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1.
Carboxylic‐Acid‐Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif
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Jonathan De Roo Dr. Yolanda Justo Katrien De Keukeleere Freya Van den Broeck Prof. Dr. José C. Martins Prof. Dr. Isabel Van Driessche Prof. Dr. Zeger Hens 《Angewandte Chemie (International ed. in English)》2015,54(22):6488-6491
Ligand exchange is central in the processing of inorganic nanocrystals (NCs) and requires understanding of surface chemistry. Studying sterically stabilized HfO2 and ZrO2 NCs using 1H solution NMR and IR spectroscopy as well as elemental analysis, this paper demonstrates the reversible exchange of initial oleic acid ligands for octylamine and self‐adsorption of oleic acid at NC surfaces. Both processes are incompatible with an X‐type binding motif of carboxylic acids as reported for sulfide and selenide NCs. We argue that this behavior stems from the dissociative adsorption of carboxylic acids at the oxide surface. Both proton and carboxylate moieties must be regarded as X‐type ligands yielding a combined X2 binding motif that allows for self‐adsorption and exchange for L‐type ligands. 相似文献
2.
Freya J. Hine Adam J. Taylor C. David Garner 《Coordination chemistry reviews》2010,254(13-14):1570-1579
The development of the coordination chemistry of dithiolene ligands is summarised, together with a consideration of the electronic structure of complexes of these ‘non-innocent’ ligands. This information provides a context for a consideration of the role of dithiolenes in natural systems, i.e. as the ligand that binds molybdenum (or tungsten) at the catalytic centre of an extensive series of enzymes. These enzymes catalyse the transfer of an oxygen atom to or from the substrate: e.g. the sulfite oxidases catalyse the conversion of sulfite to sulfate and the nitrate reductases catalyse the conversion of nitrate to nitrite. The nature of the catalytic centres of several of these enzymes has been determined and each involves one or two ‘molybdopterin’ (MPT) cofactors bound to a mononuclear metal centre via their dithiolene group. The biosynthesis of MPT is described and, given its nature, possible roles for this moiety in the function of the oxotransferase enzymes are discussed. The review concludes with a consideration of the coordination chemistry that has been stimulated by the present knowledge of the nature and function of the catalytic centres of these enzymes. 相似文献
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4.
Gooding JJ Chou A Mearns FJ Wong EL Jericho KL 《Chemical communications (Cambridge, England)》2003,(15):1938-1939
A label free electrochemical method of detecting DNA hybridisation is presented based on the change in flexibility between a single strand of DNA and a duplex causing an ion-gating effect where hybridisation opens up the electrode to access of ions. 相似文献
5.
Protein electrochemistry using aligned carbon nanotube arrays 总被引:1,自引:0,他引:1
Gooding JJ Wibowo R Liu J Yang W Losic D Orbons S Mearns FJ Shapter JG Hibbert DB 《Journal of the American Chemical Society》2003,125(30):9006-9007
The remarkable electrocatalytic properties and small size of carbon nanotubes make them ideal for achieving direct electron transfer to proteins, important in understanding their redox properties and in the development of biosensors. Here, we report shortened SWNTs can be aligned normal to an electrode by self-assembly and act as molecular wires to allow electrical communication between the underlying electrode and redox proteins covalently attached to the ends of the SWNTs, in this case, microperoxidase MP-11. The efficiency of the electron transfer through the SWNTs is demonstrated by electrodes modified with tubes cut to different lengths having the same electron-transfer rate constant. 相似文献
6.
Bachmann Freya Koch Gilbert Pfister Marc Szinnai Gabor Schropp Johannes 《Journal of Optimization Theory and Applications》2021,189(1):46-65
Journal of Optimization Theory and Applications - Providing the optimal dosing strategy of a drug for an individual patient is an important task in pharmaceutical sciences and daily clinical... 相似文献
7.
Freya Taday Dr. James Ryan Dr. Stephen P. Argent Dr. Vittorio Caprio Dr. Beatriz Maciá Dr. Elaine O'Reilly 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3729-3732
An ω-transaminase-triggered intramolecular aza-Michael reaction has been employed for the preparation of cyclic β-enaminones in good yield and excellent enantio- and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza-Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, this biocatalytic aza-Michael step was combined with annulation chemistry, affording unique stereo-defined fused alkaloid architectures. 相似文献
8.
Freya Da Costa Giuseppe Lubes Mildred Rodríguez Vito Lubes 《Journal of solution chemistry》2011,40(1):106-117
Ternary complex formation reactions were studied between vanadium(III), dipicolinic acid and small molecular weight blood
serum components: lactic, oxalic, citric and ortophosphoric acids. The electromotive force measurement permitted us to determine
the chemical speciation of the complexes formed. In the vanadium(III)–dipicolinic acid–lactic acid system the complexes detected
were: V(dipic)(lac), V(dipic)(lac)(OH)− and V(dipic)(lac)(OH)22-(\mathrm{OH})_{2}^{2-}. In the vanadium(III)–dipicolinic acid–oxalic acid system the observed complexes were: V(dipic)(ox)−, V(dipic)(ox)(Hox)2− and V(dipic)(ox)23-(\mathrm{ox})_{2}^{3-}. In the vanadium(III)–dipicolinic acid–citric acid system the complexes V(dipic)(Hcit)−, V(dipic)(cit)2−, V(dipic)(cit)(OH)3−, V(dipic)(cit)(OH)24-(\mathrm{OH})_{2}^{4-} and V(dipic)(cit)(OH)35-(\mathrm{OH})_{3}^{5-} were detected. Finally in the vanadium(III)–dipicolinic acid–phosphoric acid system the complexes V(dipic)(H2PO4) and V(dipic)(HPO4)− were observed. The UV-vis spectra allowed us to perform a qualitative characterization of the complexes formed in aqueous
solution. 相似文献
9.
Characterisation of historic plastics using terahertz time-domain spectroscopy and pulsed imaging 总被引:1,自引:0,他引:1
Pastorelli G Trafela T Taday PF Portieri A Lowe D Fukunaga K Strlič M 《Analytical and bioanalytical chemistry》2012,403(5):1405-1414
Terahertz (THz) time-domain spectroscopy and 3D THz pulsed imaging have been explored with regard to polymer materials, both
commodity and historic polymers. A systematic spectroscopic study of a wide range of different polymer materials showed significant
differences in their spectra. Polyolefins and polystyrenes generally exhibit lower absorption than other examined polymers,
various cellulose derivates, poly(vinyl chloride), poly(methyl methacrylate), polyamide, hard rubber and phenol formaldehyde
resin, the last of these exhibiting the most intense absorption over the entire range, 0.15–4.2 THz. It was also examined
how the presence of plasticisers in poly(vinyl chloride), the presence of fillers in polypropylene, and the degree of branching
in polyethylene and polystyrene affect the spectra; inorganic fillers in polypropylene affected the absorption most. With
3D THz pulsed imaging, features in polymer objects were explored, appearing either as integral parts of the material (coatings
and pores in foams) or as a consequence of physical deterioration (cracks, delamination). All of these features of various
complexities can be successfully imaged in 3D. Terahertz technology is thus shown to have significant potential for both chemical
and structural characterisation of polymers, which will be of interest to heritage science, but also to the polymer industry
and development of analytical technologies in general. 相似文献
10.
Bockstael A de Greve B Van Renterghem T Botteldooren D D'Haenens W Keppler H Maes L Philips B Swinnen F Vinck B 《The Journal of the Acoustical Society of America》2008,124(2):973-981
The use of in situ measurements of hearing protectors' (HPD's) attenuation following the microphone in real ear (MIRE) protocol is increasing. The attenuation is hereby calculated from the difference in sound levels outside the ear and inside the ear canal behind the HPD. Custom-made earplugs have been designed with an inner bore that allows inserting a miniature microphone. A thorough understanding of the difference, henceforth called transfer function, between the sound pressure of interest at the eardrum and the one measured at the inner bore of the HPD is indispensable for optimizing the MIRE technique and extending its field of application. This issue was addressed by measurements on a head-and-torso-simulator and finite difference time domain numerical simulations of the outer ear canal occluded by an earplug. Both approaches are in good agreement and reveal a clear distinction between the sound pressure at the MIRE microphone and at eardrum, but the measured transfer functions appear to be stable and reproducible. Moreover, the most striking features of the transfer functions can be traced down to the geometrical and morphological characteristics of the earplug and ear canal. 相似文献