Optically Transparent Gold Nanoparticles for DSSC Counter-Electrode: An Electrochemical Characterization

A gold nanoparticles transparent electrode was realized by chemical reduction. This work aims to compare the transparent gold nanoparticles electrode with a more commonly utilized gold-film-coated electrode in order to investigate its potential use as counter-electrode (CE) in dye-sensitized solar cells (DSSCs). A series of DSSC devices, utilizing I⁻/I³⁻ and Co(III)/(II) polypyridine redox mediators [Co(dtb)3]³⁺/²⁺; dtb = 4,4′ditert-butyl-2,2′-bipyridine)], were evaluated. The investigation focused firstly on the structural characterization of the deposited gold layers and then on the electrochemical study. The novelty of the work is the realization of a gold nanoparticles CE that reached 80% of average visible transmittance. We finally examined the performance of the transparent gold nanoparticles CE in DSSC devices. A maximum power conversion efficiency (PCE) of 4.56% was obtained with a commercial I⁻/I³⁻-based electrolyte, while a maximum 3.1% of PCE was obtained with the homemade Co-based electrolyte.     

Transition from enantioselective high performance to ultra-high performance liquid chromatography: A case study of a brush-type chiral stationary phase based on sub-5-micron to sub-2-micron silica particles

Three brush-type chiral stationary phases (CSPs) differing in the particle size of the starting silica particles have been prepared by covalent grafting of the π-acidic bis-(3,5-dinitrobenzoyl)-derivative of trans-1,2-diaminocyclohexane (DACH-DNB). Starting silica particles of 4.3, 2.6 and 1.9 micron were used to generate the final CSPs using an improved, highly reproducible synthetic methodology, that allowed to assemble and surface-graft the whole chiral selector in only two steps. The different CSPs have been packed in columns of various length and diameters, and fully characterized in terms of flow permeability, kinetic performances and enantioselectivity using a set of test solutes. Very high speed and high resolution applications together with stereodynamic HPLC examples are demonstrated on the columns with reduced particle diameters, on which separations of several enantiomeric pairs are routinely obtained with analysis times in the 15–40 s range.     

Corrigendum to “Extending homeomorphisms from punctured surfaces to handlebodies” [Topology Appl. 155 (6) (2008) 610–621]

We correct the statements of Theorems 9 and 10 of [A. Cattabriga, M. Mulazzani, Extending homeomorphisms from punctured surfaces to handlebodies, Topology Appl. 155 (2008) 610–621], by adding missing generators, and improve the statement of Theorem 10, by removing some redundant generators.     

Thiazolo[5,4-d]thiazole-2,5-dicarboxylic acid,C6H2N2O4S2, and its coordination polymers

Thiazolo[5,4-d]thiazole-2,5-dicarboxylic acid, C₆H₂N₂O₄S₂, was isolated as a polycrystalline material, and its crystal structure was determined by ab-initio X-ray powder diffraction (XRPD) methods. This species, upon deprotonation, was subsequently used in preparing the new coordination polymers Ag₂(C₆N₂O₄S₂), Mn(C₆N₂O₄S₂)(H₂O)₂, Co(C₆N₂O₄S₂)(H₂O)₂, Cu(C₆N₂O₄S₂)(H₂O) and Zn(C₆N₂O₄S₂)(H₂O)₂, fully characterized by analytical, thermal and XRPD structural methods – including in situ thermodiffractometry and simultaneous TGA and DSC. In the first-row transition metal derivatives, the [C₆N₂O₄S₂]^2? anion systematically prefers the N,O-chelating, vs. the expected O,O′-bridging, coordination mode, not allowing the formation of porous 3D frameworks. Indeed, these species are dense 1D coordination polymers. At variance, the silver derivative possesses a complex, dense 3D framework, due to the presence of μ₆-[C₆N₂O₄S₂]^2? ligands showing two μ₂-bridging carboxylates and two monohapto N-donor sites. When dehydration is viable, materials of E_n(C₆N₂O₄S₂) formulation are irreversibly recovered (n = 1 for E = Mn, Co, Zn, Cu; n = 2, for E = H).     

Hydrogen Transport and Evolution in Ni-MH Batteries by Neutron Imaging

Efficiency losses due to side reactions are one of the main challenges in battery development. Despite providing valuable insights, the results of standard analysis on the individual components cannot be simply extrapolated to the full operating system. Therefore, non-destructive, and high resolution approaches that allow the investigation of the full system are desired. Herein, we combined neutron radiography and tomography with electrical monitoring of the state of charge of commercial Ni-mischmetal hydride batteries, to track the exchange and transport of hydrogen under operating conditions. This non-destructive approach allowed both the quantification of the hydrogen distribution in the electrodes in 4D, and the distinction between the electrochemically exchanged hydrogen and the hydrogen gas pressure generated by side reactions, as a function of the applied potential and current. One of the most counter-intuitive observation is that the generation of hydrogen gas during discharge depends on the charging state of the battery. The results presented provide critical new insights in the mechanisms governing the electrochemical processes during Nimischmetal hydride battery operation, and also pave the way for the extrapolation of this approach to the investigation of state-of-the-art Li-ions batteries.     

Hölder continuity of local minimizers of vectorial integral functionals

We study the regularity of vector-valued local minimizers in $ W^{1,p}, p > 1 $, of the integral functional where is an open set in $ \mathbb{R}^N $ and f is a continuous function, convex with respect to the last variable, such that $ 0 \leq f(x,u,t)\leq C(1+t^p) $.We prove that if f = f(x, t), or f = f(x, u, t) and $ p \leq N $, then local minimizers are locally Hölder continuous for any exponent less than 1. If f = f(x, u, t) and p < N then local minimizers are Höolder continuous for every exponent less than 1 in an open set $ \Omega_0 $ such that the Hausdorff dimension of $ \Omega \backslash \Omega_0 $ is less than N–p.AMS Subject Classification: 49N60.     

Adaptation of NS cells growth and differentiation to high-throughput screening-compatible plates

Background  

There is an urgent need of neuronal cell models to be applied to high-throughput screening settings while recapitulating physiological and/or pathological events occurring in the Central Nervous System (CNS). Stem cells offer a great opportunity in this direction since their self renewal capacity allows for large scale expansion. Protocols for directed differentiation also promise to generate populations of biochemically homogenous neuronal progenies. NS (Neural Stem) cells are a novel population of stem cells that undergo symmetric cell division in monolayer and chemically defined media, while remaining highly neurogenic.