On Kinetic Constraints That Catalysis Imposes on Elementary Processes.

Catalysis, the acceleration of product formation by a substance that is left unchanged, typically results from multiple elementary processes, including diffusion of the reactants toward the catalyst, chemical steps, and release of the products. While efforts to design catalysts are often focused on accelerating the chemical reaction on the catalyst, catalysis is a global property of the catalytic cycle that involves all processes. These are controlled by both intrinsic parameters such as the composition and shape of the catalyst and extrinsic parameters such as the concentration of the chemical species at play.

Computational design of a minimal catalyst using colloidal particles with programmable interactions.

Catalysis, the acceleration of chemical reactions by molecules that are not consumed in the process, is essential to living organisms but remains absent in physical systems that aspire to emulate biological functionalities with artificial components. Here we demonstrate how to design a catalyst using spherical building blocks interacting programmable potentials, and show that a minimal catalyst design, a rigid dimer, can accelerate a ubiquitous elementary reaction, the cleaving of a bond. Combining coarse-grained molecular dynamics simulations and theory, and by comparing the mean reaction time for bond dissociation in the presence and absence of the catalyst, we derive geometrical and physical constraints for its design and determine the reaction conditions under which catalysis emerges in the system.

Self-assembly of emulsion droplets through programmable folding.

In the realm of particle self-assembly, it is possible to reliably construct nearly arbitrary structures if all the pieces are distinct, but systems with fewer flavours of building blocks have so far been limited to the assembly of exotic crystals. Here we introduce a minimal model system of colloidal droplet chains, with programmable DNA interactions that guide their downhill folding into specific geometries. Droplets are observed in real space and time, unravelling the rules of folding.

Electrostatics and domains in ferroelectric superlattices.

The electrostatics arising in ferroelectric/dielectric two-dimensional heterostructures and superlattices is revisited within a Kittel model in order to define and complete a clear paradigmatic reference for domain formation. The screening of the depolarizing field in isolated ferroelectric or polar thin films via the formation of 180° domains is well understood, where the width of the domains grows as the square-root of the film thickness , following Kittel's Law for thick enough films ( ≪ ). For thinner films, a minimum is reached for before diverging to a monodomain.