Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 16 of 16 for “"keggin"”.
-
Characterization of a Keggin Polyoxometalate on Metal and Semiconductor Surfaces
Finally, studies of alpha-[SiW12O40]4- on Si surfaces are undertaken. In the first route, the Si surface is derivatized with a multicationic layer and alpha-[SiW12O 40]4- is assembled on this layer via electrostatic attraction. Characterization of this layer indicates that there is a substantial …
-
Interactions of pure aluminium hydrolytic species Keggin polyoxocations and hydroxide with biologically relevant molecules
… aluminium reference systems (aluminium monomers, Keggin aluminium polyoxocations - Al13 and Al30, and aluminium hydroxide suspensions) were used for systematic mechanistic studies of the sol-gel transformation of aqueous solutions of aluminium-ions into aluminium (oxy) hydroxides induced by the …
-
Characterization of a platinum-substituted keggin anion and studies of robust, hydrogen-bonded polyanion aggregates
… heteropolyanions were carried out. Salts of the Keggin-type -SiPtW11O406- anion (1) were prepared through the reaction of K8SiW11O39.13H2O with K2Pt(OH)6 and acidification of the reaction solution to pH 4 with HNO3. Infrared spectra indicated cocrystallization of tetra-n-butylammonium salts of …
-
New Approaches to the Synthesis of Porous and/or High Surface Area Transition Metal Oxides
… we presented a new approach for the grafting of Keggin POMs around the core-crosslinked PB-P2VP worm-like polymer templates (A 1 and 2). The produced POM-1 exhibits high dispersion, improved surface area and is thus expected to be useful in catalytic, electrochemical and biotechnology related …
-
Synthesis and Characterization of Group 4 Organometal Oxide Complexes
The organometallic substituted Keggin polyoxoanions ($\eta\sp5$-C$\sb5$(CH$\sb3$)$\sb5$) MPW$\sb $O$\sb{39}$((n-C$\sb4$H$\sb9$)$\sb4$N) $\sb4$, M = Ti(1), Zr(2), or Hf(3), were prepared by reaction of ($\eta\sp5$-C$\sb5$(CH$\sb3$)$\sb5$) MCl$\sb3$ with the lacunary Keggin heteropolyanion …
-
ΜΕΛΕΤΗ ΤΗΣ ΦΩΤΟΧΗΜΙΚΗΣ ΣΥΜΠΕΡΙΦΟΡΑΣ ΕΤΕΡΟΠΟΛΥΕΝΩΣΕΩΝ ΒΟΛΦΡΑΜΙΟΥ ΚΑΙ ΜΟΛΥΒΔΑΙΝΙΟΥ ΣΧΕΤΙΚΑ ΜΕ ΤΗΝ ΕΦΑΡΜΟΓΗ ΤΟΥΣ ΣΕ ΦΩΤΟΗΛΕΚΤΡΟΧΗΜΙΚΑ ΣΤΟ...
HETEROPOLYCOMPOUNDS OF THE KEGGIN-DAWSON STRUCTURES UNDERGO MULTIELECTRON PHOTOREDUCTION IN THE PRESENCE OF A GREAT VARIETY OF ORGANIC REAGENTS IN NEAR VISIBLE AND UV LIGHT WITH CONCOMITANT OXIDATION OF THE ORGANIC SPECIES, WHICH IS CONSUMED DURING THE REACTION. THE PHOTOREDUCED "LIGHT" HALF CELL …
-
Sais silicotungstatos de cobalto e ácido túngstico como catalisadores em reações de acetalização do furfural e oxidação de álcoois terpênicos
… processos catalisados por heteropolissais de Keggin contendo tungstênio e cobalto foram desenvolvidos. Peróxido de hidrogênio, um oxidante inserido na química verde foi utilizado. Os compostos conhecidos como polioxometalatos do tipo Keggin, têm como importante característica a possibilidade …
-
Mesostrukturierte Metalloxide und Polyoxometallate mittels Ionogener Diblockcopolymere - Synthese, Charakterisierung und Anwendung
… Hybridmaterialien aus Heteropolysäuren des Keggin-Typ Polyoxometallates (Keggin POM), die in 1-dimensionale Polybutadien-block-poly(2-vinylpyridin) (PB-b-P2VP) Polymerbürsten eingelagert wurden, verwendet. Hierbei zeigte sich insbesondere, dass eine kurze Ultraschallbehandlungsdauer das …
-
Polyoxotitanates and their role in titania sol-gel polymerization
… metal-oxygen framework having a pentacapped Keggin structure Reaction of the complex with t-amyl alcohol led to the product $\rm\lbrack Ti\sb{18}O\sb{28}H\rbrack (OBu\sp{t})\sb{12}(OAm\sp{t})\sb5$, identified using NMR spectroscopy.
-
In-situ spectroscopic studies of the mechanism of solid super-acid catalysed methanol carbonylation
… comprising Ru-tethered polyoxometallate Keggin anions of general formula [NEt3H]+[(Ru{η5-C5H5}{L}2)2(PW12O40)]- have been synthesised where L = PPh3 or 1/2 dppe showing high activity and selectivity in Phenyl acetylene dimerisation under a heterogeneous catalytic regime. Selectivity …
-
Polyoxometalate self-assembly : from molecules to framework materials
… particular emphasis on polyanions based on the Keggin structure and lacunary derivatives thereof. In particular, an understanding is gained into the role that N,N’-bis(2-hydroxyethyl)piperazine (bhep) and morpholine (morph) play in the polyanion self-assembly process, with the successful …
-
Synthesis, characterization and high pressure propene oligomerization over heteropoly acids, SAPO-11 molecular sieves and MeAPSO-11 molecular sieves
… acid, a 12-type HPA with the Keggin anion structure, were synthesized: AI, Fe, Ce, Ni, Co, Cu, K and NH₄, as well as the AI and NH₄ salts of 12-tungstosilicic acid. Physicochemical characterization of the HPA salts revealed that, depending on the counter cation, these salts …
-
Computational investigations of the electronic structure of molecular actinide compounds
… deals with systems of plenary or lacunary Keggin phosphomolybdate coordination to actinide (Th), lanthanide (Ce, La, Lu) and transition metal (Hf, Zr) cations: [PMo12O40]3-, [PMo11O39]2 14-, [PMo12O40]2 6- and [PMo11O39][PMo12O40]10-. These large, highly anionic systems proved to be very …
-
Synthesis of Inorganic-Organic Hybrid Materials Designed For Radiation Detection, Luminescence, and Gas Storage
… compound (POM) containing a typical Keggin ion, which is charge-balanced via protonated organic ligands. POMs are one of the most studied inorganic clusters owing to their potential catalytic capabilities. A third part concerns a pseudo hybrid material consisting of boron, a …
-
Organic-inorganic hybrid materials: new functionalised polyoxotungstates
… the metal) are investigated here, those with the Keggin structure being of interest due to the relatively easy formation of lacunary anions which have a highly nucleophilic surface and can react with electrophilic groups to add functionality to the cluster. Organophosphonyl and organosilyl …
-
Synthesis, structure and mechanism of polyoxometalate self-assembly: towards designed nanoscale architectures
… framework in each is composed of tungsten Keggin clusters, i.e. [PW12O40] 3-, which are introduced into the systems as pre-formed building-blocks. Two of the compounds use derivatives of Dihydro-ImidazoPhenanthridinium (DIP) molecules as cations, i.e. (DIP-1)[PW12O40]·5DMSO·ca1H2O and …