hydroxyapatite Bioceramics
    (JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 2012) Ansar, EB; Ajeesh, M; Yokogawa, Y; Wunderlich, W; Varma, H
    A homogeneous dispersion of nano iron oxide (IO) crystallites inside the hydroxyapatite (HA) particles was achieved by a co-precipitation method. This highly stable colloidal dispersion of magnetic nano composite (HAIO) was made without the use of any surfactants. The in situ generated dispersion of the composite powders showed submicron HA particles with 5 nm iron oxide inside. The phase analysis results showed the presence of hydroxyapatite (HA) and iron oxide with no tertiary phase. The enhancement of relative peak intensities with increased percentage of iron oxide phase in X-ray diffraction analysis suggests the formation of iron oxide together with HA without affecting the phase purity of the latter, which is important when the biological behavior of HA is concerned. This also confirms the quantitative nature of the precipitated nanocomposites. The High Resolution Transmission Electron Microscope (HRTEM) of the composite shows elongated crystal flakes or platelike surfaces of HA crystallites having particle sizes in the range 70-100 nm. HRTEM with XRD analysis matches HAIO only with iron oxide particles of Magnetite (Fe3O4) and HA phases. The FTIR data confirm that the introduction of iron oxide did not produce any considerable change in the chemical structure of HA.