Ag fractal structures in electroless metal deposition systems with and without magnetic field

Abstract

Metal electrodeposition systems display tree-like structures with extensive ramification and a fractal character. Electrolysis is not a necessary route for the growth of such dendritic metal deposits. We can grow beautiful ramification patterns via a simple redox reaction. We present here a study of silver (Ag) deposits from the reduction of Ag in (AgNO) solution by metallic copper. The experiments are carried out in discotic geometry, in a Petri dish hosting a thin AgNO solution film. A variety of deposited structures and patterns is obtained at different Ag concentrations, yet with essentially the same fractal dimension averaged at 1.64, typical of diffusion-limited aggregation (DLA). A linear magnetic field of low induction (0.50-1.0 T) applied across the medium causes a notable transformation in the morphology of the deposits. In both the field off and the field on cases, the effect of vertical (hence 3D) heaving seems to be dominant, perhaps explaining the nearly constant fractal dimension.

Magnetic-Field-Induced Painting-Out of Precipitation Bands of Mn–Fe-Based Prussian Blue Analogues in Water–Glass Gels

“…In the study of magnetic effects, the magnetic field intensity and direction dependencies of systems are generally interesting subjects. In fact, such dependencies were investigated for pattern formation in silver dendrite systems. , Unfortunately, because the painting-out effect observed here was basically minimal and considerably stochastic, it is difficult to accurately examine these dependencies using the present setup. Details of the dependencies need to be investigated further using a high-power, superconducting electromagnet.…”

“…In 2014, Zhao et al 13 found that a static magnetic field (0.4 T) could change the geometric morphologies of the Liesegang bands of silver dendrite observed on the surface of a liquid. Very recently, Ibrahim et al 14 studied the magnetic-field-induced effect on the fractal structures of silver dendrite and discussed the differences between their results and those of Zhao et al 13 To the best of our knowledge, the effect of a magnetic field on the Liesegang bands that form in the gel media (i.e., the traditional Liesegang bands) has not been reported yet.…”

“…Magnetic fields can also influence the self-organization patterns that are formed by various reaction–diffusion processes, ,− even if the existent magnetic interactions are relatively weak. For example, Boga et al found that the magnetic fields cause a change of several orders of magnitude in the velocity of the propagating reaction-front in cobalt-catalyzed auto-oxidation of benzaldehyde in glacial acetic acid .…”

Random Spacing between Metal Tree Electrodeposits in Linear DLA Arrays

“…We observe random oscillations in the spacing sequence, and compute the entropy of this self-organizing system, which is shown to be consistent in all the considered sets. The present work is an extension of our previous work on electrolytic fractal growth in Zn [ 20 ], and two-metal [ 21 , 22 ] systems, and electroless growth of Ag by reduction of Ag + with Cu [ 23 ].…”

Redox-initiated diffusion-limited aggregation in biopolymer

“…The random walker moves until it reaches a site adjacent to the seed and sticks there, consequently forming a cluster. The effect of external factors like pressure [11,12], temperature [13], electric field [14][15][16][17][18] and magnetic field [19][20][21] on the DLA patterns have been studied by several groups. Fractal patterns with copper and silver aggregates have been obtained by simple displacement reaction [22,23] and chemical dissolution methods [24] in the absence of any external stimuli.…”