Self-assembly under nanoconfinement conditions

Molecular self-assembly of organic building blocks has often been used for fabricating complex functional surfaces. A sizeable part of this discipline consists of understanding the complexity of molecular recognition processes transpiring during the assembly process which occurs at the interface between an organic liquid and a crystalline solid. ln the last two decades, a wide variety of structurally diverse molecular layers have been fabricated ranging from simple lamellae to sophisticated multicomponent networks. Scanning tunneling microscopy (STM), a powerful technique that provides often submolecular resolution if the substrate is conductive, crystalline and atomically flat, have been also used to see these molecular clearly. The aim of this research has been molecule-based two dimensional (2D) crystal engineering which encompasses the control of supramolecular interactions to build complex patterns in a programmed fashion. Analogous to crystallization in bulk, the self-assembly of molecules at the liquid-solid interface is believed to proceed in discrete stages namely, nucleation, growth and ripening. A number of experimental parameters have been identified that have an impact on the surface composition and structure at the liquid-solid interface (LSl). These parameters include the type of solvent, concentration of molecules, type of substrate, temperature at which the self-assembly takes place and thermal history of the sample. Highly oriented pyrolytic graphite (HOPG), a conductive material composed of stacked graphene sheets, is an appealing susbstrate to study nucleation and growth processes by molecular self-assembly in 'corrals’, which are monolayer-deep, flat-bottomed, circular pits. Compartmentalizing the assembling molecules in corrals and on surrounding terraces can provide a handle on studying the processes that are otherwise too fast or coupled with each other. Meanwhile, extraction of crucial parameters relevant to the energetics and kinetics of the assembly process in turn will help to resolve the existing conundrum surrounding self-assembly at the LSl. Last but not the least, the knowledge gained from such studies could be used as an additional handle to influence the assembly process.