Graphene-supported nanoelectrocatalysts for fuel cells: synthesis, properties, and applications.

Functionalization of carbon nanomaterials for advanced polymer nanocomposites: A comparison study between CNT and graphene

https://hal.archives-ouvertes.fr/hal-01087663/document

Structuration, selective dispersion and compatibilizing effect of (nano)fillers in polymer blends

Heterogeneous catalysis involves solid-state catalysts, among which metal nanoparticles occupy an important position. Unfortunately, no two nanoparticles from conventional synthesis are the same at the atomic level, though such regular nanoparticles can be highly uniform at the nanometer level (e.g., size distribution ∼5%). In the long pursuit of well-defined nanocatalysts, a recent success is the synthesis of atomically precise metal nanoclusters protected by ligands in the size range from tens to hundreds of metal atoms (equivalently 1-3 nm in core diameter). More importantly, such nanoclusters have been crystallographically characterized, just like the protein structures in enzyme catalysis. Such atomically precise metal nanoclusters merge the features of well-defined homogeneous catalysts (e.g., ligand-protected metal centers) and enzymes (e.g., protein-encapsulated metal clusters of a few atoms bridged by ligands). The well-defined nanoclusters with their total structures available constitute a new class of model catalysts and hold great promise in fundamental catalysis research, including the atomically precise size dependent activity, control of catalytic selectivity by metal structure and surface ligands, structure-property relationships at the atomic-level, insights into molecular activation and catalytic mechanisms, and the identification of active sites on nanocatalysts. This Review summarizes the progress in the utilization of atomically precise metal nanoclusters for catalysis. These nanocluster-based model catalysts have enabled heterogeneous catalysis research at the single-atom and single-electron levels. Future efforts are expected to achieve more exciting progress in fundamental understanding of the catalytic mechanisms, the tailoring of active sites at the atomic level, and the design of new catalysts with high selectivity and activity under mild conditions.

Toward Active-Site Tailoring in Heterogeneous Catalysis by Atomically Precise Metal Nanoclusters with Crystallographic Structures.

Metal nanoparticles supported on two-dimensional graphenes as heterogeneous catalysts

Polymer-coated gold nanoparticles (Au NPs) with controlled size and surface chemistry were successfully synthesized and applied to tailor the structures and properties of polytriphenylamine (PTPA) and polystyrene (PS) blends. Two different polymer-coated Au NPs with sizes of 5.9 nm (Au NP-1) and 20.7 nm (Au NP-2) were designed to be thermally stable above 200 °C and neutral to both PS and PTPA phases. Hence, both Au NPs localize at the PS/PTPA interface and function as compatibilizers in the PS/PTPA blend. To show the compatibilizing effect of the particles, the morphological behaviors of PS/PTPA blends containing different particle volume fractions (ϕp) of Au NPs were observed using cross-sectional TEM, and for quantitative analysis, the size distribution of PTPA droplets in the PS matrix was obtained for each sample. The number-average droplet diameter (Dn) of the PTPA domain in the blend was dramatically reduced from 1.4 μm to 500 nm at a small ϕp of 1.0 vol % Au NP-1. The same trend of decreasing Dn w...

Size-Controlled Polymer-Coated Nanoparticles as Efficient Compatibilizers for Polymer Blends

We propose a novel and robust strategy for creating continuous conducting polymer films with ultralow percolation thresholds using polymer-coated gold nanoparticles (Au NPs) as surfactant. Continuous poly(triphenylamine) (PTPA) films of high internal phase polymeric emulsions were fabricated using an assembly of cross-linked polystyrene (PS) colloidal particles as template. Polymer-coated Au NPs were designed to be thermally stable even above 200 °C and neutral to both the PS and PTPA phases. Therefore, the Au NPs localize at the PS/PTPA interface and function as surfactant to efficiently produce a continuous conducting PTPA polymer film with very low percolation thresholds. The volume fraction threshold for percolation of the PTPA phase with insulating PS colloids (as measured by electron microscopy and conductivity measurements) was found to be 0.20. In contrast, with the addition of an extremely low volume fraction (ϕp = 0.35 vol %) of surfactant Au NPs, the volume fraction threshold for percolation of...

Creating Opal-Templated Continuous Conducting Polymer Films with Ultralow Percolation Thresholds Using Thermally Stable Nanoparticles

In this paper, a simple and powerful method of producing nanoparticle-anchored graphene oxide (GO) composites using a 'click' reaction is demonstrated. This method affords a facile means of anchoring of nanoparticles with various shapes and sizes on the GO. CuPt nanorods with controlled size, aspect ratio (from 1 to 11), and uniformity are synthesized. Transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy measurements are made to monitor the formation and characterize the properties of the CuPt nanorod-grafted GO composites. Their catalytic properties in the water phase are investigated using an o-phenylenediamine oxidation reaction. The results of this study clearly demonstrate that nonpolar CuPt nanorods immobilized on GO can function as a catalyst in an aqueous solution and that GO can be used as a catalytic nanorod support.

/pdf/click-preparation-of-cupt-nanorod-anchored-graphene-oxide-as-236w3f2j0r.pdf

'Click' preparation of CuPt nanorod-anchored graphene oxide as a catalyst in water.

CuPt nanorods, originally nonpolar, were modified by ligand exchange to become soluble in water. Three different CuPt nanorods with aspect ratios (ARs) of 1, 6, and 11 were produced with high monodispersity by a thermal decomposition method and a subsequent purification process. The synthesized nanorods were initially dispersed in nonpolar solvents such as hexane. Thiol-terminated poly(ethyleneoxide) (PEO-SH) was synthesized and attached to the surface of CuPt nanorods to impart water solubility. The nanorods were completely transferred to the aqueous phase. Their catalytic properties in the aqueous phase were investigated using a peroxidase-like reaction of o-phenylenediamine (OPD) oxidation. CuPt nanorods showed high activity for the reaction, demonstrating the excellent dispersion of nanorods in an aqueous solution. The effect of AR on the catalytic properties of nanorods was also studied.

/pdf/facile-preparation-of-water-soluble-cupt-nanorods-with-3mk5peo8bg.pdf

Facile preparation of water soluble CuPt nanorods with controlled aspect ratio and study on their catalytic properties in water

Nanoparticles (NPs) at the interface between two different polymer blends or fluid mixtures can function as compatibilizers, thereby dramatically improving the interfacial properties of the blends or the fluid mixtures. Their compatibilizing ability is strongly dependent on their size, shape, and aspect ratios (ARs), which determines their adsorption energy to the interface as well as their entropic penalty when they are being strongly segregated at the interface. Herein, we investigated the effect of the ARs of nanorod surfactants on the conducting polymer blend of poly(triphenylamine) (PTPA) templated by polystyrene (PS) colloids. The lengths of the polymer-coated CuPt nanorods (CuPt NRs) were 5, 15, and 32 nm with a fixed width of 5 nm, thus producing three different AR values of 1, 3, and 6, respectively. For quantitative analysis, the morphological and electrical behaviors of the polymer blends were investigated in terms of the volume fraction and AR of the NRs. The dramatic change in the morphologic...

Taegyun Kwon

Papers

Size-Controlled Polymer-Coated Nanoparticles as Efficient Compatibilizers for Polymer Blends

Creating Opal-Templated Continuous Conducting Polymer Films with Ultralow Percolation Thresholds Using Thermally Stable Nanoparticles

'Click' preparation of CuPt nanorod-anchored graphene oxide as a catalyst in water.

Facile preparation of water soluble CuPt nanorods with controlled aspect ratio and study on their catalytic properties in water

Aspect-Ratio Effect of Nanorod Compatibilizers in Conducting Polymer Blends