Ring Morphology and pH Effects in 2D and 1D Co(OH)<sub>2</sub> Liesegang Systems

Badr, Layla; Sultan, Rabih

doi:10.1021/jp8094984

Cited by 29 publications

(27 citation statements)

References 31 publications

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“…The highly circular patterns we observe here are consistent with 2D Co(OH) 2 patterns obtained in previous work [13,31], also in the presence of a radial field. It is thus quite interesting to realize that the presence of an electric field seems to play a crucial role in taming the morphology of 2D Liesegang rings.…”

Section: Negative Field Casesupporting

confidence: 92%

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Badr

El-Rassy

El-Joubeily

et al. 2010

Chemical Physics Letters

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Section: Negative Field Casesupporting

confidence: 92%

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Badr

El-Rassy

El-Joubeily

et al. 2010

Chemical Physics Letters

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“…It is shown that for a typical Liesegang pattern, the band spacing increases as B 0 increases, but decreases as A 0 increases. This formulation is consistent with experimental observation [25,26].…”

Section: Matalon-packter Lawsupporting

confidence: 92%

Rhythmic precipitate patterns and fractal structure

Sultan

2011

Acta Mech Sin

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Liesegang patterns of parallel precipitate bands are obtained when solutions containing co-precipitate ions interdiffuse in a 1D gel matrix. The sparingly soluble salt formed, displays a beautiful stratification of discs of precipitate perpendicular to the 1D tube axis. The Liesegang structures are analyzed from the viewpoint of their fractal nature. Geometric Liesegang patterns are constructed in conformity with the well-known empirical laws such as the time, band spacing and band width laws. The dependence of the band spacing on the initial concentrations of diffusing (outer) and immobile (inner) electrolytes (A 0 and B 0 , respectively) is taken to follow the Matalon-Packter law. Both mathematical fractal dimensions and box-count dimensions are calculated. The fractal dimension is found to increase with increasing A 0 and decreasing B 0 . We also analyze mosaic patterns with random distribution of crystallites, grown under different conditions than the classical Liesegang gel method, and report on their fractal properties. Finally, complex Liesegang patterns wherein the bands are grouped in multiplets are studied, and it is shown that the fractal nature increases with the multiplicity.

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“…In addition, our approach allows the design and synthesis of nanoparticles with particular size characteristics simply by varying the gel composition and the concentration of sodium hydroxide. The diffusion-controlled reaction technique employed in our method has been widely used to prepare Liesegang patterns 11,12 . The Liesegang phenomenon is the dynamic formation of self-organized rhythmic precipitate patterns.…”

Section: Introductionmentioning

confidence: 99%

Size-controlled synthesis of Cu2O nanoparticles via reaction-diffusion

Badr

Epstein

2017

Chemical Physics Letters

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Copper (I) oxide nanoparticles are synthesized by a simple reaction-diffusion process involving Cu + ions and sodium hydroxide in gelatin. The mean diameter and the size dispersion of the nanoparticles can be controlled by two experimental parameters, the percent of gelatin in the medium and the hydroxide ion concentration. UV-visible spectroscopy, transmission electron microscopy and X-ray diffraction are used to analyze the size, morphology, and chemical composition of the nanoparticles generated. IntroductionThe use of nanoparticles of characteristic size and narrow dispersion to form hybrid materials is gaining increasing interest in the biomedical 1,2 and electronics 3 industries. Among various metal oxide particles, copper (I) oxide has received much attention because of its distinctive characteristics and its low cost compared to silver and gold oxide nanoparticles. In particular, its electrical properties due to its low energy band gap (2.18 eV), enhanced nonlinear optical properties, photocatalytic and catalytic power 4 , and antibacterial activity 5 make it an attractive material for many applications. Methods developed for the preparation of copper (I) oxide nanoparticles utilize ultrasound 6 , chemical curing 7 , gas-phase reduction 8 and other techniques that involve the reduction of copper (II) oxide to copper (I) oxide 9,10 . In the methods proposed to date, the extent of the reduction is not easy to control; thus the nanoparticles produced may not be very pure. Careful selection of surfactants or organic additives to protect the particles from aggregation is also required. The approach we propose here is unique in the sense that it uses mild reagents and ambient experimental conditions. The problems of reduction and aggregation are circumvented by the preparation method, where the initial reaction takes place between monovalent Cu + ions and hydroxide ions in a gel medium to produce the Cu 2 O nanoparticles. In addition, our approach allows the design and synthesis of nanoparticles with particular size characteristics simply by varying the gel composition and the concentration of sodium hydroxide. The diffusion-controlled reaction technique employed in our method has been widely used to prepare Liesegang patterns 11,12 . The Liesegang phenomenon is the dynamic formation of self-organized rhythmic precipitate patterns. The proposed scenarios for the explanation of the Liesegang phenomenon can be classified as either prenucleation or postnucleation, depending on the sequence of elementary steps 13,14 . The prenucleation models are descendants of Ostwald's supersaturation theory and assume that the formation of bands is the result of a supersaturation wave. Postnucleation models assume that before bands form, the precipitate forms a homogeneous solution of solid particles, which loses its stability and arranges into periodic bands. Walliser et al. 15 employed a diffusion-controlled reaction technique to grow various size silver dichromate nanoparticles and microparticles in one step. In their study, ...

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Ring Morphology and pH Effects in 2D and 1D Co(OH)₂ Liesegang Systems

Cited by 29 publications

References 31 publications

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Rhythmic precipitate patterns and fractal structure

Size-controlled synthesis of Cu2O nanoparticles via reaction-diffusion

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Ring Morphology and pH Effects in 2D and 1D Co(OH)2 Liesegang Systems

Cited by 29 publications

References 31 publications

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Morphology of a 2D Mg2+/NH4OH Liesegang pattern in zero, positive and negative radial electric field

Rhythmic precipitate patterns and fractal structure

Size-controlled synthesis of Cu2O nanoparticles via reaction-diffusion

Contact Info

Product

Resources

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Ring Morphology and pH Effects in 2D and 1D Co(OH)₂ Liesegang Systems