Enhancing O_(2)electroreduction to H_(2)O on Ag/MnO_(2)-CHNTs by boosting a four-electron catalytic pathway

A fundamental question in the oxygen reduction reaction(ORR)is how to rationally control the electrocatalytic selectivity for opening a four-electron reaction pathway.However,it still lacks direct experimental evidence to understand the reaction mechanism.This work unravels that Ag nanoparticles and carbonizing halloysite nanotubes(CHNTs)can trigger the construction of oxygen defects in the MnO_(2),which contribute to the generation of active sites.The Ag/MnO_(2)-CHNTs delivers a superior activity toward ORR with high onset potential,half-wave potential,diffusion-limited current density,long-term durability and methanol tolerance.More importantly,combined with density functional theory calculations,triggering manganese dioxide defects upon the introduction of Ag nanoparticles and CHNTs can alter the electrocatalytic pathway from a two-electron to a direct four-electron direction for ORR,which is the nature of enhanced ORR activity.Based on the analysis of the results,this finding points out a very effective approach for exploring catalysts with the improved performance and durability for ORR reaction.

Transcriptomic and metabolomic analyses reveal that melatonin promotes melon root development under copper stress by inhibiting jasmonic acid biosynthesis

Melatonin has been shown to alleviate the effects of abiotic stress and to regulate plant development.Copper,a common heavy metal and soil pollutant,can suppress plant growth and development.In this work,we explored the protective effects of exogenous melatonin on lateral root formation in response to copper stress using melon seeds subjected to three germination treatments:CK1(control),CK2(300μmol/L CuSO4),and MT3(300μmol/L melatonin+300μmol/L CuSO4).Melatonin pretreatment increased the antioxidant enzyme activities and root vigor,and decreased the proline and malondialdehyde(MDA)contents in the roots of copper-stressed melon seedlings.We then used transcriptomic and metabolomic analyses to explore the mechanisms by which exogenous melatonin protects against copper stress.There were 70 significant differentially expressed genes(DEGs)(28 upregulated,42 downregulated)and 318 significantly differentially expressed metabolites(DEMs)(168 upregulated,150 downregulated)between the MT3 and CK2 treatments.Melatonin pretreatment altered the expression of genes related to redox and cell wall formation processes.In addition,we found that members of the AP2/ERF,BBR/BPC,GRAS,and HD-ZIP transcription factor families may have vital roles in lateral root development.Melatonin also increased the level of Glutathione(GSH),which chelates excess Cu^(2+).The combined transcriptomic and metabolomic analysis revealed DEGs and DEMs involved in jasmonic acid(JA)biosynthesis,including four lipoxygenase-related genes and two metabolites(linoleic acid and lecithin)related to melatonin’s alleviation effect on copper toxicity.This research elucidated the molecular mechanisms of melatonin’s protective effects in copper-stressed melon.

Highly sensitive H_(2)O_(2)-scavenging nano-bionic system for precise treatment of atherosclerosis

In atherosclerosis,chronic inflammatory processes in local diseased areas may lead to the accumulation of reactive oxygen species(ROS).In this study,we devised a highly sensitive H_(2)O_(2)-scavenging nanobionic system loaded with probucol(RPP-PU),to treat atherosclerosis more effectively.The RPP material had high sensitivity to H_(2)O_(2),and the response sensitivity could be reduced from 40 to 10μmol/L which was close to the lowest concentration of H_(2)O_(2)levels of the pathological environment.RPP-PU delayed the release and prolonged the duration of PU in vivo.In Apolipoprotein E deficient(ApoE-/-)mice,RPP-PU effectively eliminated pathological ROS,reduced the level of lipids and related metabolic enzymes,and significantly decreased the area of vascular plaques and fibers.Our study demonstrated that the H_(2)O_(2)-scavenging nanobionic system could scavenge the abundant ROS in the atherosclerosis lesion,thereby reducing the oxidative stress for treating atherosclerosis and thus achieve the therapeutic goals with atherosclerosis more desirably.

CeO_2/CuO catalysts using different template agent for preferential CO oxidation in H_2-rich stream

The CeO2/CuO catalysts using different template agent（F68 L64, F127 and P123） were synthesized by the simple template and impregnation method. They were characterized by FESEM, XRD, N2 physisorption and H2-TPR techniques. It is found that the CeO2/CuO catalysts are double pore distribution, and CeO2 can enter into the gap of CuO supports and form the contact interface of copper and cerium. Among the asprepared catalysts, the CeO2/CuO-F127 catalyst displays better activity at lower temperature and the CeO2/CuO-P123 catalyst presents higher activity at higher temperature. The CeO2/CuO-P123 catalyst has the smallest crystallite sizes of CuO and CeO2 as well as the largest size of cubes, which may improve the interaction of copper and cerium and enhance the performance of CO oxidation.