Thiol–Yne Click Reactions on Alkynyl–Dopamine‐Modified Reduced Graphene Oxide

The large‐scale preparation of graphene is of great importance due to its potential applications in various fields. We report herein a simple method for the simultaneous exfoliation and reduction of graphene oxide (GO) to reduced GO (rGO) by using alkynyl‐terminated dopamine as the reducing agent. The reaction was performed under mild conditions to yield rGO functionalized with the dopamine derivative. The chemical reactivity of the alkynyl function was demonstrated by post‐functionalization with two thiolated precursors, namely 6‐(ferrocenyl)hexanethiol and 1H,1H,2H,2H‐perfluorodecanethiol. X‐ray photoelectron spectroscopy, UV/Vis spectrophotometry, Raman spectroscopy, conductivity measurements, and cyclic voltammetry were used to characterize the resulting surfaces.     

Hidden electrochemistry in the thermal grafting of silicon surfaces from grignard reagents

Covalent grafting of alkyl chains on silicon can be obtained by thermal treatment in Grignard reagents. Alkyl halide present in the Grignard solution as an impurity appears to play a key role in the grafting process. Grafting efficiency is improved when the alkyl halide concentration is increased. It is also enhanced on n-type substrates as compared to p-type substrates and when alkyl bromides are present in solution rather than alkyl chlorides. The grafting reaction involves a zero-current electrochemical step. A reaction model in which simultaneous Grignard oxidation and alkyl halide reduction take place at the silicon surface accounts for all these observations. Alkyl halide reduction is the rate-determining step. Negative charging of the silicon surface lowers the energetic barrier for this reaction, allowing for efficient grafting on n-Si.     

Electrochemical impedance spectroscopy of ZnO nanostructures

The paper reports on the use of electrochemical impedance spectroscopy to determine the doping character and carrier density of freshly prepared and annealed ZnO nanostructures. The ZnO nanostructures were obtained by chemical oxidation of metallic Zn in a 5% N,N-dimethylformamide (DMF) aqueous solution at 95 °C for 24 h. The as-grown nanostructured ZnO samples display a high donor density of 3.71 ± 0.88 × 10²¹ cm^?3. Annealing at 100 and 200 °C did not have any effect on the donor density while thermal annealing at 300 °C in air for 1 h induced a decrease in the doping concentration without affecting the surface morphology.     

A robust method for automated background subtraction of tissue fluorescence

This paper introduces a new robust method for the removal of background tissue fluorescence from Raman spectra. Raman spectra consist of noise, fluorescence and Raman scattering. In order to extract the Raman scattering, both noise and background fluorescence must be removed, ideally without human intervention and preserving the original data. We describe the rationale behind our robust background subtraction method, determine the parameters of the method and validate it using a Raman phantom against other methods currently used. We also statistically compare the methods using the residual mean square (RMS) with a fluorescence‐to‐signal (F/S) ratio ranging from 0.1 to 1000. The method, ‘adaptive minmax’, chooses the subtraction method based on the F/S ratio. It uses multiple fits of different orders to maximize each polynomial fit. The results show that the adaptive minmax method was significantly better than any single polynomial fit across all F/S ratios. This method can be implemented as part of a modular automated real‐time diagnostic in vivo Raman system. Copyright © 2007 John Wiley & Sons, Ltd.     

Design and synthesis of some new tri-substituted pyrazole derivatives as anticancer agents

A new series of tri-substituted pyrazole derivatives were designed as anti-cancer agents and synthesized, starting with the formylation of semicarbazone via the Vilsmeier–Haack reaction to give 3-(4-bromophenyl)-1H-pyrazole-4-carbaldehyde I which was the precursor of compounds 1–9. The new chemical entities were screened for their anti-cancer activity on various human cancer cell lines, namely: hepatocellular carcinoma HepG2, breast cancer MCF-7, lung carcinoma A549 and prostatic cancer PC3. Most of the synthesized compounds showed remarkable activity on the tested cell lines, while compound 2 had the highest potency against the HepG2 cell line with an IC₅₀ of 9.13 µM compared with doxorubicin (IC₅₀ = 34.24 µM), the reference standard used in this study, and compound 7 was the most active on the rest of the three cell lines; MCF-7, A549 and PC3 (IC₅₀ = 16.52, 6.52 and 9.13 µM, respectively) relative to IC₅₀ = 20.85, 5.93 and 38.02 µM of the standard. Thus, some of the synthesized tri-substituted pyrazole derivatives, specially 2 and 7, have the potential to be developed into potent anticancer agents.     

Surfactant Effect on Kinetic of Reaction of Some Sulphonamides with p‐Dimethylaminobenzaldehyde: Surfactant‐Modified Determination of Sulphonamides in Aqueous Solution

Kinetics of condensation reactions of six sulpha drugs (I‐VI) with p‐dimethylaminobenzaldehyde (DAB) in a weakly acidic EthOH/H₂O solution have been studied spectrophotometrically. The reaction was found to be first order with respect to DAB and zero order with respect to sulphonamide. The rate constants, activation energies, and other related thermodynamic functions have been determined. The effect of the presence of anionic surfactant sodium dodecyl sulphate (SDS) on the kinetics of this reaction in aqueous solution has been investigated. The observed rate constants increase with increasing the amount of SDS except for those of sodium sulphacetamide (VI). The surfactant molecules enhance the reaction rates (14–113 times) in concentrations less than critical micellar concentration (cmc). A developed spectrophotometric method for determining sulphonamides in aqueous solution by their reactions with an excess of DAB in the presence of SDS and HCl (pH = 2) at a wavelength of 447 nm has been introduced. Microgram amounts of sulphonamides can be estimated with accuracy better than ± 1.5% and reproducibility less than ± 0.064%. The results of application to sulphonamides in pure form indicate that the presented method is simple, sensitive, precise, accurate, and comparable to the colorimetric Bratton‐Marshall standard procedure. The effect of interferences and application of the presented method to two pharmaceutical preparations have been investigated.     

Dielectric relaxation spectroscopy of heteronuclear cobalt(II)-copper(II) complex of 1-phenyl-3-methyl-5-pyrazolone

A bright green CoCu(PMP)(OH)2(H2O)2 complex was synthesized. Its structure was elucidated and characterized by different spectroscopic techniques. Both cobalt and copper atoms attain tetrahedral geometry. The complex was investigated by the dielectric relaxation spectroscopy. The dielectric parameters are discussed in terms of temperature and frequency changes. The conductivity of the complex decreased as the temperature increased in the temperature range 30-100 degrees C, while above this temperature range stepwise increase in the conductivity was observed.     

The space of complete embedded maximal surfaces with isolated singularities in the 3-dimensional Lorentz-Minkowski space

We prove that a complete embedded maximal surface in = (³, dx₁² + dx₂²-dx₃²) with a finite number of singularities is an entire maximal graph with conelike singularities over any spacelike plane, and so, it is asymptotic to a spacelike plane or a half catenoid. We show that the moduli space of entire maximal graphs over {x₃=0} in with n+12 singular points and vertical limit normal vector at infinity is a 3n+4-dimensional differentiable manifold. The convergence in means the one of conformal structures and Weierstrass data, and it is equivalent to the uniform convergence of graphs on compact subsets of {x₃=0}. Moreover, the position of the singular points in ³ and the logarithmic growth at infinity can be used as global analytical coordinates with the same underlying topology. We also introduce the moduli space of marked graphs with n+1 singular points (a mark in a graph is an ordering of its singularities), which is a (n+1)-sheeted covering of . We prove that identifying marked graphs differing by translations, rotations about a vertical axis, homotheties or symmetries about a horizontal plane, the corresponding quotient space is an analytic manifold of dimension 3n–1. This manifold can be identified with a spinorial bundle associated to the moduli space of Weierstrass data of graphs in .Mathematics Subject Classification (2000): 53C50, 58D10, 53C42First and second authors research partially supported by MEC-FEDER grant number MTM2004-00160Second and third authors research partially supported by Consejería de Educación y Ciencia de la Junta de Andalucía and the European Union.