Charge transport in a liquid crystalline triphenylene polymer monolayer at air-solid interface

Life at the interface: Engineering bio-nanomaterials through interfacial molecular self-assembly

Interfacial self-assembly describes the directed organization of molecules and colloids at phase boundaries. Believed to be fundamental to the inception of primordial life, interfacial assembly is exploited by a myriad of eukaryotic and prokaryotic organisms to execute physiologic activities and maintain homeostasis. Inspired by these natural systems, chemists, engineers, and materials scientists have sought to harness the thermodynamic equilibria at phase boundaries to create multi-dimensional, highly ordered, and functional nanomaterials. Recent advances in our understanding of the biophysical principles guiding molecular assembly at gas-solid, gas-liquid, solid-liquid, and liquid-liquid interphases have enhanced the rational design of functional bio-nanomaterials, particularly in the fields of biosensing, bioimaging and biotherapy. Continued development of non-canonical building blocks, paired with deeper mechanistic insights into interphase self-assembly, holds promise to yield next generation interfacial bio-nanomaterials with unique, and perhaps yet unrealized, properties. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Transition in nanoscale electrical conductivity in the Langmuir-Blodgett film of a novel liquid crystalline oligomer

We have studied the nanoscale electrical conductivity of a monolayer film of a novel star shaped liquid crystalline molecule, hexatriphenylene substituted anthraquinone (AQD6). The molecule has a central core of electron deficient anthraquinone moiety connected to six electron rich triphenylene moieties by flexible alkyl chains. The monolayer formed at air-water interface was transferred onto the solid substrates by Langmuir-Blodgett (LB) technique and its surface topography was imaged using an atomic force microscope (AFM). The limiting area obtained from the surface pressure-area per molecule isotherm and the topography of the AFM images suggest that the anthraquinone moiety of the AQD6 molecule is organized in face-on configuration on the substrate and the triphenylene moieties are in edge-on configuration extended away from the substrate. We have studied the electrical conductivity of the AQD6 monolayer deposited on gold coated silicon substrate using a current sensing AFM. Analysis of current (I) − voltage (V) characteristics of the metal-monolayer film-metal junction showed a transition from direct tunneling to an injection tunneling. Further, we have estimated the barrier height and the effective mass of electron in the metal-monolayer film-metal junction.

Arylic versus Alkylic-Hydrophobic Linkers Determine the Supramolecular Structure and Optoelectronic Properties of Tripodal Amphiphilic Push-Pull Thiazoles

The supramolecular structures and their constituents essentially determine the optoelectronic properties of thin films. The introduction of amphiphilicity to the constituents and interface assembly is one established technique to control supramolecular structures and resulting material properties. To yield amphiphilicity, rather hydrophobic chromophores are linked to hydrophilic head groups via flexible alkyl chains. In the present work, we investigate whether replacement of the alkyl linkers by a phenylene linker, that is, replacing an electrically isolating moiety with a potentially semiconducting one, increases the conductivity through the resulting layers. After investigating the influence of the linker on molecular properties of the 2-(4- N, N-dimethylaminophenyl)-4-hydroxy-5-nitrophenyl-1,3 thiazoles exemplarily used in this work, we produce supramolecular structures by means of the Langmuir-Blodgett (LB) technique. Atomic force microscopy (AFM) and UV-vis absorption spectroscopy reveal that thin films made from the more rigid thiazole bearing the arylic linker feature a more homogeneous and stable supramolecular structure as compared to those made from the thiazole dye containing the flexible alkylic linker. Finally, conductive AFM (cAFM) results disclose that the LB films made from the thiazole bearing the π-conjugated arylic linker are less conductive than their counterparts based on the alkylic linkers. In the latter layers, the alkylic linkers provide sufficient motional degrees of freedom to allow for supramolecular rearrangement upon electrical operation during cAFM measurements, hence yielding supramolecular structures featuring increased conductivity with successive cAFM measurements. This work highlights the importance of supramolecular structures for optoelectronic properties by presenting a case where supramolecular effects excel the property changes introduced by molecular modifications.

Current mapping of lead phthalocyanine thin films in the presence of gaseous dopants

Iodine doping in nonplanar Pb(ii)phthalocyanine causes significant structural reorganization and enhanced conductance with nanoscale conducting pathways and improved sensitivity towards other gaseous adsorbates.

Dual photoluminescence and charge transport in an alkoxy biphenyl benzoate ferroelectric liquid crystalline–graphene oxide composite

GO has been dispersed in a ferroelectric liquid crystalline material to prepare a FLC–GO composite.

Influence of the side-chain structure and molecular weight on the re-entrant behaviors of mesogen-jacketed liquid crystalline polymers

The influence of the alkyl spacer length and the terminal group volume influence on the phase behavior and structure of mesogen-jacketed liquid-crystalline polymers.