Kinetic control of molecular assembly on surfaces

Chiara Paris,Simon Aeschlimann,Julia Neff,Felix Kling,Angelika Kühnle,Andrea Floris,Lev Kantorovich

doi:10.1038/s42004-018-0069-0

Abstract

It is usually assumed that molecules deposited on surfaces assume the most thermodynamically stable structure. Here we show, by considering a model system of dihydroxybenzoic acid molecules on the (10.4) surface of calcite, that metastable molecular architectures may also be accessed by choosing a suitable initial state of the molecules which defines the observed transformation path. Moreover, we demonstrate that the latter is entirely controlled by kinetics rather than thermodynamics. We argue that molecules are deposited as dimers that undergo, upon increase of temperature, a series of structural transitions from clusters to ordered striped and then dense networks, and finally to a disordered structure. Combining high-resolution dynamic atomic force microscopy experiments and density-functional theory calculations, we provide a comprehensive analysis of the fundamental principles driving this sequence of transitions. Our study may open new avenues based on kinetic control as a promising strategy for achieving tailored molecular architectures on surfaces.

Highlights

It is usually assumed that molecules deposited on surfaces assume the most thermodynamically stable structure
Elucidating the role played by the thermodynamics and kinetics in determining the specific sequence of the observed networks is highly promising as it provides a route towards tailoring molecular structure formation on surfaces by kinetic control
Using a combination of high-resolution dynamic atomic force microscopy (AFM) and ab initio density-functional theory (DFT) calculations, we provide a comprehensive explanation of the mechanisms driving the structural transformations of dihydroxybenzoic acid (DHBA) molecules after their deposition on the calcite surface

Summary

Introduction

It is usually assumed that molecules deposited on surfaces assume the most thermodynamically stable structure. To the best of our knowledge, this level of theoretical analysis of the kinetics of structural transitions is unprecedented This enables us to suggest (i) the atomistic mechanisms of dissolution and growth of each network; (ii) the composition of disordered structures along the transformation path; (iii) the rate-limiting steps in the formation of the dense network and, (iv) some peculiar catalytic phenomena at play during its growth. If thermodynamics establishes the most stable structure under given external conditions (e.g., coverage and temperature), kinetics provides the particular path towards this structure via a sequence of metastable states that require the highest transition rates to reach. This is highly relevant as it provides a route towards tailoring molecular structure formation on surfaces by kinetic control

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Conclusion