Home About us Contact
|
Home About us Contact | ||
|
|
||
Molecular Precursor (molecular + precursor)
Selected AbstractsSynthesis and Characterisation of Novel Complexes Containing Group 15 Elements and Their Potential Use as Molecular Precursors for the Formation of Transition Metal PnictidesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2005Manfred Scheer Abstract The reaction of [{W(CO)5}2PCl] with K[Co(CO)4] yields the novel compounds [{W(CO)4Co2(CO)6}{µ3 -PW(CO)5}2] (3) and [{(CO)4WCo3(CO)6}{µ3 -PW(CO)5}3] (4) along with known derivatives [Co2(CO)6{,,,2 -PW(CO)5}2] (1) and [Co3(CO)9{,3 -PW(CO)5}] (2). The complex [{W2(CO)8(,-CO)}{,,,2:,1:,1 -PW(CO)5}2)] (5) was synthesised by treating Na2[W2(CO)10] with PBr3. Reaction of K[Mn(CO)5] with SbCl3 affords [Sb{Mn(CO)5}3] (6) in high yields. The spectroscopic and structural characterisation of the novel products is discussed, as well as the thermolytic behaviour of 2, 3 and 6 for the potential formation of novel phases of transition metal pnictides. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Small-angle X-ray scattering study of the smart thermo-optical behavior of zirconyl aqueous colloidsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000L.A. Chiavacci The smart thermo-optical systems studied here are based on the unusual thermoreversible sol-gel transition of zirconyl chloride aqueous solution modified by sulfuric acid in the molar ratio Zr/SO4:3/1. The transparency to the visible light changes during heating due to light scattering. This feature is related to the aggregates growth that occurs during gelation. These reversible changes can be controlled by the amount of chloride ions in solution. The thermoreversible sol-gel transition temperature increases from 323 to 343 K by decreasing the molar ratio Cl/Zr from 7.0 to 1.3. In this work the effect of the concentration of chloride ions on the structural characteristics of the system has been analyzed by in situ SAXS measurements during the sol-gel transition carried out at 323 and 333 K. The experimental SAXS curves of sols exhibit three regions at small, medium and high scattering vectors characteristics of Guinier, fractal and Porod regimes, respectively. The radius of primary particles, obtained from the crossover between the fractal and Porod regimes, remains almost invariable with the chloride concentration, and the value (4 Å) is consistent with the size of the molecular precursor. During the sol-gel transition the aggregates grow with a fractal structure and the fractal dimensionality decreases from 2.4 to 1.8. This last value is characteristic of a cluster-cluster aggregation controlled by a diffusion process. Furthermore, the time exponent of aggregate growth presents values of 0.33 and 1, typical of diffusional and hydrodynamic motions. A crossover between these two regimes is observed. [source] Morphology Control over the Organic Nanoparticles of 1, 3-Diphenyl-5-(9-anthryl)-2-pyrazolineCHINESE JOURNAL OF CHEMISTRY, Issue 12 2003Lu Xi Abstract The organic nanoparticles of a blue-light-emitting molecule, 1, 3-diphenyl-5-(9-anthryl)-2-pyrazoline, were prepared by reprecipitation method using acetonitrile as the solvent for the molecular precursor. Three morphologies, spherical, doughnut-shaped and cubic, could be observed on the silicon substrate for the nanoparticles by the volume-controlled addition of acetonitrile. The evolution of particle morphology as a function of acetonitrile addition was attributed to the variation of the growth habits of the particles in the different environment. The nanoparticles exhibit the novel photoluminescence spectra as compared to those of monomer and the bulk crystals. [source] Controlled Synthesis of CdSe Nanowires by Solution,Liquid,Solid MethodADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Zhen Li Abstract Semiconductor nanowires prepared by wet chemical methods are a relatively new field of 1D electronic systems, where the dimensions can be controlled by changing the reaction parameters using solution chemistry. Here, the solution,liquid,solid approach where the nanowire growth is governed by low-melting-point catalyst particles, such as Bi nanocrystals, is presented. In particular, the focus is on the preparation and characterization of CdSe nanowires, a material which serves a prototype structure for many kinds of low dimensional semiconductor systems. To investigate the influence of different reaction parameters on the structural and optical properties of the nanowires, a comprehensive synthetic study is presented, and the results are compared with those reported in literature. How the interplay between different reaction parameters affects the diameter, length, crystal structure, and the optical properties of the resultant nanowires are demonstrated. The structural properties are mainly determined by competing reaction pathways, such as the growth of Bi nanocatalysts, the formation and catalytic growth of nanowires, and the formation and uncatalytic growth of quantum dots. Systematic variation of the reaction parameters (e.g., molecular precursors, concentration and concentration ratios, organic ligands, or reaction time, and temperature) enables control of the nanowire diameter from 6 to 33,nm, while their length can be adjusted between several tens of nanometers and tens of micrometers. The obtained CdSe nanowires exhibit an admixture of wurtzite (W) and zinc blende (ZB) structure, which is investigated by X-ray diffraction. The diameter-dependent band gaps of these nanowires can be varied between 650 and 700,nm while their fluorescence intensities are mainly governed by the Cd/Se precursor ratio and the ligands used. [source] Structural Evolution of Self-Assembling Nanohybrid Thin Films from Functionalized Urea Precursors,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007I. Karatchevtseva Abstract Hybrid organic-inorganic thin films exhibiting patterned structuring on the nanometer scale have been prepared through the controlled hydrolysis-condensation of enantiomerically pure chiral urea-based silyl compounds. The thin films are obtained by spin-coating of sols obtained via acid- or base-catalyzed hydrolytic condensation of these molecular precursors. A self-templating process is demonstrated via atomic force and transmission electron microscopy, showing the formation of nanometer size aggregates consisting of interconnected spherulates under acidic condition and of assembled fibers under basic conditions. [source] | ||||||||||