Cathodoluminescence emission of hydrothermally grown antimony doped ZnO nanostructures with different antimony doping (2.5, 4.8, and 11.8 at%) was studied in a scanning electron microscope (CL-SEM). Incorporation of antimony results in formation of mostly nanorods with low aspect ratio together with some Sb-rich nanoparticles. Transmissibn electron microscopy (TEM) of the Sb-doped samples revealed delaminated {10-10} planes produced by antimony surface segregation. CL spectra of the as-grown samples revealed well defined emission bands centered at 3.2, 2.74 and 2.0 eV, attributed to excitonic recombination, and the so-called blue and yellow emissions, respectively. It was observed that the intensity of the blue emission depends strongly on antimony content, suggesting the formation of point defects on Sb doping. While the yellow emission red-shifted after thermal annealing, either in argon or oxygen atmosphere, the intensity of the blue band decreases considerably; such behavior is explained through the reduction of the population of Zn(i) defects.

The monitoring of heavy metals in the marine environment is often carried out by using bioindicator organisms. In most cases metal concentrations in an area are evaluated using pooled samples from a single sampling site. Thus, a large number of individuals are analysed per site, but neither the statistical distribution of the data nor the intra-site variability are known. In order to optimise the monitoring of heavy metals using this kind of samples, some authors have suggested that the variability among individuals should be studied at least in one site. This work was designed to know the frequency distribution and the inter-individual variability of Hg, Cd, Pb, Cr, Ni, As, Ag, Cu and Zn in four bioindicator organisms (the blue mussel Mytilus galloprovincialis, the clam Venerupis pullastra, the king scallop Pecten maximus and the cockle Cerastoderma edule). In most cases metals in one-individual samples were shown to follow a log-normal distribution. As the pooled samples included more individuals they approached the normal distribution but still being closer to the log-normal one, suggesting that, in all cases, a logarithmic transformation should be used to normalise the data. The inter-individual variability observed indicated that at least two pooled samples of 30 individuals (a hundred in few cases) must be analysed to detect differences of 25% (both between sites and with time).

The yellow emission of thermally treated undoped and In doped ZnO nanostructures was studied by the cathodoluminescence (CL) technique. CL spectra acquired at room temperature of the as-grown samples revealed two emissions at about 3.2 eV and 2.13 eV, corresponding to the near band edge and defect related emissions, respectively. On annealing the samples at 600 degrees C in Ar and O-2 atmospheres, the defect emission suffers a red shift, irrespective of the annealing atmosphere. This red shift is explained in terms of variations in the relative intensities of the two component bands centered at about 2.24 eV and 1.77 eV, which were clearly resolved in the CL spectra acquired at low temperature of the annealed samples. A decrease of the relative intensity of the yellow emission (2.24 eV) was observed for all thermally annealed samples. The annealing of zinc interstitial point defects is proposed as a possible mechanism to explain this intensity decrease. (C) 2008 Elsevier Ltd. All rights reserved.

The increased use of biomass as a fuel in thermochemical conversion processes over the coming years, makes the research of a clean and efficient process necessary. The experiments were carried out in a pilot atmospheric fluidised bed combustion plant of 1 MW[th], where the parameters had been optimised to obtain a clean biomass combustion process.All types of combustion produce organic compounds, especially polycyclic aromatic hydrocarbons (PAHs). The distribution of PAHs was isolated from the eight size particle fractions collected in the fly ash emitted from the biomass combustion process. The particle size distribution was carried out with a multistage cascade impactor system (Andersen Mark III) with a diameter cut ranging from 0.01 to 4.00nm.It was observed that most of the heavy PAHs are adsorbed on particles having an aerodynamic diameter of less than 2 mum and an unimodal distribution was deduced from the results of the scanning mobility particle size.Polycyclic aromatic hydrocarbons pollutants were studied on a gas chromatograph coupled to a mass spectrometer operating in an ion monitoring mode. High concentrations of heavy PAHs were measured in a small particle size distribution. A high combustion efficiency reduced the PAH emissions.Under stable combustion conditions, the particle emission in the size range 0.1-1 mum was increased and mass concentration was reduced considerably. This was due to a reduction in the number of coarse particles. (C) 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Science Ltd.