Diffraction lattices in precious opal

Baier, Ernst

doi:10.1007/bf01897686

Cited by 5 publications

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“…The streaks of colour are considered to come from reciprocal lattice rods produced by the disordered stacking of layers of silica particles. It seems more likely that this structure results naturally from the closest packing of the particles of silica settling under the influence of gravity, than from the pseudomorphic replacement of a twinned calcite structure such as Baier (1966) suggested. Darragh, Gaskin, Terrell & Sanders (1965) have suggested a probable mode of formation of opal by the precipitation of silica to form a gel in which primary particles, a few hundred ~ in diameter, are produced and then aggregate to produce the spherical particles which pack to make the optical grating.…”

Section: Discussionmentioning

confidence: 99%

“…Baier (1932) made extensive optical measurements on opals, and suggested that opal was a pseudomorph of calcite (Baier, 1966) and that the colours arose by diffraction from regularly spaced sets of planes which originated in the twinned structure of the calcite. Raman & Jayaraman (1953) as well as Baier (1932) noted the high degree of monochromatism in the colour; they realized that this must be due to diffraction, and suggested an arrangement of equally spaced parallel plates of two forms of silica of different refractive indices.…”

Section: Introductionmentioning

confidence: 99%

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Diffraction of light by opals

Sanders¹

1968

Acta Cryst A

145

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427and 26% for the (220) structure factors of the copper data. Because of the restriction rc,,* > rMo* it is clearly impossible to obtain a self-consistent interpretation of the combined copper and molybdenum data without taking the Rorrmann effect into account.It is a most surprising result to find such a high degree of perfection (as illustrated by the large values for r and g) for a crystal which has been ground into a sphere. The pure extinction effect is very great for both radiations firstly because r* is large, and secondly because of the simplicity of the structure which allows F~/V to be very large for many reflections. For the same two reasons, with the additional condition ¢t0R>l, the Borrmann effect becomes very great for the copper data.The good agreement between theory and experiment suggests that the intensity formula presented in the preceding paper is satisfactory even for extreme conditions of extinction. However, further experimental tests of the theory are needed. Gem opals were examined in an optical diffractometer and found to give several types of diffraction pattern which are interpreted by analogy with conventional three-dimensional X-ray theory to give the structure of the opal. The results show that the spherical silica particles in opals are arranged hexagonally in layers which are usually stacked randomly. In some specimens there are parallel domains of ordered packing, commonly in a f.c.c, sequence and sometimes in a h.c.p, sequence. Although the silica particles cannot be resolved by optical microscopy, bands parallel to the layers and fringes across the bands can be seen in images with the diffracted light.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diffraction of light by opals

Sanders¹

1968

Acta Cryst A

145

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“…k T ER 12 r 0 B 2 (5) where ε 0 and ε r are the permittivities of the vacuum and the solution, respectively, k B is the Boltzmann constant, T is the temperature, ζ is the zeta-potential, E is the external electric field strength, and R is the radius of the particle. When Pe ≪ 1, Brownian motion dominates, and deposition most likely occurs and b show Pe for spherical particles as a function of the particle size for different values of the electric fields and zeta-potentials.…”

Section: Pementioning

confidence: 99%

“…Initial interest probably already arose during the earliest colloid experiments by Perrin in 1908 with gamboge particles (see the discussion by Achinstein). Subsequently, the availability of a variety of monodisperse colloid particles encouraged interest in self-assembly, , while the discovery in the early 1960s that monodisperse colloidal silica was responsible for the iridescence in opals also inspired interest in the use of colloid structures to create unusual optical effects. − …”

Section: Introductionmentioning

confidence: 99%

Electrophoretic Deposition of Single Nanoparticles

Zhang,

Liu,

Dong

et al. 2024

Langmuir

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The controlled assembly of colloid particles on a solid substrate has always been a major challenge in colloid and surface science. Here we provide an overview of electrophoretic deposition (EPD) of single charge-stabilized nanoparticles. We demonstrate that surface templated EPD (STEPD) assembly, which combines EPD with top-down nanofabrication, allows a wide range of nanoparticles to be built up into arbitrary structures with high speed, scalability, and excellent fidelity. We will also discuss some of the current colloid chemical limitations and challenges in STEPD assembly for sub-10 nm nanoparticles and for the fabrication of densely packed single particle arrays.

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Submicron Structure of “Amorphous” Opal

Greer

1969

Nature

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Diffraction lattices in precious opal

Cited by 5 publications

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Diffraction of light by opals

Diffraction of light by opals

Electrophoretic Deposition of Single Nanoparticles

Submicron Structure of “Amorphous” Opal

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