We show that one-dimensional (1D) nanostructures and two-dimensional (2D) supramolecular crystals of organic semiconductors can be grown on substrates under ambient conditions directly from three-dimensional (3D) organic crystals. The approach does not require dissolving, melting or evaporating of the source crystals and is based on the Organic SolidSolid Wetting Deposition (OSWD). We exemplify our approach by the pigment quinacridone (QAC). Scanning Tunnelling Microscopy (STM) investigations show that the structures of the resulting 2D crystals are similar to the chain arrangement of the alpha and beta QAC polymorphs and are independent of the 3D source crystal polymorph (gamma). Furthermore, distinct 1D chains can be produced systematically.

Supramolecular self-assembly at the solid-solid interface enables the deposition and monolayer formation of insoluble organic semiconductors under ambient conditions. The underlying process, termed as the organic solid-solid wetting deposition (OSWD), generates two-dimensional adsorbates directly from dispersed three-dimensional organic crystals. This straightforward process has important implications in various fields of research and technology, such as in the domains of low-dimensional crystal engineering, the chemical doping and band gap engineering of graphene, and in the area of field-effect transistor fabrication. However, to date, lack of an in-depth understanding of the physicochemical basis of the OSWD prevented the identification of important parameters, essential to achieve a better control of the growth of monolayers and supramolecular assemblies with defined structures, sizes, and coverage areas. Here we propose a detailed model for the OSWD, derived from experimental and theoretical results that have been acquired by using the organic semiconductor quinacridone as an example system. The model reveals the vital role of the ζ potential and includes Casimir-like fluctuation-induced forces and the effect of dewetting in hydrophobic nanoconfinements. Based on our results, the OSWD of insoluble organic molecules can hence be applied to environmental friendly and low-cost dispersing agents, such as water. In addition, the model substantially enhances the ability to control the OSWD in terms of adsorbate structure and substrate coverage.

Organic Solid-Solid Wetting Deposition (OSWD) enables the fabrication of supramolecular architectures without the need for solubility or vacuum conditions. The technique is based on a process which directly generates two-dimensional monolayers from three-dimensional solid organic powders. Consequently, insoluble organic pigments and semiconductors can be made to induce monolayer self-assembly on substrate surfaces, such as graphene and carbon nanotubes, under ambient conditions. The above factuality hence opens up the potential of the OSWD for bandgap engineering applications within the context of carbon based nanoelectronics. However, the doping of graphene via OSWD has not yet been verified, primarily owing to the fact that the classical OSWD preparation procedures do not allow for the analysis via Raman spectroscopyone of the main techniques to determine graphene doping. Hence, here we describe a novel approach to induce OSWD on graphene leading to samples suitable for Raman spectroscopy. The analysis reveals peak shifts within the Raman spectrum of graphene, which are characteristics for p-type doping. Additional evidence for chemical doping is found via Scanning Tunneling Spectroscopy. The results open up a very easily applicable, low-cost, and eco-friendly way for doping graphene via commercially available organic pigments.