The fundamental role of halide anions in the seed-mediated
synthesis
of anisotropic noble metal nanostructures has been a subject of debate
within the nanomaterials community. Herein, we systematically investigate
the roles of chloride, bromide and iodide anions in mediating the
growth of anisotropic Au nanostructures. A high-purity surfactant
solution of hexadecyltrimethylammonium bromide (CTABr) is used to
reliably probe the role of each halide anion without interference
from impurities. Our investigation reveals that bromide anions are
required for the formation of Au nanorods, while the controlled combination
of both bromide and iodide anions are necessary for the production
of high-quality Au nanoprisms. Chloride anions, however, are ineffective
at promoting anisotropic architectures and are detrimental to nanorod
and/or nanoprism growth at high concentrations. We examine the seed
structure and propose a growth model based on facet-selective adsorption
on low-index Au facets to rationalize the nanostructures obtained
by these methods. Our approach provides a facile synthesis of anisotropic
Au nanostructures by way of a single growth solution and yields the
desired morphologies with high purity. These results demonstrate that
appropriate combinations of halide anions provide a versatile paradigm
for manipulating the morphological distribution of Au nanostructures.
In this paper, we present a general method to constrain the classical energy of a vibrational mode to be greater than a specifled amount. In particular, zero-point energy constraints can be applied with this method to (zero-order) vibrational modes of a polyatomic system or complex. A demonstration of the method is made for a model two-mode Henon–Heiles Hamiltonian.
Cyan-emitting Ca2YHf2Al3O12:xCe3+ garnet phosphors with a high photoluminescence quantum efficiency of up to 89.5% were developed for fabricating high color rendering warm-white LEDs.
Studies of the cross sections for electron-impact excitation of the valence states of carbon monoxide, i.e. , the a H, A 'll, a' X+, e'X, d'6, I'X, and D '6 states, have been carried out using the Schwinger multichannel variational method. Both differential and integral cross sections are obtained and compared with available experimental data. Reasonable agreement between the present results and experiment is seen for most of the states, and some differences are discussed. Estimates of the total cross section for electronic excitation of CO by low-energy electrons are provided.PACS number(s): 34.80.6s
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