Nanoceria Research Articles

Nanoceria: A Rare-Earth Nanoparticle as a Novel Anti-Angiogenic Therapeutic Agent in Ovarian Cancer

Ovarian cancer (OvCa) is the fifth most common cause of death from all cancers among women in United Sates and the leading cause of death from gynecological malignancies. While most OvCa patients initially respond to surgical debulking and chemotherapy, 75% of patients later succumb to the disease. Thus, there is an urgent need to test novel therapeutic agents to counteract the high mortality rate associated with OvCa. In this context, we have developed and engineered Nanoceria (NCe), nanoparticles of cerium oxide, possessing anti-oxidant properties, to be used as a therapeutic agent in OvCa. We show for the first time that NCe significantly inhibited production of reactive oxygen species (ROS) in A2780 cells, attenuated growth factor (SDF1, HB-EGF, VEGF165 and HGF) mediated cell migration and invasion of SKOV3 cells, without affecting the cell proliferation. NCe treatment also inhibited VEGF165 induced proliferation, capillary tube formation, activation of VEGFR2 and MMP2 in human umbilical vascular endothelial cells (HUVEC). NCe (0.1 mg/kg body weigh) treatment of A2780 ovarian cancer cells injected intra-peritoneally in nude mice showed significant reduction (p<0.002) in tumor growth accompanied by decreased tumor cell proliferation as evident from reduced tumor size and Ki67 staining. Accumulation of NCe was found in tumors isolated from treated group using transmission electron microscopy (TEM) and inductively coupled plasma mass spectroscopy (ICP-MS). Reduction of the tumor mass was accompanied by attenuation of angiogenesis, as observed by reduced CD31 staining and specific apoptosis of vascular endothelial cells. Collectively, these results indicate that cerium oxide based NCe is a novel nanoparticle that can potentially be used as an anti-angiogenic therapeutic agent in ovarian cancer.

Characterization and optical properties of Eu-doped cubic nano ceria synthesized by using the co-precipitation-hydrothermal route

A series of nano ceria samples containing 0 to 2 mol% europium were synthesized following the co-precipitation hydrothermal technique. The X-ray diffraction patterns showed peaks corresponding to the fluorite structure of cubic ceria with shifting of the peak positions, but did not show any Eu-related peaks. The fourier transform infrared (FTIR) spectra of all the samples showed four bands that could be attributed to Ce-O stretching vibrations, formation of nano-crystalline particles, -HOH bending, and -OOH and -OH stretching vibrations. The Raman spectra of all the samples showed a sharp and intense Raman shift at around 460–462 cm−1 corresponding to the triplydegenerate F2g mode. The intensity of the Raman peaks showed variations in intensities. The transmission electron microscope (TEM) images of typical samples revealed that the shapes and the sizes of the particles were not much affected after Eu doping in the studied range though Eu doping resulted in agglomerations of nanoparticles. Broad absorption peaks centered at 292, 332, 336, 310, and 294 nm were observed for 0, 0.25, 0.5, 1, and 2 mol % Eu-doped ceria in the UVVis spectra with direct band gaps of 3.6, 2.75, 2.75, 2.75, and 3.25 eV, respectively. The smaller values of the indirect band gap indicated that Eu-doped nanoparticles were available to assist the indirect electron transition from the valence band to the conduction band. The emission peaks for the spectra obtained by exciting at 300 nm were observed at 355, 405, 396, 387, and 380 nm for pure ceria sample and 0.25, 0.5, 1, and 2 mol% Eu-doped samples, confirming the red shift in all the doped samples. The spectra for Eu-doped samples obtained by exciting at 500 nm showed three peaks in the orange-red region corresponding to the 5D0 → 7Fj (j = 0 − 4) transitions of Eu3+.

Modification of carbidic austempered ductile iron with nano ceria for improved mechanical properties and abrasive wear resistance

Carbidic austempered ductile iron (CADI) is a new type of ductile cast iron containing carbides, providing enhanced wear resistance, compared to conventional ADI. However, the improvement in the wear resistance due to the introduced hard carbides is generally accompanied by a decrease in the impact toughness, which limits its applications. Controlling the morphology, size and quantity of carbides is an approach to achieve the optimal combination of wear resistance and impact toughness. In this work, we modified CADI by adding nano ceria to tailor the morphology, size and quantity of carbides and investigated effects of the added nano ceria on mechanical properties and abrasion resistance of the CADI. It was demonstrated that carbides were refined by the nano ceria, which improved the toughness of the CADI in addition to raised hardness. The abrasive wear resistance of the material was correspondingly enhanced with the change in hardness, largely benefiting from the variations in the volume fraction and size of carbides. However, only a small amount of nano ceria was effective; the benefits of nano ceria diminished if excessive nano ceria was added.

Polyurethane nanocomposite films containing nano-cerium oxide as UV absorber; Part 2: Structural and mechanical studies upon UV exposure

Degradation of a water-based polyurethane clear coat containing nano-sized cerium oxide was investigated. Nanoparticles at different concentrations were dispersed in a water-reducible polyol polyacrylate dispersion resin, followed by mixing with polyisocayanate hardener from which wet films of 90μm thick were prepared. Samples were exposed to 700h of accelerated artificial weathering (QUV).Their performances were then accessed by DMTA and ATR–FTIR spectroscopy. It was revealed that the glass transition temperature (Tg) of films systematically increased with increase in nano ceria content. Due to UV absorption and decrease in photo-oxidation and chain scission reactions, the storage moduli of clear coats containing nano ceria were shown higher than that of the blank polyurethane after UV exposure. Tg for both pure blank polyurethane and nano-ceria embedded clear coats increased with increase in degradation time. Most of variations in Tgs occurred in the first 150h of exposure. ATR–FTIR spectra also proved these results by showing depreciation in intensities of CH and NH peaks. It was seen that the surface of the clear coats as analyzed by ATR–FTIR was polyurea-rich and contained urea functionality at least as much as polyurethane. During weathering, the photo-oxidation of CH groups to carbonyl groups occurred.

CeO2/H2O2 system catalytic oxidation mechanism study via a kinetics investigation to the degradation of acid orange 7

Nano ceria with cubic lattice was prepared and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Degradation kinetics of acid orange 7 (AO7) was investigated to understand the catalytic oxidation mechanism of the CeO2 with H2O2. The degradation of AO7 relies significantly on its adsorption on the surface of CeO2 with an apparent order of 2.40. Increasing the concentration of H2O2 increases the degradation reaction rate constant of AO7 in a positive linear relationship at the initial stage, but later hinders further degradation of AO7 due to over-complexation of Ce3+ with H2O2. The catalytic kinetics of CeO2 in pre-adsorbed mode (AO7 pre-adsorbed on CeO2 before the addition of H2O2) and pre-mixed mode (CeO2 pre-mixed with H2O2 before the addition of AO7) is quite different. The pre-mixed mode is unfavorable for AO7 degradation, as almost all of surface Ce3+ are pre-oxidized into surface peroxide species with H2O2 and hence reduces adsorption of AO7 as well as the activation of AO7 degradation. Reversely, the reactivity of CeO2 can slowly be recovered by adsorption of AO7, which competitively adsorbs on the CeO2 and gradually initiates the release of the surface Ce3+ by consuming the surface peroxide species. The AO7 degradation kinetics investigation in this work verifies that the degradation of organics in CeO2/H2O2 system is adsorption-triggered and the Ce3+ in reduced state is essential for activating the catalytic oxidation activity of surface peroxide species. EPR studies show that the surface peroxide species oxidizes the organics via hydroxyl adduct route.

Mechanical Properties and Thermal Shock Resistance of HVOF Sprayed NiCrAlY Coatings Without and With Nano Ceria

NiCrAlY coatings without and with 0.2 wt.% nano ceria were prepared by high velocity oxygen fuel spraying. The microstructure, mechanical properties, and thermal shock resistance of as-sprayed coatings were investigated. The results showed that in the as-sprayed coatings, the number of un-melted particles was reduced drastically, the microstructure was refined and compact due to the refinement of sprayable powders. Both the hardness and adhesive strength of the NiCrAlY increased due to the refinement of microstructure and the decrease of the defects, such as pores and oxides, after adding nano ceria. The thermal cycle life of NiCrAlY coatings was improved by 15% after adding 0.2 wt.% nano ceria, which is attributed to the low content of spinel NiCr2O4 and high content of Cr2O3 in the thermal cycling, the refined and compact microstructure, and increased interfacial boundary.

Structural characteristics of quantum-size ceria nano particles synthesized via simple ammonia precipitation

Nanoscale, high surface area spherical cerium oxide was prepared from aqueous cerium nitrate by homogeneous precipitation using ammonia. This synthesis route offers a versatile, low cost and environmental friendly method to produce nano ceria. The specimen powder was characterized with XRD, SEM, HRTEM, and UV–vis spectrophotometry. Cubic cerianite crystallites (CeO 2) were detected by powder XRD pattern, while Ce 3+ was also evident from XPS spectra and DR UV spectroscopy study. XPS spectra indicated that cerium in the nano crystals was predominantly tetravalent. Both Ce 2O 3 as well as oxygen vacancy contributed towards the presence of Ce 3+ in the sample. The particle size of the system was calculated from TEM analysis, XRD study and BET surface area analysis. The characterization revealed the particles to be spherical in shape with typical size 4–5 nm, which is a favourable characteristic feature for many applications. The direct optical band gap estimated from DR UV absorption spectrum was blue-shifted evidently with respect to the bulk material and indicated quantum-size confinement effect in nano crystallites.

ChemInform Abstract: Nano Ceria Catalyzed Synthesis of α‐Aminophosphonates under Ultrasonication.

AbstractVarious aromatic amines and benzyl amine can be used in the preparation of the biologically interesting title compounds.

Effect of Submicron Grains on Ionic Conductivity of Nanocrystalline Doped Ceria

Doped ceria has been considered for high oxygen ion conductivity for solid oxide fuel cells. In the present study, 20 mole% samarium doped nano ceria powder was prepared by wet chemical synthesis and sintered at different temperatures to retain submicron grains (> 92-96% density). ionic conductivity of the sintered pellets was measured using impedance spectroscopy as a function of temperature (200-800 degrees C). The total maximum conductivity was 1.0 x 10(-2)S.cm(-1) (at 600 degrees C) for samples sintered at 1200 degrees C. The activation energy at higher test temperature decreases with the decrease in the sintering temperature (by 25%). The grain boundary, grain interior conductivity and activation energy of the electrolyte were correlated to the resulting microstructure. It has been demonstrated that use of doped nano ceria powder as precursor not only reduced the sintering temperature but also provided segregation free grain boundary for engineering higher conductivity dense electrolytes.

Microhardness and fracture toughness of Ce 0.9Gd 0.1O 1.95 for manufacturing solid oxide electrolytes

Synthesis of nanocrystalline gadolinium doped ceria (Ce 0.9Gd 0.1O 1.95) was attempted by nitrate-fuel combustion technique involving different organic fuels namely urea, citric acid, glycine and poly ethylene glycol. As-combusted ceria precursors were calcined at 700 °C for 2 h for obtaining fully dense, nanocrystalline ceria powders. Cylindrical ceria discs were fabricated by uni-axial pressing and sintered intentionally at low temperature of 1200 °C for 2 h for assessing the sintering characteristics of the nano powders as well as the mechanical performance of the sintered ceria body. The study confirms that the nano powders could be sintered to 98% theoretical sintered density at 1200 °C with a grain size of 400 nm to 1 μm. The sintered samples exhibited the Vickers microhardness of 8.82 ± 0.2 GPa and the fracture toughness of 1.75 ± 0.3 MPa m 1/2 at a load 20 N for glycine and citric acid fuels derived ceria, respectively. A comparison between the fuels was made with respect to the sintering and mechanical properties of doped ceria. Citric acid and glycine fuels resulted in sintered ceria with high hardness where as the urea and polyethylene fuels derived nano ceria resulted in high fracture toughness.

Effect of Particle Size of Ceria Coated Silica and Polishing Pressure on Chemical Mechanical Polishing of Oxide Film

Submicron colloidal silica coated with ceria were prepared by mixing of silica and nano ceria particles and modified by hydrothermal reaction. The polishing efficiency of the ceria coated silica slurry was tested over oxide film on silicon wafer. By changing the polishing pressure in the range of <TEX>$140{\sim}420g/cm^2$</TEX> with the ceria coated silica slurries in <TEX>$100{\sim}300nm$</TEX>, rates, WIWNU and friction force were measured. The removal rate was in the order of 200, 100, and 300 nm size silica coated with ceria. It was known that the smaller particle size gives the higher removal rate with higher contact area in Cu slurry. In the case of oxide film, the indentation volume as well as contact area gives effect on the removal rate depending on the size of abrasives. The indentation volume increase with the size of abrasive particles, which results to higher removal rate. The highest removal rate in 200 nm silica core coated with ceria is discussed as proper combination of indentation and contact area effect.