Showing papers by "Christopher B. Murray published in 1999"

Method for producing nanoparticles of transition metals

Abstract: A method of forming nanoparticles includes steps of forming a metal precursor solution from a transition metal, injecting the metal precursor solution to the surfactant solution, adding a flocculent to cause nanoparticles to precipitate out of solution without permanent agglomeration, and adding a hydrocarbon solvent to redisperse or repeptize the nanoparticles.

Controlled Assembly of Monodisperse ε-Cobalt-Based Nanocrystals

Abstract: General synthetic routes to monodisperse c-cobalt (β-Mn type phase) nanocrystals (e-Co) and controlled assembly of these nanocrystals are presented in this paper. The e-Co particles are obtained by superhydride reduction of cobalt chloride (anhydrous or hexahydrate) in a high temperature solution phase (200°C) in the presence of a combination of long chain diol, oleic acid and trialkylphosphine. Monodisperse nanocrystals are isolated by size selective precipitation. As synthesized cobalt particles are each a single crystal with a complex cubic structure related to the beta phase of elemental manganese (β-Mn). Self-assembly of these uniform cobalt particles on solid substrates is induced by evaporation of the carrier solvent producing 2-D and 3-D magnetic superlattices. Annealing of assembled e-Co nanocrystal arrays converts them to the hcp cobalt crystal arrays. The inter-particle distance can be adjusted by selected thermal treatments or by chemical ligand exchange. This control over particle dimensions, crystallinity and assembly offers a model system for the study of ultra-high density recording media.

Production of transition metal nanograin

Abstract: PROBLEM TO BE SOLVED: To provide a method for producing nanograins. SOLUTION: This method contains a step in which a metallic precursory soln. is formed from a transition metal, a step in which this metallic precursory soln. is injected into a surfactant soln., a step in which the soln. is added with a coagulant and nanograins are precipitated from the soln. without causing permanent coagulation and a step in which the nanograins are added with a hydrocarbon solvent ad the nanograins are redispersed or converted into a colloid again.

Synthesis and nonlinear optical properties of functionalised polydiacetylenes and their complexes with transition metals

Abstract: New polydiacetylenes (PDAs) have been prepared in which a ligating 2,2′-bipyridyl substituent is incorporated in the side-chain, 3a-d. The formation of complexes of these polymers, and of a related (diethylamino)alkyl substituted PDA 4, with transition metals has been studied. Coordination polymers containing nickel(II) 5a,b, copper(II) 5c,d, ruthenium(II) 6 and molybdenum(O) 7a-c have been formed and characterised spectroscopically by comparison with appropriate model coordination compounds, including species derived from corresponding monomeric 1,3-diynes 1. The nonlinear optical properties of PDA 4 and the coordination polymers 5-7 in solution have been investigated by the z-scan procedure. Values for the nonlinear absorption coefficient, α 2 , and the nonlinear refractive index, n 2 , have been derived and these are discussed in relation to the structures of the PDAs.