Search results for "Chemisorption"
showing 10 items of 53 documents
Ultrathin Organic Multilayer Films Via Salt Formation: Easy Access To Tailor-made Coatings In The Thickness Range Of 1 Nm To 500 Nm
2005
The state of the art technologies for the preparation of well defined ultrathin films in the submicron range are the Langmuir-Blodgett (LB) technique and self-assembly (SA) methods based on chemisorption [l]. Whereas the LBtechnique requires sophisticated apparatus and is generally limited to small film areas [2], the SA-methods are relatively simple [3,4], hut have not been employed for the preparation of films thicker than 8 layers ( 20nm) [4], probably due to the loss of chemical functionality. Our approach avoids these limits and extends the SA-concept by emploing salt formation as the driving force for the construction of multilayer supramolecular assemblies.
Chemisorption of hydrogen on charged vanadium clusters
1996
Abstract The chemisorption of hydrogen on positively charged vanadium clusters, V n + ( n = 1–17), was studied by measuring reaction rates and saturation coverages. Vanadium clusters are produced by laser vaporization and are injected into a Penning trap. Rates of the reaction V n + +H 2 → V n + H 2 are measured by axial ejection of all ions out of the trap after variable storage times and subsequent time-of-flight detection. An odd-even effect of the reaction rate is observed with odd clusters being more reactive. Clusters with low reactivity are found to be highly stable, as reflected by the respective separation energies of atoms. The number of adsorbed hydrogen atoms, m , is determined …
Superficial oxidation of molybdenum at high pressure and low temperature: RHEED and AES analyses of the molybdenum oxide formation
1991
Abstract Numerous studies relate to the interaction of the molybdenum surface with oxygen at low pressure and high temperature. They give results about oxygen chemisorption, surface facetting and the epitaxial formation of MoO 2 crystallites. This work deals with the interaction of Mo(100), Mo(110) and Mo(111) surfaces with oxygen at high pressure (10 4 Pa) and low temperature (620–820 K). RHEED and AES analyses results prove that, in these oxidation conditions: MoO 2 and non-stoichiometric molybdenum oxide such as Mo 4 O 11 are not evidenced in any of the molybdenum oxidation steps. The MoO 3 phase nucleates directly from any Mo surface. The structure and orientation of MoO 3 nuclei are ch…
Determination of Photoadsorption Capacity of Polychrystalline TiO2 Catalyst in Irradiated Slurry
2009
WOS: 000322711800002
Surface functionalization and surface recognition: Plasmon optical detection of molecular recognition at self assembled monolayers
1991
The synthesis of biotin- functionalized organic mercaptans and their chemisorption on gold surfaces is described. Biotin bound covalently to self assembled monolayers is recognized by streptavidin from aqueous buffer solutions. Spacer length and packing density of the biotin labels on the organic surface determine the docking kinetics. With a flexible and hydrophilic spacer very fast -diffusion controlled-docking is observed. As an alternative method of self assembly the spreading of organic mercaptans on water surfaces is established. Pressure-area diagrams of different functionalized mercaptans and disulfides are shown and their monolayer properties are discussed.
Carbohydrate-supramolecular gels : adsorbents for chromium(VI) removal from wastewater.
2019
Abstract Hypothesis To overcome the contamination of water by heavy metals the adsorption of the pollutant on gel phases is an attractive solution since gels are inexpensive, potentially highly efficient and form a distinct phase while allowing diffusion of the contaminated water throughout the material. This work tests the chromium(VI) adsorbent capacity of new supramolecular gels for Chromium(VI) removal from wastewater. Experiments First hydrophobic imidazolium salts of carbohydrate anions were synthesised as new gelators. Subsequently, they were dissolved in a solvent by heating and, after cooling overnight, to give the formation of supramolecular gels. The properties of the resulting g…
Solvent-Free Synthesis of ZIFs Compatible with Iron: A Route Towards the Elusive Fe(II) Analogue of ZIF-8
2019
Herein we report the synthesis of an elusive metal-organic framework, the iron(II) analogue of ZIF-8, with formula Fe(2-methylimidazolate)2, here denoted as MUV-3. The preparation of this highly interesting porous material, inaccessible by common synthetic procedures, occurs in a solvent-free reaction upon addition of an easily detachable template molecule, yielding single crystals of MUV-3. This methodology is extensive to other metals and imidazolate derivatives, allowing the preparation of ZIF-8, ZIF-67 and other unprecedented iron(II) ZIFs, Fe(2-ethylimidazolate)2 and Fe(2-methylbenzimidazolate)2. The different performance of MUV-3 towards NO sorption, compared to ZIF-8, results from th…
Synthesis, Characterization and Sorption Capacity Examination for a Novel Hydrogel Composite Based on Gellan Gum and Graphene Oxide (GG/GO)
2020
A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditi…
Evaluating Thermal Corrections for Adsorption Processes at the Metal/Gas Interface
2019
International audience; Adsorption and desorption steps are key for active catalysts and rely on a subtle balance between enthalpic and entropic terms. While the enthalpic term is becoming ever more accurate through density functional development, the entropic term remains underrated and its precise determination a great challenge. In this work, we have performed extensive first principles thermodynamic integration (TI) simulations for the 1 adsorption of small (e.g., CO) to larger (e.g., phenol) molecules at metallic surfaces and compared their adsorption free energies to the values obtained by vertical, static statistical mechanics approximations to thermal corrections invoking three diff…
Solvent-free synthesis of ZIFs: a route toward the elusive Fe(II) analogue of ZIF-8
2019
Herein we report the synthesis of an elusive metal-organic framework, the iron(II) analogue of ZIF-8 with the formula Fe(2-methylimidazolate) , here denoted as MUV-3. The preparation of this highly interesting porous material, inaccessible by common synthetic procedures, occurs in a solvent-free reaction upon addition of an easily detachable template molecule, yielding single crystals of MUV-3. This methodology can be extended to other metals and imidazolate derivatives, allowing the preparation of ZIF-8, ZIF-67, and the unprecedented iron(II) ZIFs Fe(2-ethylimidazolate) and Fe(2-methylbenzimidazolate) . The different performance of MUV-3 toward NO sorption, in comparison to ZIF-8, results …