J. P. S. Badyal

Three-Dimensional Hierarchical Structures for Fog Harvesting

Conventional fog-harvesting mechanisms are effectively pseudo-2D surface phenomena in terms of water droplet-plant interactions. In the case of the Cotula fallax plant, a unique hierarchical 3D arrangement formed by its leaves and the fine hairs covering them has been found to underpin the collection and retention of water droplets on the foliage for extended periods of time. The mechanisms of water capture and release as a function of the surface 3D structure and chemistry have been identified. Of particular note is that water is retained throughout the entirety of the plant and held within the foliage itself (rather than in localized regions). Individual plant hairs form matlike structures capable of supporting water droplets; these hairs wrap around water droplets in a 3D fashion to secure them via a fine nanoscale groove structure that prevents them from easily falling to the ground.

Ultrafast Oleophobic–Hydrophilic Switching Surfaces for Antifogging, Self-Cleaning, and Oil–Water Separation

Smooth copolymer-fluorosurfactant complex film surfaces are found to exhibit fast oleophobic-hydrophilic switching behavior. Equilibration of the high oil contact angle (hexadecane = 80°) and low water contact angle (<10°) values occurs within 10 s of droplet impact. These optically transparent surfaces display excellent antifogging and self-cleaning properties. The magnitude of oleophobic-hydrophilic switching can be further enhanced by the incorporation of surface roughness to an extent that it reaches a sufficiently high level (water contact angle <10° and hexadecane contact angle >110°), which, when combined with the inherent ultrafast switching speed, yields oil-water mixture separation efficiencies exceeding 98%.

Hydroxyl accessibility in celluloses

Abstract The crystalline content of a range of celluloses has been evaluated by X-ray diffraction and infrared spectroscopy. Chemical derivatization of these materials with trifluoroacetic anhydride in conjunction with X-ray photoelectron spectroscopy has been used to measure hydroxyl accessibility. A linear relationship is found between cellulose crystallinity and the rate of hydroxyl labelling.

Diels–Alder chemistry at furan ring functionalized solid surfaces

A substrate-independent method for Diels-Alder chemistry at solid surfaces is described for the first time.

A simple method for the quantitative analysis of resin bound thiol groups

Abstract Non-aqueous solutions of Ellmans reagent [5,5′-dithio(2-nitrobenzoic acid), DTNB] can be used to quantify thiols supported on macroporous polystyrene and TentaGel resins. Organic solutions of Ellmans reagent may also be used as a qualitative tests for thiols on a wider range of solid supports.

Atmospheric silent discharge versus low-pressure plasma treatment of polyethylene, polypropylene, polyisobutylene, and polystyrene

Polyethylene, polypropylene, polyisobutylene, and polystyrene films have been exposed to high- and low-pressure non-equilibrium electrical air discharges. The modified surfaces have been characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Atmospheric silent discharge treatment causes a greater level of topographical disruption, whereas surface oxygenation is dependent on the chemical nature of the polymer substrate and its reactivity towards the electrical discharge medium. Oxygen incorporation occurs much more readily for the unsaturated polystyrene surface than for the saturated polyethylene, polypropylene, and polyisobutylene substrates.

Molecular mechanism of heterogeneous alkene epoxidation: A model study with styrene on Ag(111)

Abstract On atomically clean Ag(111) oxygen adatoms selectively oxidise styrene (phenylethene) to the epoxide with high efficiency, providing strong and direct confirmation of the mechanism advanced earlier for ethene epoxidation on single crystal Ag and on Ag catalysts. The effects of coadsorbed promoter species (K and Cl) are in good accord with the view that the principal mode of action of such species involves an electronic interaction which modifies the ability of adsorbed atomic oxygen to act as an electrophilic reagent towards the adsorbed alkene.

A model oxide catalyst system for the activation of methane: Lithium-doped NiO on Ni(111)

Abstract The highly active methane coupling catalyst LiNiO 2 has been modelled on a planar substrate and characterised by Auger, UP and XP spectroscopies. In situ oxidation of Ni(111) followed by lithium doping generates Li 2 O 2 /NiO/Ni(111), subsequent annealing to ∼ 600 K yields LiNiO 2 at the surface. Three distinct surface oxygen species (O 2− , O − , O − 2 ), are observed and their chemical significance is discussed.

Molecular mechanism of alkene epoxidation: A model study with 3,3-dimethyl-1-butene on Ag(111)

On chlorine-promoted Ag(111) oxygen adatoms selectively oxidise 3,3-dimethyl-1-butene (DMB) to the corresponding epoxide with very high selectivity providing direct verification of the mechanism advanced earlier for alkene epoxidation over single crystal silver and silver catalysts.

Atomic force microscopy and permeability study of stretching-induced gas barrier loss of AlOx layers

Gas permeation through oxygen-rich and metal-rich AlOx layers deposited onto polyethylene terephthalate film has been studied as a function of uniaxial stretching, by quadrupole mass spectrometry. The breakdown in the gas barrier is compared with microstructural changes taking place at the surface, using atomic force microscopy.