A PVP-stabilized cerium oxide-platinum nanocomposite synthesized in TEG: pro-/antioxidant activities.

Cerium oxide nanoparticles (CeNPs) represent a highly promising material for a number of chemical and biological applications involving oxidation-reduction processes. However, the impact of synthesis conditions, as well as the incorporation of synergistic agents of a different catalytic nature, on the antioxidant or prooxidant properties of CeNPs remains a subject of ongoing investigation. In this study, non-stoichiometric CeNPs (∼10% Ce) stabilized by polyvinylpyrrolidone (PVP) were synthesized through the thermal autoxidative decomposition of cerium(iii) nitrate in a high-boiling glycol.

Unraveling the Effects of Reducing and Oxidizing Pretreatments and Humidity on the Surface Chemistry of the Ru/CeO Catalyst during Propane Oxidation.

This work investigates the surface chemistry of the Ru/CeO catalyst under varying pretreatment conditions and during the oxidation of propane, focusing on both dry and humid environments. Our results show that the Ru/CeO catalyst calcined in O at 500 °C initiates propane oxidation at 200 °C, achieves high conversion rates above 400 °C, and demonstrates almost no change in activity in the presence of water vapor across the entire studied temperature range of 200-500 °C. Prereduction of the oxidized Ru/CeO catalyst in H significantly enhances its activity, though this enhancement diminishes at higher temperatures.

Balancing Activity and Stability through Compositional Engineering of Ternary PtNi-Au Alloy ORR Catalysts.

Achieving the optimal balance between cost-efficiency and stability of oxygen reduction reaction (ORR) catalysts is currently among the key research focuses aiming at reaching a broader implementation of proton-exchange membrane fuel cells (PEMFCs). To address this challenge, we combine two well-established strategies to enhance both activity and stability of platinum-based ORR catalysts. Specifically, we prepare ternary PtNi-Au alloys, where each alloying element plays a distinct role: Ni reduces costs and boosts ORR activity, while Au enhances stability.

Electronic and Structural Properties of Thin Iron Oxide Films on CeO.

Modification of CeO (ceria) with 3d transition metals, particularly iron, has been proven to significantly enhance its catalytic efficiency in oxidation or combustion reactions. Although this phenomenon is widely reported, the nature of the iron-ceria interaction responsible for this improvement remains debated. To address this issue, we prepared well-defined model FeO/CeO(111) catalytic systems and studied their structure and interfacial electronic properties using photoelectron spectroscopy, scanning tunneling microscopy, and low-energy electron diffraction, coupled with density functional theory (DFT) calculations.

Microstructure, chemical composition, and dielectric response of CaCuTiO ceramics doped with F, Al, and Mg ions.

Ceramics with nominal chemical composition CaCuTiO (CCTO), CaCuTiAlOF (CCTOAF), and CaMgCuTiAlOF (CCTOMAF) were prepared by the solid-state reactions technique. Using SEM, EDX, XPS, EPR, NMR, and complex impedance spectroscopy, the microstructure, elements distribution, chemical composition of grains and grain boundaries, and the dielectric response of ceramics were investigated. In the ССТО, CCTOAF, and CCTOMAF series, the average grain size increases, the degree of copper segregation at the grain boundaries is inversely related to grain size, and the dielectric loss decreases from 0.

Role of the redox state of cerium oxide on glycine adsorption: an experimental and theoretical study.

The role of the oxidation state of cerium cations in a thin oxide film in the adsorption, geometry, and thermal stability of glycine molecules was studied. The experimental study was performed for a submonolayer molecular coverage deposited in vacuum on CeO(111)/Cu(111) and CeO(111)/Cu(111) films by photoelectron and soft X-ray absorption spectroscopies and supported by calculations for prediction of the adsorbate geometries, C 1s and N 1s core binding energies of glycine, and some possible products of the thermal decomposition. The molecules adsorbed on the oxide surfaces at 25 °C in the anionic form the carboxylate oxygen atoms bound to cerium cations.

Optimal Pt-Au Alloying for Efficient and Stable Oxygen Reduction Reaction Catalysts.

Stabilization of cathode catalysts in hydrogen-fueled proton-exchange membrane fuel cells (PEMFCs) is paramount to their widespread commercialization. Targeting that aim, Pt-Au alloy catalysts with various compositions (PtAu, PtAu, and PtAu) prepared by magnetron sputtering were investigated. The promising stability improvement of the Pt-Au catalyst, manifested in suppressed platinum dissolution with increasing Au content, was documented over an extended potential range up to 1.

In Situ Spectroscopy and Microscopy Insights into the CO Oxidation Mechanism on Au/CeO(111).

In this work, we prepared and investigated in ultra-high vacuum (UHV) two stoichiometric CeO(111) surfaces containing low and high amounts of step edges decorated with 0.05 ML of gold using synchrotron-radiation photoelectron spectroscopy (SRPES) and scanning tunneling microscopy (STM). The UHV study helped to solve the still unresolved puzzle on how the one-monolayer-high ceria step edges affect the metal-substrate interaction between Au and the CeO(111) surface.

Metal-Support Interaction and Charge Distribution in Ceria-Supported Au Particles Exposed to CO.

Understanding how reaction conditions affect metal-support interactions in catalytic materials is one of the most challenging tasks in heterogeneous catalysis research. Metal nanoparticles and their supports often undergo changes in structure and oxidation state when exposed to reactants, hindering a straightforward understanding of the structure-activity relations using only ex situ or ultrahigh vacuum techniques. Overcoming these limitations, we explored the metal-support interaction between gold nanoparticles and ceria supports in ultrahigh vacuum and after exposure to CO.

Comparison of Antibacterial Mode of Action of Silver Ions and Silver Nanoformulations With Different Physico-Chemical Properties: Experimental and Computational Studies.

The aim of this study was to compare the antibacterial mode of action of silver ions (Ag) and selected silver nanoformulations against strains ( J53, BW25113 and its derivatives: Δ A, Δ C, Δ F, Δ R, ompRG596AcusSG1130A, cusSG1130A). In this research we used various experimental methods and techniques such as determination of the minimal inhibitory concentration, flow cytometry, scanning electron microscopy, circular dichroism as well as computational methods of theoretical chemistry. Thanks to the processing of bacteria and silver samples (ions and nanoformulations), we were able to determine the bacterial sensitivity to silver samples, detect reactive oxygen species (ROS) in the bacterial cells, visualize the interaction of silver samples with the bacterial cells, and identify their interactions with proteins.

Growth Inhibition of Gram-Positive and Gram-Negative Bacteria by Zinc Oxide Hedgehog Particles.

Purpose: Nanomaterials for antimicrobial applications have gained interest in recent years due to the increasing bacteria resistance to conventional antibiotics. Wound sterilization, water treatment and surface decontamination all avail from multifunctional materials that also possess excellent antibacterial properties, eg zinc oxide (ZnO). Here, we assess and compare the effects of synthesized hedgehog-like ZnO structures and commercial ZnO particles with and without mixing on the inactivation of bacteria on surfaces and in liquid environments.

Colloidal stability and catalytic activity of cerium oxide nanoparticles in cell culture media.

One of the biggest challenges for the biomedical applications of cerium oxide nanoparticles (CeNPs) is to maintain their colloidal stability and catalytic activity as enzyme mimetics after nanoparticles enter the human cellular environment. This work examines the influences of CeNP surface properties on their colloidal stability and catalytic activity in cell culture media (CCM). Near-spherical CeNPs stabilized different hydrophilic polymers were prepared through a wet-chemical precipitation method.

New Insights towards High-Temperature Ethanol-Sensing Mechanism of ZnO-Based Chemiresistors.

In this work, we investigate ethanol (EtOH)-sensing mechanisms of a ZnO nanorod (NRs)-based chemiresistor using a near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). First, the ZnO NRs-based sensor was constructed, showing good performance on interaction with 100 ppm of EtOH in the ambient air at 327 °C. Then, the same ZnO NRs film was investigated by NAP-XPS in the presence of 1 mbar oxygen, simulating the ambient air atmosphere and O/EtOH mixture at the same temperature.

In situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy Reveals the Influence of Photon Flux and Water on the Stability of Halide Perovskite.

For several years, scientists have been trying to understand the mechanisms that reduce the long-term stability of perovskite solar cells. In this work, we examined the effect of water and photon flux on the stability of CH NH PbI perovskite films and solar cells using in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), field emission scanning electron microscopy (FESEM), and current density-voltage (J-V) characterization. The used amount of water vapor (up to 1 mbar) had a negligible impact on the perovskite film.

Unraveling the Surface Chemistry and Structure in Highly Active Sputtered PtY Catalyst Films for the Oxygen Reduction Reaction.

Platinum is the most widely used and best performing sole element for catalyzing the oxygen reduction reaction (ORR) in low-temperature fuel cells. Although recyclable, there is a need to reduce the amount used in current fuel cells for their extensive uptake in society. Alloying platinum with rare-earth elements such as yttrium can provide an increase in activity of more than seven times, reducing the amount of platinum and the total amount of catalyst material required for the ORR.

Room-Temperature Atomic-Layer-Deposited Al O Improves the Efficiency of Perovskite Solar Cells over Time.

Electrical characterisation of perovskite solar cells consisting of room-temperature atomic-layer-deposited aluminium oxide (RT-ALD-Al O ) film on top of a methyl ammonium lead triiodide (CH NH PbI ) absorber showed excellent stability of the power conversion efficiency (PCE) over a long time. Under the same environmental conditions (for 355 d), the average PCE of solar cells without the ALD layer decreased from 13.6 to 9.

Inhibition of E. coli Growth by Nanodiamond and Graphene Oxide Enhanced by Luria-Bertani Medium.

Nanodiamonds (NDs) and graphene oxide (GO) are modern carbon-based nanomaterials with promising features for the inhibition of microorganism growth ability. Here we compare the effects of nanodiamond and graphene oxide in both annealed (oxidized) and reduced (hydrogenated) forms in two types of cultivation media-Luria-Bertani (LB) and Mueller-Hinton (MH) broths. The comparison shows that the number of colony forming unit (CFU) of is significantly lowered (45%) by all the nanomaterials in LB medium for at least 24 h against control.

In situ electrochemical AFM monitoring of the potential-dependent deterioration of platinum catalyst during potentiodynamic cycling.

A platinum catalyst undergoes complex deterioration process during its operation as a cathode in a proton exchange membrane fuel cell. By using in situ electrochemical atomic force microscopy (EC-AFM) with super-sharp probes, we quantitatively describe the roughening of platinum thin films during electrochemical cycling to different upper potentials, which simulate critical operation regimes of the proton exchange membrane fuel cell. The comprehensive quantitative analysis of morphology changes obtained using common roughness descriptors such as the root mean square roughness, the correlation length and the roughness exponent is correlated with cyclic voltammetry performed simultaneously.

Creating single-atom Pt-ceria catalysts by surface step decoration.

Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, single metal atoms are stabilized by specific adsorption sites on catalyst substrates. Here we show by combining photoelectron spectroscopy, scanning tunnelling microscopy and density functional theory calculations that Pt single atoms on ceria are stabilized by the most ubiquitous defects on solid surfaces--monoatomic step edges.

Heteroepitaxy of Cerium Oxide Thin Films on Cu(111).

An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties.

Revealing chemical ordering in Pt-Co nanoparticles using electronic structure calculations and X-ray photoelectron spectroscopy.

The high catalytic activity of Pt-Co nanoalloys in oxygen reduction and other reactions is usually attributed to their Pt-rich surfaces. However, identification of the precise near-surface structure is by no means easily achievable experimentally. In this work we systematically analyzed the chemical ordering and surface composition of PtXCo(79-X) and PtXCo(140-X) bimetallic nanoparticles by means of a recently developed method based on topological energy expressions and electronic structure calculations.

Growth and composition of nanostructured and nanoporous cerium oxide thin films on a graphite foil.

The morphology and composition of CeOx films prepared by r.f. magnetron sputtering on a graphite foil have been investigated mainly by using microscopy methods.

Maximum noble-metal efficiency in catalytic materials: atomically dispersed surface platinum.

Platinum is the most versatile element in catalysis, but it is rare and its high price limits large-scale applications, for example in fuel-cell technology. Still, conventional catalysts use only a small fraction of the Pt content, that is, those atoms located at the catalyst's surface. To maximize the noble-metal efficiency, the precious metal should be atomically dispersed and exclusively located within the outermost surface layer of the material.

Preparation of magnetron sputtered thin cerium oxide films with a large surface on silicon substrates using carbonaceous interlayers.

The study focuses on preparation of thin cerium oxide films with a porous structure prepared by rf magnetron sputtering on a silicon wafer substrate using amorphous carbon (a-C) and nitrogenated amorphous carbon films (CNx) as an interlayer. We show that the structure and morphology of the deposited layers depend on the oxygen concentration in working gas used for cerium oxide deposition. Considerable erosion of the carbonaceous interlayer accompanied by the formation of highly porous carbon/cerium oxide bilayer systems is reported.