We studied the possible correlations between defects and photoluminescence spectra in ZnO nanoparticles of sizes ranging from 43 nm to 73 nm in diameter. The defects and impurity contents were characterized by Fourier-transform infrared (FTIR) spectroscopy. The results show fewer carboxylate and hydroxyl impurities for particles of larger sizes. No significant variation in oxygen vacancy content was found among samples. Annealing in vacuum at 300 °C significantly reduces the carboxylate and hydroxyl impurities in the samples. The total luminescence intensity (UV + visible) increases as the particle size grows for both the unannealed and annealed samples. This suggests that both types of luminescence are subject to nonradiative quenching by near surface defect centers, possibly carboxylate and hydroxyl impurities. There may be quenching due to intrinsic lattice defects too. It is found that annealing in vacuum enhances the visible luminescence both absolutely and relative to the UV exciton luminescence. In addition to the 2.5 eV green luminescence peak, a peak centered at 2.8 eV can also be resolved, espeically for the 43 nm sample. . Understanding the roles of defects and especially surface defects are important for these applications utilizing nano-structured ZnO. During or after nanostructure synthesis, the surfaces can often be easily contaminated by impurities and other defects. These surface defects usually reduce the performance for such applications. For example, surface defects such as hydroxyl are known to quench the exciton luminescence in ZnO [4]. It can also prevent efficient charge transfer between ZnO and adsorbed molecules at the interfaces. The most obvious trend versus particle size is that the surface-to-volume ratio increases for smaller particles, and the transport distance from any interior point to surface traps and recombination sites decreases in the same trend. Examining nanoparticle ZnO photoluminescence (PL) spectra provides us a way to understand the roles of defects in the above photon-excited processes. In this paper, we report our study of ZnO nanoparticles ranging from 43 to 73 nm. The defect and impurity content in these materials were characterized by Fourier transfer infrared spectroscopy (FTIR). We correlate the particle size and defects/impurities to the measured PL spectra. It is found that annealing treatment significantly reduces the surface impurities.

Obtaining spherical-shaped semiconductor nanoparticles of uniform size is essential for the fabrication of photonic crystals. We report the synthesis of nanometer-size spherical titania particles with narrow size distribution from glycolated precursors. Through controlled hydrolysis of glycolated precursors, particles of 683 to 50 nm average diameters, with narrow size distribution, could be produced for the first time. Effects of air annealing on the morphology, size shrinkage, and phase transition of the nanoparticles are studied by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and high-resolution electron microscopy techniques. Probable mechanisms for formation of titania nanoparticles and their size control are discussed.

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BackgroundSocioeconomic status (SES) is an important determinant of health and potential modifier of the effects of environmental contaminants. There has been a lack of comprehensive indices for measuring overall SES in Canada. Here, a more comprehensive SES index is developed aiming to support future studies exploring health outcomes related to environmental pollution in Canada.MethodsSES variables (n = 22, Census Canada 2006) were selected based on: cultural identities, housing characteristics, variables identified in Canadian environmental injustice studies and a previous deprivation index (Pampalon index). Principal component analysis with a single varimax rotation (factor loadings ≥ │60│) was performed on SES variables for 52974 census dissemination areas (DA). The final index was created by averaging the factor scores per DA according to the three components retained. The index was validated by examining its association with preterm birth (gestational age < 37 weeks), term low birth weight (LBW, <2500 g), small for gestational age (SGA, <10 percentile of birth weight for gestational age) and PM2.5 (particulate matter ≤ 2.5 μm) exposures in Edmonton, Alberta (1999–2008).ResultsIndex values exhibited a relatively normal distribution (median = 0.11, mean = 0.0, SD = 0.58) across Canada. Values in Alberta tended to be higher than in Newfoundland and Labrador, Northwest Territories and Nunavut (Pearson chi-square p < 0.001 across provinces). Lower quintiles of our index and the Pampalon’s index confirmed know associations with a higher prevalence of LBW, SGA, preterm birth and PM2.5 exposure. Results with our index exhibited greater statistical significance and a more consistent gradient of PM2.5 levels and prevalence of pregnancy outcomes.ConclusionsOur index reflects more dimensions of SES than an earlier index and it performed superiorly in capturing gradients in prevalence of pregnancy outcomes. It can be used for future research involving environmental pollution and health in Canada.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-1992-y) contains supplementary material, which is available to authorized users.

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Spatial variation in particulate matter–related health and toxicological outcomes is partly due to its composition. We studied spatial variability in particle composition and induced cellular responses in Mexico City to complement an ongoing epidemiologic study. We measured elements, endotoxins, and polycyclic aromatic hydrocarbons in two particle size fractions collected in five sites. We compared the in vitro proinflammatory response of J774A.1 and THP-1 cells after exposure to particles, measuring subsequent TNFα and IL-6 secretion. Particle composition varied by site and size. Particle constituents were subjected to principal component analysis, identifying three components: C1 (Si, Sr, Mg, Ca, Al, Fe, Mn, endotoxin), C2 (polycyclic aromatic hydrocarbons), and C3 (Zn, S, Sb, Ni, Cu, Pb). Induced TNFα levels were higher and more heterogeneous than IL-6 levels. Cytokines produced by both cell lines only correlated with C1, suggesting that constituents associated with soil induced the inflammatory response and explain observed spatial differences.

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