Concurrent Amorphization and Nanocatalyst Formation in Cu-Substituted Perovskite Oxide Surface: Effects on Oxygen Reduction Reaction at Elevated Temperatures.

The activity and durability of chemical/electrochemical catalysts are significantly influenced by their surface environments, highlighting the importance of thoroughly examining the catalyst surface. Here, Cu-substituted La0.6Sr0.4Co0.2Fe0.8O3-δ is selected, a state-of-the-art material for oxygen reduction reaction (ORR), to explore the real-time evolution of surface morphology and chemistry under a reducing atmosphere at elevated temperatures. Remarkably, in a pioneering observation, it is discovered that the perovskite surface starts to amorphize at an unusually low temperature of approximately 100 °C and multicomponent metal nanocatalysts additionally form on the amorphous surface as the temperature raises to 400 °C. Moreover, this investigation into the stability of the resulting amorphous layer under oxidizing conditions reveals that the amorphous structure can withstand a high-temperature oxidizing atmosphere (≥650 °C) only when it has undergone sufficient reduction for an extended period. Therefore, the coexistence of the active nanocatalysts and defective amorphous surface leads to a nearly 100% enhancement in the electrode resistance for the ORR over 200 h without significant degradation. These observations provide a new catalytic design strategy for using redox-dynamic perovskite oxide host materials.

Eu(III)-Chelated Polymeric Hybrid Nanoplatform for Luminescence Resonance Energy Transfer (LRET)-Based Real-Time Monitoring of Organic Cargo Release.

The real-time monitoring of specific guest release from nanoscale assemblies has been of great interest for the potential application in nanomedicine. Herein, we present a facile one-pot strategy to achieve a metal-chelated nanoscale platform that enables a highly efficient luminescence resonance energy transfer (LRET) for the monitoring of hydrophobic cargo release. To this end, Eu(III) as a lanthanide luminophore was employed to induce the metal-mediated self-assembly of chelating block copolymers in the presence of fluorescent Nile Blue (NB) as an organic cargo, which can then produce a nanoscale assembly containing a hybrid polyionic complex (HPIC) of Eu(III) and NB as LRET pairs. Exploiting this Eu(III)-chelated, NB-incorporated polymeric assembly as a luminescent platform that allows for the intermolecular distance-sensitive LRET, we further demonstrate that the facile monitoring of NB release from the carriers was made possible upon the addition of serum albumin as a protein reservoir for the released hydrophobic guest molecules.

Cholesterol-Functionalized Linear/Brush Block Copolymers for Metal-Incorporated Nanostructures with Modulated Core Density and Enhanced Self-Assembly Efficiency.

Metal-mediated self-assembly of chelating double-hydrophilic block copolymer has become a facile preparation strategy of great importance for the metal-chelated hybrid nanostructures. Herein, we present a delicate control over the morphology regulation of metal-chelated nanostructures by a terminal modification of polymer building blocks with mesogenic cholesterol. Such a molecular design motif at an end of chelating linear/brush-type block copolymer imparts not only additional hydrophobicity for enhanced cohesive force to facilitate the metal-mediated self-assembly, but also significant morphological alteration of a metal-chelated core that otherwise generally forms a spherical interior with cholesterol-free block copolymers. The presence of cholesterol entities localized at the central core further allows for the density modulation of the final PtII-chelated nanostructures while maintaining the colloidal stability, comparable to that of the cholesterol-free nanoparticles in physiological conditions. This metal-mediated assembly strategy with modified polymer building blocks can provide a potential platform for the delivery of inorganic agents.