Mechanistic investigation on Ag-Cu_(2)O in electrocatalytic CO_(2) to CH_(4) by in situ/operando spectroscopic and theoretical analysis

Silver-copper electrocatalysts have demonstrated effectively catalytic performance in electroreduction CO_(2) toward CH_(4),yet a revealing insight into the reaction pathway and mechanism has remained elusive.Herein,we construct chemically bonded Ag-Cu_(2)O boundaries,in which the complete reduction of Cu_(2)O to Cu has been strongly impeded owing to the presence of surface Ag shell.The interfacial confinement effect helps to maintain Cu^(+)sites at the Ag-Cu_(2)O boundaries.Using in situ/operando spectroscopy and theoretical simulations,it is revealed that CO_(2) is enriched at the Ag-Cu_(2)O boundaries due to the enhanced physisorption and chemisorption to CO_(2),activating CO_(2) to form the stable intermediate^(*)CO.The boundaries between Ag shell and the Cu_(2)O mediate local^(*)CO coverage and promote^(*)CHO intermediate formation,consequently facilitating CO_(2)-to-CH_(4) conversion.This work not only reveals the structure-activity relationships but also offers insights into the reaction mechanism on Ag-Cu catalysts for efficient electrocatalytic CO_(2) reduction.

Synchronous activation of Ag nanoparticles and BiOBr for boosting solar-driven CO_(2)reduction

Artificial photosynthesis of valuable chemicals from CO_(2)is a potential way to achieve sustainable carbon cycle.The CO_(2)conversion activity is still inhibited by the sluggish charge kinetics and poor CO_(2)activation.Herein,Ag nanoparticles coupled Bi OBr have been constructed by in-situ photoreduction strategy.The crafting of interface between Ag nanoparticles and Bi OBr nanosheets,achieving an ultra-fast charge transfer.The Bi OBr semiconductor excited electrons and plasmonic Ag nanoparticles generated high-energy hot electrons synchronous accelerates the C=O double bond activation.Thus,the optimized Ag/BiOBr-2 heterostructure shows excellent CO_(2)photoreduction activity with CO production of 133.75 and 6.83μmol/g under 5 h of 300 W Xe lamp and visible light(λ>400 nm)irradiation,which is 1.51 and 2.81 folds versus the pristine Bi OBr,respectively.The mechanism of CO_(2)photoreduction was in-depth understood through in-situ FT-IR spectrum and density functional theory calculations.This study provides some new perspectives into efficient photocatalytic CO_(2)reduction.

Oxygen vacancy enhanced biomimetic superoxide dismutase activity of CeO_(2)-Gd nanozymes

Cerium oxide-based nanozymes have recently drawn much attention in the field of biomedical and antioxidant applications,because of their unique regenerative or autocatalytic properties.Herein,we studied the biomimetic superoxide dismutase(SOD)nanozymes CeO_(2)-Gd that combines the fluorescence properties of rare earth Gd with the antioxidant properties of CeO_(2)nanoparticles,which was prepared via facile route.The structure and composition of the CeO_(2)-Gd were measured and verified by X-ray powder diffraction(XRD),Raman spectroscopy,transmission electron microscopy(TEM),energydispersive X-ray spectroscopy(EDX),and X-ray electron spectroscopy(XPS).Confocal microscopy was used to image cells.Antioxidant performance and cell viability of these nanozymes were measured in vitro using BGC-803 cell.CeO_(2)-Gd nanozymes with a higher Ce^(3+)/Ce^(4+)ratio show higher superoxide dismutase(SOD)mimetic activity.Their antioxidant activity and fluorescence properties of CeO_(2)-Gd in BGC-803 cancer cells are enhanced by oxygen vacancies generated by doping rare-earth elements Gd.This work may guide the future design of CeO_(2)-Gd-based biomimetic nanozymes for anticancer and antioxidant applications.

In-Situ Synthesis of CQDs/BiOBr Material via Mechanical Ball Milling with Enhanced Photocatalytic Performances

Designing simple, efficient, and environmentally friendly methods to construct high-efficient photocatalysts is an important strategy to promote the further development of the field of photocatalysis. Herein, flower-like carbon quantum dots(CQDs)/Bi OBr composite photocatalysts have been prepared via in-situ synthesis by mechanical ball milling in the existence of ionic liquid. The CQDs/Bi OBr composites exhibit higher photo-degradation performance for tetracycline(TC) than Bi OBr monomer and the commercial Bi_(2)O_(3) under visible light irradiation. For comparison, the different Br sources and synthetic methods are chosen to prepare Bi OBr and CQDs/Bi OBr composites. Photocatalysts prepared by ball milling and ionic liquid present significantly enhanced photocatalytic performance for removing TC. In addition, the introduction of CQDs could distinctly enhance the photocatalytic performances of pure Bi OBr. The reason is that CQDs as electron acceptor effectively separate electrons and holes and inhibit their recombination. The intermediates during photocatalytic degradation were tested using liquid chromatography-mass spectrometry(LC-MS) and possible degradation pathways were given. During degradation, ·OH, O_(2)^(·-)and h^(+) were identified to be the main active species based on electron spin resonance(ESR) spectra and free radical trapping experiments. A possible mechanism of CQDs/Bi OBr with enhanced photocatalytic performances was further proposed.

Phenolic glycosides from the stems of Homalium stenophyllum

The phytochemical investigation of the stems of Homalium stenophyllum afforded seven new phenolic glycosides(1-5 and 8-9)and two known compounds(6 and 7).Their structures were elucidated by comprehensive analyses of NMR spectroscopic,mass spectrometric data and chemical hydrolysis.Additionally,their anti-inflammatory activities against the NO production in LPS-induced macrophages were evaluated.

Ce(Ⅲ)-modulation over non-enzymatic Pt/CeO_(2)/GO biosensor with outstanding sensitivity and stability for lactic acid detection

A series of non-enzymatic graphene functionalized biosensors was developed via deposition precipitation method for lactic acid(LA) detection,which we re characterized by transmission electron micro scopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),gas chromatography-mass spectrometry,liquid chromatography-mass spectro metry,and proton nuclear magnetic re sonance(~1H NMR).The electrochemical performances of the non-enzymatic biosensors were measured by means of the electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV) method.The comprehensive analysis of structures shows that Pt,CeO_(2),and GO components interact with each other.During the storing and releasing oxygen,the valence ratio of Ce^(3+)/Ce^(4+) and the number of oxygen vacancies in CeO_(2) change accordingly,which can be conducive to increasing electronic transmission capacity and finally leads to the improvement of electrocatalytic performance.Among them,the Pt/CeO_(2)/GO biosensor containing 0.47 at% platinum exhibits an excellent electrochemical detection performance with high sensitivity of 12.3 μA·L/(mmol·cm^(2)) and a low limit of detection(LOD) of 5.12 μmol/L in a wide linear range from 10 to 900 μmol/L.In addition,the proposed biosensor possesses a promising anti-interference capability,as well as high stability and good reproducibility,which was assessed by testing the cyclic voltammogram in 0.1 mol/L lactic acid one year later.The underlying mechanism was proposed for electrochemical oxidation of LA to carbon dioxide and acetic acid with the synergistic effect among Pt,CeO_(2),and GO.Furthermore,the results of the standard addition method in real samples(human serum and urine samples) reveal that the lactic acid detection of the non-enzymatic Pt/CeO_(2)/GO biosensor is accompanied by high reliability.Thus,it will be a valuable biosensor for in vitro detection of lactic acid level in clinical samples.

Meroterpenoids Possessing Diverse Rearranged Skeletons with Anti-inflammatory Activity from the Mangrove-Derived Fungus Penicillium sp. HLLG-122

Fifteen new meroterpenoids, littoreanoids A—O (1—15), including three rearranged skeleton meroterpenoids (1—3), were isolated from the mangrove-derived fungus Penicillium sp. HLLG-122. Compound 1 was a novel berkeleyacetal-derived meroterpenoid featuring an unusual spirocyclic 2-oxaspiro[5.5]undeca-4,7-dien-3-one moiety. Compound 2 possessed an unusual 6/6/6/6/6 pentacyclic system with a novel 1-hydroxy-7,7-dimethyl-2-oxabicyclo[2.2.2]octan-5-yl acetate moiety. Compound 3 was an unusual 6/7/6/5/6/5/4 polycyclic systems containing a β-lactone ring. The structures and absolute configurations of new compounds were elucidated by HRESIMS, NMR spectroscopy, single crystal X-ray diffraction analysis, and electronic circular dichroism calculations. The plausible biosynthetic pathways of 1—3 were also proposed. Compounds 6 and 11 exhibited anti-inflammatory effects with IC_(50) values of 30.41 and 19.02 μmol/L, respectively. The bioactive compound 11 was selected for the investigation of preliminary mechanism using molecular docking and Western blotting experiments. Compound 11 could suppress the levels of TNF-α and IL-6, and down-regulate the protein expression of iNOS and COX-2 in RAW 264.7 cells.