Cowan D.A.,University of the Western Cape |
Fernandez-Lafuente R.,CSIC - Institute of Catalysis
Enzyme and Microbial Technology | Year: 2011
The immobilization of proteins (mostly typically enzymes) onto solid supports is mature technology and has been used successfully to enhance biocatalytic processes in a wide range of industrial applications. However, continued developments in immobilization technology have led to more sophisticated and specialized applications of the process. A combination of targeted chemistries, for both the support and the protein, sometimes in combination with additional chemical and/or genetic engineering, has led to the development of methods for the modification of protein functional properties, for enhancing protein stability and for the recovery of specific proteins from complex mixtures. In particular, the development of effective methods for immobilizing large multi-subunit proteins with multiple covalent linkages (multi-point immobilization) has been effective in stabilizing proteins where subunit dissociation is the initial step in enzyme inactivation. In some instances, multiple benefits are achievable in a single process.Here we comprehensively review the literature pertaining to immobilization and chemical modification of different enzyme classes from thermophiles, with emphasis on the chemistries involved and their implications for modification of the enzyme functional properties. We also highlight the potential for synergies in the combined use of immobilization and other chemical modifications. © 2011 Elsevier Inc.
Conesa J.C.,CSIC - Institute of Catalysis
Catalysis Today | Year: 2013
The electronic structure of ZnTiO3, Zn2TiO 4 and Zn2Ti3O8 is investigated using a hybrid DFT method in which the exchange mixing coefficient is obtained through its relation with the dielectric constant (also computed at the hybrid DFT level). Bandgaps higher than those of the simple oxides are predicted, in agreement with some experimental data; but in the case of spinel structures bandgaps also appear to depend significantly on the (dis)ordering of the cations at octahedral sites, implying a strong influence of the preparation details on the final gap values. The change in the electronic structure of the spinel titanates which occurs when they are nitrided can lead to photocatalytic activity with visible light, as is known to happen with TiO2 and other oxides; but here the cation vacancy suppression effect which accompanies the transformation makes the nitridation process much more favourable, as shown by total energy DFT calculations. These zinc titanate spinels are thus promising candidates to achieve via nitridation efficient and robust photocatalysts active with visible light. All these compounds show a lower conduction band edge constituted mainly by Ti-centred orbitals; this may have influence on the details of the photocatalytic reaction mechanisms. © 2012 Elsevier B.V.
Carrasco J.,CSIC - Institute of Catalysis |
Hodgson A.,University of Liverpool |
Michaelides A.,University College London
Nature Materials | Year: 2012
Water/solid interfaces are relevant to a broad range of physicochemical phenomena and technological processes such as corrosion, lubrication, heterogeneous catalysis and electrochemistry. Although many fields have contributed to rapid progress in the fundamental knowledge of water at interfaces, detailed molecular-level understanding of water/solid interfaces comes mainly from studies on flat metal substrates. These studies have recently shown that a remarkably rich variety of structures form at the interface between water and even seemingly simple flat surfaces. In this Review we discuss the most exciting work in this area, in particular the emerging physical insight and general concepts about how water binds to metal surfaces. We also provide a perspective on outstanding problems, challenges and open questions. © 2012 Macmillan Publishers Limited. All rights reserved.
Banares M.A.,CSIC - Institute of Catalysis
Advanced Materials | Year: 2011
Progress in nanomaterials and catalysis stands on three pillars: 1) synthesis of nanomaterials, including the preparation of hierarchically dispersed nanoparticles; 2) theoretical studies of materials that enable experimental results to be understood; and 3) advanced, in situ characterization during operation (operando methodology). This Research News brings a perspective on how these three pillars are blending for research in materials science, with particular emphasis on catalysis. Progress in nanomaterials and catalysis is founded on the simultaneous implementation of three strategies: the synthesis of nanomaterials and hierarchically dispersed nanoparticles; the theoretical study of materials that enable experimental results to be understood; and advanced, in situ characterization during operation (operando methodology). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Conesa J.C.,CSIC - Institute of Catalysis
Journal of Physical Chemistry C | Year: 2012
The band alignment at semiconductor interfaces can be theoretically computed using periodic slab models together with hybrid functional density functional theory methods in which Hartree-Fock exchange mixing coefficients are properly chosen (as justified by their relationship with the dielectric constant), and the calculated electrostatic potential inside each slab is used as reference for the band-edge energies. This principle is applied here to the interface between wurtzite-type ZnO and anatase-type TiO 2, two oxides with nearly identical band gap widths. According to the results, in a composite of both materials the conduction and valence bands of ZnO will lie ca. 0.3 eV lower in energy than those of anatase, influencing the way in which photogenerated electrons and holes will be routed in photocatalytic or photovoltaic systems which include interfaces between these two oxides. The performance improvement observed in dye-sensitized solar cells based on a nanostructured ZnO electrode when the surface of the latter is covered by a thin TiO 2 layer is thus justified. The system may serve as an example for the estimation of the band alignment in other semiconductor junctions of interest in different kinds of devices. © 2012 American Chemical Society.