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      Shape transformation from silver triangular nanoprisms to nanodisks: Raman characterization and sculpturing mechanism

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          Abstract

          The sculpturing action of chloride ions on silver nanoplates is investigated. Recent reports show that the shape transformation from silver triangular nanoprisms to nanodisks by addition of chloride ion occurs after a threshold concentration. In this work, a chemical study of this threshold concentration is presented. There is theoretical and experimental evidence that the morphological change only depends on the chloride ion concentration and not on the Cl-/Ag molar ratio. Besides, the chloride ion etching ability is attributed to the (AgCl)° complex, which controls the morphology change through a stepwise process where a silver atom is removed from the (110) plane, and is subsequently deposited on the (111) plane (i.e. from the nanoplate vertex to the basal plane). The threshold chloride ion concentration in the shape transformation coincides with the point where Ag+ ion and (AgCl)° concentrations are the same. On the other hand, the quantitative formation of AgCl-2 avoids the stepwise process, and then the colloidal system is destabilized. Furthermore, the analysis of the Raman spectra supports the transformation mechanisms.

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          Most cited references 68

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          Rapid planetesimal formation in turbulent circumstellar discs

          The initial stages of planet formation in circumstellar gas discs proceed via dust grains that collide and build up larger and larger bodies (Safronov 1969). How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem (Dominik et al. 2007): boulders stick together poorly (Benz 2000), and spiral into the protostar in a few hundred orbits due to a head wind from the slower rotating gas (Weidenschilling 1977). Gravitational collapse of the solid component has been suggested to overcome this barrier (Safronov 1969, Goldreich & Ward 1973, Youdin & Shu 2002). Even low levels of turbulence, however, inhibit sedimentation of solids to a sufficiently dense midplane layer (Weidenschilling & Cuzzi 1993, Dominik et al. 2007), but turbulence must be present to explain observed gas accretion in protostellar discs (Hartmann 1998). Here we report the discovery of efficient gravitational collapse of boulders in locally overdense regions in the midplane. The boulders concentrate initially in transient high pressures in the turbulent gas (Johansen, Klahr, & Henning 2006), and these concentrations are augmented a further order of magnitude by a streaming instability (Youdin & Goodman 2005, Johansen, Henning, & Klahr 2006, Johansen & Youdin 2007) driven by the relative flow of gas and solids. We find that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes. Gravitational collapse happens much faster than radial drift, offering a possible path to planetesimal formation in accreting circumstellar discs.
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            Simple analytical expression for the peak-frequency shifts of plasmonic resonances for sensing

            We derive a closed-form expression that accurately predicts the peak frequency-shift and broadening induced by tiny perturbations of plasmonic nanoresonators without critically relying on repeated electrodynamic simulations of the spectral response of nanoresonator for various locations, sizes or shapes of the perturbing objects. The force of the present approach, in comparison with other approaches of the same kind, is that the derivation is supported by a mathematical formalism based on a rigorous normalization of the resonance modes of nanoresonators consisting of lossy and dispersive materials. Accordingly, accurate predictions are obtained for a large range of nanoparticle shapes and sizes, used in various plasmonic nanosensors, even beyond the quasistatic limit. The expression gives quantitative insight, and combined with an open-source code, provides accurate and fast predictions that are ideally suited for preliminary designs or for interpretation of experimental data. It is also valid for photonic resonators with large mode volumes.
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              Probing quantum confinement within single core-multishell nanowires

              Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging, and calls for further studies on the underlying mechanisms of optoelectronic nanodevices.
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                Author and article information

                Journal
                rmf
                Revista mexicana de física
                Rev. mex. fis.
                Sociedad Mexicana de Física (México, DF, Mexico )
                0035-001X
                April 2015
                : 61
                : 2
                : 77-82
                Affiliations
                León Guanajuato orgnameUniversidad Nacional Autónoma de México orgdiv1Unidad León orgdiv2Escuela Nacional de Estudios Superiores México
                San Nicolás de los Garza Nuevo León orgnameUniversidad Autónoma de Nuevo León orgdiv1Facultad de Ciencias Químicas orgdiv2Laboratorio de Materiales I México
                Juriquilla Querétaro orgnameUniversidad Nacional Autónoma de México orgdiv1Centro de Física Aplicada y Tecnología Avanzada orgdiv2Deparamento de Nanotecnología México genoveva@ 123456unam.mx
                Article
                S0035-001X2015000200001 S0035-001X(15)06100200001

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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                Figures: 0, Tables: 0, Equations: 0, References: 43, Pages: 6
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