The self-assembly of multicomponent networks at the liquid-solid interface between Au(111) or highly oriented pyrolytic graphite (HOPG) and organic solvents was investigated using scanning tunneling microscopy. Alkoxylated dehydrobenzo[12]annulene (DBA) derivatives form hexagonal nanoporous networks, which trap either single molecules of coronene (COR) or small clusters of COR and isophthalic acid to form multicomponent networks. The pattern of interdigitation between alkyl chains from DBA molecules produces hexagonal pores that are either chiral or achiral. On Au(111) substrates multicomponent networks display an ordered superlattice arrangement of chiral and achiral pores. In comparison, similar networks on HOPG display only chiral pores. The unique superlattice structure observed on Au(111) is related to a lower energetic preference for chiral pores than on HOPG and increased diffusion barriers for guest molecules. The increased diffusion barriers for guests allow them to act as nucleation sites for the formation of achiral pores. Following the initial nucleation of an achiral pore, restrictions imposed by the accommodation of guests within the porous network mean that subsequent growth naturally leads to the formation of the superlattice structure.

A model is introduced to investigate structure, stability, dynamics, and properties of MoS(2). The tribological behavior of the material is obtained from the autocorrelation function, ACF, of the forces, using the Green-Kubo equation, and by the classical Amontons' laws. In the idealized system, i.e. without defects, junctions, vacancies, asperities, and impurities, both models find a superlubrication regime, in agreement with some experiments. In nanotubes, NTs, friction is an order of magnitude lower than in the layered systems. The calculations also show that there is a substantial stabilization, per atom, for the formation of multiwall NTs with at least four walls.

Understanding the formation of crystalline polymorphs is of importance for various applications of materials science. Polymorphism of Schiff base derivatives has recently attracted considerable attention because of its influence on photochromic and thermochromic properties of their 3D crystals. The present investigation extends the study of Schiff base polymorphism to the molecular level by using a combination of scanning tunneling microscopy at the liquid/solid interface and molecular modeling. It is demonstrated that polymorphism of 4-(dodecyloxy)-N-(4-dodecylphenyl)-2-hydroxybenzaldimine (PHB), a Schiff base substituted by alkyl side chains, can occur in 2D crystals when PHB is adsorbed on a surface that is able to exchange charge with the molecule. In particular, on Au(111), PHB molecules self-organize not only into a columnar packing but also in dimer structures. Theoretical and experimental results demonstrate that the dimer-based structure observed on Au(111) originates from molecule/surface interactions, which in turn modify molecule/molecule interactions. The results highlight that the Au(111) substrate is far from being a passive part of the self-assembled system and plays a crucial role in the morphology of 2D polymorphs.

The high stability of gold makes its surface an attractive substrate for the deposition of molecular materials and their functioning in devices. There are many substantial and profound experimental and theoretical issues that the use of any metal interacting with molecules requires to address. Here, we examine in some detail a semi-empirical computational model able to describe the metal-molecules interactions and provide an overview of the measure of success that it has reached. A number of specific examples are illustrated for a variety of rather large molecular systems. Challenges and future goals are also discussed.