Can a Procedure for the Growth of Single-layer Graphene on Copper be used in Different Chemical Vapor Deposition Reactors?

In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm²-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.     

Cymodienol and cymodiene: new cytotoxic diarylheptanoids from the sea grass Cymodocea nodosa

The two new diarylheptanoids, cymodienol (1), and cymodiene (2), obtained from specimens of the sea grass Cymodocea nodosa, collected from the coastal areas of central Greece, are the first members of this class isolated from marine organisms. The chemical structures of the two metabolites were assigned on the basis of their NMR and MS spectroscopic data, including information obtained by 1D- and 2D-NMR experiments. Metabolite 2 possesses an unprecedented skeleton that might be biosynthetically related to metabolite 1. Cymodienol (1) was found to exhibit significant cytotoxic activity against two lung cancer cell lines.     

Flow-injection spectrophotometric determination of chloramben

Abstract

A method for the dechlorination of PCB mixtures (Aroclor formulations) to biphenyl was extended to soils. The contaminated sample was mixed with magnesium flakes, potassium hexachloropalladiate (K₂PdCl₆), propan-2-ol and water then permitted to react for up to six hours. Biphenyl, recovered by extraction into hexane, was quantified by gas chromatography with flame ionization detection. The reaction was very efficient in propan-2-ol / water (～95%), surfactant emulsion or sand mixture and virtually complete in soil provided that excess magnesium (2 g) and the K₂PdCl₆ were added to the sample prior to the addition of water. Higher PCB loadings were readily determined in field contaminated soils either by direct determination within the matrix or by standard additions. However, analyte concentrations were appreciably over-estimated in Soxhlet or sonication extracts of a certified reference material that contained sub-ppm levels of analyte. The over-estimation is considered to result from the conversion in part of natural organic matter to biphenyl.     

Spectrophotometric method for determination of atrazine and its application to commercial formulations and real samples

A simple sensitive spectrophotometric method has been developed for the determination of atrazine in herbicide formulations and real samples. The method was based on the reaction of atrazine with pyridine to form a quaternary halide which in the presence of alkali forms a carbinol base. The heterocyclic ring of the carbinol base breaks and forms the glutaconic dialdehyde. The glutaconic dialdehyde group was coupled with sulfanilic acid to form a yellow coloured product having λ _max 450 nm or coupled with aniline to form a orange red coloured product having λ _max 480 nm. The Beer's law was obeyed over the range from 0.1 to 25 µg mL^?1 and molar absorptivity 1.5 × 10⁴ L mol^?1 cm^?1 for sulfanilic acid, and from 0.08 to 12 µg mL^?1 and molar absorptivity 1.3 × 10⁴ L mol^?1 cm^?1 for aniline were observed. The reaction conditions and other analytical parameters were optimised. The proposed method has been successfully applied for the analysis of commercial formulations and real samples.     

Selective Uptake of Cylindrical Poly(2‐Oxazoline) Brush‐AntiDEC205 Antibody‐OVA Antigen Conjugates into DEC‐Positive Dendritic Cells and Subsequent T‐Cell Activation

To achieve specific cell targeting by various receptors for oligosaccharides or antibodies, a carrier must not be taken up by any of the very many different cells and needs functional groups prone to clean conjugation chemistry to derive well‐defined structures with a high biological specificity. A polymeric nanocarrier is presented that consists of a cylindrical brush polymer with poly‐2‐oxazoline side chains carrying an azide functional group on each of the many side chain ends. After click conjugation of dye and an anti‐DEC205 antibody to the periphery of the cylindrical brush polymer, antibody‐mediated specific binding and uptake into DEC205⁺‐positive mouse bone marrow‐derived dendritic cells (BMDC) was observed, whereas binding and uptake by DEC205^? negative BMDC and non‐DC was essentially absent. Additional conjugation of an antigen peptide yielded a multifunctional polymer structure with a much stronger antigen‐specific T‐cell stimulatory capacity of pretreated BMDC than application of antigen or polymer–antigen conjugate.     

Mechanism of Host–Guest Complex Formation and Identification of Intermediates through NMR Titration and Diffusion NMR Spectroscopy

The formation of host–guest (H‐G) complexes between 1,8‐bis[(diethylgallanyl)ethynyl]anthracene (H) and the N‐heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host–guest structures in solution were compared with those of tailor‐made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host–guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H₂?H₂κ¹‐G₁?HG₂ is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H₂→H₁κ²‐G₁?HG₂ is observed (the formation of a 1:1 aggregate is the second step).     

The role that conduction band tail states play in determining the optical response of hydrogenated amorphous silicon

We aim to explore the role that conduction band tail states play in shaping the optical response of hydrogenated amorphous silicon. We do so within the framework of an empirical model for the valence band and conduction band density of states functions, one that considers valence band band, valence band tail, conduction band band, and conduction band tail states. We examine the sensitivity of the joint density of states function to variations in the conduction band tail breadth, all other parameters being held fixed at their nominal hydrogenated amorphous silicon values. We find that when the conduction band tail is narrower than the valence band tail, its role in shaping the corresponding spectral dependence of the joint density of states function is relatively minor. This justifies the use of a simplified empirical model for the density of states functions that neglects the presence of the conduction band tail states in the characterization of the optical response of this material. Experimental data corresponding to hydrogenated amorphous silicon, demonstrating that the conduction band tail breadth is always less than the valence band tail breadth for this material, is then presented. Finally, fundamental reasons for the observed asymmetry in the band tail breadths are reviewed.     

Wolff–Denjoy theorems in nonsmooth convex domains

We give a short proof of Wolff–Denjoy theorem for (not necessarily smooth) strictly convex domains. With similar techniques we are also able to prove a Wolff–Denjoy theorem for weakly convex domains, again without any smoothness assumption on the boundary.     

Determination of starane (fluroxypyr) herbicide using flow injection spectrophotometry.

The starane herbicide was spectrophotometrically determined by the diazotization method in a flow injection assembly. Since starane is a substituted pyridyl compound the NH2 group at the p-position was exploited for diazotization. Starane was diazotized with nitrite and the diazotized product is coupled with beta-naphthol. The absorbance of the resulting azo dye was measured at 395 nm with a molar absorptivity of 1.5 x 10(4) L mol(-1) cm(-1). The calibration graph was linear over the range of 0.6 to 10 microg/mL, with a relative standard deviation (RSD) of 1.67% and a sampling through put of 60 samples h(-1). The % recovery for the determination of starane was found to be 96%. The method was successfully applied to the determination of the active ingredient of starane herbicide in its formulation as well as in food samples.