Oxygen diffusion and vacancy migration thermally-activated govern high-temperature magnetism in ceria

Effect of Exposed Facets and Oxidation State of CeO2 Nanoparticles on CO2 Adsorption and Desorption

CeO2 nanoparticles exhibit potential as solid adsorbents for carbon dioxide (CO2) capture and storage (CCS), offering precise control over various facets and enhancing their efficiency. This study investigated the adsorption and desorption behaviors of two types of CeO2 nanoparticles: cubic CeO2 with primarily {001} facets and polyhedral CeO2 with mainly {111} facets. The results showed that despite polyhedral CeO2's lower quantity, it demonstrated successful adsorption-desorption cycles in both oxidized and reduced states. However, reduced CeO2-x exhibited a higher adsorption capacity but displayed irreversible adsorption-desorption cycles. Reversible adsorption occurred through weak bond formation with CO2, while cubic CeO2 with a high oxygen vacancy concentration exhibited irreversible adsorption due to strong bond formation. These insights contribute significantly to understanding CeO2 nanoparticle characteristics and their impact on the CO2 adsorption and desorption processes, aiding in the development of advanced CCS techniques.

Unveiling the Power of Gabapentin-Loaded Nanoceria with Multiple Therapeutic Capabilities for the Treatment of Dry Eye Disease

Dry eye (DE) disease, which is primarily linked to aqueous deficiency, is an escalating health issue worldwide, mainly due to the widespread use of electronic devices. The major obstacles in DE pharmacotherapy include insufficient therapeutic efficacy and low ocular bioavailability. This study presents the development of a ceria-based nanosystem to carry gabapentin (GBT), aiming to offer comprehensive relief from DE symptoms. We prepared multifunctional nanoceria capped with thiolated gelatin followed by cross-linking with glutaraldehyde, yielding a nanocarrier with desirable biocompatibility and antioxidant, anti-inflammatory, antiangiogenic, antiapoptotic, and neuronal protective activities. Specifically, the highly abundant thiol groups on gelatin increased the cellular uptake of the nanocarrier by 2.3-fold and its mucin-binding efficiency by 10-fold, thereby extending ocular retention and amplifying therapeutic activity. Moderate cross-linking of the thiolated gelatin not only enhanced the ocular bioavailability of the nanoceria but also provided slow, degradation-controlled release of GBT to promote the lacrimal stimulation to restore the tear film. In a rabbit model of DE, topical administration of our GBT/nanoceria nanoformulation resulted in comprehensive alleviation of symptoms, including repairing corneal epithelial damage, preserving corneal nerve density, and stimulating tear secretion, demonstrating superior performance in comparison to the free drug. These results underscore the safety and potential of this innovative nanoformulation for DE pharmacotherapy.

Unexpected Ferromagnetism—A Review

The study of magnetism in materials without partially filled d or f bands has gained much attention in the past years. Even though it has challenged the understanding of traditional magnetism, there is a wide range of studies debating the nature of magnetism in such materials. Theories on whether the exhibited ferromagnetic behavior is due to sample impurities or intrinsic structural defects have been published throughout the years. Materials such as hexaborides, non-magnetic oxides, and carbon nanostructures have been of great interest due to their potential applications. For a better understanding, herein, we present a literature review combining past and up-to-date studies on these materials.

Structural relaxation in layered, non-stoichiometric Fe7S8

In this study, we investigate the kinetics of the enantiotropic solid-solid β-transition in Fe7S8 pyrrhotite, which presents a prominent example of a metal-nonmetal compound with layered crystal structure. The low-temperature (4C) and high-temperature (1C) modifications differ in their crystallographic unit-cell dimension, vacancy distribution, and magnetic ordering in the crystal lattice. Fast differential scanning calorimetry (FDSC) reveals that cooling of the paramagnetic 1C phase below the transformation temperature Tβ = 597 K, which is also the Curie temperature, generates a metastable phase that transforms into the ferrimagnetic 4C phase with high vacancy order upon further annealing below Tβ. Upon fast cooling, the low-temperature modification shows an energetically excited phase with higher entropy that relaxes towards the equilibrated pyrrhotite polymorph. The kinetics of the superheating and the structural relaxation as obtained from FDSC experiments provide deeper insight into the stability of Fe7S8 polymorphs. This may pave a new path to decipher in detail the kinetics of solid-solid phase transformations and the long-term lifespan of defects in Earth and synthetic materials.

Kinetics Study of the Hydrodeoxygenation of Xylitol over a ReOx-Pd/CeO2 Catalyst

In this study, we elucidate the reaction kinetics for the simultaneous hydrodeoxygenation of xylitol to 1,2-dideoxypentitol and 1,2,5-pentanetriol over a ReOx-Pd/CeO2 (2.0 weight% Re, 0.30 weight% Pd) catalyst. The reaction was determined to be a zero-order reaction with respect to xylitol. The activation energy was elucidated through an Arrhenius relationship as well as non-Arrhenius kinetics. The Arrhenius relationship was investigated at 150–170 °C and a constant H2 pressure of 10 bar resulting in an activation energy of 48.7 ± 10.5 kJ/mol. The investigation of non-Arrhenius kinetics was conducted at 120–170 °C and a sub-Arrhenius relation was elucidated with activation energy being dependent on temperature, and ranging from 10.2–51.8 kJ/mol in the temperature range investigated. Internal and external mass transfer were investigated through evaluating the Weisz–Prater criterion and the effect of varying stirring rate on the reaction rate, respectively. There were no internal or external mass transfer limitations present in the reaction.