Joan M. Raitano

Controlled synthesis of Co3O4 nanopolyhedrons and nanosheets at low temperature

Cobalt oxide (Co(3)O(4)) nanopolyhedrons and nanosheets were controlled synthesized at the low temperature of 80 degrees C via a novel, simple, aqueous method; the obtained nanosheets are only 2-3 nm thick.

Phase stability in ceria-zirconia binary oxide nanoparticles: The effect of the Ce3+ concentration and the redox environment

The stability of the cubic phase (c′) of Ce1−xZrxO2−y nanoparticles was studied by x-ray absorption near edge spectroscopy (XANES), time-resolved high temperature x-ray diffraction (XRD), and room temperature XRD. A clear relationship between the phase stability of the c′ phase and the Ce3+ concentration was found in zirconia-doped ceria, prepared in an oxidizing environment. The percentage of the 3+ oxidation state of cerium was measured from the relative Ce3+ peak intensity at the CeLIII edge in XANES. A concentration of 11% of the larger Ce3+ ions, among all cerium ions, helps to release the local stress induced by the smaller Zr4+ ions and stabilizes the c′ phase even under high zirconia concentrations of 40%–60%. A smaller particle size enhances this effect. XANES results at the ZrLIII edge supported the cubic phase stabilization. When the homogenization anneal was performed under a reducing environment instead of in air, the solubility limit of the cubic phase Ce1−xZrxO2−y was extended to above 90% ...

In situ ultra-small-angle X-ray scattering study of the solution-mediated formation and growth of nanocrystalline ceria

Results are presented for an in situ synchrotron-based ultra-small-angle X-ray scattering (USAXS) study of the solution-mediated formation and growth of nanocrystalline ceria (n-CeO2) using a new remote-controlled, isothermal, circulating fluid flow cell. The fluid flow mitigates or reduces X-ray beam-induced damage, air bubbles or particulate flocculation within the bulk solution, but prevents any coarse particulates that do form from settling out from suspension. Combined with the large-scale range accessible in USAXS studies, the flow cell has enabled measurement, in situ and in real time, of structural characteristics from 10 A to a few micrometres in size as a function of the changing physical and chemical conditions. By applying a multi-component model, the nanoparticle formation and growth component has been identified. Control and online monitoring of flow rate, temperature and pH suspension conditions have permitted real-time studies of the formation and growth of the individual n-CeO2 particles from homogeneous dilute solution over several hours. Aspects of the nanoparticle nucleation and growth are revealed that have not been observed directly in measurements on this system.

Accessing the genomic effects of naked nanoceria in murine neuronal cells.

UNLABELLED Cerium oxide nanoparticles (nanoceria) are engineered nanoparticles whose versatility is due to their unique redox properties. We and others have demonstrated that naked nanoceria can act as antioxidants to protect cells against oxidative damage. Although the redox properties may be beneficial, the genome-wide effects of nanoceria on gene transcription and associated biological processes remain elusive. Here we applied a functional genomic approach to examine the genome-wide effects of nanoceria on global gene transcription and cellular functions in mouse neuronal cells. Importantly, we demonstrated that nanoceria induced chemical- and size-specific changes in the murine neuronal cell transcriptome. The nanoceria contributed more than 83% of the population of uniquely altered genes and were associated with a unique spectrum of genes related to neurological disease, cell cycle control, and growth. These observations suggest that an in-depth assessment of potential health effects of naked nanoceria and other naked nanoparticles is both necessary and imminent. FROM THE CLINICAL EDITOR Cerium oxide nanoparticles are important antioxidants, with potential applications in neurodegenerative conditions. This team of investigators demonstrated the genomic effects of nanoceria, showing that it induced chemical- and size-specific changes in the murine neuronal cell transcriptome.

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

Amorphous hafnia (HfO2−y), zirconia (ZrO2−y), and hafnia-zirconia (xHfO2−y–(1−x)(ZrO2−y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2⋅8H2O), zirconium dichloride oxide (ZrOCl2⋅8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M–0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structu...