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The optical properties of non-functionalized silver nanoparticles in ethanol solution have been analyzed and a progressive shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. To understand this occurrence, the interaction of glucose molecules with the silver nanoparticle surface has been investigated using Raman spectroscopy. In addition, high resolution transmission electron microscopy shows the presence of superstructures on the silver nanoparticle surface that can be imputed to the presence of glucose.

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The production of II -VI semiconductor compound -polymer matrix nanocomposites by a direct in-situ thermolysis process is described. Metal-thiolate precursor molecules embedded in a polymer matrix decompose by a thermal annealing and the nucleation of semiconductor nanocrystals occurs. It is shown that the nucleation of nanoparticles and the formation of the nanocomposite can be also achieved by laser beam irradiation; this opens the way towards a "lithographic" in-situ nanocomposite production process. A possible growth and nanocomposite formation mechanism, describing the structural and chemical transformation of the precursor molecules, their decomposition and the formation of the nanoparticles, is presented.

In this work we report on the growth of CdS and ZnS semiconductor nanocrystals embedded in a polymeric matrix (polystyrene) by synthesizing a metal thiolate precursor and its subsequent thermolysis at about 300°C after dispersion in the polymer. The crystallinity, shape and size of the metal sulfide nanocrystals were investigated by x-ray diffraction and transmission electron microscopy. The microstructural analysis demonstrates that our synthesis procedure allows us to control the nanocrystal growth in order to form nanoparticles with diameter as small as Ø=2nm. In particular, XRD analysis reveals that only CdS and ZnS nanocrystals of zincblende structure are formed. TEM images show that the metal sulfide nanocrystals are monocrystals of spherical shape and the size dispersion is <20%. Our experiments indicate that the nanocrystal capping agent is performed by the sulfur atoms at the surface of the nanoparticle bound to alkyl chain of the thiolate.

The structural, electrical, and optical properties of crystalline Si codoped with Er and O by molecular beam epitaxy (MBE) have been investigated in detail. Si:Er:O layers (∼250 nm thick) have been grown by MBE, realizing uniform dopant concentrations in the range 8×1018–1.5×1020 cm−3 for Er and up to 5×1020 cm−3 for O. The O:Er ratio was varied between 0 and ∼20. Samples have been subsequently annealed at 900 °C for 1 h. We observed that clear constraints to the Er and O contents exist in order to incorporate them in a good quality single crystal. We also found that the O:Er ratio represents the main parameter in determining the properties of this system. For instance, Er is observed to behave as a donor in MBE grown samples and the donor concentration increases with the O:Er ratio until a saturation regime is achieved for a ratio higher than 6–8. All the samples emit light at 1.54 μm and similar behavior is also found for the optical activation of the Er ions. The thermal process usually increases the number of light emitting Er ions which is also increased by increasing the O:Er ratio; however, for O:Er ratios higher than 6–8, no further activation is measured. In contrast, the most intense room temperature photoluminescence (PL) peak is obtained in samples having an O:Er ratio ∼2, for which PL temperature quenching is strongly reduced. Indeed, the coupling of these observations with structural measurements allows us to clearly identify the best conditions for an MBE grown Si:Er:O sample. These phenomena are investigated in detail and discussed.

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