The authors report the area-selective deposition of cobalt (II) oxide on polystyrene-patterned SiO2/Si and MgO(001) substrates at 180 °C by atomic layer deposition (ALD) using bis(N-tert butyl, N′-ethylpropionamidinato) cobalt (II) and water as coreactants. The patterned CoO films are carbon-free, smooth, and were reduced with atomic deuterium at 220 °C to produce Co metal patterns without shape deformation. CoO ALD is facile on starting surfaces that features hydroxyl groups favoring CoO nucleation and growth. Polystyrene (PS) is very effective in blocking ALD of CoO. The PS is patterned using UV-crosslinked 40 nm-thick PS films to generate μm-size features or using self-assembled 40 nm-thick polystyrene-block-polymethylmethacrylate (PS-b-PMMA) films to generate nm-size features. The unexposed PS in UV-crosslinked PS films is dissolved away with toluene, or the PMMA component in self-assembled PS-b-PMMA films is selectively removed by a plasma etch to expose the underlying oxide surface. The magnetic properties of the Co metal patterns grown by area-selective atomic layer deposition are presented.
Hydrophobic interactions drive the binding of nonpolar ligands to the oily pockets of proteins and supramolecular species in aqueous solution. As such, the wetting of host pockets is expected to play a critical role in determining the thermodynamics of guest binding. Here we use molecular simulations to examine the impact of pressure on the wetting and dewetting of the nonpolar pockets of a series of deep-cavity cavitands in water. The portals to the cavitand pockets are functionalized with both nonpolar (methyl) and polar (hydroxyl) groups oriented pointing either upward or inward toward the pocket. We find wetting of the pocket is favored by the hydroxyl groups and dewetting is favored by the methyl groups. The distribution of waters in the pocket is found to exhibit a two-state-like equilibrium between wet and dry states with a free energy barrier between the two states. Moreover, we demonstrate that the pocket hydration of the cavitands can be collapsed onto a unified adsorption isotherm by assuming the effective pressures within each cavitand pocket differ by a shift pressure that depends on the chemical identity and number of functional groups placed about the portal. These observations support the development of a two-state capillary evaporation model that accurately describes the equilibrium between states and naturally gives rise to the effective shift pressures observed from simulation. This work demonstrates that the hydration of host pockets can be tuned following simple design rules that in turn are expected to impact the thermodynamics of guest complexation.
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