Search results for "silica."

2020

Biomolecules, and particularly proteins, bind on nanoparticle (NP) surfaces to form the so-called protein corona. It is accepted that the corona drives the biological distribution and toxicity of NPs. Here, the corona composition and structure were studied using silica nanoparticles (SiNPs) of different sizes interacting with soluble yeast protein extracts. Adsorption isotherms showed that the amount of adsorbed proteins varied greatly upon NP size with large NPs having more adsorbed proteins per surface unit. The protein corona composition was studied using a large-scale label-free proteomic approach, combined with statistical and regression analyses. Most of the proteins adsorbed on the N…

Studies on the Stereoselective Selenolactonization, Hydroxy and Methoxy Selenenylation of α- and β-Hydroxy Acids and Esters. Synthesis of δ- and γ-La…

2003

Abstract The diastereoselective synthesis of hydroxy substituted γ- and δ-lactones was accomplished following two approaches. A 5- or 6-endo cyclization promoted by electrophilic selenium reagents of α- or β-hydroxy acids and a 5- or 6-exo cyclization of hydroxy esters obtained through a diastereoselective hydroxy selenenylation reaction of α- or β-hydroxy esters. Moreover, the diastereoselective methoxy selenenylation of the above compounds was investigated showing a case in which the compound that was unreactive in the hydroxy selenenylation conditions gave, in the methoxy selenenylation conditions, the deprotected diol. The usefulness of the methoxy selenenylation procedure was proven by…

New multicomponent catalysts for the selective aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine

2014

Aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine was carried out on new gold-based catalysts using as support bimodal UVM-7-like mesoporous silica containing Ni and Ce (or Sn) as oxide nanodomains partially embedded inside the mesoporous UVM-7 silica walls. These nanodomains acted as effective and stable inorganic anchors favoring the nucleation, growth and stability of supported gold particles. Following the atrane method (a “one-pot” strategy able to harmonize the hydrolytic reactivity of different heteroelements through the use of complexes containing triethanolamine-derived ligands (atranes) as precursors) the stability of the oxide nanodomains during oxidation …

Silica gel chemistry

1994

Hydrodynamic chromatography of macromolecules on 2 μm non-porous spherical silica gel packings

1989

Non-porous spherical 2μm silica gel particles have been tested as packing for hydrodynamic chromatography of macromolecules (HDC). Columns packed with these particles in 250×4.6mm i.d. columns can be operated very efficiently (e.g. a reduced plate height of about 2) when the detection cell is miniaturized. The packing is suitable for the separation of polystyrenes of Mw of 104–107 by hydrodynamic chromatography and the retention behaviour of polystyrenes agrees well with the known theoretical models. Preliminary results on the applicability of HDC for the separation of biopolymers are presented.

Thin-layer chromatography of chlorinated catechols on a silica gel 60 layer

1981

Large-Scale Synthesis of Mammalian Gonadoliberin without protection of side-chain functions

1991

A simple, Large-scale preparation of mammalian gonadoliberin was elaborated using classical solution methods without protecting side-chain functions. At the final stage, a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained decapeptide was purified by a single chromatographic procedure on silica gel. The total efficiency of the whole synthesis and the purity of the product amounted to 34% and 98.3%, respectively.

NMR and Infrared Spectroscopies of C-S-H and Al-Substituted C-S-H Synthesised in Alkaline Solutions

1998

(C,N)-(S,A)-H samples have been synthesised from mixes of different CaO/SiO2 and AI(OH)3/SiO2 ratios in stirred suspensions in more or less concentrated soda solutions. The stoichiometry and spectroscopic characteristics of samples have been studied by FTIR, 27A1 and 29Si MAS NMR spectroscopies. The structural changes induced by substitutions have been discussed on the basis of the dreiketten structure of the tobermorite silicate chains.

Electrical tree growth in EVA-layered silicate nanocomposites

2006

This work deals with the growth of electrical treeing in different EVA-layered silicate nanostructured compounds. The experimental activity evidenced that the intercalated nanocomposites have longer lifetimes than pure EVA under the same constant AC stress conditions. A monitoring of the tree growth morphology allowed to evidence very interesting features of the intercalated nano-compounds showing a barrier effect to the treeing path. A preliminary investigation on the possible arrangement of the filler particles inside the matrix was also carried out.

Polyfurfuryl alcohol composite as adsorbent of polychlorinated biphenyls and pyrethroid insecticides

2007

Abstract Composites from furfuryl alcohol and silica gel were prepared in dichloromethane using trifluoroacetic acid as catalyst and characterized by means of thermogravimetric analysis, transmission electron microscopy and nitrogen adsorption–desorption isotherms. The polymer content in the composites ranged between 19.5% and 32.9%. The capability to adsorb polychlorinated biphenyls and pyrethroid insecticides was tested for composite samples containing different percentages of polymer. Pyrethroids are retained almost totally by composites containing around 24–33% of polymer, while recovery of PCBs close to 80% is obtained with all the composites. No selectivity between compounds of the sa…