Influence of wettability contrasts and contact angle hysteresis on drop velocity and surface energy analysis describing the drop motion.

We have investigated the (001) surface structure of lithium titanate (Li2TiO3) using auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). Li2TiO3 is a potential fusion reactor blanket material. After annealing at 1200 K, LEED demonstrated that the Li2TiO3(001) surface was well ordered and not reconstructed. STM imaging showed that terraces are separated in height by about 0.3 nm suggesting a single termination layer. Moreover, hexagonal patterns with a periodicity of ∼0.4 nm are observed. On the basis of molecular dynamics (MD) simulations, these are interpreted as a dynamic arrangement of Li atoms.

Supported metal nanoparticles form the basis of heterogeneous catalysts. Above a certain nanoparticle size, it is generally assumed that adsorbates bond in an identical fashion as on a semiinfinite crystal. This assumption has allowed the database on metal single crystals accumulated over the past 40 years to be used to model heterogeneous catalysts. Using a surface science approach to CO adsorption on supported Pd nanoparticles, we show that this assumption may be flawed. Near-edge X-ray absorption fine structure measurements, isolated to one nanoparticle, show that CO bonds upright on the nanoparticle top facets as expected from single-crystal data. However, the CO lateral registry differs from the single crystal. Our calculations indicate that this is caused by the strain on the nanoparticle, induced by carpet growth across the substrate step edges. This strain also weakens the COmetal bond, which will reduce the energy barrier for catalytic reactions, including CO oxidation.nanoparticle | carpet growth | surface strain | adsorption | scanning tunneling microscopy N anoparticles exhibit properties distinct from their bulk counterparts (1-3). For instance, semiconductor particles smaller than ∼10 nm act as quantum dots (1-4) and oxide-supported gold nanoparticles are active for a variety of reactions including CO oxidation (5), water-gas-shift reaction (6), and epoxidation (7), whereas gold itself is not. Nanoclusters composed of ∼10 atoms have been shown to be exceptionally catalytically active for some reactions on some metals (8, 9). When the particle size is reduced, the relative number of undercoordinated atoms at the edges and corners increases. The proportion of perimeter sites at the interface between the metal and the support also increases. All these sites have been shown to play a crucial role in some reactions (10, 11). Reducing the particle size can also lead to a decrease in the interatomic bond length in small metal clusters (12, 13), which in the case of Pd nanoparticles results in lower adsorption energies for both CO (14,15) and O 2 (16), although such weakening of CO binding on the nanoparticle can also arise from other factors such as encapsulation of the nanoparticles by the support (17).The role of the support in modifying nanoparticle properties has also been recognized. For instance, the strong metal support interaction has been known for some time (2) and charge transfer either to or from the nanoparticles can lead to enhanced reactivity (18). More recently, it has come to light that the particle size itself may be governed by the interaction with the support (19). However, one effect that has not been discussed and yet should be present in any nanoparticle-support system is the influence of the support morphology such as steps.Here, we investigate the role of the support morphology on the reactivity of metal nanoparticles using scanning tunneling microscopy (STM). As our test system we choose Pd nanoparticles (20, 21) supported on TiO 2 (110) (22) simply because much is known about bo...

Research into evaporating droplets on patterned surfaces has grown exponentially, since the capacity to control droplet morphology has proven to have significant technological utility in emerging areas of fundamental research and industrial applications. Here, we incorporate two interest domains-complex wetting patterns of droplets on structured surfaces and the ubiquitous coffee-ring phenomenon of nanofluids containing dispersed aluminium oxide particles. We lay out the surface design criteria by quantifying the effect of pillar density and shape on the wetting footprint of droplets, yielding complex polygon droplet geometries. Our work is not constrained to pure liquids only, as we delve into the shape selection of particle-laden droplets of different concentrations. We visualise the deposition patterns through microscopy on surfaces exhibiting different features and further establish the ordering of particles on microscale surface asperities. At a high nanofluid concentration, we observe intriguing self-assembly of particles into highly ordered intricate structures. The collective findings of this work have the potential to enhance many industrial technologies, particularly attractive for high performance optical and electrical devices.

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Acetic acid is a common pollutant for which photocatalytic degradation over titania provides a mitigating strategy. Knowledge of the bonding of acetate/acetic acid to this substrate is needed to aid interpretation of the photocatalytic data. In this work we use ambient pressure near edge X-ray absorption fine structure to measure the coverage and geometry of acetate in the TiO2( 110) contact layer as well as acetic acid in an additional layer. A saturation coverage of 0.5 monolayers in both layers is found up to an acetic acid pressure of 10 -1 Torr at 266 K.The geometry of acetate appears to be unchanged by adsorption of an additional layer of acetic acid, which involves a majority species bidentate bonded to neighboring Ti5c sites and a minority species bonded in a perpendicular geometry. Acetic acid has a similar geometry dictated by hydrogen bonding to the contact layer as well as the substrate.

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