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In this study, the synthesis of Co/Al hydrotalcite (layered double hydroxides: LDHs) using insoluble Al[(OH).sub.3] by a hydrothermal method is described. The syntheses were conducted under various conditions. The as-prepared Co/Al-C[O.sub.3.sup.2-]-LDH was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The tribological properties of the products were evaluated in base oil using four-ball and Plint friction testers. The LDH thus synthesized displays perfect hexagonal platelike morphology having a disk diameter in the range of 0.2-1.5 µm with a thickness of 40 nm. The addition of the product Co/Al-C[O.sub.3.sup.2-]-LDH, as an additive to the base oil, significantly reduces the friction coefficient (22.3%) and wear (26.1%) compared to base oil alone. The morphology and chemistry of the worn surface were characterized by SEM, atomic force microscopy (AFM), and X-ray absorption near-edge structure (XANES) spectroscopy. The results show that the structural distortion of LDH induced by mechanochemical processes during friction consumes the friction force between the rubbed surfaces, and as a result, the friction and the wear is reduced. Thus, our results show that the LDH sheets absorbed on the worn surface can prevent direct contact between the friction pairs (surfaces) and decreases the roughness of the worn surface. Key words: Co/Al hydrotalcites, antifriction, tribochemistry, X-ray absorption near-edge structure (XANES). La presente etude decrit la synthese d'hydrotalcite de Co/Al (hydroxydes doubles lamellaires ou HDL) a l'aide d'Al[(OH).sub.3] insoluble par methode hydrothermale. Les syntheses ont ete realisees dans diverses conditions. Les Co/Al-C[O.sub.3.sup.2-]-HDL ainsi prepares ont ete caracterises par diffractometrie de rayons X (DRX) et microscopie electronique a balayage (MEB). Les proprietes tribologiques des produits ont ete etudiees dans de l'huile de base a l'aide de bancs d'essai de frottement a quatre billes et de tribometres Plint. Les HDL ainsi synthetises presentent une morphologie hexagonale parfaite en plaque dont le diametre de disque est compris entre 0,2 et 1,5 µm et l'epaisseur egale a 40 nm. L'ajout du produit Co/Al-C[O.sub.3.sup.2-]-HDL, comme additif a l'huile de base, reduit considerablement le coefficient de frottement (22,3%) et l'usure (26,1%), par rapport a l'huile de base seule. La morphologie et la chimie de la surface usee ont ete caracterisees par MEB, microscopie a force atomique (MFA) et spectroscopie de structure pres du front d'absorption de rayons X. Les resultats montrent que la distorsion structurale des HDL provoquee par les processus mecanochimiques ayant lieu lors des frottements reduit la force de frottement presente entre les surfaces enduites, ce qui entraine une diminution du frottement et de l'usure. Nos resultats demontrent ainsi que les feuilles d'HDL absorbees sur la surface usee peuvent empecher les paires de frottement (surface) d'etre en contact et reduisent la rugosite de la surface usee. [Traduit par la Redaction] Mots-cles: hydrotalcites de Co/Al, antifriction, tribochimie, spectroscopie de structure pres du front d'absorption de rayons X., Introduction Layered double hydroxides (LDHs) are a class of layered anionic clays having the general formula of [[M.sub.(1-x).sup.2+][M.sub.x.sup.3+][(OH).sub.2]][([A.sup.n-]).sub.x/n] x z[H.sub.2]O, where [M.sup.2+] (Mg, Mn, Fe, Co, Ni, Cu, Zn, etc.) [...]

Photoemission spectroscopy (PES) has been used widely to study the electronic structure of valence and core levels. However, conventional PES is surface-sensitive. To probe the interface and bulk properties of materials, hard X-ray photoemission spectroscopy (HXPES) has received increasing interest in the last decade, because of the deep probing ability of photoelectrons with higher kinetic energies (2-10 keV). Recently, a HXPES system was developed at the Canadian Light Source, using the high-energy version of a R4000 electron analyzer-based spectrometer connected to a medium-energy beamline, the soft X-ray microcharacterization beamline (SXRMB). Excellent performance of the beamline and the spectrometer is demonstrated herein using Au Fermi and 4f core lines; and the controlled probing depth of HXPES at SXRMB is demonstrated by tuning the photon energy (2-9 keV) in the study of a series of Si[O.sub.2]/SiC multilayer samples. Combined with the high-resolution X-ray absorption spectroscopy available at the SXRMB, the HXPES offers a powerful nondestructive technique for studying bulk properties of various materials. Key words: XPS, medium energy beamline, bulk property, interface structure, HXPES. La spectroscopie de photoemission (XPS) a ete largement utilisee pour etudier les structures electroniques des couches de valence et de coeur. Toutefois, la spectroscopie XPS classique est dependante de la surface. Afin de permettre l'exploration des proprietes internes et d'interface des materiaux, la spectroscopie de photoemission induite par les rayons X durs (HXPES ou hard X-ray photoemission spectroscopy) a suscite un interet grandissant au cours de la derniere decennie, en raison de la plus grande capacite penetrante qu'offrent les photoelectrons de haute energie cinetique (de 2 a10 keV). Recemment, le Centre canadien de rayonnement synchrotron a mis au point un appareil HXPES, en utilisant un spectrometre constitue d'un analyseur d'electrons de modele R4000 en version a haute energie connecte a une source de rayonnement d'energie intermediaire, soit la source de rayonnement Soft X-Ray Microcharacterization (SXRMB) [rayonnement synchrotron X mou pour la microcaracterisation des materiaux]. En etudiant une serie d'echantillons multicouches de SiO2/SiC, nous faisons ici la demonstration des excellentes performances de la source de rayonnement et du spectrometre, grace a l'etude des bandes du niveau de Fermi et de la couche de coeur 4f de l'or (Au), ainsi que la demonstration de la profondeur de sondage reglable du spectrometre HXPES de la SXRMB, grace au reglage de l'energie des photons (de 2 a 9 keV). Couplee a la spectroscopie d'absorption des rayons X a haute resolution rendue possible par la SXRMB, la spectroscopie HXPES constitue une technique non destructive puissante pour l'etude des proprietes internes de divers materiaux. [Traduit par la Redaction] Mots-cles : XPS, source de rayonnement d'energie intermediaire, proprietes internes, structure d'interface, HXPES., Introduction Photoemission spectroscopy (PES) is a versatile and powerful technique for studying the electronic structure of matter by measuring the kinetic energies of photoelectrons ejected upon the irradiation of atoms [...]

Freestanding Ti[O.sub.2] nanograss-nanotube hierarchical membranes are synthesized from a Ti metal foil by electrochemical anodization. It is found that the two nanostructures exhibit different luminescence properties, which are also affected by the crystal phases upon phase transformation. An unusual near-UV luminescence is observed from the amorphous nanograss, which is found to be excitation element specific. The amorphous nanotube shows no luminescence. Upon calcination, both nanograss and nanotubes are crystalized into the anatase phase with some rutile phase present, and both structures emit visible green luminescence at slightly different energies. The luminescence mechanism is explored using UV-vis spectroscopy, X-ray absorption near-edge structures (XANES), and X-ray excited optical luminescence (XEOL), and its implications are presented. Key words: Ti[O.sub.2] nanotubes, hierarchical membranes, X-ray absorption near-edge structure, X-ray excited optical luminescence. Des membranes hierarchiques composees de nanoherbe-nanotubes de Ti[O.sub.2] sont synthetisees a partir d'une feuille de Ti metallique par anodisation electrochimique. On constate que les deux nanostructures presentent des proprietes de luminescence differentes, par ailleurs influencees par les phases cristallines apres transformation de phase. Une luminescence inhabituelle dans le proche UV est observee, provenant de la nanoherbe amorphe, qui semble etre propre a l'element d'excitation. Le nanotube amorphe ne montre aucune luminescence. Apres calcination, la nanoherbe et les nanotubes sont cristallises sous forme d'anatase, en presence d'un peu de rutile, les deux structures emettant une luminescence dans le vert-visible a des energies legerement differentes. Le mecanisme de luminescence est etudie a l'aide de la spectroscopie UV-visible, de la spectroscopie de structure pres du front d'absorption de rayons X (X-ray absorption near-edge structures ou XANES) et de la luminescence optique excitee par les rayons X (X-ray excited optical luminescence ou XEOL) et les consequences associees a ce mecanisme sont presentees. [Traduit par la Redaction] Mots-cles: nanotubes de Ti[O.sub.2], membranes hierarchiques, spectroscopie de structure pres du front d'absorption de rayons X, luminescence optique excitee par les rayons X., Introduction The chemical and physical properties of Ti[O.sub.2] have been widely studied since it was found to be an excellent candidate for dye-sensitized solar cell (DSSC) and photocatalysis applications. (1-4) [...]

The electrochemical CO2 reduction to CH4 has been extensively demonstrated, but still suffers from relatively poor activity and requires high overpotentials especially at large electrolysis rates. Perovskite oxides (AxByO) are one type of promising electrocatalyst for the CO2 reduction due to their tunable electronic structures. In this work, a Ca2CuO3 perovskite oxide catalyst is developed with alkaline‐earth A‐sites, featuring an inherently strong basic strengthand outstanding capability for CO2 adsorption, as well as the undercoordinated Cu sites generated through partial surface Ca2+ cation leaching. The Ca2CuO3 catalyst exhibitsa high partial current density of 517 ± 23 mA cm−2 for producing CH4 at a low applied potential of −0.30 V versus reversible hydrogen electrode, which further reached to a peak value of 1452 ± 156 mA cm−2. Density functional calculations show that the undercoordinated Cu sites allowed to promote the hydrogenation of *CO and subsequent *CHO intermediates, thus leading to the high CH4 activity. This work suggests an attractive design strategy for tuning the A‐sites in perovskite oxides to realize high‐rate CO2‐to‐CH4 electrosynthesis with low overpotentials. [ABSTRACT FROM AUTHOR]

Photothermal catalytic conversion of waste plastics into fuels and/or feedstocks using renewable solar energy can achieve solar‐to‐chemical conversion, resource sustainability, and environmental remediation simultaneously. However, the construction of photothermal catalysts with strong light absorption and high catalytic activity remains a great challenge. In this work, integrated cobalt single‐site catalysts (Co SSCs), coupled with strong photothermal conversion, high catalytic activity, and stability, are employed to catalyze the glycolysis of polyesters. The unique coordination‐unsaturated CoO5 single‐site can coordinate with the carbonyl groups in polyester, thus boosting the nucleophilic addition elimination processes. As a result, the space‐time yield of Co SSCs is an order of magnitude higher than that of general catalysts. In addition, the polyethylene terephthalate (PET) conversion and bis(2‐hydroxyethyl) terephthalate yield in photothermal catalysis are 5.4 and 6.6 times higher than those of thermal catalysis under the same conditions, which are contributed by the localized heating effect. Technical economic analysis shows that the recycling of 105 tons of waste PET by photothermal catalysis consumes 146.4 GW·h electrical energy and misses 7.44 × 104 tons of CO2 emission. Therefore, a high‐efficient photothermal catalytic plastic recycling system is of great significance for waste plastic valorization. [ABSTRACT FROM AUTHOR]

ZnO nanostructures of various morphologies and crystallinities were fabricated by thermal evaporation from Zn powder in a tube furnace in the presence of oxygen. It was found that the morphology of ZnO nanostructures was affected by synthesis parameters, such as growth temperature, carrier gas flow, and the presence of catalyst on the surface of the substrate. Representative ZnO nanostructures were studied by X-ray excited optical luminescence (XEOL) and cathodoluminescence (CL) methods. The luminescence from these samples exhibits a morphology dependence of the branching ratio of the near band gap (NBG) emission in the UV and defect emission in the green (GE). The appearance of the optical emission also depends on the excitation method. X-ray absorption near-edge structures (XANES) at the O K-edge and Zn L-edge are also presented and their implications discussed. Key words: ZnO nanostructures, XEOL, XANES, cathodoluminescence. Faisant appel a une methode d'evaporation thermique d'une poudre de Zn dans un four electrique a tube en presence d'oxygene, on a fabrique des nanostructures de ZnO de morphologies et de cristallinites diverses. On a trouve que la morphologie des nanostructures de ZnO est affectee par divers parametres de la synthese, telle la temperature de croissance, la vitesse d'ecoulement du gaz et la presence de catalyseur sur la surface du substrat. On a etudie les structures de nanostructures de ZnO representatives en faisant appel aux methodes de luminescence optique excitee par rayons-X (LOEX) et de cathodoluminescence (CL). La luminescence dans ces echantillons presente, dans l'UV, une relation entre la morphologie sur le rapport de ramification et l'emission de la bande interdite rapprochee (BIR) et l'emission de defaut dans le vert (EV). L'apparition d'une emission optique depend aussi de la methode d'excitation. On a aussi determine les structures d'absorption des rayons-X pres du seuil (' XANES ') au seuil K de l'oxygene et au seuil L du zinc et on discute de leurs implications. Mots-cles : nanostructures du ZnO, luminescence optique excitee par rayons X (LOEX), structures d'absorption des rayons X pres du seuil (<< XANES >>), cathodoluminescence. [Traduit par la Redaction], Introduction Zinc oxide, a versatile technological material for light emitting and photonic applications (e.g., solid-state lasers and LEDs), is a semiconductor with a wide band gap (~3.37 eV) and large [...]

The 2023 Canadian Chemistry Conference and Exhibition featured a synchrotron research symposium that showcased the diversity of the field. The symposium included 13 distinguished invited speakers and 22 contributing talks and posters from researchers around the world. Topics covered a wide range of research fields, including sustainable energy, catalysis, biomedicine, and the use of synchrotron techniques in cultural heritage. The symposium was organized by a team of researchers from Western University and the Canadian Light Source, and it highlighted the importance of international collaboration and the involvement of graduate students in synchrotron research. The event marked a milestone in the field and demonstrated the ongoing commitment to advancing synchrotron research through future events and workshops. [Extracted from the article]

ZnO nanostructures have been synthesized by thermal evaporation on Si substrates. It is found that the morphologies of the nanostructures are governed by growth conditions such as temperature, carrier-gas flow rate, and the nature of the substrate (with and without a catalyst). We report X-ray excited optical luminescence from ZnO nanostructures of distinctly different morphologies in the energy and time domain using excitation photon energies across the Zn K-edge. X-ray excited optical luminescence (XEOL) and X-ray absorption near edge structure (XANES) study has clearly shown the morphology dependence of the ZnO optical properties. A correlation of luminescence with morphology, size, and crystallinity emerges. Key words: ZnO nanostructures, XEOL, TRXEOL, XANES, vapour deposition. Resume : On a synthetise des nanostructures de ZnO par evaporation thermique de substrats contenant de l'etain. On a trouve que les morphologies des nanostructures sont gouvernees par les conditions de croissance, la vitesse d'ecoulement du gaz porteur et la nature du substrat, avec ou sans catalyseur. Utilisant des energies photoniques d'excitation sur l'arete K du zinc, on a pu observer de la luminescence optique excitee par les rayons X a partir de nanostructures de ZnO de morphologies comportant des differences importantes dans le domaine du temps et de l'energie. Des etudes de luminescence optique excitee par les rayons X << XEOL >> et par la spectroscopie de la structure fine d'absorption des rayons X pres du seuil << XANES >> ont clairement demontre l'importance de la morphologie sur les proprietes optiques du ZnO. Il en emerge une correlation entre la luminescence et la morphologie, la taille et la cristallinite. Mots-cles : nanostructures de ZnO, luminescence optique excitee par les rayons X << XEOL >>, spectroscopie de la structure fine d'absorption des rayons X pres du seuil << XANES >>, depot de vapeur. [Traduit par la Redaction], Introduction Zinc oxide, a wide-band-gap semiconductor ([E.sub.g] = 3.37 eV at room temperature), ranks high among oxide semiconductors for its unique properties. With suitable doping, the band gap of ZnO [...]

We report the chemical synthesis and structural studies of thiol-capped Au nanoparticles (NPs) using extended X-ray absorption fine structures (EXAFS) and high-resolution transmission electron microscopy (HRTEM). Synthesis of Au NPs was conducted in one case in a toluene/water two-phase system using alkanethiols with varied hydrocarbon chain length (C6, C12, and C18), resulting in NPs of sizes ranging from 1.6 nm to 5.4 nm. Au [L.sub.3]-edge EXAFS reveals a systematical trend of the local structure of Au in the NPs when the Au/S ratio and chain-length of thiols are varied. In another synthesis, thiol-capped Au NPs were prepared on the surface of silicon nanowires, which act as both substrates and reducing agents. HRTEM reveals that not only spherical particles but also very small quasi-1D nanostructures of Au were formed. The formation and structure of these Au NPs was discussed in terms of ligand and template effect associated with the silicon nanowire substrates. Key words: thiol-capped Au nanoparticles, EXAFS, silicon nanowires, electroless deposition, quasi-1D Au nanostructures. On a realise la synthese de nanoparticules (NP) d'or coiffees d'un thiol et on en a fait des etudes structurales en faisant appel a la methode des structures fines d'absorption des rayons X etendue(SFAXE) et a la microscopie electronique de transmission a haute resolution (METHR). La synthese des NP d'or a ete realise, dans un cas, dans un systeme binaire toluene/eau et en utilisant des alcanethiols avec des chaenes carbonees de diverses (C6, C12 et C18) conduisant a des NP dont la taille allait de 1,6 a 5,4 nm. Les etudes de SFAXE a la limite [L.sub.3] revelent la presence d'une tendance systematique de la structure locale de l'or dans les NP avec une variation du rapport Au/S et des longueurs des chaenes des thiols. Dans une autre methode de synthese, les NP d'or coiffees de thiol ont ete preparees a la surface de nanofils de silicium qui agissent a la fois comme substrats et comme agents reducteurs. La METHR revele qu'il y a formation non seulement de particules spheriques, mais aussi de tres petites nanostructures quasi unidimensionnelles d'or. On discute de la formation et des structures de ces NP d'or en termes de ligand et d'effet de gabarit associe aux substrats nanofils de silicium. Mots-cles : nanoparticules d'or coiffees d'un thiol, SFAXE, nanofils de silicium, depot sans electrode, nanostructures d'or quasi unidimensionnelles. [Traduit par la Redaction], Introduction During the past decade or so, thiol-capped gold nanoparticle (NP) has emerged as a prototype of nano-structured materials whose important role can be found in a variety of fundamental [...]

Abstract: In this study, we show that colour centres can be produced by irradiating calcium oxide with soft X-rays from a synchrotron radiation source. Using the X-ray excited optical luminescence [...]

Abstract: CdSe nanocrystals (NCs), capped with trioctylphosphine oxide and 1-octadecanamine, have been synthesized with colloidal methods. Both UV-vis absorption and photoluminescence spectra show that the prepared nanostructures exhibit a quantum [...]

X-ray absorption near-edge structure (XANES) was used to study the cubic boron nitride (c-BN) content in the BN films deposited on various substrates by different physical vapor deposition or plasma-enhanced chemical vapor deposition methods. By fitting the XANES curves of thinfilm samples using standard spectra of pure c-BN and [sp.sup.2]-bonded BN in the films with suitable weight factors, the c-BN contents at the film's surface region and across the film's thickness have been determined quantitatively. The results agree well with the previous transmission electron microscopic observations. The method is proved to be independent of the optical properties of thin film and provides a possibility to evaluate the cubic content of BN films accurately.