1,721,128 research outputs found
The identification by Raman microscopy and x-ray diffraction of iron-oxide pigments and of the red pigments found on Italian pottery fragments
No full textThe technique of Raman microscopy has been used to identify and characterise the pigments used in red shards of medieval and earlier items of pottery which have been found in various archaeological sites in the South of Italy. The research has led to the identification, on the basis of their characteristic Raman/resonance Raman spectra, of the red pigments as iron(III) oxide (e.g. Indian Red, Red Ochre or Venetian Red) and the yellow pigments as hydrated iron(III) oxyhydroxide (e.g. Yellow Ochre and Mars Yellow). X-ray powder diffraction experiments confirm the conclusions drawn above
Synthesis and characterization of Q-sized CdS particles in a four-components “water in oil” microemulsion”
No full textEmerging methods for fabricating functional structures by patterning and assembling engineered nanocrystals
No full textInorganic nanocrystals and nanoparticles have aroused increasing attention in the last years due to their original optoelectronic, thermodynamic, mechanical and catalytic properties, which are extremely attractive for fundamental understanding as well as for their huge potential in applications. The ability to strongly exploit the original potential of such nano-objects and access their properties relies on the ability to bridge the gap between the nanoscopic and mesoscopic scale. Indeed, to integrate nanoparticles in structures, materials and finally devices, their incorporation in processable systems, and their organization in morphologically controlled assembly and/or ordered arrays is crucial. The fabrication of 2/3 D patterned micro- and nanostructure is a promising strategy for integrating the nanoparticles in macroscopic entities in order to properly exploit their unprecedented functionality for biomedical, electronic, catalytic materials and devices. In this paper, different and complementary strategies able to engineer inorganic colloidal nanocrystals due to their organization in original functional materials and structures will be described
Reverse micellar systems: self organised assembly as effective route for the synthesis of coll oidal semiconductor nanocrystals
No full textNanoparticles can be obtained by using self-assembly molecules as a template, exploiting confined growth inside the surfactant film of microemulsion system. In this work, the feasibility of using quaternary water-in-oil microemulsion (CTAB/hexane/pentanol/water) to synthesise nanometer-sized structures of semiconductor material (CdS) with desired size distribution is described. Stochastic kinetic simulations have been utilised to account for the observed template effect of the microernulsion aggregate size on the nanocluster growth
Optical properties of nanocomposites based on (CdSe)ZnS core shell nanocrystals in cyclic olefin copolymer
No full textIn this work, organic capped CdSe and (CdSe)ZnS core shell colloidal nanocrystals (NCs), prepared by means of thermolysis of organometallic precursors and with high control on size and size dispersion, were dispersed into a transparent and thermoplastic cyclic olefin copolymer, namely TOPAS, by using toluene as common solvent. The obtained nanocomposite material was deposited by spin coating in thin films that were investigated by UV–vis spectroscopy as well as by TEM analysis. A preliminary comparison of the luminescence properties of CdSe core and (CdSe)ZnS core shell NCs in polymer was carried out. The effect of NC concentration, time and temperature on the optical properties of the composites was determined with the aim of a potential use of these materials for permanent photonic applications. The incorporation of luminescent (CdSe)ZnS NCs in the TOPAS copolymer can be potentially effective for the fabrication of novel optical devices by nanoimprint lithography
Improved optical properties of CdS quantum dots by ligand exchange
No full textHigh-quality CdS nanocrystals with highly efficient and narrow band edge emission have been prepared by means of decomposition of suitable precursors in non-coordinating solvents at high temperature. The role played by capping ligands, solvents and their interactions has been investigated by optical measurements. Capping layer exchange treatments with different amines have been carried out suggesting a possible influence of alkylic chain length in modifying the optical properties of CdS nanocrystals. Enhancement of band edge emission has been demonstrated with octylamine ligand. © 2003 Elsevier B.V. All rights reserved
Calorimetric study of CdS nanoparticle formation in w/o microemulsions
No full textThe formation of CdS nanocrystals in ternary w/o microemulsions of sodium bis(2-ethylhexyl) solfosuccinate/water/isooctane and in quaternary w/o microemulsions of cetyltrimethylammonium bromide (CTAB)/ n -pentanol/water/ n -hexane was studied by calorimetric measurements. In order to gain information on the role played by the various factors governing the formation of nanoparticles, the enthalpy of formation of CdS nanocrystals in microemulsion was investigated as a function of W 0, the molar ratio between water and surfactant and P 0, the molar ratio between alcohol and surfactant. Different energetic states of CdS nanocrystals in microemulsions and in water and a dependence of them on the composition and nature of the microemulsive system are evidenced. © 2003 Elsevier B.V. All rights reserved
Photochemical sensitisation process at photosynthetic pigments/Q-sized colloidal semiconductor hetero-junctions
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