Aerosol characterization and apportionment using cascade impactors and activation analysis

The use of particle-size distribution measurements and techniques for aerosol physical characterization, together with composition data for 30 elements, has led to useful deductions about the sources of airborne particulates. Collections with cascade impactors operated at three locations in Toronto, Canada, were analyzed by INAA and photonuclear activation (IPAA). The efficiency and reliability of impactors for aerosol size-distribution characterization was studied by scanning electron microscopy and calculating equivalent aerodynamic diameters; values obtained in this way were in close agreement with predicted values. Toronto aerosols exhibited both expected and unusual particle-size distribution patterns with many elements exhibiting either size distributions biased toward large (e.g. Al, Sc, Ti, Fe) or small particles (e.g. Br, Cl, Cu). Other elements (viz. Pb, Zn, As, Sb) exhibited different and unusual size distributions, presumably from different sources. Factor analysis and chemical mass balance (CMB) applied to data for a suburban site allowed emission source identification and aeorosol apportionment with a fair degree of certainty, and, preliminary results using factor analysis for size-fractionated samples, indicate a potential for relatively accurate source apportionment in more complex airsheds.     

Bulky triarylarsines are effective ligands for palladium catalysed Heck olefination

The four arsines, As{C6H3(o-CH3)(p-Z)}3{Z=H (2a) or OMe (2b)} and As{C6H3(o-CHMe2)(p-Z)}3{Z=H (2c) or OMe (2d)} react with [PdCl2(NCPh)2] or [PtCl2(NCBu(t))2] to give trans-[MCl2L2] or trans-[M2Cl2(mu-Cl)2L2]. The crystal structures of trans-[PdCl2(2a)2] and [PtCl2(2d)2] have been determined, the latter as its dichloromethane solvate. The structures show that in these complexes, the ligands adopt gga type conformations as do all analogous tri-o-tolyl- and tri-o-isopropylphenylphosphines in square-planar and octahedral complexes. The variable-temperature NMR behaviour of the complexes shows that they are fluxional due to restricted As-C bond rotation. The rate of the fluxionality is more rapid than in the analogous phosphine complexes and this is associated with longer As-C and As-M bonds allowing more free movement. The catalytic activity of the palladium complexes of the arsines and their phosphine analogues for the reaction of 4-bromoacetophenone and n-butyl acrylate has been screened. The results show that the arsines are generally superior to the phosphines as ligands for this catalysis. Tri(o-isopropylphenyl)phosphine and tri(o-isopropylphenyl)arsine are superior to tri-o-tolylphosphine as ligands for this Heck reaction and a p-methoxy substituent improves the arsine catalyst but not the phosphine catalyst. The phosphine catalysts are superior to the arsine catalysts for the reaction of 4-chloroacetophenone and n-butyl acrylate. These observations are discussed in the context of ligand stereoelectronic effects, as measured by the Tolman electronic parameter, nuCO of the [NiL(CO)3]{L=AsAr3 or PAr3}.     

A Mössbauer effect study of Y2Fe17 and Y2Fe17N2.6

The Mössbauer effect spectra of Y₂Fe₁₇ and Y₂Fe₁₇N_2.6, obtained at 85 K, are analyzed with a model consistent with their crystallographic structures and band structure calculations of their magnetic moments. The increases in the individual site isomer shifts and hyperfine fields upon nitrogenation correlate well with the increases in both the individual Wigner-Seitz cell volumes and the magnetic moments. The spectral analysis, which requires ten sextets, indicates that the magnetization lies in a general direction in the hexagonal basal plane of these compounds.     

Porphyrin dye-sensitised solar cells utilising a solid-state electrolyte

We describe a porphyrin dye-sensitised solar cell utilising a solid state electrolyte containing the I(-)/I(3)(-) redox couple, which yields a performance of 5.3% under moderate light intensity and 4.8% at full sun.