Revealing the growth of copper on polystyrene-block-poly(ethylene oxide) diblock copolymer thin films with in situ GISAXS

Copper (Cu) as an excellent electrical conductor and the amphiphilic diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) as a polymer electrolyte and ionic conductor can be combined with an active material in composite electrodes for polymer lithium-ion batteries (LIBs). As interfaces are a key issue in LIBs, sputter deposition of Cu contacts on PS-b-PEO thin films with high PEO fraction is investigated with in situ grazing-incidence small-angle X-ray scattering (GISAXS) to follow the formation of the Cu layer in real-time. We observe a hierarchical morphology of Cu clusters building larger Cu agglomerates. Two characteristic distances corresponding to the PS-b-PEO microphase separation and the Cu clusters are determined. A selective agglomeration of Cu clusters on the PS domains explains the origin of the persisting hierarchical morphology of the Cu layer even after a complete surface coverage is reached. The spheroidal shape of the Cu clusters growing within the first few nanometers of sputter deposition causes a highly porous Cu-polymer interface. Four growth stages are distinguished corresponding to different kinetics of the cluster growth of Cu on PS-b-PEO thin films: (I) nucleation, (II) diffusion-driven growth, (III) adsorption-driven growth, and (IV) grain growth of Cu clusters. Percolation is reached at an effective Cu layer thickness of 5.75 nm.

Influencing the Electron Density of Nanosized Au Colloids via Immobilization on MgO to Stimulate Surface Reaction Activities

Heterogenization of colloidal gold on MgO is demonstrated to facilitate its catalytic surface reactivity. We show that the electron density on Au influenced by its immobilization on MgO along with the ensued metal-support interaction is one of the key parameters to obtain high activity. As elucidated by X-ray absorption spectroscopic (X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and extended X-ray absorption fine structure) studies, the presence of well-dispersed nanosized Au on MgO is observed to result in an enhancement in the electron density of Au. The consequence of this electron-rich gold on the catalytic activity is then investigated using the nitroarene reduction as a model reaction with a detailed kinetic study. The kinetic study is an attempt to use a true heterogeneous system rather than the usually studied quasi-homogeneous systems. The results obtained reveal that the Au/MgO catalyst has a surface rate constant of ∼1.39 × 10^-3 mol m^-2 s^-1, which is significantly higher than those of the reported catalysts. While it validates the higher catalytic activity with a TOF of 9456 h^-1 observed for Au/MgO, the increased adsorption constant for 4-nitrophenol on Au/MgO further reflects the efficacy of MgO as the support. This not only allows effective heterogenization of the Au nanoparticles keeping the catalyst stable under the reaction conditions and being reused several times but also renders a capability in reduction of other nitro group-containing substrates. Therefore, the results are believed to be of importance in designing heterogeneous catalysts utilizing the distinctive properties of the nanosized colloids and tuning their surface reactivity as well.

Sub-monolayer Au9 cluster formation via pulsed nozzle cluster deposition

Submonolayer coverages of chemically synthesised triphenylphosphine-protected Au₉ clusters on mica and TiO₂ substrates were achieved through the development of a Pulsed Nozzle Cluster Deposition (PNCD) technique under high vacuum conditions. This method offers the deposition of pre-prepared, solvated clusters directly onto substrates in a vacuum without the potential for contamination from the atmosphere. AFM and TEM were used to investigate the rate of gold cluster deposition as a function of cluster solution concentration and the number of pulses, with pulse number showing the most effective control of the final deposition conditions. TEM and XPS were used to determine that the clusters retained their unique properties through the deposition process. Methanol solvent deposited in the PNCD process has been shown to be removable through post-deposition treatments. A physical model describing the vapour behaviour and solvent evaporation in a vacuum is also developed and presented.

Regulation of Ni-CNT Interaction on Mn-Promoted Nickel Nanocatalysts Supported on Oxygenated CNTs for CO2 Selective Hydrogenation

Mn-promoted Ni nanoparticles (NPs) supported on oxygen-functionalized carbon nanotubes (CNTs) were synthesized for CO₂ hydrogenation to methane. This novel metal-carbon catalytic system was characterized by both experimental and computational studies. An anomalous metal-support interaction mode (i.e., a higher temperature would lead to a weakened Ni-CNT interaction) was observed. Deep investigation confirmed that surface oxygen groups (SOGs) on CNTs played a key role in tuning the Ni-CNT interaction. We proposed that high calcination temperature would firstly lead to the decomposition of SOGs (>400 °C), then causing a loss of anchoring sites and the anchoring effect of SOGs on Ni NPs, thus cutting off the connection between interfacial Ni atoms and CNT body, resulting in the migration and coalescence of fine flat Ni NPs into larger sphere ones at 550 °C (geometric effect). Density functional theory calculation study clarified that this kind of anchoring effect stemmed from the formation of covalent bonding between the interfacial Ni atom and C or O elements of SOGs, causing the electrons to be transferred from Ni atoms to CNT support because of the intrinsic electronegativity of -COOH (electronic effect). Besides, Mn promotion notably boosts the activity compared with unpromoted catalysts, which was irrelevant to the size effect, but enhanced CO₂ adsorption and conversion according to the result of CO₂-temperature programmed desorption and transient response experiment. The optimized NiMn350 catalyst endowed with Mn promotion and robust Ni-CNT interaction showed both high activity and sintering resistance for more than 140 h. Our findings paved the way to reasonably design the metal-carbon catalyst with both high activity and stability.

On the Dimensional Control of 2 D Hybrid Nanomaterials

Thermotropic smectic liquid crystalline polymers were used as a scaffold to create organic/inorganic hybrid layered nanomaterials. Different polymers were prepared by photopolymerizing blends of a hydrogen bonded carboxylic acid derivative and a 10 % cross-linker of variable length in their liquid crystalline phase. Nanopores with dimensions close to 1 nm were generated by breaking the hydrogen bonded dimers in a high pH solution. The pores were filled with positively charged silver (Ag) ions, resulting in a layered silver(I)-polymeric hybrid material. Subsequent exposure to a NaBH4 reducing solution allowed for the formation of supported hybrid metal/organic films. In the bulk of the film the dimension of the Ag nanoparticles (NPs) was regulated with subnanometer precision by the cross-linker length. Ag nanoparticles with an average size of 0.9, 1.3, and 1.8 nm were produced inside the nanopores thanks to the combined effect of spatially confined reduction and stabilization of the nanoparticles by the polymer carboxylic groups. At the same time, strong Ag migration occurred in the surface region, resulting in the formation of a nanostructured metallic top layer composed of large (10-20 nm) NPs.

Kinetic investigation into the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds catalyzed by Ni(0) nanoparticles

Nickel nanoparticle chemoselective hydrogenation catalytic activity revealed: The catalytic role of high active chemoselective magnetic Ni(0) nanocatalysts for olefin hydrogenation of α,β-unsaturated carbonyl compounds was investigated by kinetic means.

Investigating Polymer-Metal Interfaces by Grazing Incidence Small-Angle X-Ray Scattering from Gradients to Real-Time Studies

Tailoring the polymer-metal interface is crucial for advanced material design. Vacuum deposition methods for metal layer coating are widely used in industry and research. They allow for installing a variety of nanostructures, often making use of the selective interaction of the metal atoms with the underlying polymer thin film. The polymer thin film may eventually be nanostructured, too, in order to create a hierarchy in length scales. Grazing incidence X-ray scattering is an advanced method to characterize and investigate polymer-metal interfaces. Being non-destructive and yielding statistically relevant results, it allows for deducing the detailed polymer-metal interaction. We review the use of grazing incidence X-ray scattering to elucidate the polymer-metal interface, making use of the modern synchrotron radiation facilities, allowing for very local studies via in situ (so-called "stop-sputter") experiments as well as studies observing the nanostructured metal nanoparticle layer growth in real time.

High-Resolution Metal Nanopatterning by Means of Switchable Block Copolymer Templates

In this review, recent developments in the fabrication of hexagonal and parallel ordered arrays of metallic nanodomains on a substrate are described. We focus on the nanopatterning approach by means of switchable block copolymer thin films. This approach is highly advantageous, because it can lead to extremely regular patterns with metal subunits of only a few nanometers in diameter and center-to-center distances of tens of nanometers. Hence, the resulting 1D or 2D periodic arrays of metal nanodots and nanowires on silicon substrates can be fabricated with extremely high unit densities and on very large areas. The templated deposition of presynthesized metal nanoparticles on functional block copolymers is described in detail. Current challenges are discussed and an outlook for further developments is given.

Patterned Diblock Co-Polymer Thin Films as Templates for Advanced Anisotropic Metal Nanostructures

We demonstrate glancing-angle deposition of gold on a nanostructured diblock copolymer, namely polystyrene-block-poly(methyl methacrylate) thin film. Exploiting the selective wetting of gold on the polystyrene block, we are able to fabricate directional hierarchical structures. We prove the asymmetric growth of the gold nanoparticles and are able to extract the different growth laws by in situ scattering methods. The optical anisotropy of these hierarchical hybrid materials is further probed by angular resolved spectroscopic methods. This approach enables us to tailor functional hierarchical layers in nanodevices, such as nanoantennae arrays, organic photovoltaics, and sensor electronics.

Investigation on properties of Pd/CeO2-ZrO2-Pr2O3 catalysts with different Ce/Zr molar ratios and its application for automotive emission control

Pd/CeO2-ZrO2-Pr2O3 (CZP) catalysts with different Ce/Zr molar ratios were synthesized and systematically investigated by XRD, N2 adsorption-desorption, XPS, H2-TPR, OSC and in situ DRIFTS techniques. The results of XPS, in situ DRIFTS, etc., show that the number of oxygen vacancies increases with the increasing Zr content and thus leads to the enhanced metal-support interaction and the accelerative formation rate of nitrate, formate, acetate and carbonate species, resulting in improving catalytic performance for HC and NO elimination, especially for Pd/CZP catalysts with Ce/Zr from 1/2 to 1/3. While Pd/CZP catalysts with higher OSC value (Ce/Zr=4/1-1/2) exhibit better catalytic activity of CO and NO2 elimination. An appropriate concentration of Zr facilitates the diffusion of Pr from the surface to the bulk of the CZP supports, thus forming more homogeneous CZP solid solution and improving the structure/textual stability, which promotes the thermal stability of catalysts. Pd/CZP catalysts with Ce/Zr from 2/1 to 1/2 exhibit good thermal stability.

Effect of graphene with nanopores on metal clusters

Graphene with nanopores can enhance the stability of metal clusters and decrease the CO adsorption. Pd supported on graphene with nanopores will act as a superior CO tolerance catalyst.