Bottom-up Solution Synthesis of Graphene Nanoribbons with Precisely Engineered Nanopores.

The incorporation of nanopores into graphene nanostructures has been demonstrated as an efficient tool in tuning their band gaps and electronic structures. However, precisely embedding the uniform nanopores into graphene nanoribbons (GNRs) at the atomic level remains underdeveloped especially for in-solution synthesis due to the lack of efficient synthetic strategies. Herein we report the first case of solution-synthesized porous GNR (pGNR) with a fully conjugated backbone via the efficient Scholl reaction of tailor-made polyphenylene precursor (P1) bearing pre-installed hexagonal nanopores. The resultant pGNR features periodic subnanometer pores with a uniform diameter of 0.6 nm and an adjacent-pores-distance of 1.7 nm. To solidify our design strategy, two porous model compounds (1 a, 1 b) containing the same pore size as the shortcuts of pGNR, are successfully synthesized. The chemical structure and photophysical properties of pGNR are investigated by various spectroscopic analyses. Notably, the embedded periodic nanopores largely reduce the π-conjugation degree and alleviate the inter-ribbon π-π interactions, compared to the nonporous GNRs with similar widths, affording pGNR with a notably enlarged band gap and enhanced liquid-phase processability.

Selected Psychological Aspects of Meat Consumption-A Short Review.

Eating meat is deeply entrenched in Western culture. It is often associated with wealth and a highly nutritional diet; and for many people it is also an established habit that is difficult to change. The second half of the 20th century was a period of rapid growth in meat consumption, which resulted in intensified meat production. At the same time, eating meat has recently become subject to criticism for health-related, environmental or humanitarian reasons. This review aims to signal the potential consequences of a change of diet or switching to diets that are rich/poor in certain ingredients on the functioning of the hormonal and nervous system, which translates into changes in mood and behavior. This paper discusses the psychological phenomena which underlie the difficulty of changing one's food preferences and problems encountered while adding new products to the daily diet. Finally, this study summarizes the limitations of modifying eating habits that have resulted from established attitudes and habits.

Positional Isomers of Chromophore-Peptide Conjugates Self-Assemble into Different Morphologies.

Ordering π-systems into defined supramolecular structures is important for the development of organic functional materials. In recent years, peptides with defined secondary structures and/or self-assembly properties were introduced as powerful tools to order peptide-chromophore conjugates into different morphologies. This work explores whether or not the directionality of peptides can be used to control the self-assembly. The position of the π-system in conjugates between oligoprolines and perylene monoimide (PMI) chromophores was varied by attaching the PMI moiety to the second-to-last residue from the C- and N-termini, respectively. Microscopic and diffraction analysis revealed that the positional isomers form distinctly different supramolecular architectures that extend into the micrometer regime. NMR spectroscopic studies in solution phase allowed correlation of the self-assembly properties with markedly different conformational preferences of the isomeric building blocks. These insights enabled the design of building blocks with predictable self-assembly properties. Thus, the directionality of peptides offers exciting opportunities for controlling the self-assembly and electronic properties of π-systems.

Effect of Structural Modifications on the Self-Assembly of Oligoprolines Conjugated with Sterically Demanding Chromophores.

Conjugates between oligoprolines and sterically demanding perylene monoimides (PMIs) form hierarchical supramolecular self-assemblies. The influence of the length and stereochemistry at the attachment site between the peptide backbone and the chromophore on the self-assembly properties of the conjugates was explored. Comparison between oligoprolines bearing 4R- or 4S-configured azidoprolines (Azp) for the conjugation with the PMIs revealed that diastereoisomers with 4R configuration guide the self-assembly consistently better than conjugates with 4S configuration. Elongating the peptide chain beyond nine proline residues or introducing structural "errors", by altering the absolute configuration of one stereogenic center at the outside of the functionalizable oligoproline helix, lowered the efficacy of self-assembly significantly, both in solution phase and in the solid state. The results showed how subtle structural modifications allow for tuning the self-assembly of chromophores and provided further design principles for the development of peptide-chromophore conjugates into nanostructured materials.

Bottom-Up Synthesis of Necklace-Like Graphene Nanoribbons.

Graphene nanoribbons (GNRs) with an unprecedented "necklace-like" structure were synthesized through a bottom-up chemical approach, based on the oxidative cyclodehydrogenation of tailor-made polyphenylene precursors. A polycyclic aromatic hydrocarbon consisting of 84 sp(2) carbons (C84) was also synthesized and characterized as a model compound. Characterizations by a combination of MALDI-TOF MS and FTIR, Raman, and UV/Vis absorption spectroscopy validated the formation of the necklace-like GNRs. The absorption spectrum and DFT calculations revealed a bandgap of approximately 1.4 eV for this novel GNR system, which has not been attained with other GNR structures, enabling further fine-tuning of GNR bandgaps by structural modulation.

Solvent-free liquid crystals and liquids based on genetically engineered supercharged polypeptides with high elasticity.

A series of solvent-free elastin-like polypeptide liquid crystals and liquids are developed by electrostatic complexation of supercharged elastin-like polypeptides with surfactants. The smectic mesophases exhibit a high elasticity and the values can be easily tuned by varying the alkyl chain lengths of the surfactants or the lengths of the elastin-like polypeptides.

A crown ether decorated dibenzocoronene tetracarboxdiimide chromophore: synthesis, sensing, and self-organization.

A macrocyclic dibenzocoronene tetracarboxdiimide containing two benzo-21-crown-7 groups has been synthesized. It shows liquid-crystalline behavior and selectively binds Pb(2+) or K(+) to form 1:2 complexes in solution. The complexation leads to a significant increase of fluorescence; the surface organization of discotic columnar structures, in the solid-state, can be controlled by selective ion binding.

Functionalization of self-assembled hexa-peri-hexabenzocoronene fibers with peptides for bioprobing.

A novel water-soluble hexa-peri-hexabenzocoronene (HBC) derivative with peripheral functional groups, which facilitates a two-step assembly process in water that includes fiber formation via pi stacking and subsequent peptide probing via electrostatic interactions, is reported. In the first step, the HBC derivative self-assembles into water-soluble red-fluorescent fibers that serve as templates for further functionalization with biomolecules. In the second assembly step, the peripheral functional groups bind green-fluorescent fluorescein-conjugated peptides, leading to the formation of well-defined fibers that were visualized as dual-color fibers in double-fluorescence imaging.

Spongelike structures of hexa-peri-hexabenzocoronene derivatives enhance the sensitivity of chemiresistive carbon nanotubes to nonpolar volatile organic compounds of cancer.

Cancer is a leading health hazard, and lung cancer is its most common form. Breath testing is a fast, noninvasive diagnostic method which links specific volatile organic compounds (VOCs) in exhaled breath to medical conditions. Arrays of sensors based on carbon nanotubes (CNTs) could in principle detect cancer by differentiating between the VOCs found in the breath of healthy and sick persons, but the notoriously low sensitivity of CNT sensors to nonpolar VOCs limits their accuracy. In this study, we have achieved a marked improvement of the sensitivity and selectivity of random networks (RNs) of CNT chemiresistors to nonpolar VOCs by functionalizing them with self-assembled, spongelike structures of discotic hexa-peri-hexabenzocoronene (HBC) derivatives. We observed swelling of the organic film by monitoring the changes of organic film thickness during exposure and propose that the expansion of the spongelike organic overlayer creates scattering centers in the underlying RN-CNTs by physically distancing the CNTs at their intersections. The results presented here could lead to the development of robust sensors for nonpolar VOCs of cancer breath, which have hitherto been difficult to trace.