Direct observation of the dynamic reconstructed active phase of perovskite LaNiO3 for the oxygen-evolution reaction.

Ni-based transition metal oxides are promising oxygen-evolution reaction (OER) catalysts due to their abundance and high activity. Identification and manipulation of the chemical properties of the real active phase on the catalyst surface is crucial to improve the reaction kinetics and efficiency of the OER. Herein, we used electrochemical-scanning tunnelling microscopy (EC-STM) to directly observe structural dynamics during the OER on LaNiO3 (LNO) epitaxial thin films. Based on comparison of dynamic topographical changes in different compositions of LNO surface termination, we propose that reconstruction of surface morphology originated from transition of Ni species on LNO surface termination during the OER. Furthermore, we showed that the change in surface topography of LNO was induced by Ni(OH)2/NiOOH redox transformation by quantifying STM images. Our findings demonstrate that in situ characterization for visualization and quantification of thin films is very important for revealing the dynamic nature of the interface of catalysts under electrochemical conditions. This strategy is crucial for in-depth understanding of the intrinsic catalytic mechanism of the OER and rational design of high-efficiency electrocatalysts.

Honokiol Reduces Mitochondrial Dysfunction and Inhibits Apoptosis of Nerve Cells in Rats with Traumatic Brain Injury by Activating the Mitochondrial Unfolded Protein Response.

This study was designed to determine the effects and underlying mechanism of honokiol (HNK) on traumatic brain injury (TBI). A rat TBI model was constructed using the modified Feeney free-fall percussion method and treatment with HNK via intraperitoneal injection. The brain tissues of the rats in each group were assessed using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay to detect the level of neuronal apoptosis. Western blots were used to detect the expression levels of apoptosis-related proteins (Bcl-2 and Bax), and ELISAs were used to measure the levels of pro-inflammatory cytokines (IL-18 and IL-1ß) and the activity of caspase-1. In addition, the mitochondrial membrane potential, reactive oxygen species (ROS), and adenosine 5'-triphosphate (ATP) were also measured. Western blots and qRT-PCRs were used to determine the relative expression levels of the mitochondrial unfolded protein response (UPRmt)-related proteins and mRNAs. Based on the experimental results, treatment with HNK was associated with a decrease in the number of TUNEL-positive cells, downregulated Bax expression levels, elevated Bcl-2 expression levels, and inhibition of neuronal apoptosis in the brain tissue of TBI rats. HNK also suppressed neuroinflammation by decreasing IL-1ß and IL-18 levels and caspase-1 activity. Additionally, HNK lowered the mitochondrial membrane potential and ROS levels, increased ATP levels, and improved mitochondrial dysfunction in neural cells. Furthermore, in the investigation of the mechanism of HNK on TBI, we observed that HNK could activate UPRmt by upregulating the mRNA and protein expression levels of HSPA9, CLPP, and HSP60 in the brain tissues of TBI rats. Collectively, HNK reduced mitochondrial dysfunction, inhibited the apoptosis of nerve cells, and attenuated inflammation in the brains of TBI rats. The protective effect of HNK may be achieved through the activation of UPRmt.

In Situ Anodic Oxidation Tuning of NiFeV Diselenide to the Core-Shell Heterojunction for Boosting Oxygen Evolution.

Developing non-noble metal-based core-shell heterojunction electrocatalysts with high catalytic activity and long-lasting stability is crucial for the oxygen evolution reaction (OER). Here, we prepared novel core-shell Fe,V-NiSe2@NiFe(OH)x heterostructured nanoparticles on hydrophilic-treated carbon paper with high electronic transport and large surface area for accelerating the oxygen evolution rate via high-temperature selenization and electrochemical anodic oxidation procedures. Performance testing shows that Fe,V-NiSe2@NiFe(OH)x possesses the highest performance for OER compared to as-prepared diselenide core-derived heterojunctions, which only require an overpotential of 243 mV at 10 mA cm-2 and a low Tafel slope of 91.6 mV decade-1 under basic conditions. Furthermore, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) confirm the morphology and elementary stabilities of Fe,V-NiSe2@NiFe(OH)x after long-term chronopotentiometric testing. These advantages are largely because of the strong synergistic effect between the Fe,V-NiSe2 core with high conductivity and the amorphous NiFe(OH)x shell with enriched defects and vacancies. This study also presents a general approach to designing and synthesizing more active core-shell heterojunction electrocatalysts for OER.

Novel steroidal saponin isolated from Trillium tschonoskii maxim. exhibits anti-oxidative effect via autophagy induction in cellular and Caenorhabditis elegans models.

BACKGROUND: Emerging evidences indicate the important roles of autophagy in anti-oxidative stress, which is closely associated with cancer, aging and neurodegeneration. OBJECTIVE: In the current study, we aimed to identify autophagy inducers with potent anti-oxidative effect from traditional Chinese medicines (TCMs) in PC-12 cells and C. elegans. METHODS: The autophagy inducers were extensively screened in our herbal extracts library by using the stable RFP-GFP-LC3 U87 cells. The components with autophagic induction effect in Trillium tschonoskii Maxim. (TTM) was isolated and identified by using the autophagic activity-guided column chromatography and Pre-HPLC technologies, and MS and NMR spectroscopic analysis, respectively. The anti-oxidative effect of the isolated autophagy inducers was evaluated in H2O2-induced PC-12 cells and C. elegans models by measuring the viability of PC-12 cells and C. elegans, with quantitation on the ROS level in vitro and in vivo using H2DCFDA probe. RESULTS: The total ethanol extract of TTM was found to significantly increase the formation of GFP-LC3 puncta in stable RFP-GFP-LC3 U87 cells. One novel steroidal saponin 1-O-[2,3,4-tri-O-acetyl-α-L-rhamnopyranosyl-(1→2)-4-O-acetyl-α-L-arabinopyranosyl]-21-Deoxytrillenogenin, (Deoxytrillenoside CA, DTCA) and one known steroidal saponin 1-O-[2,3,4-tri-O-acetyl-α-L-rhamnopyranosyl-(1→2)-4-O-acetyl-α-L-arabinopyranosyl]-21-O-acetyl-epitrillenogenin (Epitrillenoside CA, ETCA) were isolated, identified and found to have novel autophagic effect. Both DTCA and ETCA could activate autophagy in PC-12 cells via the AMPK/mTOR/p70S6K signaling pathway in an Atg7-dependent. In addition, DTCA and ETCA could increase the cell viability and decrease the intracellular ROS level in H2O2-treated PC-12 cells and C. elegans, and the further study demonstrated that the induced autophagy contributes to their anti-oxidative effect. CONCLUSION: Our current findings not only provide information on the discovery of novel autophagy activators from TTM, but also confirmed the anti-oxidative effect of the components from TTM both in vitro and in vivo.

Superior activity of Pd nanoparticles confined in carbon nanotubes for hydrogen production from formic acid decomposition at ambient temperature.

Designing highly efficient and low-cost catalysts is essential toward realizing the practical application of hydrogen generation by formic acid decomposition (FAD) under ambient conditions. Herein, we report the synthesis of a hybrid material of Pd nanoparticles encapsulated within carbon nanotubes (CNTs) (Pd-CNTs-in). Transmission electron microscopy images show that most Pd nanoparticles (mean diameter 4.2 ±â€¯0.8 nm) are located inside the nanotubes. Temperature-programmed reduction studies of H2 reveal that the average reduction temperature of the Pd(II) species adsorbed on the interior wall of the CNTs is 12 °C lower than those adsorbed on the outer walls of the CNT. Moreover, the as-prepared Pd-CNTs-in catalysts show extremely high FAD activity and durability at ambient temperature. The turn over frequency (TOF) value is as high as 1135 h-1 for the initial 10 min and does not decay significantly during the consecutive 3-time recycling studies. X-Ray photoelectron spectroscopy (XPS), surface-enhanced infrared spectroscopy (SEIRAS), and gas chromatography (GC) studies indicate that CNT confinement induced electronic structure modulation of Pd could be the major reason for the enhancement of FAD catalysis on the Pd-CNTs-in surface. This work could provide promising strategies for the fabrication of cost-effective and high-active Pd-based catalysts for formic acid dehydrogenation.