Glassy Carbon Electrodes Modified with Multiwall Carbon Nanotubes Dispersed in Polylysine

We report the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multiwall carbon nanotubes (MWCNT) in polylysine (Plys) (GCE/MWCNT‐Plys). The resulting electrodes show an excellent electrocatalytic activity towards different bioanalytes like ascorbic acid, uric acid and hydrogen peroxide, with important decrease in their oxidation overvoltages. The dispersion of 1.0 mg/mL MWCNT in 1.0 mg/mL polylysine is highly stable, since after 2 weeks the sensitivity for hydrogen peroxide at GCE modified with this dispersion remained in a 90% of the original value. The MWCNT‐Plys layer immobilized on glassy carbon electrodes has been also used as a platform to build supramolecular architectures by self‐assembling of polyelectrolytes based on the polycationic nature of the polylysine used to disperse the nanotubes. The self‐assembling of glucose oxidase has allowed us to obtain a supramolecular multistructure for glucose biosensing. The influence of glucose oxidase concentration and adsorption time as well as the effect of using polylysine or MWCNT‐Plys as polycationic layers for further adsorption of GOx is also evaluated.     

Synthesis of hybrid polymeric fibers of different functionalized alkoxysilane coupling agents obtained via sol–gel and electrospinning technique: effect on the morphology by addition of PVA

Journal of Sol-Gel Science and Technology - Hybrid functionalized alkoxysilane/PDMS-OH and alkoxysilane/PDMS-OH/PVA polymers were synthesized through acid catalysis sol–gel technique and...     

Synthesis,magnetic properties and Mössbauer spectroscopy for the pyrochlore family Bi2BB′O7 with B=Cr and Fe and B′=Nb,Ta and Sb

The samples Bi₂BB′O₇, with B=Cr and Fe and B′=Nb, Ta and Sb were prepared by solid state method. The crystallographic structure was investigated on the basis of X-ray powder diffraction data. Rietveld refinements show that the crystal structure is cubic, space group Fd-3m. The Bi³⁺ cation on the eight-coordinate pyrochlore A-site shows displacive disorder, as a consequence of its lone pair electron con?guration. There is also a considerable A-site disorder shown by Rietveld Analysis and confirmed in the case of the iron containing samples with Mössbauer spectroscopy. The magnetic measurements show paramagnetic behavior at all temperatures for the Cr oxides. The Fe pyrochlores show antiferromagnetic order around 10 K.     

Anti-Kählerian Geometry on Lie Groups

Let G be a Lie group of even dimension and let (g, J) be a left invariant anti-Kähler structure on G. In this article we study anti-Kähler structures considering the distinguished cases where the complex structure J is abelian or bi-invariant. We find that if G admits a left invariant anti-Kähler structure (g, J) where J is abelian then the Lie algebra of G is unimodular and (G, g) is a flat pseudo-Riemannian manifold. For the second case, we see that for any left invariant metric g for which J is an anti-isometry we obtain that the triple (G, g, J) is an anti-Kähler manifold. Besides, given a left invariant anti-Hermitian structure on G we associate a covariant 3-tensor ?? on its Lie algebra and prove that such structure is anti-Kähler if and only if ?? is a skew-symmetric and pure tensor. From this tensor we classify the real 4-dimensional Lie algebras for which the corresponding Lie group has a left invariant anti-Kähler structure and study the moduli spaces of such structures (up to group isomorphisms that preserve the anti-Kähler structures).     

Comparative study of the electrochemical behavior and analytical applications of (bio)sensing platforms based on the use of multi-walled carbon nanotubes dispersed in different polymers

This review present a critical comparison of the electrochemical behavior and analytical performance of glassy carbon electrodes (GCE) modified with carbon nanotubes (CNTs) dispersed in different polymers: polyethylenimine (PEI), PEI functionalized with dopamine (PEI-Do), polyhistidine (Polyhis), polylysine (Polylys), glucose oxidase (GOx) and double stranded calf-thymus DNA (dsDNA). The comparison is focused on the analysis of the influence of the sonication time, solvent, polymer/CNT ratio, and nature of the polymer on the efficiency of the dispersions and on the electrochemical behavior of the resulting modified electrodes. The results allow to conclude that an adequate selection of the polymers makes possible not only an efficient dispersion of CNTs but also, and even more important, the building of successful analytical platforms for the detection of different bioanalytes like NADH, glucose, DNA and dopamine.     

Polar factorization of conformal and projective maps of the sphere in the sense of optimal mass transport

Let M be a compact Riemannian manifold and let μ, d be the associated measure and distance on M. Robert McCann, generalizing results for the Euclidean case by Yann Brenier, obtained the polar factorization of Borel maps S: M → M pushing forward μ to a measure ν: each S factors uniquely a.e. into the composition S = T ? U, where U: M → M is volume preserving and T: M → M is the optimal map transporting μ to ν with respect to the cost function d²/2.In this article we study the polar factorization of conformal and projective maps of the sphere S ⁿ . For conformal maps, which may be identified with elements of O_o(1, n+1), we prove that the polar factorization in the sense of optimal mass transport coincides with the algebraic polar factorization (Cartan decomposition) of this Lie group. For the projective case, where the group GL+(n + 1) is involved, we find necessary and sufficient conditions for these two factorizations to agree.     

Adsorption and Electrooxidation of Nucleic Acids at Glassy Carbon Electrodes Modified with Multiwalled Carbon Nanotubes Dispersed In Polylysine

We report the advantages of the adsorption and electrooxidation of oligonucleotides and calf‐thymus double stranded DNA (dsDNA) at glassy carbon electrodes (GCE) modified with a dispersion of multiwalled carbon nanotubes (MWCNT) in poly‐L ‐lysine (Plys) (GCE/MWCNT‐Plys). Important enhancement in the guanine oxidation signal was obtained by adsorptive stripping voltammetry (AdSV) due to a most favorable interaction between the negatively charged DNAs and the positively charged Plys that support the MWCNT. The layer of oligo(dG)₁₁ immobilized at GCE/MWCNT‐Plys was successfully used for the selective detection of the hybridization event using oligo(dG)₁₁/oligo(dC)₁₁ as model.