Carbon Nanotube‐Adsorbed Electrospun Nanofibrous Membranes as Coating for Electrochemical Sensors for Sulfhydryl Compounds

A new method to modify electrodes with carbon nanotubes (CNT) was developed. Multiwalled carbon nanotubes (MWNT) were adsorbed on the electrospun nylon‐6 nanofibrous membranes (Ny‐6‐NFM) and used as a coating to modify conventional glassy carbon electrodes. The modified electrode was designed for the amperometric detection of sulfhydryl compounds with the potential held at +0.3 V vs. Ag/AgCl. The modified electrode showed a linear response for cysteine up to 0.4 mM (R²=0.997), with a sensitivity of 5.1 µA/mM and a detection limit of 15 µM. Other sulfhydryl compounds showed similar results. After use, the Ny‐6‐NFM was easily peeled off, leaving the bare electrode surface back to its original electrochemical behaviour. This is the first attempt to use a disposable membrane functionalized with MWNT for electroanalytical purposes.     

Anti-Kasha's rule fluorescence emission in (2-ferrocenyl)indene generated by a twisted intramolecular charge-transfer (TICT) process

A twisted intramolecular charge-transfer (TICT) process has been identified in (2-ferrocenyl)indene. This photochemical process explains the anti-Kasha's rule fluorescence emission observed for this system. Experimental and model investigations on (2-ferrocenyl)tetramethylindene and (2-ferrocenyl)-hexamethylindene were also performed, in order to evaluate the effect of a steric hindrance on the TICT mechanism. The energy of the lowest main excited states was computed with a TD-DFT approach, as a function of the rotation of the dihedral angle between the indene and the cyclopentadienyl planes. To the best of our knowledge, this is the first example of TICT generated by metal-to-ligand charge transfer (MLCT) in a ferrocene-containing complex and, more generally, the first case of complexes in which a metal center is directly involved.     

The effects of contact area and applied load on the morphology of in vitro worn ultra‐high molecular weight knee prostheses: a micro‐Raman and gravimetric study

Ultra‐high molecular weight polyethylene knee prostheses of two different sizes (i.e. characterised by different contact areas) were run on a knee wear simulator in two tests differing for the applied load. Gravimetric and micro‐Raman spectroscopic analyses were performed to investigate at macroscopic and molecular levels the effects of contact area and applied load on the morphology of the knee components. The larger prostheses showed a higher mass loss in both tests, while Raman spectroscopy showed a more significant polymer degradation in the smaller prostheses, suggesting that a lower contact area is responsible for a higher wear at the molecular wear, but for a lower gravimetric wear. Raman measurements showed that in the second test (using a higher applied load), the wear mechanism changed with respect to the first test: the less severe conditions used in the latter resulted in an increase in the orthorhombic content, while the more severe conditions used in the former determined an increase and rearrangement of the amorphous phase. The results here reported allow to gain more insights into the effects of contact area, applied load and contact stress on wear. Preliminary micro‐Raman analyses on in vivo worn knee prostheses confirmed the results obtained in vitro: the retrievals of smaller size were found more degraded at molecular level than those of larger size. These findings showed that the conditions used in the in vitro tests well simulate the knee kinematics of the knee joint and thus the in vivo wear. Copyright © 2014 John Wiley & Sons, Ltd.     

Amperometric detection of carbohydrates and thiols by using a glassy carbon electrode coated with Co oxide/multi-wall carbon nanotubes catalytic system

A glassy carbon electrode coated with cobalt oxide/multi-wall carbon nanotubes (MWCNT) system was used for the detection of carbohydrates and thiols. The modification of the glassy carbon electrode increased the anodic current response of these organic compounds and decreased their overvoltage. The amperometric responses were extremely stable with no loss of sensitivity over many days of storage. Such attractive performance characteristics indicate great promise for using this new catalytic system for monitoring in fast and simple way compounds of great interest for food industry, biotechnology and clinical diagnostics.     

Formation of a solubilized cobalt block oligomer from a M2L-type double helicate

The multi-dentate ligand, 2,3,5,6-tetrakis(2,2'-bipyridyl)pyrazine (L) and divalent cobalt self-assemble to a block co-polymer-like oligomer in solution, which contains at least the L(7)Co(8) fragment. The extent of oligomerization is sensitive to the water content in acetonitrile solution. In the solid state, the simple monomer [LCo(2)(CH(3)CN)(4)][ClO(4)](4) is isolated. The X-ray structure of the crystallized material (containing four CH(3)CN solvate molecules) reveals a double-helical complex with two heptadentate Co(II) sites, and a helical pitch of approximately 28.1 A. Coupled Co(I/II) redox processes are observed between the two metal centres.