Cerium oxide nanoparticles (CNPs) are of significant interest to the scientific community due to their widespread applications in a variety of fields. It is proposed that size-dependent variations in the extent of Ce3+ and Ce4+ oxidation states of cerium in CNPs determine the performance of CNPs in application environments. To obtain greater molecular and structural understanding of chemical state transformations previously reported for ceria of ≈3 nm nanoparticles (CNPs) in response to changing ambient conditions, micro-XRD and Raman measurements were carried out for various solution conditions. The particles were observed to undergo a reversible transformation from a defective ceria structure to a non-ceria amorphous oxyhydroxide/peroxide phase in response to the addition of 30% hydrogen peroxide. For CNPs made up of ∼8 nm crystallites, a partial transformation was observed, and no transformation was observed for CNPs made up of ∼40 nm crystallites. This observation of differences in size-dependent transition behavior may help explain the benefits of using smaller CNPs in applications requiring regenerative property.

Abstract: Introduction to the special issue on surface analysis, providing thumbnail sketches of several popular techniques. A table gives the capabilities of each technique.

Tissue engineering and regenerative medicine aim to achieve functional restoration of tissue or cells damaged through disease, aging, or trauma. Advancement of tissue engineering requires innovation in the field of three-dimensional scaffolding and functionalization with bioactive molecules. Nanotechnology offers advanced materials with patterned nano-morphologies for cell growth and different molecular substrates that can support cell survival and functions. Cerium oxide nanoparticles (nanoceria) can control intracellular as well as extracellular reactive oxygen and nitrogen species. Recent findings suggest that nanoceria can enhance long-term cell survival, enable cell migration and proliferation, and promote stem cell differentiation. Moreover, the self-regenerative property of nanoceria permits a small dose to remain catalytically active for an extended time. This review summarizes the possibilities and applications of nanoceria in the field of tissue engineering and regenerative medicine.

A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ∼50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ∼2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

The nanoporous materials prepared from iron-iron oxide core-shell nanoparticles are of great interest due to their enhanced possibilities for distribution in the environment, a high rate of chemical reactivity and also the possibility to enhance environmentally friendly reaction paths. However, production of these nanoparticle porous materials by conventional methods is difficult. Therefore, we use a cluster deposition system, which prepares the iron nanoclusters and iron-iron oxide core shell nanoclusters at room temperature. The nanoporous films are synthesized by using the nanoclusters as building blocks. These films are characterized using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and the Brunauer-Emmett-Teller (BET) method for surface area determination.

A method has been developed for specifying the growth location of Cu2O nanodotson SrTiO3 (100) substrates. Growth location has been specified by using a focused ion beam (FIB) to modify microscopic and nanoscopic regions of the SrTiO3substrate prior to Cu2O deposition. Deposition onto the modified regions under carefully selected process conditions has generated nanodot growth at the edge of microscopic FIB-induced features and on top of nanoscopic FIB-induced features. For this work, an array of evenly spaced FIB implants was first patterned into several regions of each substrate. Within each sub-division of the array, the FIB implants were identical in Ga+ energy and dosage and implant diameter and spacing. After FIB surface modification and subsequent in-situ substrate cleaning, Cu2O nanodots were synthesized on the patterned SrTiO3 substrates using oxygen plasma assisted molecular beam epitaxy. The substrates and nanodots were characterized using atomic force microscopy at various stages of the process; in-situ X-ray photoelectron spectroscopy and Auger electron spectroscopy analysis demonstrated that the final stoichiometry of the nanodots was Cu2O. The photocatalytic decomposition of water on Cu2O under visible light irradiation has been reported. If the Cu2O can be located in the form ofislands on a carefully selected substrate, then it could be possible to greatly enhance the efficiency of the photochemical process.

We demonstrated an ability to control the location of the porous silicon formation during electro-chemical etching by the introduction of micro- fabricated defects. This ability may open new doors for chemical and biological applications of porous silicon. In this paper, we have focused on the experimental procedure used to form this site-specific porous silicon area on micro- fabricated silicon surface. We also compared our results with work carried out by Saraf et al[1] during the early stage of porous silicon formation in conventional electrochemical etching.