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Universidade Federal Rural da Amaz?nia. Programa de P?s-Gradua??o em Aquicultura e Recursos Aqu?ticos Tropicais. Bel?m, PA, Brazil. Universidade Federal Rural da Amaz?nia. Instituto S?cio Ambiental e dos Recursos H?dricos. Bel?m, PA, Brazil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Ananindeua, PA, Brasil. Universidade Federal do Par?. Faculdade de Engenharia Sanit?ria e Ambiental. Bel?m, PA, Brazil. Universidade Federal Rural da Amaz?nia. Programa de P?s-Gradua??o em Aquicultura e Recursos Aqu?ticos Tropicais. Bel?m, PA, Brazil. The Furo of Laura is an economically important river in the Amazon estuary. Thus, in the present study, we evaluated the metal distribution (Al, Cd, Co, Cu, Cr, Fe, Ni, and Mg) in the bottom sediments of this river. The sediments were sampled at four points every 2 months for a year with an Ekman-Birge sampler. After microwave acid digestion, the metal levels were determined by optical emission spectrometry with inductively coupled plasma. The particle size and organic matter content influenced the concentration of the metals. The sediments were not enriched by the analyzed metals; the estuary therefore retained the characteristics of an uncontaminated environment, thus serving as a reference environment for comparison.

Glass-embedded Cd1−xCoxS quantum dots (QDs) with mean radius of R ≈ 1.70 nm were successfully synthesized by a novel protocol on the basis of the melting-nucleation synthesis route and herein investigated by several experimental techniques. Incorporation of Co2+ ions into the QD lattice was evidenced by X-ray diffraction and magnetic force microscopy results. Optical absorption features with irregular spacing in the ligand field region confirmed that the majority of the incorporated Co2+ ions are under influence of a low-symmetry crystal field located near to the Cd1−xCoxS QD surface. Electron paramagnetic resonance data confirmed the presence of Co2+ ions in a highly inhomogeneous crystal field environment identified at the interface between the hosting glass matrix (amorphous) and the crystalline QD. The acoustic-optical phonon coupling in the Cd1−xCoxS QDs (x ≠ 0.000) was directly observed by Raman measurements, which have shown a high-frequency shoulder of the longitudinal optical phonon peak. This effect is tuned by the size-dependent sp-d exchange interaction due to the magnetic doping, causing variations in the coupling between electrons and longitudinal optical phonon. Copyright © 2013 John Wiley & Sons, Ltd.

This work reports evidence of the induced migration of Mn 2+ ions in Cd (1− x ) Mn x S nanocrystals (NCs) by selecting a specific thermal treatment for each sample. The growth and characterization of these magnetic dots were investigated by atomic force microscopy (AFM), optical absorption (OA), and electronic paramagnetic resonance (EPR) techniques. The comparison of experimental and simulated EPR spectra confirms the incorporation of Mn 2+ ions both in the core and at the dot surface regions. The thermal treatment of a magnetic sample, via selected annealing temperature and/or time, affects the fine and hyperfine interaction constants which modify the shape and the intensity of the EPR transition spectrum. The identification of these changes has allowed tracing the magnetic ion migration from core to surface regions of a dot as well as inferring the local density of the magnetic impurity ions.

Optical phonon modes confined in CdSxSe1-x nanocrystal (NC) quantum dots (≈ 2 nm in radius) grown in a glass matrix by the melting-nucleation method, were studied by means of resonant Raman scattering (RRS)spectroscopy and theoretical modelling. The formation of nanocrystalline quantum dots (QDs) is evidenced by the observation of absorption peaks and theoretically expected resonance bands in the RRS excitation spectra. Since the underlying material is a ternary alloy, this system offers the possibility to investigate the nterplay between the effects of phonon localization by disorder and phonon confinement by the NC/matrix interface. Based on the concept of propagating optical phonons, accepted for two-mode pseudo-binary alloys in their bulk form, we extended the continuous lattice dynamics model that has successfully been used for nearly-spherical NCs of binary materials, to the present case. After determining the alloy composition for NCs (that can be evaluated with only 2-3% uncertainty using the bulk longitudinal optical phonon frequencies) and the NC size (using atomic force microscopy and optical absorption data), the experimental RRS spectra were described rather well by this theory, including the lineshape and polarization dependence of the scattering intensity. Even though the presence of a compressive strain in the NCs, introduced by the matrix masks the expected downward shift owing to the phonons’ spatial quantization, the asymmetric broadening of both Raman peaks is similar to that characteristic of NCs of pure binary materials. Although with some caution, we suggest that both CdSe-like and CdS-like optical phonon modes indeed are propagating within the NC size (and not localized by disorder at a shorter length scale) unless the alloy is considerably heterogeneous., Portuguese Foundation for Science and Technology (FCT)

We report on the strong temperature-dependent thermal expansion, D, in CdS quantum dots (QDs) embedded in a glass template. We have performed a systematic study by using the temperature-dependent first-order Raman spectra, in CdS bulk and in dot samples, in order to assess the size dependence of D, and where the role of the compressive strain provoked by the glass host matrix on the dot response is discussed. We report the Gr¨ uneisen mode parameters and the anharmonic coupling constants for small CdS dots with mean radius R 2:0 nm. We found that parameters change, with respect to the bulk CdS, in a range between 20 and 50%, while the anharmonicity contribution from two-phonon decay channel becomes the most important process to the temperature-shift properties. (Some figures may appear in colour only in the online journal)