Positioning of absolute energy levels and the quantitative description of occupied levels obtained for TiO₂ nanopowders, combining UPS and UV-Vis spectroscopies.

We report the synthesis and first electronic characterization of an atomically thin two dimensional π-conjugated polymer. Polymerization via Ullmann coupling of a tetrabrominated tetrathienoanthracene on Ag(111) in ultra-high vacuum (UHV) produces a porous 2D polymer network that has been characterized by scanning tunnelling microscopy (STM). High-resolution X-ray photoelectron spectroscopy (HRXPS) shows that the reaction proceeds via two distinct steps: dehalogenation of the brominated precursor, which begins at room temperature (RT), and C–C coupling of the resulting Ag-bound intermediates, which requires annealing at 300 °C. The formation of the 2D conjugated network is accompanied by a shift of the occupied molecular states by 0.6 eV towards the Fermi level, as observed by UV photoelectron spectroscopy (UPS). A theoretical analysis of the electronic gap reduction in the transition from monomeric building blocks to various 1D and 2D oligomers and polymers yields important insight into the effect of topology on the electronic structure of 2D conjugated polymers.

Two-dimensional molecular self-assembly at the liquid/solid interface is a widely employed approach in surface science to pattern surfaces at the nanometre scale. A multitude of supramolecular structures can be realized depending on parameters such as the functionalization of the molecular building blocks, the temperature at which self-assembly takes place, the type of solvent and solute concentration. How these and other parameters influence the kinetics and thermodynamics of the self-assembly process is the subject of this review.