Search results for "Metals"
showing 10 items of 2013 documents
Effect of air on oxygen p-doped graphene on SiO2
2016
Stability in ambient air or in vacuum-controlled atmosphere of molecular oxygen-induced p-type doping of graphene monolayer on SiO2 substrate on Si is investigated by micro-Raman spectroscopy and atomic force microscopy (AFM). The Raman 2D and G bands spectral positions and amplitude ratio are affected by the permanence in air atmosphere in a time scale of months whereas the vacuum safely maintains the doping effects determined through Raman bands. No morphological effects are induced by the doping and post-doping treatments. A reactivity of ambient molecular gas with stably trapped oxygen is suggested to induce the doping modification. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Validation of a method for neutron dosimetry and spectrometry using neutron activation of metal discs
2009
A technique for neutron dosimetry and spectrometry based on neutron activation of different metal discs has been studied. After exposure to a neutron field, the radionuclides produced in the discs are detected using low-level gamma-ray spectrometry and the neutron spectrum is obtained using a spectrum unfolding technique. In order to validate the method, irradiation was performed in a well-characterised (252)Cf neutron reference field. Furthermore, the detector was used to determine the neutron fluence rate and spectrum at a storage place for MOX nuclear fuel. The results of the two measurements are reported and discussed.
Preparation of polyelectrolyte-modified membranes for heavy metal ions removal
2017
ABSTRACTPolyethersulfone membranes were modified by polyelectrolyte (PE) multilayers, made of poly(allylamine hydrochloride) with poly(styrene sulfonate), to remove Cu2+, Zn2+ and Ni2+ heavy metal cations from aqueous solutions in a wide range of metal concentration (50–1200 ppm). After characterization of the modified membranes, the efficiency of the process was estimated for single heavy metal ions solution leading to high rejection rates (>90% for 50 ppm) and good adsorption capacities (7.0–8.5 mg cm−2) whatever the metal ion tested. The stability in time of the modified membranes was proved by repeating successive filtrations with the same membrane. The filtration process was also used …
Acetylcholine-responsive cargo release using acetylcholinesterase-capped nanomaterials
2019
[EN] Mesoporous silica nanoparticles capped with acetylcholinesterase, through boronic ester linkages, selectively release an entrapped cargo in the presence of acetylcholine.
The Effect of Interferences on the Uptake of Heavy Metals by Sodium (iron) Titanates from Waste Water
2007
Sodium hexatitanate, sodium trititanate, sodium nonatitanate, and a new iron doped sodium nonatitanate were synthesized. Common interferences present in waste waters that hinder the removal of heavy metals by these ion exchangers were investigated. The presence of K+, Mg2+ and Ca2+ at 0.001-0.05 M concentration had minor effect on the amount of Pb2+, Cr3+, and Ni2+ uptake. EDTA on the other hand, interferes tremendously with the metal uptake. Both in ternary and in single system, the selectivity series is in the order: Pb2+>Cr3+>Ni2+. This order changed to Cr3+>Pb2+>Ni2+, in the presence of 0.001-0.1 M EDTA at pH 5.
A surface EXAFS study of thin nickel deposits on (110) TiO2 surfaces
1997
Abstract The first stages of nickel deposition on a clean (110) TiO 2 surface were studied using surface extended X-ray absorption fine structure (EXAFS). Experiments were performed on two kinds of nickel deposits, one of 0.8 equivalent monolayers and another of 1.6 equivalent monolayers. Depositions were performed on well characterized TiO 2 (110)-p(1 × 1) surfaces. The correlation of Auger experiments with EXAFS results showed that no islands were present on the surface; only two-dimensional growth of nickel was observed. Moreover, it was shown, in the case of the thinner deposit, that a model with nickel atoms forming chains in the channels determined by oxygen atoms on the surface is co…
Novel organo-modifier for thermally-stable polymer-layered silicate nanocomposites
2015
A new novel approach for the stabilisation of polymer-clay nanocomposites has been investigated based on reacting chemically an antioxidant function, a hindered phenol moiety, with an organic modifier based on a quaternary ammonium salt. The chemically linked antioxidant-containing organic modifier (AO-OM) was then introduced into natural montmorillonite (MMt) through a cation-exchange reaction resulting in antioxidant-containing organo-modified clay (AO-OM-MMt). The new antioxidant-containing modified clay, along with other organo-modified clays having a similar organo-modifier but without the reacted antioxidant, were characterised by spectroscopic, thermogravimetric and x-ray diffraction…
Dimensional encapsulation of I− I 2 I− in an organic salt crystal matrix
2010
Bis(trimethylammonium)hexane diiodide encapsulates iodine from solution and through a gas/solid reaction yielding in a predictable and controllable manner the selective formation of the rare polyiodide species I(-)...I-I...I(-), which matches in length to the chosen dication.
Diastereomeric control of enantioselectivity: evidence for metal cluster catalysis
2014
Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P–P*)] (P–P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru3 clusters. A catalytic mechanism involving Ru3 clusters has been established by DFT calculations. peerReviewed
Tetracyclic silaheterocycle formed through a pericyclic reaction cascade including a two-fold intramolecular C–C bond activation
2022
Reductive debromination of the tribromoamidosilane 2 gave the tetracyclic silaheterocycle 3 through a unique reaction cascade involving unprecedented two-fold intramolecular cycloaddition by transient silylenes. Experimental and computational analyses of the reaction mechanism allowed the identification of the key intermediates that lead to the silaheterocycle 3 or, alternatively, to the cyclotrisilene 19. peerReviewed