Transmission electron microscopy studies of (111) twinned silver halide microcrystals

EMAT, University of Antwerp, Belgium.
Microscopy Research and Technique (Impact Factor: 1.15). 07/1998; 42(2):85-99. DOI: 10.1002/(SICI)1097-0029(19980715)42:2<85::AID-JEMT3>3.0.CO;2-M
Source: PubMed


The present paper covers the results of different transmission electron microscopy studies on silver halide microcrystals. Pure AgBr as well as core-shell AgBr-AgBrI crystals are investigated. In the former parallel and non-parallel twinning modes yielding tabular and needle- or tetrahedral-shaped microcrystals, respectively, are discussed. Also the short-range-order of Ag+ interstitials around the twin planes as determined from diffuse intensity in reciprocal space is described. The latter yields a technique to determine the variant in which dislocations are located in certain core-shell microcrystals. The introduction of iodine also results in the presence of inclined stacking faults in the shell and of long-range iodine ordering on the crystal surface.

Download full-text


Available from: Dominique Schryvers, Apr 21, 2014
10 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Studies of silver halide (AgX) photographic materials and individual microcomponents by TEM/STEM/SEM/EDX, CL, EFTEM/EELS and digital image analysis techniques are reviewed. Electron-beam-AgX interactions are discussed to clarify relationships between the signals analysed in various operating AEM modes. An optimum strategy of structural and analytical diagnosis of complex silver halide photographic systems by a number of AEM methods is considered, using a number of examples (colour and black-and-white films, AgX microcrystals, and colour coupler dispersions). AEM applications to study of the main stages of the photographic process, i.e., chemical ripening, spectral sensitisation, latent image formation and development are also presented. Current trends and future directions in research of AgX-based photographic systems by AEM techniques are outlined.
    Micron 02/2000; 31(1):55-95. DOI:10.1016/S0968-4328(99)00055-4 · 1.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Examples of gold and silver anisotropic colloids, such as prisms and rods, have appeared in the literature for many years. In most cases, the morphologies of these thermodynamically unfavorable particles have been explained by the particular reaction environment in which they were synthesized. The mechanisms used to explain the growth generally fall into two categories, one in which chemically adsorbed molecules regulate the growth of specific crystal faces kinetically, and the other where micelle-forming surfactants physically direct the shape of the particle. This paper raises questions about the growth of anisotropic metal colloids that the current mechanisms cannot adequately address, specifically, the formation of multiple shapes in a single homogeneous reaction and the appearance of similar structures in very different synthesis schemes. These observations suggest that any growth mechanism should primarily take into consideration nucleation and kinetics, and not only thermodynamics or physical constrictions. The authors suggest an alternative mechanism where the presence and orientation of twin planes in these face-centered cubic (fcc) metals direct the shape of the growing particles. This explanation follows that used for silver halide crystals, and has the advantage of explaining particle growth in many synthesis methods. In this mechanism, twin planes generate reentrant grooves, favorable sites for the attachment of adatoms. Shape and structural data are presented for gold and silver particles synthesized using several different techniques to support this new model. Triangular prisms are suggested to contain a single twin plane which directs that growth of the initial seed in two dimensions, but limits the final size of the prism. Hexagonal platelets are suggested to contain two parallel twin planes that allow the fast growing edges to regenerate one another, allowing large sizes and aspect ratios to form. Rods and wires were found to have a fivefold symmetry, which may only allow growth in one dimension. It is expected that a superior mechanistic understanding will permit shape-selective synthesis schemes to be developed.
    Advanced Functional Materials 07/2005; 15(7):1197 - 1208. DOI:10.1002/adfm.200400091 · 11.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size- and shape-dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid-chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state-of-the-art morphology control in noble metal nanoparticles.
    Advanced Materials 04/2010; 22(16):1781-804. DOI:10.1002/adma.200901271 · 17.49 Impact Factor
Show more