http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Colloidal particles act in many ways like surfactant molecules, particularly if adsorbed to a fluid–fluid interface. Just as the water or oil-liking tendency of a surfactant is quantified in terms of the hydrophile–lipophile balance (HLB) number, so can that of a spherical particle be described in terms of its wettability via contact angle. Important differences exist, however, between the two types of surface-active material, due in part to the fact that particles are strongly held at interfaces. This review attempts to correlate the behaviour observed in systems containing either particles or surfactant molecules in the areas of adsorption to interfaces, partitioning between phases and solid-stabilised emulsions and foams.

Particles as surfactants—similarities and differences

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

The aim of this critical review is to provide a broad but digestible overview of mechanochemical synthesis, i.e. reactions conducted by grinding solid reactants together with no or minimal solvent. Although mechanochemistry has historically been a sideline approach to synthesis it may soon move into the mainstream because it is increasingly apparent that it can be practical, and even advantageous, and because of the opportunities it provides for developing more sustainable methods. Concentrating on recent advances, this article covers industrial aspects, inorganic materials, organic synthesis, cocrystallisation, pharmaceutical aspects, metal complexes (including metal–organic frameworks), supramolecular aspects and characterization methods. The historical development, mechanistic aspects, limitations and opportunities are also discussed (314 references).

/pdf/mechanochemistry-opportunities-for-new-and-cleaner-synthesis-15fcwynvnd.pdf

Mechanochemistry: opportunities for new and cleaner synthesis

/pdf/the-surface-chemistry-of-amorphous-silica-zhuravlev-model-4kfs2lx66q.pdf

The surface chemistry of amorphous silica. Zhuravlev model

Pretreatments of Co3O4 at moderate temperature for CO oxidation at −80 °C

Influence of the Support and the Size of Gold Clusters on Catalytic Activity for Glucose Oxidation

Propene epoxidation with dioxygen catalyzed by gold clusters.

Gold could be deposited as clusters smaller than 2.0 nm in diameter on TS-1 by solid grinding (SG) of the support with dimethyl Au(III) acetylacetonate after TS-1 was pretreated in aqueous solution of alkaline metal hydroxides. While in C3H6 epoxidation with O2 and H2 mixture Au nanoparticles larger than 2.0 nm deposited on TS-1 without alkaline treatment gave a very low PO formation rate of 11 gPO kgcat.−1 h−1, Au clusters on alkaline treated TS-1 presented a greatly enhanced rate as high as 137 gPO kgcat.−1 h−1, which was comparable to the best data reported so far. In addition, very high H2 efficiency reaching 47% could be obtained by gold clusters on alkaline treated TS-1.

Gold clusters supported on alkaline treated TS-1 for highly efficient propene epoxidation with O2 and H2

Gold can be deposited as nanoparticles (NPs) with diameters of 2–5 nm and clusters with diameters less than 2 nm on a variety of materials such as oxides, carbides, and sulfides of transition metals, carbons, and organic polymers. Such supported gold NPs and clusters exhibit surprisingly high catalytic activities for many reactions, with both gas- and liquid-phase reactants, in particular, at temperatures below 573 K. Until now, more than 10 techniques have been developed for depositing gold as NPs and clusters. The atomic scale structures of supported NPs and clusters have been extensively and intensively investigated with a high-resolution transmission electron microscopy. The mechanisms of catalysis by supported gold NPs have recently been elucidated by using real powder catalysts and model single-crystal catalysts for the low-temperature oxidation of CO. Another simple reaction that has recently been investigated is dihydrogen dissociation, for which gold NP catalysts are still poorly active. Both of these reactions have been demonstrated to take place at perimeter interfaces around the gold NPs. This result means that there is a great chance for gold to exhibit high catalytic activity for hydrogenation reactions by an appropriate choice of metal oxide supports and by minimizing the diameters of gold particles. The catalytic nature of gold clusters has also been investigated theoretically in relation to the effect of cluster size and the influence of organic ligands and polymers. The catalytic performance of gold NPs and clusters has been explored extensively for reactions of both gases and liquids. Supported gold catalysts are useful for air cleaning at room temperature, and they are valuable for green production of bulk and fine chemicals. Supported gold clusters are expected to open new doors for simple chemistry for the selective manufacture of needed products. Size and structure specificity are expected to present opportunities for selective conversions. It is recommended that researchers explore the magic numbers and structures of gold and suitable support materials for selected target reactions.

Takashi Takei

Papers

Pretreatments of Co3O4 at moderate temperature for CO oxidation at −80 °C

Influence of the Support and the Size of Gold Clusters on Catalytic Activity for Glucose Oxidation

Propene epoxidation with dioxygen catalyzed by gold clusters.

Gold clusters supported on alkaline treated TS-1 for highly efficient propene epoxidation with O2 and H2

Heterogeneous Catalysis by Gold