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Project

CSC-2019-61

Title: Rationale and positioning with regard to the state-of-the-art The formation of organic self-assembled molecular networks (SAMNs) on a solid support holds great potential for the bottom-up fabrication of nanomaterials. The key strength of this approach is the ability to impart specific functionality to the surface by modifyingattaining physical and chemical properties in a nanopatterned fashion. The ability to predict SAMN structures formed at the interface is crucial for the development of applications in emerging fields such as organic (opto- )electronics, sensing, and molecular motors. 2D self-assembly at the liquid-solid interface is a highly dynamical process that typically proceeds via three distinct stages: slow nucleation is followed by rapid growth, and eventually slow ripening. At thermodynamic equilibrium, SAMNs are characterized by steady state ad-, and desorption dynamics. To achieve the desirable goal of predicting SAMN structures, a myriad of SAMNs have been studied over the last three decades, and the dependence of their structure on experimental variables such as temperature,concentration, and solvent has been described. Nonetheless, the current predictive power over the assembly process is still unsatisfactory, primarily because a thorough understanding of the thermodynamics and kinetics of the assembly process is missing. Typically, only qualitative considerations are made, whereas advancing our understanding of the competition between thermodynamics and kinetics requires quantitative measures. In view of this knowledge gap, new approaches have been suggested to specify the thermodynamic functions in a quantitative manner.In analogy, new methods to quantify the rates of dynamical processes taking place at the interface are urgently needed. Experimentally, scanning probe microscopy is the preferred technique to obtain structural information on SAMNs. Atomic force microscopy (AFM), and especially scanning tunneling microscopy (STM) are well-suited to probe molecular adlayers in a liquid environment. Under the right conditions, these techniques allow to attain (sub-)molecular resolution. In fact, much of the current knowledge on SAMN formation derives from the imaging capabilities of these techniques. However, scanning probe techniques are typically slow with image acquisition times on the order of tens of seconds to minutes. Consequently, only correspondingly slow processes can be monitored, such as Ostwald ripening or steady state ad- and desorption dynamics. Nucleation and growth dynamics, which are generally much faster, have therefore often remained invisible and as a consequence their mechanisms constitute a topic of intense scientific debate.

Date:7 Oct 2020 →  Today
Keywords:self-assembly
Disciplines:Surface and interface chemistry
Project type:PhD project