[1] Nanoparticles are ubiquitous in nature. Their large surface areas and consequent chemical reactivity typically result in their aggregation into clusters. Their chemical and physical properties depend on cluster shapes, which are commonly complex and unknown. This is the first application of electron tomography with a transmission electron microscope to quantitatively determine the threedimensional (3D) shapes, volumes, and surface areas of nanoparticle clusters. We use soot (black carbon, BC) nanoparticles as an example because it is a major contributor to environmental degradation and global climate change. To the extent that our samples are representative, we find that quantitative measurements of soot surface areas and volumes derived from electron tomograms differ from geometrically derived values by, respectively, almost one and two orders of magnitude. Global sensitivity studies suggest that the global burden and direct radiative forcing of fractal BC are only about 60% of the value if it is assumed that BC has a spherical shape.

*Send correspondence to hamiche@ca.sandia.gov A scanning mobility particle sizer was used to measure changes in size distributions of soot particles when exposed to laser radiation at 532 or 1064 nm with fluences up to 0.8 J/cm 2 . Laser-induced production of carbon nanoparticles was observed at fluences above 0.12 J/cm 2 at 532 nm and 0.22 J/cm 2 at 1064 nm. Near-edge x-ray absorption fine structure spectra showed predominantly graphitic (sp 2 -hybridized) carbon in the non-irradiated particles and significantly different features in the irradiated particles. These results are consistent with differences in the fine structure between irradiated and non-irradiated samples observed by transmission electron microscopy.Copyright 2

Three bis(N-alkyldithiocarbamato)cadmium(II) complexes [Cd(S(2)CNHR)(2)] (1, R = n-C(3)H(7); 2, R = n-C(5)H(11); 3, n-C(12)H(25)) were prepared by metathesis of the corresponding lithium salt, Li[S(2)CNHR], with cadmium chloride. The crystal structures of 2 and 3 consist of planar molecular units of [Cd(S(2)CNHR)(2)] connected by intermolecular Cd.S interactions to give a one-dimensional chain. The chains are connected by a network of intermolecular N-H.S hydrogen bonds between the dithiocarbamato nitrogen atom and bridging sulfur atoms in neighboring chains. In solution, the (113)Cd NMR spectrum of 2 is dependent on concentration and temperature, indicative of a dimerization equilibrium mediated by similar Cd.S intermolecular bridging interactions. In the solid state, thermal gravimetric analyses show that all three complexes decompose smoothly via a heterolytic C-S bond cleavage reaction to give the corresponding alkyl isothiocyanate and cadmium sulfide as the primary products, with the formation of primary amine and CS(2) as coproducts. These products can result only from the net transfer of protons between N-alkyldithiocarbamato ligands in the solid state. Thus, the C-S bond cleavage reaction is interpreted in terms of the topochemical arrangement of molecular units in the crystalline state, which provides a pathway for proton transfer between ligands via N-H.S hydrogen bonds. Decomposition was also initiated by addition of a tertiary amine to a solution of [Cd(S(2)CNHR)(2)]. This confirms that C-S bond cleavage must be coupled to deprotonation of the -NH group, and explains why dialkylated derivatives [Cd(S(2)CNR(2))(2)] are inert to this particular mode of C-S bond cleavage. This system thus constitutes an unusual example of heterolytic, nonoxidative C-S bond cleavage that appears to proceed by a topochemical transfer of protons, which has implications for C-S bond cleavage processes in single-source precursors for II-VI semiconductor materials.

The reaction of AlMe(3) and [((t)Bu)(2)Al(micro-OPh)](2) with pyrazine (pyz), 4,4'-bipyridine (4-4'-bipy), 1,2-bis(4-pyridyl)ethane (bpetha) and 1,2-bis(4-pyridyl)ethylene (bpethe) yields (Me(3)Al)(2)(micro-pyz)(1), (Me(3)Al)(2)(micro-4,4'-bipy)(2), (Me(3)Al)(2)(micro-bpetha)(3), (Me(3)Al)(2)(micro-bipethe)(4), Al((t)Bu)(2)(OPh)(pyz)(5), [((t)Bu)(2)Al(OPh)](2)(micro-4,4-bipy)(6a), [((t)Bu)(2)Al(OPh)](2)(micro-bpetha)(7a), [((t)Bu)(2)Al(OPh)](2)(micro-bipethe)(8a). Compounds 1-4, 6a and 7a have been confirmed by X-ray crystallography. In solution compounds 1-4 undergo a rapid ligand-dissociation equilibrium resulting in a time-average spectrum in the (1)H NMR. In contrast, the solution equilibria for compounds 5-8a are sufficiently slow such that the mono-aluminium compounds may be observed by (1)H NMR spectroscopy: Al((t)Bu)(2)(OPh)(4,4-bipy)(6b), Al((t)Bu)(2)(OPh)(bpetha)(7b) and Al((t)Bu)(2)(OPh)(bpethe)(8b). The inability to isolate [((t)Bu)(2)Al(OPh)](2)(micro-pyz) and the relative stability of each complex is discussed with respect to the steric interactions across the bridging ligand (L) and the electronic effect on one Lewis acid-base interaction by the second Lewis acid-base interaction on the same ligand.