Complementary experimental and theoretical results on the coalescence of nanoparticles demonstrate the importance of the crystallographic orientation on the coalescence process. In situ hot-stage transmission electron microscopy studies on self-supporting films consisting of indium tin oxide nanoparticles clearly show rotations of neighboring particles preceding their coalescence. Both rotation and coalescence are observed well below half the melting temperature. The coalescence of two adjacent nanoparticles is simulated by means of a combination of the kinetic Monte Carlo method for atomic diffusion with an integration of the equations of motion for the rigid body degrees of freedom of the two particles. This allows analyzing the reorientation of the two crystal lattices prior to the merging process. Thus, nanoparticle coalescence has theoretically as well as experimentally been shown to be a two-step process: first a reorientation of adjacent nanoparticles, and second their complete or incomplete coalescence depending on the matching of the crystallographic orientations.

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Microsymposia the size-property correlation in these MoS2 nanosheets. Our results imply that nanostructured films with a high density of edge spins can give rise to magnetism even though the bulk material is nonmagnetic. For the first time, we show that Arsenic(ii) sulfide nanocrystal could be fabricated by a wet process of cluster-mediated nucleation method from the bulk material. Arsenic sulfide nanocrystals can show sizedependent fluorescences ranging from 287nm to 450 nm as well as two-photon upconverion. In China, realgar was also reported to be used as a drug in traditional Chinese medicine for more than 1500 years although arsenic is well known to be a highly toxic material. Preliminary pharmakinetic studies showed that arsenic sulfide quantum dots may afford good potential in anti-cancer treatment.Keywords: nanocrystals, arsenic sulfide, molybdenum sulfide MS.87.4 Acta Cryst. (2008). A64, C147In-situ transmission electron microscopy and theoretical studies on the coalescence of nanoparticles The production of low-cost nanoparticulate devices based on a bottom-up approach is subject of current research activities. One of the important questions on the way to sustainable devices concerns the question of their mechanical, thermal or electrical stability. Several routes of bottom-up integration of nanoparticulate systems are under investigation, including chemical linking, hybrid integration in a stable matrix and thermal processing. This presentation will focus on aspects of the thermal processing of nanoparticulate films and demonstrate a variety of different processes, which are directly related to the chemical bonding of the material. The thermally activated densification and sintering processes have been studied using time resolved in-situ hot-stage transmission electron microscopy of self-supporting films. The experiments were documented as live stream with a TV-rate CCD camera on a hard disc recorder. Varying mechanisms were found for the different materials: a) for ionic ITO particles, an adjustment of the crystal orientation prior to the coalescence is observed at temperatures well below of half the melting temperature; b) for covalent silicon, a melting and subsequent wetting process of the nanoparticles is observed; c) metallic silver particles form area defects during their coalescence, which migrate out of the particles afterwards. These observed mechanisms go clearly beyond the models of classical sintering theory. Our experiments clearly demonstrate that a more sophisticated treatment is necessary in order to understand the sintering processes in nanoparticles, which needs to takes into account the chemical bonding and crystallographic orientation. DFT and KMC and MD Simulations support and substantiate the presented experimental results. We present results, which open the way towards generating novel materials utilizing the electron spin. We propose to create such materials, by producing the appropriate inclusions in a semiconductor matrix. Bulk MnSb has a TC of 587 K, being therefore a good ...