Structure and Mobility of Acetic Acid at the Anatase (101)/Acetonitrile Interface

Acetic acid is one of the simplest molecules containing a carboxylic moiety, a common anchoring groups used to functionalize TiO₂-based devices. The behavior of acetic acid in proximity of the anatase (101) surface has been investigated by means of first-principles density functional theory (DFT) calculations, including explicit liquid solvent in the simulations. A novel acetic acid binding mode, characterized by proton insertion below the first layer of oxide atoms, has been found employing a sufficiently thick anatase slab model. Hybrid DFT calculations show that the subsurface proton insertion leads to a trap-state for excess electrons, favoring localization below the surface edge. Proton deintercalation represents the largest barrier for acid mobility and desorption. However, if the proton is adsorbed on top of the surface, the acid molecule can partially detach from the surface and easily move toward a thermodynamically more stable state. A series of consecutive changes in the adsorption mode can lead to long-range diffusion of the molecule along the [010] direction of the surface, with a barrier of only <i>E</i>_act = 20.3 kJ/mol. Similarly, the free energy barrier to completely detach an acetic acid molecule from the surface into the solvent has been computed to be <i>E</i>_act = 51.0 kJ/mol, if the proton is adsorbed on top of the anatase slab. Where significant, a comparison between the “explicit liquid” environment and the more often employed “solvent monolayer” environment has been carried out, highlighting the importance of solvent interactions

Synthesis of Two-Dimensional Analogues of Copolymers by Site-to-Site Transmetalation of Organometallic Monolayer Sheets

Monolayer sheets have gained attention due to the unique properties derived from their two-dimensional structure. One of the key challenges in sheet modification/synthesis is to exchange integral parts while keeping them intact. We describe site-to-site trans­metalation of Zn²⁺ in the netpoints of cm²-sized, metal–organic sheets by Fe²⁺, Co²⁺, and Pb²⁺. This novel transformation was done both randomly and at predetermined patterns defined by photo­lithography to create monolayer sheets composed of different netpoints. All trans­metalated sheets are mechanically strong enough to be spanned over 20 × 20 μm² sized holes. Density functional theory calculations provide both a model for the molecular structure of an Fe²⁺-based sheet and first insights into how trans­metalation proceeds. Such trans­metalated sheets with random and patterned netpoints can be considered as two-dimensional analogues of linear copolymers. Their nanoscale synthesis presents an advance in monolayer/polymer chemistry with applications in fields such as surface coating, molecular electronics, device fabrication, imaging, and sensing

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃

A Polar Corundum Oxide Displaying Weak Ferromagnetism at Room Temperature

Combining long-range magnetic order with polarity in the same structure is a prerequisite for the design of (magnetoelectric) multiferroic materials. There are now several demonstrated strategies to achieve this goal, but retaining magnetic order above room temperature remains a difficult target. Iron oxides in the +3 oxidation state have high magnetic ordering temperatures due to the size of the coupled moments. Here we prepare and characterize ScFeO₃ (SFO), which under pressure and in strain-stabilized thin films adopts a polar variant of the corundum structure, one of the archetypal binary oxide structures. Polar corundum ScFeO₃ has a weak ferromagnetic ground state below 356 Kthis is in contrast to the purely antiferromagnetic ground state adopted by the well-studied ferroelectric BiFeO₃