Search results for "visual"

Chemical modification of porous calcium hydroxyapatite surfaces by grafting phenylphosphonic and phenylphosphite acids

2006

Abstract It is well known that the incorporation of organic molecules can provide an effective route to modify the surface properties of apatite ceramics. The present study shows that phosphonates can react with calcium ions to control the formation of the hydroxyapatite structures. The grafting of C6H5PO(OH)2 (PPOH) and C6H5PO(OH)H (PPH) was used to increase the specific surface area as well as the porosity of hydroxyapatite materials. The higher specific surface area for HAp treated by PPOH is around 267 m2/g compared to the pure HAp (140 m2/g). The phenyl (C6H5) groups are removed by thermal treatment around 500 °C. After treatment at 800 °C, organoapatites (PP-HAp) are converted to stoi…

Understanding the microscopic origin of gold nanoparticle anisotropic growth from molecular dynamics simulations.

2013

We use molecular dynamics simulations in order to understand the microscopic origin of the asymmetric growth mechanism in gold nanorods. We provide the first atomistic model of different surfaces on gold nanoparticles in a growing electrolyte solution, and we describe the interaction of the metal with the surfactants, namely, cetyltrimethylammonium bromide (CTAB) and the ions. An innovative aspect is the inclusion of the role of the surfactants, which are explicitly modeled. We find that on all the investigated surfaces, namely, (111), (110), and (100), CTAB forms a layer of distorted cylindrical micelles where channels among micelles provide direct ion access to the surface. In particular,…

Design of molecular materials combining magnetic, electrical and optical properties †

2000

The possibilities offered by hybrid functional materials formed by two molecular networks in the context of crystal engineering are illustrated with two different examples: (i) hybrid magnets constructed from combination of an extended ferromagnetic or ferrimagnetic inorganic network, with a molecular paramagnetic metal complex acting as template. (ii) Hybrid organic–inorganic compounds combining an organic π-electron donor network that furnishes the pathway for electronic conductivity, with inorganic metal complexes that act as structural and/or magnetic components. These examples illustrate how this hybrid approach allows the design of molecular materials combining non-conventional magnet…

Determination of the composition of isomeric mixtures of allylstannanes by means of 119Sn and 13C NMR measurements

1993

Abstract Allylstannanes of the type Bun3Sn(C3H3) ((C3H3 = allenyl and propargyl) Me3Sn(C4H7), Bun3Sn(C4H7), Ph3Sn(C4H7), Me3Sn(C4H7)2 and Bun3Sn(C4H7)2 [C4H7 = (E)-but-2-enyl, (Z-but-2-enyl, and but-1-en-3-yl] were prepared via Grignard reactions as isomeric mixtures whose compositions can be directly determined by 119Sn and 13C NMR spectrometry. The 119Sn and 13C δ-values of all possible isomers together with the isomeric compositions of freshly prepared compounds and after isomerization in dry methanol under reflux are reported. The course of isomerization of some compounds in anhydrous methanol at room temperature or in the presence of Bu3SnCl was followed by 119Sn NMR spectrometry.

An Inorganic Double Helix Sheathing Alkali Metal Cations: ANb2P2S12(A=K, Rb, Cs), A Series of Thiophosphates Close to the Metal-Nonmetal Boundary-Cha…

2004

The new quaternary niobium thiophosphates ANb 2 P 2 S 1 2 (A=K, Rb, Cs) have been prepared and characterized. The title compounds were synthesized by reacting Nb metal, A 2 S, P 2 S 5 , and S at 600-700°C in evacuated silica tubes. They crystallize as "stuffed" variants of the tetragonal TaPS 6 structure type in the tetragonal space group I42d with eight formula units per unit cell and lattice constants a=15.923(2) and c=13.238(3) A for CsNb 2 P 2 S 1 2 , a= 15.887(3) and c=13.132(3) A for RbNb 2 P 2 S 1 2 , and a=15.850(2) and c= 13.119(3) A for KNb 2 P 2 S 1 2 . Their structures are based on double helices formed from interpenetrating, noninteracting spiral chains of binuclear [Nb 2 S 1 2…

Frontispiece: Low‐Temperature Miniemulsion‐Based Routes for Synthesis of Metal Oxides

2020

Modes of complexation of non-substituted and substituted tetraazamacrocycles with Group 6 metal carbonyls. X-ray structure of [(permethylcyclam)Mo(CO…

1995

Abstract Reactions of complexation of tetraazamacrocycles L with Group 6 metal carbonyls [M(CO)6](M = Cr, Mo, or W) lead to [LM(CO)4], [LM(CO)3] or [LM(CO)2] entities, depending both on the size of the macrocycle and on the metal M. The structure of one representative complex [(permethylcyclam)Mo(CO)4] has been determined by X-ray diffraction (permethylcyclam: 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane).

The role of metal oxides as promoters of V2O5/γ-Al2O3 catalysts in the oxidative dehydrogenation of propane

1997

Summary The physicochemical properties of potassium-, bismuth-, phosphorous- and molybdenum-doped (Me/V atomic ratios of 0 to 1) V 2 O 5 /γ-Al 2 O 3 catalysts and their catalytic behavior in the oxidative dehydrogenation of propane have been compared. The incorporation of metal oxides modifies the catalytic behavior of alumina-supported vanadia catalysts by changing both their redox and their acid-base properties. In this way, the addition of potassium leads to the best increase in the selectivity to propylene. This performance can be related to the modification of the acid character of the surface of the catalysts. The possible role of both redox and acid-base properties of catalysts on th…

Preparation and characterization of organofunctionalized bentonite clay bearing aminophosphonic groups in heavy metal uptake

2019

Abstract Bentonite (Bnt) with covalently immobilized N-propylaminodi(methylenephosphonic) groups (Bnt-ADPA) was obtained through a two-step synthesis including aminosilanization and phosphorylation of resulting aminobentonite through Moedritzer-Irani reaction. The grafting of an aminosilane layer in the interplanar space of the bentonite was investigated by XRD, and the presence of N and P-containing groups was confirmed by FTIR, 31P and 29Si MAS NMR. The immobilization of the organic functional groups increased the interplanar distance in bentonite matrix at 52% that essentially improved filtration properties compared to raw bentonite. The number of surface acid groups was evaluated to 0.8…

Synthesis, structure and biological properties of several binary and ternary complexes of copper(II) with ciprofloxacin and 1,10 phenanthroline

2009

In this study, a new binary complex [Cu(HCip) 2 ](NO 3 ) 2  · 6H 2 O ( 1 ) has been synthesized and then characterized by X-ray structure analyses. In this compound, each ciprofloxacin acts as a bidentate ligand resulting in a crystallographically planar configuration; the nitrate anions are located in apical positions with an axial distance significantly larger than the equatorial distances, which would be consistent with a very weak metal ion interaction due to the Jahn–Teller effect. In addition, both the synthesis and characterization of two new ternary complexes of ciprofloxacin–copper(II)–1,10-phenanthroline, [Cu(phen)(Cip)](NO 3 ) · 4H 2 O ( 2 ) and Cu(phen)(HCip)(NO 3 ) 2  · H 2 O (…