An aqueous method for the controlled manganese (Mn(2+)) substitution in superparamagnetic iron oxide nanoparticles for contrast enhancement in MRI.

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 Mn(2+) was performed in SPION and a series of ferrite particles, MnxFe1-xFe2O4 with a varying molar ratio of Mn(2+) : Fe(2+) 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.

Critical nuclei size, initial particle size and packing effect on the phase stability of sol-peptization-gel-derived nanostructured titania.

The influence of the initial particle size and packing of anatase crystallites on the phase stability of nanostructured titania was investigated. Dried anatase gels with different degrees of particle packing were prepared through the peptization-induced electrostatic stabilization of primary particles in the sol. The initial size of anatase primary particles was varied by precalcination prior to the anatase-rutile phase transformation that occurred during final calcination. In the case of well-packed titania, the initial size of anatase primary particles does not influence the phase-transformation behavior whereas loosely packed titania shows a strong initial anatase primary particle size dependence on the phase-transformation behavior.

Preparation and Photocatalytic Properties of CdS and ZnS Nanomaterials Derived from Metal Xanthate.

In this paper, we report a new, simple method for the synthesis of CdS and ZnS nanoparticles (NPs) prepared in a basic aqueous medium using metal xanthate as the sulfur source. The structure, morphology, size distribution, optical band gap, and photocatalytic properties of the newly obtained nanomaterials were investigated by UV-Vis spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that both CdS and ZnS crystallized in cubic phase and formed NPs with average sizes of 7.0 and 4.2 nm for CdS and ZnS, respectively. A blue shift of UV-Vis absorbance band and higher energy band gap values were observed for both materials in comparison with their bulk counterparts, which is in accordance with the quantum confinement effect. The as-prepared nanomaterials were tested in visible-light driven photocatalytic decomposition of methylene blue (MB). After irradiation for 180 min, the degradation rate of MB with a concentration of 8 × 10-6 mol/L mixed with a photocatalyst (CdS or ZnS, both 10 mg in 100 mL solution of MB) was found to be 72% and 61%, respectively. The CdS NPs showed better photocatalytic activity than ZnS, which could be explained by their lower energy band gap and thus the ability to absorb light more efficiently when activated by visible-light irradiation.

Laser-Ablated ZnO Nanoparticles and Their Photocatalytic Activity toward Organic Pollutants.

This work aimed to prepare nanostructures of ZnO with various lasers, testing them as photocatalysts, and comparing their morphology and activity in the degradation of organic pollutants in aqueous media. ZnO nanospheres (ns-ZnO) and ZnO nanorods (ms-ZnO) were prepared via the laser ablation of a Zn metal plate in water using nanosecond- and millisecond-pulsed lasers, respectively. The obtained materials were characterized using a set of optical, structural, and surface-science techniques, such as UV-vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Under visible-light irradiation, both nanostructures were found to be catalytically active toward the oxidation of methylene blue, which was used as a model compound. The ZnO nanorods fabricated with the millisecond laser showed better photocatalytic performance than their spherically shaped counterparts obtained by means of the nanosecond laser, which could be assigned to a larger number of defects on the ms-ZnO surface.