Length-dependent symmetry in narrow chevron-like graphene nanoribbons.

We report the structural and electronic properties of narrow chevron-like graphene nanoribbons (GNRs), which depending on their length are either mirror or inversion symmetric. Additionally, GNRs of different length can form molecular heterojunctions based on an unusual binding motif.

Self-Assembly of a Triphenylene-Based Electron Donor Molecule on Graphene: Structural and Electronic Properties.

In this study, we report on the self-assembly of the organic electron donor 2,3,6,7,10,11-hexamethoxytriphenylene (HAT) on graphene grown epitaxially on Ir(111). Using scanning tunneling microscopy and low-energy electron diffraction, we find that a monolayer of HAT assembles in a commensurate close-packed hexagonal network on graphene/Ir(111). X-ray and ultraviolet photoelectron spectroscopy measurements indicate that no charge transfer between the HAT molecules and the graphene/Ir(111) substrate takes place, while the work function decreases slightly.

Comparing Cyanophenyl and Pyridyl Ligands in the Formation of Porphyrin-Based Metal-Organic Coordination Networks.

In recent studies, porphyrin derivatives have been frequently used as building blocks for the fabrication of metal-organic coordination networks (MOCNs) on metal surfaces under ultrahigh vacuum conditions (UHV). The porphyrin core can host a variety of 3d transition metals, which are usually incorporated in solution. However, the replacement of a pre-existing metal atom in the porphyrin core by a different metallic species has been rarely reported under UHV.

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms.

The self-assembly of a nickel-porphyrin derivative (Ni-DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni-DPPyP onto Au(111) gave rise to a close-packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two-dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules.

Engineering Long-Range Order in Supramolecular Assemblies on Surfaces: The Paramount Role of Internal Double Bonds in Discrete Long-Chain Naphthalenediimides.

Achieving long-range order with surface-supported supramolecular assemblies is one of the pressing challenges in the prospering field of non-covalent surface functionalization. Having access to defect-free on-surface molecular assemblies will pave the way for various nanotechnology applications. Here we report the synthesis of two libraries of naphthalenediimides (NDIs) symmetrically functionalized with long aliphatic chains (C and C) and their self-assembly at the 1-phenyloctane/highly oriented pyrolytic graphite (1-PO/HOPG) interface.

Thiol-free self-assembled oligoethylene glycols enable robust air-stable molecular electronics.

Self-assembled monolayers (SAMs) are widely used to engineer the surface properties of metals. The relatively simple and versatile chemistry of metal-thiolate bonds makes thiolate SAMs the preferred option in a range of applications, yet fragility and a tendency to oxidize in air limit their long-term use. Here, we report the formation of thiol-free self-assembled mono- and bilayers of glycol ethers, which bind to the surface of coinage metals through the spontaneous chemisorption of glycol ether-functionalized fullerenes.

Coverage-Dependent Structural Transformation of Cyano-Functionalized Porphyrin Networks on Au(111) via Addition of Cobalt Atoms.

The self-assembly process of a cobalt-porphyrin derivative (Co-TCNPP) containing cyanophenyl substituents at all four meso positions on Au(111) was studied by means of scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) under ultrahigh vacuum conditions. Deposition of Co-TCNPP onto Au(111) gave rise to the formation of a close-packed H-bonded network, which was independent of coverage as revealed by STM and LEED. However, a coverage-dependent structural transformation took place upon the deposition of Co atoms.

Low-Dimensional Metal-Organic Coordination Structures on Graphene.

We report the formation of one- and two-dimensional metal-organic coordination structures from -hexaphenyl-dicarbonitrile (NC-Ph-CN) molecules and Cu atoms on graphene epitaxially grown on Ir(111). By varying the stoichiometry between the NC-Ph-CN molecules and Cu atoms, the dimensionality of the metal-organic coordination structures could be tuned: for a 3:2 ratio, a two-dimensional hexagonal porous network based on threefold Cu coordination was observed, while for a 1:1 ratio, one-dimensional chains based on twofold Cu coordination were formed. The formation of metal-ligand bonds was supported by imaging the Cu atoms within the metal-organic coordination structures with scanning tunneling microscopy.

Coverage-Controlled Polymorphism of H-Bonded Networks on Au(111).

We report on the self-assembly of a conformational flexible organic compound on Au(111) using scanning tunneling microscopy and low-energy electron diffraction measurements. We observed different conformers of the compound upon adsorption on the reconstructed Au(111) surface. Increasing the molecular coverage enhanced the lateral pressure, that is, parallel to the surface, favoring a coverage-controlled transition from a supramolecular network displaying only one molecular organization, into a polymorphic array with two coexisting arrangements.

Comparing the Self-Assembly of Sexiphenyl-Dicarbonitrile on Graphite and Graphene on Cu(111).

A comparative study on the self-assembly of sexiphenyl-dicarbonitrile on highly oriented pyrolytic graphite and single-layer graphene on Cu(111) is presented. Despite an overall low molecule-substrate interaction, the close-packed structures exhibit a peculiar shift repeating every four to five molecules. This shift has hitherto not been reported for similar systems and is hence a unique feature induced by the graphitic substrates.

Confinement properties of 2D porous molecular networks on metal surfaces.

Quantum effects that arise from confinement of electronic states have been extensively studied for the surface states of noble metals. Utilizing small artificial structures for confinement allows tailoring of the surface properties and offers unique opportunities for applications. So far, examples of surface state confinement include thin films, artificial nanoscale structures, vacancy and adatom islands, self-assembled 1D chains, vicinal surfaces, quantum dots and quantum corrals.

Potential effects of sediment contaminants on diatom assemblages in coastal lagoons of New Jersey and New York States.

Sediment samples from the coastal lagoons and estuaries of New York and New Jersey were used to investigate the influence of contaminants on diatom assemblages. Multivariate analyses demonstrated correspondence between composition of diatom assemblages and concentrations of several metals and total PAH. The effects of the individual contaminants were difficult to disentangle because of the considerable correlations between their concentrations.

Nitrogen Deposition Effects on Diatom Communities in Lakes from Three National Parks in Washington State.

The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (<100 μS/cm), and acid neutralizing capacities (<400 μeq/L).

Controlling the dimensionality and structure of supramolecular porphyrin assemblies by their functional substituents: dimers, chains, and close-packed 2D assemblies.

Repulsive interactions: a staging of supramolecular aggregation from (0D) clusters to (1D) chains and (2D) assemblies as a function of molecular coverage of dipolar porphyrins adsorbed on the Ag(111) surface is described. It displays a complex interplay of both attractive and repulsive molecule-molecule interactions, the emergence of chirality, and the registry of the substrate.

STM fingerprint of molecule-adatom interactions in a self-assembled metal-organic surface coordination network on Cu(111).

A novel approach of identifying metal atoms within a metal-organic surface coordination network using scanning tunnelling microscopy (STM) is presented. The Cu adatoms coordinated in the porous surface network of 1,3,8,10-tetraazaperopyrene (TAPP) molecules on a Cu(111) surface give rise to a characteristic electronic resonance in STM experiments. Using density functional theory calculations, we provide strong evidence that this resonance is a fingerprint of the interaction between the molecules and the Cu adatoms.

Effect of prenatal stress on alcohol preference and sensitivity to chronic alcohol exposure in male rats.

Rationale: In rats, prenatal restraint stress (PRS) induces persistent behavioral and neurobiological alterations leading to a greater consumption of psychostimulants during adulthood. However, little is known about alcohol vulnerability in this animal model.

Objectives: We examined in adolescent and adult male Sprague Dawley rats the long-lasting impact of PRS exposure on alcohol consumption.

Aggregation and contingent metal/surface reactivity of 1,3,8,10-tetraazaperopyrene (TAPP) on Cu(111).

The structural chemistry and reactivity of 1,3,8,10-tetraazaperopyrene (TAPP) on Cu(111) under ultra-high-vacuum (UHV) conditions has been studied by a combination of experimental techniques (scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy, XPS) and DFT calculations. Depending on the deposition conditions, TAPP forms three main assemblies, which result from initial submonolayer coverages based on different intermolecular interactions: a close-packed assembly similar to a projection of the bulk structure of TAPP, in which the molecules interact mainly through van der Waals (vDW) forces and weak hydrogen bonds; a porous copper surface coordination network; and covalently linked molecular chains. The Cu substrate is of crucial importance in determining the structures of the aggregates and available reaction channels on the surface, both in the formation of the porous network for which it provides the Cu atoms for surface metal coordination and in the covalent coupling of the TAPP molecules at elevated temperature.

Modification of supramolecular binding motifs induced by substrate registry: formation of self-assembled macrocycles and chain-like patterns.

The self-assembly properties of two Zn(II) porphyrin isomers on Cu(111) are studied at different coverage by means of scanning tunneling microscopy (STM). Both isomers are substituted in their meso-positions by two voluminous 3,5-di(tert-butyl)phenyl and two rod-like 4'-cyanobiphenyl groups, respectively. In the trans-isomer, the two 4'-cyanobiphenyl groups are opposite to each other, whereas they are located at right angle in the cis-isomer.

Conformation-controlled networking of H-bonded assemblies on surfaces.

A temperature-induced phase transition of a 2D H-bonded assembly, enabling quadruple H-bonding interactions, from a hexagonal porous network into a close-packed rhombic arrangement has been observed on Ag(111) by STM imaging.

Ethanol attenuates spatial memory deficits and increases mGlu1a receptor expression in the hippocampus of rats exposed to prenatal stress.

Background: Although it is generally believed that chronic ethanol consumption impairs learning and memory, results obtained in experimental animals are not univocal, and there are conditions in which ethanol paradoxically improves cognitive functions. In the present work, we investigated the effects of prenatal stress and of chronic ethanol exposure during adulthood on spatial memory in rats.

Methods: Rats were subjected to a prenatal stress delivered as 3 daily 45-minute sections of restraint stress to the mothers during the last 10 days of pregnancy (PRS rats).

Polycystic hepatic disease.

Polycystic hepatic disease is a very rare hereditary disease. Most of the patients have no symptoms but sometimes they present abdominal discomfort, fever, jaundice. Almost half of the patients associate renal cysts.

A rare case of pulmonary emphysema.

Alpha-1-antitrypsin deficiency (AAT) is one of the three most common lethal genetic diseases in the caucasian population (together with cystic fibrosis and Down syndrome). Its primary manifestation is early-onset panacinar emphysema. Slowly progressive dyspnea is the primary symptom, although some patients initially have symptoms of cough, sputum production, or wheezing.

Giant iliac artery aneurysm--a rare cause of hydronephrosis.

The presence of arterial aneurysm--an abnormal dilatation of an arterial segment due to various causes--might lead to compression effects and to various symptoms. Finding an etiology for unilateral hydronephrosis represents in some cases a real challenge for the clinician and targeted investigations must be ordered for the diagnostic approach. The abdominal ultrasound examination is one of the first imaging modalities but the abdominal computed tomography is helpful for definitive conclusions.