Understanding the Growth of Electrodeposited PtNi Nanoparticle Films Using Correlated In Situ Liquid Cell Transmission Electron Microscopy and Synchrotron Radiation.

Electrodeposition is a versatile method for synthesizing nanostructured films, but controlling the morphology of films containing two or more elements requires a detailed understanding of the deposition process. We used liquid cell transmission electron microscopy to follow the electrodeposition of PtNi nanoparticle films on a carbon electrode during cyclic voltammetry. These in situ observations show that the film thickness increases with each cycle, and by the fourth cycle, branched and porous structures could be deposited. Synchrotron studies using in situ transmission X-ray microscopy further revealed that Ni was deposited in the oxide phase. Ex situ studies of bulk electrodeposited PtNi nanoparticle films indicated the number of cycles and the scanning rate were the most influential parameters, resulting in a different thickness, a different homogeneity, a different nanoparticle size, and a different surface structure, while the precursor concentration did not have a significant influence. By varying the potential range, we were able to obtain films with different elemental compositions.

Hierarchical Porous Wood Cellulose Scaffold with Atomically Dispersed Pt Catalysts for Low-Temperature Ethylene Decomposition.

Despite the excellent catalytic properties of individual nanoparticles and atomic clusters, the current capabilities to assemble them into a complex system are insufficient for many practical applications. An objective of this work is to develop a fabrication technology that allows for the simultaneous control of the nanoparticle surface chemistry, elemental distribution, microscale geometry, and large-scale assembly. Using a cellulose structure derived from wood, we fabricate hierarchical porous cellulose scaffolds combining with cerium-doped TiO2. This hybrid material serves as the support for atomically dispersed Pt catalysts and is used to successfully decompose ethylene at 0 °C. The fabrication concept developed in this work would allow mitigating the conflict between the required large active surfaces and the difficulties in handling nanopowders in environmental catalysis, including food preservation and indoor air purification. We thus discover a promising route to manufacture multifunctional materials with complex structures by combining a controllable chemical synthesis with the nature-designed wood scaffold.

A triaxial supramolecular weave.

Despite recent advances in the synthesis of increasingly complex topologies at the molecular level, nano- and microscopic weaves have remained difficult to achieve. Only a few diaxial molecular weaves exist-these were achieved by templation with metals. Here, we present an extended triaxial supramolecular weave that consists of self-assembled organic threads. Each thread is formed by the self-assembly of a building block comprising a rigid oligoproline segment with two perylene-monoimide chromophores spaced at 18 Å. Upon π stacking of the chromophores, threads form that feature alternating up- and down-facing voids at regular distances. These voids accommodate incoming building blocks and establish crossing points through CH-π interactions on further assembly of the threads into a triaxial woven superstructure. The resulting micrometre-scale supramolecular weave proved to be more robust than non-woven self-assemblies of the same building block. The uniform hexagonal pores of the interwoven network were able to host iridium nanoparticles, which may be of interest for practical applications.

Electron energy loss spectroscopy investigation through a nano ablated uranium dioxide sample.

A lamella of uranium dioxide (∼10 × âˆ¼10 × âˆ¼0.02-0.20 µm) was produced by focused ion beam for transmission electron and electron energy loss spectroscopy (EELS) examinations. This sample allows quantitative analysis of the EEL spectra recorded for UO2 as a function of the thickness. The M, N, O and P edges were recorded over zero loss to 4000 eV loss. The edges allow reconstruction of the electronic transitions, the lowest energy loss edges for P transitions corresponds to P3 electron transition (17.2 eV) from U6p3/2 level. The edge analysis allows also better interpretation of the loss spectrum with identification of the plasmon peak of the core electron transition edges. In addition, the energy lost was studied through a range of thicknesses going from ∼20 to ∼200 nm to derive the electron mean free path and cross section for inelastic scattering in the plasmon part of the spectrum. The mean free path of inelastic electron for uranium dioxide is compared with that reported earlier for other oxides from Be to Bi and for 200 keV incidents electrons. The present study emphasises the potential of combining FIB and EELS for the analysis of actinide compounds.