Water gas shift reaction on Cu and Au nanoparticles supported on CeO2(111) and ZnO(0001): intrinsic activity and importance of support interactions.
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Journal Article↗
Biomedical subjects
José A Rodriguez
Publications and source records attributed to José A Rodriguez.
Unravelling the origin of the high-catalytic activity of supported Au: a density-functional theory-based interpretation.
Using first principles DF calculations we have studied the structural and catalytic properties of Au supported on TiOx-Mo(112) films. Our theoretical models are consistent with an initial (8 x 2) Mo(112)-Ti2O3 pattern which after Au deposition gives rise to ordered Au films that completely wet the surface. The oxidation of CO on model surfaces at coverage 1, 4/3, and 5/2 ML has been analyzed. The oxidation proceeds through a peroxo-like complex in which molecular oxygen is simultaneously bound to the CO and the surface. The energy barrier computed for a Au coverage of 4/3 ML is found significantly lower in agreement with the unusual high activity observed for this catalyst. The detailed analysis of the geometry and electronic structure provides a fundamental understanding of the reaction.
Journal Article↗
Water-gas-shift reaction on molybdenum carbide surfaces: essential role of the oxycarbide.
Density functional theory (DFT) was employed to investigate the behavior of Mo carbides in the water-gas-shift reaction (WGS, CO + H(2)O --> H(2) +CO(2)). The kinetics of the WGS reaction was studied on the surfaces of Mo-terminated Mo(2)C(001) (Mo-Mo(2)C), C-terminated Mo(2)C(001) (C-Mo(2)C), and Cu(111) as a known active catalyst. Our results show that the WGS activity decreases in a sequence: Cu > C-Mo(2)C > Mo-Mo(2)C. The slow kinetics on C-Mo(2)C and Mo-Mo(2)C is due to the fact that the C or Mo sites bond oxygen too strongly to allow the facile removal of this species. In fact, due to the strong O-Mo and O-C interactions, the carbide surfaces are likely to be covered by O produced from the H(2)O dissociation. It is shown that the O-covered Mo-terminated Mo(2)C(001) (O_Mo-Mo(2)C) surface displays the lowest WGS activity of all. With the Mo oxide in the surface, O_Mo-Mo(2)C is too inert to adsorb CO or to dissociate H(2)O. In contrast, the same amount of O on the C-Mo(2)C surface (O_C-Mo(2)C) does not lead to deactivation, but enhances the rate of the WGS reaction and makes this system even more active than Cu. The good behavior of O_C-Mo(2)C is attributed to the formation of a Mo oxycarbide in the surface. The C atoms destabilize O-poisoning by forming CO species, which shift away from the Mo hollow sites when the surface reacts with other adsorbates. In this way, the Mo sites are able to provide a moderate bond to the reaction intermediates. In addition, both C and O atoms are not spectators and directly participate in the WGS reaction.
Journal Article↗
Gas-phase interaction of thiophene with the Ti(8)C(12)(+) and Ti(8)C(12) met-car clusters.
The reactivity of the Ti(8)C(12)(+) met-car cation toward thiophene was investigated using density functional theory (DFT) and mass selective ion chemistry. It is shown that the experimentally observed mass spectrum can be well described by the DFT calculations. In contrast to the weak bonding interactions seen for thiophene on a TiC(001) surface, the Ti(8)C(12)(+) met-car cation is able to interact strongly with up to four thiophene molecules with the cluster staying intact. In the most stable conformation, the thiophene molecules bond to the four low-coordinated Ti(0) sites of Ti(8)C(12)(+) via a eta(5)-C,S coordination. The stability and the activity of the Ti(8)C(12)(+) met-car is observed to increase with an increasing number of attached thiophene molecules at the Ti(0) sites, which is associated with a significant transfer of electron density from thiophene to the cluster. The additional electron density on the Ti(8)C(12)(+) cation cluster, however, is not sufficient to cleave the C-S bonds of thiophene and the dissociation reaction of thiophene is predicted to be a highly activated process. By contrast, DFT calculations for the neutral Ti(8)C(12) met-car predict that the dissociation reaction leading to adsorbed S and C(4)H(4) fragments is energetically favorable for the first thiophene molecule. The binding behavior for subsequent addition of thiophene molecules to the neutral met-car is also presented and compared to that of the cation.
Journal Article↗
Predictive factors for outcome in a phase II study of gefitinib in second-line treatment of advanced esophageal cancer patients.
PURPOSE: The efficacy of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) gefitinib was assessed in a phase II study in patients with advanced esophageal cancer. Several biologic features were investigated as potential markers of gefitinib activity. PATIENTS AND METHODS: Patients with advanced esophageal cancer, who had failed one line of prior chemotherapy, were administered gefitinib 500 mg/d. Response was evaluated every 8 weeks. Tumor material obtained before gefitinib treatment was investigated for gene mutations in EGFR, k-ras, and PIK3CA; protein expression levels of EGFR, p-Akt, and p-Erk; and EGFR gene amplification. RESULTS: Of the 36 enrolled patients, one (2.8%) achieved a partial response, 10 (27.8%) had stable disease, 17 (47.2%) experienced progression on treatment, and eight (22.2%) were not assessable for response. The progression-free survival time was 59 days, and the median overall survival time was 164 days. Although EGFR or PIK3CA mutations were absent, k-ras mutations were found in two patients with progressive disease. High EGFR gene copy number was identified in two patients experiencing partial response or progressive disease. A higher disease control rate (response plus stable disease) was observed in females (P = .038) and in patients with squamous cell carcinoma (SCC; P = .013) or high EGFR expression (P = .002). CONCLUSION: Gefitinib has a modest activity in second-line treatment of advanced esophageal cancer. However, the patient outcome was significantly better in female patients and in patients demonstrating high EGFR expression or SCC histology. The selection of esophageal cancer patients for future studies with EGFR-TKIs based on the level of EGFR expression in their tumors or SCC histology should be considered.
Adult↗
In situ studies of the active sites for the water gas shift reaction over Cu-CeO2 catalysts: complex interaction between metallic copper and oxygen vacancies of ceria.
New information about the active sites for the water gas shift (WGS) reaction over Cu-CeO2 systems was obtained using in-situ, time-resolved X-ray diffraction (TR-XRD), X-ray absorption spectroscopy (TR-XAS, Cu K and Ce L3 edges), and infrared spectroscopy (DRIFTS). Cu-CeO2 nanoparticles prepared by a novel reversed microemulsion method (doped Ce1-xCuxO2 sample) and an impregnation method (impregnated CuOx/CeO2 sample) were studied. The results from all of the samples indicate that both metallic copper and oxygen vacancies in ceria were involved in the generation of active sites for the WGS reaction. Evidence was found for a synergistic Cu-Ovacancy interaction. This interaction enhances the chemical activity of Cu, and the presence of Cu facilitates the formation of O vacancies in ceria under reaction conditions. Water dissociation occurred on the Ovacancy sites or the Cu-Ovacancy interface. No significant amounts of formate were formed on the catalysts during the WGS reaction. The presence of strongly bound carbonates is an important factor for the deactivation of the catalysts at high temperatures. This work identifies for the first time the active sites for the WGS reaction on Cu-CeO2 catalysts and illustrates the importance of in situ structural studies for heterogeneous catalytic reactions.
Catalysis↗
Enhanced cytotoxicity induced by gefitinib and specific inhibitors of the Ras or phosphatidyl inositol-3 kinase pathways in non-small cell lung cancer cells.
In this study, we have characterized a panel of NSCLC cell lines with differential sensitivity to gefitinib for activating mutations in egfr, pik3ca, and k-ras, and basal protein expression levels of PTEN. The egfr mutant NSCLC cell line H1650 as well as the egfr wild type cell lines H292 and A431 were highly sensitive to gefitinib treatment, indicating that other factors determine gefitinib-sensitivity in egfr wild type cells. Activating k-ras mutations were specifically detected in gefitinib-resistant cells, suggesting that the occurrence of k-ras mutations is correlated with resistance to EGFR antagonists. No pik3ca mutations were detected within the panel of cell lines, and PTEN protein expression levels did not correlate with gefitinib sensitivity. Gefitinib effectively blocked Akt and Erk phosphorylation in two gefitinib-sensitive NSCLC cell lines, further supporting our previous findings that persistent activity of the PI3K/Akt and/or Ras/Erk pathways is associated with gefitinib-resistance of NSCLC cell lines. Gefitinib-resistant NSCLC cell lines, showing EGFR-independent activity of the PI3K/Akt or Ras/Erk pathways, were treated with gefitinib in combination with specific inhibitors of mTOR, P13K, Ras, and MEK. Additive cytotoxicity was observed in A549 cells co-treated with gefitinib and the MEK inhibitor U0126 or the farnesyl transferase inhibitor SCH66336 and in H460 cells treated with gefitinib and the PI3K inhibitor LY294002, but not in H460 cells treated with gefitinib and rapamycin. These data suggest that combination treatment of NSCLC cells with gefitinib and specific inhibitors of the PI3K/Akt and Ras/Erk pathways may provide a successful strategy.
Antibiotics, Antineoplastic↗
Acetabular fixation options: notes from the other side.
The basis of cement fixation is the interdigitation of cement into the cancellous bone while being supported by the cortical bone. If this is achieved, socket fixation is durable for 10 to 15 years. Cementless socket fixation using a titanium hemispherical socket with a porous surface has had excellent clinical results. Titanium fibermesh cups with supplemental screw fixation have the longest published results for uncemented sockets, with a survivorship of 99% using fixation failure as the end point. Similar findings at 8- to 10-year follow-up have been shown for sintered bead surfaces, as well as plasma spray surfaces, with and without hydroxyapatite coating. Regardless of the fixation technique chosen, a physical, 3-dimensional interlocking between the socket and the supporting bone is necessary for long-term fixation.
Acetabulum↗
Theoretical studies of manganese and iron superoxide dismutases: superoxide binding and superoxide oxidation.
Density-functional calculations indicate that the second sphere of coordination around the metal centers of manganese and iron superoxide dismutases (MnSODs and FeSODs) plays an important role in the binding of O2(-). In these systems, O2(-) prefers to bind to Mn or Fe in end-on configurations. For human and E. coli MnSODs, the bound O2(-) forms hydrogen bonds with the tyrosine and glutamine amino acid residues in the second sphere of coordination. In the cases of E. coli and T. elongates FeSODs, hydrogen bonding occurs between the bound O2(-) and the tyrosine amino acid only because the glutamine is too far away for an effective bonding interaction. The manner in which the O2(-) binds to the metal center in MnSODs and FeSODs can affect the rate of subsequent protonation and determine the mechanism for the formation of H2O2. Both Mn- and Fe-containing superoxide dismutases contain a metal-bound solvent molecule that has been suggested to be involved in the uptake of a H+ upon reduction of the metal center [Bull, C.; Fee, J. A. J. Am. Chem. Soc. 1985, 107, 3295; Miller, A.-F.; Padmakumar, K.; Sorkin, D. L.; Karapetian, A.; Vance, C. K. J. Inorg. Biochem. 2003, 93, 71]. Using density-functional theory, we confirm this suggestion and show the involvement of the second sphere of coordination in the process. We show that the oxidation of superoxide by Mn- or Fe-containing superoxide dismutases is facilitated by a cooperative effect between superoxide binding, protonation of the OH- bound to the metal, and electron transfer from the superoxide molecule to the oxidized metal. In particular, proton transfer through tyrosine-34 on the absence of a bound superoxide is uphill while, once superoxide is bound, the energetic barrier is lowered. It is this barrier that likely keeps the resting state (Mn(III)SOD) of the enzyme with a bound hydroxide, instead of a water. This work provides a model for the mechanism of reaction of superoxide with the oxidized form of the metal within Mn- and FeSODs.
Hydrogen Bonding↗
Unusual physical and chemical properties of Cu in Ce(1-x)Cu(x)O(2) oxides.
The structural and electronic properties of Ce(1-x)Cu(x)O(2) nano systems prepared by a reverse microemulsion method were characterized with synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, Raman spectroscopy, and density functional calculations. The Cu atoms embedded in ceria had an oxidation state higher than those of the cations in Cu(2)O or CuO. The lattice of the Ce(1)(-x)Cu(x)O(2) systems still adopted a fluorite-type structure, but it was highly distorted with multiple cation-oxygen distances with respect to the single cation-oxygen bond distance seen in pure ceria. The doping of CeO(2) with copper introduced a large strain into the oxide lattice and favored the formation of O vacancies, leading to a Ce(1-x)Cu(x)O(2-y) stoichiometry for our materials. Cu approached the planar geometry characteristic of Cu(II) oxides, but with a strongly perturbed local order. The chemical activities of the Ce(1-x)Cu(x)O(2) nanoparticles were tested using the reactions with H(2) and O(2) as probes. During the reduction in hydrogen, an induction time was observed and became shorter after raising the reaction temperature. The fraction of copper that could be reduced in the Ce(1-x)Cu(x)O(2) oxides also depended strongly on the reaction temperature. A comparison with data for the reduction of pure copper oxides indicated that the copper embedded in ceria was much more difficult to reduce. The reduction of the Ce(1-x)Cu(x)O(2) nanoparticles was rather reversible, without the generation of a significant amount of CuO or Cu(2)O phases during reoxidation. This reversible process demonstrates the unusual structural and chemical properties of the Cu-doped ceria materials.
Journal Article↗
Catalysts for hydrogen evolution from the [NiFe] hydrogenase to the Ni2P(001) surface: the importance of ensemble effect.
Density functional theory (DFT) was employed to investigate the behavior of a series of catalysts used in the hydrogen evolution reaction (HER, 2H(+) + 2e(-) --> H(2)). The kinetics of the HER was studied on the [NiFe] hydrogenase, the [Ni(PS3*)(CO)](1)(-) and [Ni(PNP)(2)](2+) complexes, and surfaces such as Ni(111), Pt(111), or Ni(2)P(001). Our results show that the [NiFe] hydrogenase exhibits the highest activity toward the HER, followed by [Ni(PNP)(2)](2+) > Ni(2)P > [Ni(PS3*)(CO)](1)(-) > Pt > Ni in a decreasing sequence. The slow kinetics of the HER on the surfaces is due to the fact that the metal hollow sites bond hydrogen too strongly to allow the facile removal of H(2). In fact, the strong H-Ni interaction on Ni(2)P(001) can lead to poisoning of the highly active sites of the surface, which enhances the rate of the HER and makes it comparable to that of the [NiFe] hydrogenase. In contrast, the promotional effect of H-poisoning on the HER on Pt and Ni surfaces is relatively small. Our calculations suggest that among all of the systems investigated, Ni(2)P should be the best practical catalyst for the HER, combining the high thermostability of the surfaces and high catalytic activity of the [NiFe] hydrogenase. The good behavior of Ni(2)P(001) toward the HER is found to be associated with an ensemble effect, where the number of active Ni sites is decreased due to presence of P, which leads to moderate bonding of the intermediates and products with the surface. In addition, the P sites are not simple spectators and directly participate in the HER.
Catalysis↗
Kahalalide F induces necrosis-like cell death that involves depletion of ErbB3 and inhibition of Akt signaling.
Kahalalide F (KF) is a novel marine-derived antitumor agent that is currently undergoing phase II clinical trials. The mechanism of action of KF is not well understood. In line with previous reports, we show that KF caused rapid and potent cytotoxicity in the breast cancer cell lines SKBR3 and BT474, characterized by cytoplasmic swelling and DNA clumping. Several markers of caspase-dependent apoptosis, such as phosphatidyl-serine externalization, cytochrome c release, and caspase-3 and poly-(ADP-ribose) polymerase cleavage were negative after KF exposure. Inhibitors of caspases or cathepsins failed to protect against KF cytotoxicity. Altogether, these data indicate that KF-induced cell death is a necrosis-like process. The sensitivity to KF in a panel of human tumor cell lines derived from breast (SKBR3, BT474, and MCF7), vulval (A431), non-small-cell lung (H460, A549, SW1573, and H292), and hepatic (Skhep1, HepG2, and Hep3B) carcinomas positively correlated with ErbB3 (HER3) protein levels. A KF-resistant subline of colon carcinoma cells, HT29/KF, expressed significantly reduced levels of all ErbB receptors, but short-term KF exposure of sensitive cell lines such as SKBR3 selectively induced down-regulation of ErbB3. On the other hand, stable transfection of an ErbB3-expressing plasmid increased the KF sensitivity of H460 cells, the most resistant cell line in our panel. Finally, we found that KF efficiently inhibited the phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway in sensitive cell lines and that ectopic expression of a constitutively active Akt mutant reduced KF cytotoxicity in this cell line. In summary, our results identify ErbB3 and the downstream PI3K-Akt pathway as important determinants of the cytotoxic activity of KF in vitro.
Antineoplastic Agents↗
The structural and electronic properties of nanostructured Ce1-x-yZrxTbyO2 ternary oxides: unusual concentration of Tb3+ and metal<-->oxygen<-->metal interactions.
Ceria-based ternary oxides are widely used in many areas of chemistry, physics, and materials science. Synchrotron-based time-resolved x-ray diffraction, x-ray absorption near-edge spectroscopy (XANES), Raman spectroscopy, and density-functional calculations were used to study the structural and electronic properties of Ce-Zr-Tb oxide nanoparticles. The nanoparticles were synthesized following a novel microemulsion method and had sizes in the range of 4-7 nm. The Ce1-x-yZrxTbyO2 ternary systems exhibit a complex behavior that cannot be predicted as a simple extrapolation of the properties of Ce1-xZrxO2, Ce1-xTbxO2, or the individual oxides (CeO2, ZrO2, and TbO2). The doping of ceria with Zr and Tb induces a decrease in the unit cell, but there are large positive deviations with respect to the cell parameters predicted by Vegard's rule for ideal solid solutions. The presence of Zr and Tb generates strain in the ceria lattice through the creation of crystal imperfections and O vacancies. The O K-edge and Tb LIII-edge XANES spectra for the Ce1-x-yZrxTbyO2 nanoparticles point to the existence of distinctive electronic properties. In Ce1-x-yZrxTbyO2 there is an unexpected high concentration of Tb3+, which is not seen in TbO2 or Ce1-xTbxO2 and enhances the chemical reactivity of the ternary oxide. Tb<-->O<-->Zr interactions produce a stabilization of the Tb(4f,5d) states that is responsible for the high concentration of Tb(3+) cations. The behavior of Ce1-x-yZrxTbyO2 illustrates how important can be metal<-->oxygen<-->metal interactions for determining the structural, electronic, and chemical properties of a ternary oxide.
Journal Article↗
Desulfurization reactions on Ni2P(001) and alpha-Mo2C(001) surfaces: complex role of P and C sites.
X-ray photoelectron spectroscopy and first-principles density-functional calculations were used to study the interaction of thiophene, H(2)S, and S(2) with Ni(2)P(001), alpha-Mo(2)C(001), and polycrystalline MoC. In general, the reactivity of the surfaces increases following the sequence MoC < Ni(2)P(001) < alpha-Mo(2)C(001). At 300 K, thiophene does not adsorb on MoC. In contrast, Ni(2)P(001) and alpha-Mo(2)C(001) can dissociate the molecule easily. The key to establish a catalytic cycle for desulfurization is in the removal of the decomposition products of thiophene (C(x)H(y) fragments and S) from these surfaces. Our experimental and theoretical studies indicate that the rate-determining step in a hydrodesulfurization (HDS) process is the transformation of adsorbed sulfur into gaseous H(2)S. Ni(2)P is a better catalyst for HDS than Mo(2)C or MoC. The P sites in the phosphide play a complex and important role. First, the formation of Ni-P bonds produces a weak "ligand effect" (minor stabilization of the Ni 3d levels and a small Ni --> P charge transfer) that allows a high activity for the dissociation of thiophene and molecular hydrogen. Second, the number of active Ni sites present in the surface decreases due to an "ensemble effect" of P, which prevents the system from deactivation induced by high coverages of strongly bound S. Third, the P sites are not simple spectators and provide moderate bonding to the products of the decomposition of thiophene and the H adatoms necessary for hydrogenation.
Journal Article↗
Chemical activity of iron in [2Fe-2S]-protein centers and FeS2(100) surfaces.
Iron atoms bonded to sulfur play an important role in proteins, heterogeneous catalysts, and gas sensors. First-principles density functional calculations were used to investigate the structure and chemical activity of a unique [2Fe-2S] center in the split-Soret cytochrome c (Ssc) from Desulfovibrio desulfuricans. In agreement with a previously proposed structural model [Abreu et al., J. Biol. Inorg. Chem. 2003, 8, 360], it is found that the [2Fe-2S] cluster is located in a surface pocket of the Ssc and bonded to only three cysteines. The [2Fe-2S] center in the Ssc is nonplanar and somewhat distorted with respect to canonical [2Fe-2S] centers seen in proteins where the iron-sulfur unit is bonded to four cysteines. In the Ssc, the lack of one Fe-cysteine bond is partially compensated by the separation between the cysteines that minimizes electrostatic repulsion among these ligands. The unique structure of the [2Fe-2S] center in the Ssc makes the center more chemically active than canonical [2Fe-2S] centers in proteins, (RS)(4)[2Fe-2S] inorganic complexes, and an FeS2(100) surface. A [2Fe-2S] center in the Ssc interacts efficiently with electron acceptors (O2, NO, CO) and poorly with a Lewis base such as H2O. The interaction with molecular oxygen is so strong that eventually oxidatively destroys the [2Fe-2S] unit. The bonding energy of the ligands to the [2Fe-2S] centers and FeS2(100) surface increases following the sequence: H2O << CO < NO < O2. The higher the electron affinity of the ligand, the larger its bonding energy. A relatively large positive charge on the Fe cations in FeS2(100) makes this sulfide surface less reactive toward O2, CO, and NO than the [2Fe-2S] centers in proteins and inorganic complexes.
Chemistry, Physical↗
Nuclear targeting and cell cycle regulatory function of human BARD1.
The BARD1 gene is mutated in a subset of breast and ovarian cancers, implicating BARD1 as a potential tumor suppressor. BARD1 gains a ubiquitin E3 ligase activity when heterodimerized with BRCA1, but the only known BRCA1-independent BARD1 function is a p53-dependent proapoptotic activity stimulated by nuclear export to the cytoplasm. We described previously the nuclear-cytoplasmic shuttling of BARD1, and in this study, we identify the transport sequences that target BARD1 to the nucleus and show that they are essential for BARD1 regulation of the cell cycle. We used deletion mapping and mutagenesis to define two active nuclear localization signals (NLSs) present in human BARD1 that are not conserved in rodent BARD1. Site-directed mutagenesis of the primary bipartite NLS abolished BARD1 nuclear import and caused its cytoplasmic accumulation. Using flow cytometry and 5-bromo-2-deoxyuridine incorporation assays, we discovered that transiently expressed BARD1 can elicit a p53-independent cell cycle arrest in G1 phase, and that this was abrogated by mutation of the BARD1 NLS but not by mutation of the nuclear export signal. Thus, BARD1 regulation of the cell cycle is a nuclear event and may be linked to its induced expression during mitosis and its possible involvement in the DNA damage checkpoint.
Amino Acid Sequence↗
The chemical activity of metal compound nanoparticles: importance of electronic and steric effects in M8C12 (M=Ti, V, Mo) metcars.
Density functional theory was employed to investigate the chemical activity of metal carbide nanoparticles. The present calculations indicate that M(8)C(12) (M=Ti, V, Mo) nanoparticles exhibit a unique behavior compared to metal [M(001)] and metal carbide surfaces [M(2)C(001) and MC(001)]. It is found that the nanoparticles behave very reactive in spite of the high carbon concentration in some reactions, while surprisingly inert in other cases. Our study reveals that the unexpected activity is the result of the interplay of shifts in the metal d-bands and distortions in the geometry of the metal carbide nanoparticles.
Journal Article↗
The behavior of mixed-metal oxides: physical and chemical properties of bulk Ce1-xTbxO2 and nanoparticles of Ce1-xTbxOy.
The physical and chemical properties of bulk Ce(1-x)Tb(x)O(2) and Ce(1-x)Tb(x)O(y) nanoparticles (x Tb exchange nor the introduction of oxygen vacancies in Ce(1-x)Tb(x)O(y) significantly affect the charge on the Ce cations. In contrast, the O K-edge and Tb L(III)-edge XANES spectra for Ce(1-x)Tb(x)O(y) nanoparticles show substantial changes with respect to the corresponding spectra of Ce and Tb single oxide references. The Ce(0.5)Tb(0.5)O(y) compounds exhibit a much larger Tb(3+)/Tb(4+) ratio than TbO(1.7). A comparison with the properties of Ce(1-x)Zr(x)O(y) and Ce(1-x)Ca(x)O(y) shows important differences in the charge distribution, the magnitude of the dopant induced strain in the oxide lattice, and a superior behavior in the case of the Ce(1-x)Tb(x)O(y) systems. The Tb-containing oxides combine stability at high temperature against phase segregation and a reasonable concentration of O vacancies, making them attractive for chemical and catalytic applications.
Journal Article↗