by Keyword: Cobalt

Arnau, M, Turon, P, Aleman, C, Sans, J, (2023). Hydroxyapatite-based catalysts for CO2 fixation with controlled selectivity towards C2 products. Phenomenal support or active catalyst? Journal Of Materials Chemistry a 11, 1324-1334

Permanently polarized hydroxyapatite (p-HAp) has been reported as a feasible green alternative to conventional catalysts for the selective conversion of CO2 into highly valuable chemical products. However, structural control and enhanced electrical properties achieved on p-HAp clearly contrast with other reported catalytic systems, where hydroxyapatite mainly acts as a support receiving much less attention. In this work we take advantage of the knowledge obtained on p-HAp to develop an HAp-based catalytic system composed of TiO2 nanoparticles deposited on p-HAp. It is important to stress that p-HAp is not only considered as a mechanical support but has been put in the spotlight for catalyst preparation and as an active catalytic part. Therefore, the use of p-HAp in this system has unveiled exceptional synergies with TiO2 attributed to the enhanced electrical properties of p-HAp, capable of attracting the photo-electrons generated in TiO2 nanoparticles avoiding electron-hole recombination. CO2 fixation reactions carried out under mild conditions (120 degrees C, 6 bar and under UV exposure) result in complete selectivity control of the C2 products, shifting from ethanol (201 mu mol g(catalyst)(-1)) for p-HAp alone to acetic acid (381 mu mol g(catalyst)(-1)) when TiO2 nanoparticles are loaded in the system. Considering the challenging CO2 activation energy and the high control of the selectivity achieved, we do believe that this novel approach can be considered as a starting point to explore other systems and reactions where control of the crystal structure and the enhanced electrical properties of HAp can play a crucial role in the final products, reaction conditions, yields and selectivities.

JTD Keywords: Behavior, Cobalt, Conversion, Methane, Ni, Oxidation, Performance, Reduction, Syngas production, Tio2

Schieber, R, Mas-Moruno, C, Lasserre, F, Roa, JJ, Ginebra, MP, Mücklich, F, Pegueroles, M, (2022). Effectiveness of Direct Laser Interference Patterning and Peptide Immobilization on Endothelial Cell Migration for Cardio-Vascular Applications: An In Vitro Study Nanomaterials 12, 1217

Endothelial coverage of an exposed cardiovascular stent surface leads to the occurrence of restenosis and late-stent thrombosis several months after implantation. To overcome this difficulty, modification of stent surfaces with topographical or biochemical features may be performed to increase endothelial cells’ (ECs) adhesion and/or migration. This work combines both strategies on cobalt-chromium (CoCr) alloy and studies the potential synergistic effect of linear patterned surfaces that are obtained by direct laser interference patterning (DLIP), coupled with the use of Arg-Gly-Asp (RGD) and Tyr-Ile-Gly-Ser-Arg (YIGSR) peptides. An extensive characterization of the modified surfaces was performed by using AFM, XPS, surface charge, electrochemical analysis and fluorescent methods. The biological response was studied in terms of EC adhesion, migration and proliferation assays. CoCr surfaces were successfully patterned with a periodicity of 10 µm and two different depths, D (≈79 and 762 nm). RGD and YIGSR were immobilized on the surfaces by CPTES silanization. Early EC adhesion was increased on the peptide-functionalized surfaces, especially for YIGSR compared to RGD. High-depth patterns generated 80% of ECs’ alignment within the topographical lines and enhanced EC migration. It is noteworthy that the combined use of the two strategies synergistically accelerated the ECs’ migration and proliferation, proving the potential of this strategy to enhance stent endothelialization.

JTD Keywords: adhesion, bare-metal, biofunctionalization, biomaterials, cell adhesive peptides, cobalt-chromium alloy, direct laser interference patterning (dlip), endothelial cell migration, functionalization, matrix, proliferation, selectivity, shear-stress, surfaces, Direct laser interference patterning (dlip), Drug-eluting stents, Endothelial cell migration

Landa-Castro, Midori, Sebastián, Paula, Giannotti, Marina I., Serrà, Albert, Gómez, Elvira, (2020). Electrodeposition of nanostructured cobalt films from a deep eutectic solvent: Influence of the substrate and deposition potential range Electrochimica Acta 359, 136928

The purpose of this systematic study was to investigate the effects of specific substrates and potential conditions applied while tailoring the morphology and chemical composition of nanostructured Co films. In particular, Co electrodeposition in sustainable choline chloride-urea deep eutectic solvent was assessed, using glassy carbon and two metals widely employed in electrocatalysis and biocompatible purposes, Pt and Au, as substrates for modification with Co. Various in situ electrochemical techniques were combined with a broad range of ex-situ characterization and chemical-composition techniques for a detailed analysis of the prepared Co films. Among the results, nanostructured Co films with high extended active surface areas and variable composition of oxo and hydroxyl species could be tuned by simply modulating the applied potential limits, and without using additives or surfactant agents. The study highlights the effectiveness of using deep eutectic solvent as suitable electrolyte for surface modification by controlled deposition of nanostructured Co films with further application in electrocatalysis.

JTD Keywords: Cobalt electrodeposition, Deep eutectic solvent, First growth stages, Substrate influence