On-Surface Debromination of 2,3-Bis(dibromomethyl)- and 2,3-Bis(bromomethyl)naphthalene: Dimerization or Polymerization?

We describe the on-surface dehalogenative homocoupling of benzylic bromides, namely bis-bromomethyl- and bis-gem-(dibromomethyl) naphthalene as a potential route to either hydrocarbon dimers or conjugated polymers on Au(111). While bis-gem-(dibromomethyl) naphthalene affords different dimers with naphthocyclobutadiene as the key intermediate, bis-bromomethyl naphthalene furnishes a poly(o-naphthylene vinylidene) as a non-conjugated polymer which undergoes dehydrogenation toward its conjugated derivative poly(o-naphthylene vinylene) upon mild annealing. A combination of scanning tunneling microscopy, non-contact atomic force microscopy and density functional theory calculations provides deep insights into the prevailing mechanisms.

Gate-controlled electron transport in coronenes as a bottom-up approach towards graphene transistors.

Graphene is considered to be a large aromatic molecule, the limiting case of the family of polycyclic aromatic hydrocarbons. This fascinating two-dimensional material has many potential applications, including field effect transistors (FETs). However, the graphene sheets in these devices have irregular shapes and variable sizes, and contain various impurities and defects, which are undesirable for applications. Moreover, the bandgap of graphene is zero and, consequently, the on/off ratios of graphene FETs are small, making it difficult to build logic circuits. To overcome these difficulties, we report here a bottom-up attempt to fabricate nanoscale graphene FETs. We synthesize structurally well-defined coronene molecules (consisting of 13 benzene rings) terminated with linker groups, bridge each molecule to source and drain electrodes through the linkers, measure conductance and demonstrate the FET behaviour of the molecule.

Tailored Albumin-based Copolymers for Receptor-Mediated Delivery of Perylenediimide Guest Molecules.

The synthesis of a novel and multifunctional copolymer based on a human serum albumin backbone bearing several folic acid as well as PEO groups was presented. In solution, this side-chain copolymer adopts a globular architecture and about five molecules of the water-insoluble chromophore PDI were successfully incorporated into these micelles for receptor-mediated cell uptake investigations. A significant uptake of these bioconjugates via receptor-mediated endocytosis was detected for cells expressing folic acid receptors in the cell membrane. These novel albumin-based copolymers could serve as efficient and biocompatible carrier systems facilitating the directed delivery of lipophilic drug molecules into cancer cells and they allow investigating vesicle formation and trafficking even at the single molecule level.

Diffusion in polymer solutions studied by fluorescence correlation spectroscopy.

We employed fluorescence correlation spectroscopy (FCS) to study the diffusion of molecular and macromolecular tracers in polystyrene solutions over a broad range of concentrations (c) and molecular weights (M(w,m)) of the matrix polymer. Molecular tracer diffusion scales only with the matrix concentration and superimposes on a single, nonpolymer specific, curve. On the contrary, the diffusion of macromolecular tracers in solutions of matrix polymers with M(w,m) sufficiently larger than the tracer molecular weight scales with c/c(p)*, where c(p)* is the tracer overlap concentration. We further demonstrate that FCS can address local and global dynamics simultaneously.

Nanoscale architectures for molecular electronics: vibrational spectroscopy and structure of solid hexa-n-dodecyl-hexa-peri-hexabenzocoronene.

The solid columnar discotic and liquid-crystalline phases formed by hexa-n-dodecyl-hexa-peri-hexabenzocoronene (HBC-C12) have been investigated by IR and Raman vibrational spectroscopies. IR spectra clearly show the two phase transitions at 42 and at 107 degrees C already reported in literature and allow us to understand the conformational modifications of the n-alkyl chains that take place through the transitions. Thanks to the collected data, we propose a model of the structure of HBC-C12 in the solid-crystalline phase below 42 degrees C which includes the structure of the alkyl chains. This model is also confirmed by dichroic infrared microscopy measurements on highly oriented samples.