Molecules-oligomers-nanowires-graphene nanoribbons: a bottom-up stepwise on-surface covalent synthesis preserving long-range order.

We report on a stepwise on-surface polymerization reaction leading to oriented graphene nanoribbons on Au(111) as the final product. Starting from the precursor 4,4″-dibromo-p-terphenyl and using the Ullmann coupling reaction followed by dehydrogenation and C-C coupling, we have developed a fine-tuned, annealing-triggered on-surface polymerization that allows us to obtain an oriented nanomesh of graphene nanoribbons via two well-defined intermediate products, namely, p-phenylene oligomers with reduced length dispersion and ordered submicrometric molecular wires of poly(p-phenylene). A fine balance involving gold catalytic activity in the Ullmann coupling, appropriate on-surface molecular mobility, and favorable topochemical conditions provided by the used precursor leads to a high degree of long-range order that characterizes each step of the synthesis and is rarely observed for surface organic frameworks obtained via Ullmann coupling.

Fractional exhaled nitric oxide and mortality in asthma and chronic obstructive pulmonary disease in a national cohort aged 40 years and older.

BACKGROUND: Little is known about Fractional concentration of exhaled Nitric Oxide (FeNO) as a predictor of mortality in persons with asthma or chronic obstructive pulmonary disease (COPD). OBJECTIVE: This study tested the hypotheses that FeNO level ≥ 25 ppb was associated with mortality in a national cohort of persons with asthma or COPD age ≥ 40 years. METHODS: In the 2007-2012 National Health and Nutrition Examination Survey (NHANES), FeNO was measured using an electrochemical sensor. Mortality was determined through 2015 using linkage to the National Death Index. Weighted Cox proportional hazards survival analysis was performed taking the complex survey design into account using STATA V.17. RESULTS: Among the 611 participants with current asthma, 5.16% died during the follow-up period. FeNO ≥ 25 ppb was associated with a hazard ratio (HR) of 0.20, (p = 0.006, 95% CI:0.068-0.618) alone or with little change after controlling for confounding variables. Due to effect modification, the analysis was repeated in persons with and without a history of emergency department (ED) visit for asthma in the previous year. In 522 persons without ED visits, FeNO ≥ 25 ppb was significantly associated with mortality HR 0.094, 95 CI 0.034-0.26, p < 0.001. In 83 persons with ED visits no significant association remained after controlling for all confounders. (Six persons were omitted from this analysis due to missing data on confounders in the extended regression model.) Among 614 with COPD, FeNO ≥ 25 ppb was not associated with mortality. CONCLUSION: In persons with current asthma at baseline, FeNO ≥ 25 ppb was associated with reduced hazard of mortality during follow up among those with no history of ED visits in the previous year. No significant association of FeNO with mortality was seen in persons with COPD.

Tunable Band Alignment with Unperturbed Carrier Mobility of On-Surface Synthesized Organic Semiconducting Wires.

The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursors, the product's energy level alignment can be tuned without compromising the charge carrier's mobility.

On-surface photo-dissociation of C-Br bonds: towards room temperature Ullmann coupling.

The surface-assisted synthesis of gold-organometallic hybrids on the Au(111) surface both by thermo- and light-initiated dehalogenation of bromo-substituted tetracene is reported. Combined X-ray photoemission (XPS) and scanning tunneling microscopy (STM) data reveal a significant increase of the surface order when mild reaction conditions are combined with 405 nm light irradiation.