Ceria nanocrystallites with different morphologies and crystal planes were hydrothermally prepared, and the effects of ceria supports on the physicochemical and catalytic properties of Pd/CeO 2 for the CO and propane oxidation were examined. The results showed that the structure and chemical state of Pd on ceria were affected by ceria crystal planes. The Pd species on CeO 2 -R (rods) and CeO 2 -C (cubes) mainly formed Pd x Ce 1−x O 2−σ solid solution with −Pd 2+ −O 2− −Ce 4+ − linkage. In addition, the PdO x nanoparticles were dominated on the surface of Pd/CeO 2 -O (octahedrons). For the CO oxidation, the Pd/CeO 2 -R catalyst showed the highest catalytic activity among three catalysts, its reaction rate reached 2.07 × 10 −4 mol g Pd −1 s −1 at 50 °C, in which CeO 2 -R mainly exposed the ( 110) and (100) facets with low oxygen vacancy formation energy, strong reducibility, and high surface oxygen mobility. TOF of Pd/CeO 2 -R (3.78 × 10 −2 s −1 ) was much higher than that of Pd/CeO 2 -C (6.40 × 10 −3 s −1 ) and Pd/CeO 2 -O (1.24 × 10 −3 s −1 ) at 50 °C, and its activation energy (E a ) was 40.4 kJ/mol. For propane oxidation, the highest reaction rate (8.08 × 10 −5 mol g Pd −1 s −1 at 300 °C) was obtained over the Pd/CeO 2 -O catalyst, in which CeO 2 -O mainly exposed the (111) facet. There are strong surface Ce−O bonds on the ceria (111) facet, which favors the existence of PdO particles and propane activation. The turnover frequency (TOF) of the Pd/CeO 2 -O catalyst was highest (3.52 × 10 −2 s −1 ) at 300 °C and its E a value was 49.1 kJ/mol. These results demonstrate the inverse facet sensitivity of ceria for the CO and propane oxidation over Pd/ ceria.

The theoretically proposed graphene/single-walled carbon nanotube (G/SWCNT) hybrids by placing SWCNTs among graphene planes through covalent C-C bonding are expected to have extraordinary physical properties and promising engineering applications. However, the G/CNT hybrids that have been fabricated differ greatly from the proposed G/SWCNT hybrids because either the covalent C-C bonding is not well constructed or only multiwalled CNTs/carbon nanofibers rather than SWCNTs are available in the hybrids. Herein, a novel G/SWCNT hybrid was successfully fabricated by a facile catalytic growth on layered double hydroxide (LDH) at a high temperature over 950 °C. The thermally stable Fe nanoparticles and the uniform structure of the calcined LDH flakes are essential for the simultaneously catalytic deposition of SWCNTs and graphene. The SWCNTs and the CVD-grown graphene, as well as the robust connection between the SWCNTs and graphene, facilitated the construction of a high electrical conductive pathway. The internal spaces between the two stacked graphene layers and among SWCNTs offer room for sulfur storage. Therefore, the as obtained G/SWCNT-S cathode exhibited excellent performance in Li-S batteries with a capacity as high as 650 mAh g(-1) after 100 cycles even at a high current rate of 5 C. Such a novel G/SWCNT hybrid can serve not only as a prototype to shed light on the chemical principle of G/CNT synthesis but also as a platform for their further applications in the area of nanocomposites, heterogeneous catalysis, drug delivery, electrochemical energy storage, and so on.

Crystalline high-entropy ceramics (CHC), a new class of solids that contain five or more elemental species, have attracted increasing interest because of their unique structure and potential applications. Up to now, only a couple of CHCs (e.g., high-entropy metal oxides and diborides) have been successfully synthesized. Here, a new strategy for preparing high-entropy metal nitride (HEMN-1) is proposed via a soft urea method assisted by mechanochemical synthesis. The as-prepared HEMN-1 possesses five highly dispersed metal components, including V, Cr, Nb, Mo, Zr, and simultaneously exhibits an interesting cubic crystal structure of metal nitrides. By taking advantage of these unique features, HEMN-1 can function as a promising candidate for supercapacitor applications. A specific capacitance of 78 F g is achieved at a scan rate of 100 mV s in 1 m KOH. In addition, such a facile synthetic strategy can be further extended to the fabrication of other types of HEMNs, paving the way for the synthesis of HEMNs with attractive properties for task-specific applications.

There exists a bidirectional communication system between the gastrointestinal tract and the brain. Increasing evidence shows that gut microbiota can play a critical role in this communication; thus, the concept of a gut microbiota and brain axis is emerging. Here, we review recent findings in the relationship between intestinal microbes and brain function, such as anxiety, depression, stress, autism, learning, and memory. We highlight the advances in modulating brain development and behavior by probiotics, prebiotics, and diet through the gut microbiota-brain axis. A variety of mechanisms including immune, neural, and metabolic pathways may be involved in modulation of the gut microbiota-brain axis. We also discuss some future challenges. A deeper understanding of the relationship between the gut bacteria and their hosts is implicated in developing microbial-based therapeutic strategies for brain disorders.

Genetics alone cannot explain most cases of rheumatoid arthritis (RA). Thus, investigating environmental factors such as the gut microbiota may provide new insights into the initiation and progression of RA. In this study, we performed 16S rRNA sequencing to characterise the gut microbiota of DBA1 mice that did or did not develop arthritis after induction with collagen. We found that divergence in the distribution of microbiota after induction was pronounced and significant. Mice susceptible to collagen-induced arthritis (CIA) showed enriched operational taxonomic units (OTUs) affiliated with the genus Lactobacillus as the dominant genus prior to arthritis onset. With disease development, the abundance of OTUs affiliated with the families Bacteroidaceae, Lachnospiraceae, and S24-7 increased significantly in CIA-susceptible mice. Notably, germ-free mice conventionalized with the microbiota from CIA-susceptible mice showed a higher frequency of arthritis induction than those conventionalized with the microbiota from CIA-resistant mice. Consistently, the concentration of the cytokine interleukin-17 in serum and the proportions of CD8+T cells and Th17 lymphocytes in the spleen were significantly higher in the former group, whereas the abundances of dendritic cells, B cells, and Treg cells in the spleen were significantly lower. Our results suggest that the gut microbiome influences arthritis susceptibility.

Supported gold (Au) nanocatalysts hold great promise for heterogeneous catalysis; however, their practical application is greatly hampered by poor thermodynamic stability. Herein, a general synthetic strategy is reported where discrete metal nanoparticles are made resistant to sintering, preserving their catalytic activities in high-temperature oxidation processes. Taking advantage of the unique coating chemistry of dopamine, sacrificial carbon layers are constructed on the material surface, stabilizing the supported catalyst. Upon annealing at high temperature under an inert atmosphere, the interactions between support and metal nanoparticle are dramatically enhanced, while the sacrificial carbon layers can be subsequently removed through oxidative calcination in air. Owing to the improved metal-support contact and strengthened electronic interactions, the resulting Au nanocatalysts are resistant to sintering and exhibit excellent durability for catalytic combustion of propylene at elevated temperatures. Moreover, the facile synthetic strategy can be extended to the stabilization of other supported catalysts on a broad range of supports, providing a general approach to enhancing the thermal stability and sintering resistance of supported nanocatalysts.

Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs’ crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. The same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

The self‐assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high‐resolution transmission electron microscopy, and X‐ray diffraction demonstrate that the HRP–GSs bionanocomposites feature ordered hierarchical nanostructures with well‐dispersed HRP intercalated between the GSs. UV‐vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS‐functionalized GSs. Furthermore, the HRP–GSs composites are utilized for the fabrication of enzyme electrodes (HRP–GSs electrodes). Electrochemical measurements reveal that the resulting HRP–GSs electrodes display high electrocatalytic activity to H2O2 with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport efficiency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP–GSs bionanocomposites toward H2O2. As graphene can be readily non‐covalently functionalized by “designer” aromatic molecules with different electrostatic properties, the proposed self‐assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications.