Electrochemical Actuation of Growing Copper Dendrimers in Water (original) (raw)
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Overpotential controls a morphology of electrolytically produced copper dendritic forms
Journal of the Serbian Chemical Society
The morphologies of copper dendritic forms obtained in both potentiostatic and galvanostatic regimes of electrolysis with various amounts of the electricity were analyzed by the scanning electron microscopy (SEM) technique. Irrespective of amount of passed electricity, 3D (three dimensional) pine-like dendrites with sharp tips were formed in the potentiostatic regime of electrolysis. On the other hand, the amount of passed electricity had a strong effect on the shape of the 3D pine-like dendrites formed in the galvanostatic regime of electrolysis. Dendrites with sharp tips were formed with smaller amount of passed electricity, while dendrites with globular tips were formed with larger amounts. The change in the shape of the galvanostatically synthesized 3D pine-like dendrites was explained by comparison with copper deposits obtained potentiostatically at overpotentials that corresponded to the final overpotentials during galvanostatic regime of electrolysis for the analyzed amounts ...
Overpotential controls the morphology of electrolytically produced copper dendritic forms
Journal of the Serbian Chemical Society, 2019
The morphologies of copper dendritic forms obtained in both poten-tiostatic and galvanostatic regimes of electrolysis with various amounts of the electricity were analyzed by the scanning electron microscopy (SEM) technique. Irrespective of amount of passed electricity, 3D (three dimensional) pine-like dendrites with sharp tips were formed in the potentiostatic regime of electrolysis. On the other hand, the amount of passed electricity had a strong effect on the shape of the 3D pine-like dendrites formed in the galvanostatic regime of electrolysis. Dendrites with sharp tips were formed with smaller amount of passed electricity, while dendrites with globular tips were formed with larger amounts. The change in the shape of the galvanostatically synthesized 3D pine-like dendrites was explained by comparison with copper deposits obtained potentiostatically at overpotentials that corresponded to the final over-potentials during galvanostatic regime of electrolysis for the analyzed amounts of electricity. Based on the similarity of the obtained morphologies at the macro level, it was concluded that the overpotential plays a crucial role in the formation of the electrolytically synthesized dendrites and that the controlled conditions of electrolysis could represent a suitable way for a synthesis of spherical Cu particles by electrolysis.
Conductive dendrimers obtained by click chemistry
Nanophotonic Materials VII, 2010
First generation dendrimers having a high level of size/shape/symmetry homogeneity were fabricated using a synthetic scheme that employs highly quantitative copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions in combination with a molecular architecture that favors homogeneity. An "outside-in" or convergent synthetic approach was employed wherein dendrons having Sierpinski triangular fractal architectures were coupled to core structures having D 2h or D 3h point group symmetries to form the desired dendrimers. The individual dendrons consisted of branched-backbone conductive polymers having benzene branch points and 1,2,3-triazole linkages with uninterrupted π-electron cloud overlap throughout. Each dendron was then coupled to a benzene core structure having acetylene substituents by means of a CuAAC reaction so as to extend the uninterrupted π-conjugation from the dendron to the core structure for imparting conductivity throughout the entire dendrimer. The resulting dendrimers maintained the point group symmetry of their core structure, with the core structure serving to electronically couple the dendrons to one another by extension of their uninterrupted π-electron systems. Synthesis of these first generation dendrimers provides a proof of principle for the synthesis of higher generation conductive dendrimers. Since the nanophotonic properties of conductive dendrimers may be dependent, at least in some instances, upon their size, shape, and symmetry, enhancements with respect to their homogeneity may unmask new nanophotonic properties.
A Novel Route for Electrolytic Production of Very Branchy Copper Dendrites under Extreme Conditions
Journal of The Electrochemical Society, 2021
Copper electrodeposition in a form of powder was examined using the pulsating overpotential (PO) regime from the sulfate electrolyte without or with an addition of various concentrations of chloride ions. Morphological and structural characteristics of the produced particles were analyzed by the scanning electron microscope (SEM) and the X-ray diffraction (XRD) method. The final morphology of Cu powders was determined with two parallel processes: a) suppression of hydrogen evolution reaction due to pause duration considerably longer than the deposition time, and b) catalytic effect of added chlorides. Depending on the amplitude of overpotential applied, addition of chlorides into the solution led to either an appearing of dendrites or to formation of very branchy dendrites, what confirms a catalytic effect of these ions on the process of Cu electrolysis. The novel forms of copper dendrites, such as the needle-like and the 2D (two dimensional), were identified in this investigation, and the catalytic effect of chlorides on copper electrodeposition has been just discussed by morphological analysis of these dendritic forms. The XRD analysis of the copper dendrites obtained with an addition of chlorides showed predominantly oriented the Cu crystallites in (111) plane.
Electrochemical aspects of formation of dendrites
Zastita materijala, 2016
The one of the main contributions of Belgrade Electrochemical School to the field of metal electrodeposition is investigation of a mechanism of formation and growth of the disperse deposits. Spongy-like, cauliflower-like, needle-like, carrot-like, dendrites of various shapes, etc. are the typical disperse forms obtained by the electrodeposition processes. From the electrochemical point of view, a dendrite, as the most significant disperse form, is defined as an electrode surface protrusion that grow under activation or mixed control, while deposition to the flat part of the electrode surface is under complete diffusion control. In this paper, all electrochemical aspects concerning mechanism of formation and growth of dendrites are reviewed.
Electrochemical Examination of Dendritic Growth on Electronic Devices in HCl Electrolytes
CORROSION, 1990
As part of an investigation of electrochemical failure mechanisms occurring in electronic devices, factors affecting the formation and growth rate of dendrites on a model microelectronic device substrate have been examined. Experiments have been performed by immersing the devices in selected electrolytes and using a potentiostat to apply a constant cathodic potential or a constant potential bias. The effects of electrolyte composition and cathodic overpotential on dendrite formation and growth rate in HCl electrolytes have been delineated. Dendrites were observed at lower pH, but none were observed when the pH > 5.0, due to the formation of insoluble copper corrosion products such as Cu20. Several features of the growth of dendrites in 0.1 M HCl electrolytes were observed to be similar to previous investigations: a minimum cathodic potential (approximately-0.450 V vs a saturated calomel electrode [SCE]) was required for the appearance and propagation of copper dendrites; at constant cathodic overpotential, the growth rate of dendrites was found to have a linear dependence on copper ion concentration; and the induction time prior to the detection of dendrites decreased as the cathodic overpotential increased. Although, experimentally measured dendrite growth rates were found to be up to three orders of magnitude smaller than theoretical predictions based on a maximum growth velocity model of dendrite growth, the model is stijl useful for predicting the functional dependence of velocity on a variety of electrochemical parameters. Suggestions for the development of an alternate, more accurate model are provided.
Journal of The Electrochemical Society, 2021
This work deals with the formation of dendritic structures by electrodeposition of Cu2+ and Ag+ without supporting electrolyte in Hele-Shaw cells. The transition between the two main patterns, ramified branches and dendrites, is specifically addressed at the scale of branch microstructure using careful SEM observations. Ramified branches, composed only of grain assemblies, are obtained at low current densities because of a re-nucleation process induced by space charge dynamics (Fleury, Nature, 1997). For current densities higher than a given threshold, ramified branches are also formed by re-nucleation but another growth mode, the dendritic growth, is also observed while, at the macro-scale, the pattern remains fractal and isotropic. This shows that 1) pattern transition originates from a morphological transition at microstructure scale and 2) the re-nucleation process enables a freedom in local growth direction allowing the pattern to be fractal at the macro-scale. The onset of the...
Characterization of starburst dendrimers by the EPR technique. 1. Copper complexes in water solution
Journal of the American Chemical Society, 1994
The structure of Cu(I1) complexes formed with anionic starburst dendrimers (n.5 G-SBD) in aqueous solution has been investigated by the electron paramagnetic resonance (EPR) technique. The line shapes of the EPR spectra of the complexes at room temperature show a distinction between earlier (n < 3) and later (n 1 3) generations and are consistent with a change of the dendrimer shape, which supports the results of molecular simulation of the dendrimer morphology as a function of generation. The earlier generations appear to possess a more open structure, which leads to a greater mobility of the copper complexes. Three different complexes of copper with groups composing the dendrimer structure are identified by analyzing the spectra as a function of the dendrimer size (generation), the pH, and the temperature. The magnetic parameters, evaluated at low temperature with the aid of spectral computation, indicate that the copper ions form monomeric carboxylate complexes at low p H (signal C). With an increase of pH, the ions interact with nitrogen centers in the internal porous structure of the dendrimers. The complex formed at intermediate pH is identified as a Cu(II)-N202 complex (signal A). Such a complex, which involves both the carboxylic groups a t the dendrimer interface and the internal nitrogen centers, is preferentially formed by Iow-generation dendrimers. This result is consistent with the morphology of the dendrimer structure. The higher generation dendrimers present a wide number of internal sites in which the tightly packed structure appears to facilitate the interaction with more than two nitrogens. This Cu(II)-N30 or Cu(I1)-N4 complex gives a third signal (termed signal B), which increases its intensity at the expense of signal A, both with the increase of generation and with the increase of pH. However, the interaction with nitrogen centers in both cases is not strong enough to give superhyperfine structure in the EPR spectra. For freshly prepared samples, formation of the complex with the larger nitrogen coordination corresponds to enhancement in the EPR room temperature spectra of a signal of a nitrogen-centered radical species, which is also observed in the spectra of pure dendrimers. The spectral features of this radical are identified, by spectral computation, as resulting from an unpaired electron which couples with one nitrogen and four protons from two slightly nonequivalent CHz groups. Aging of the samples leads to an increase in intensity of signal B, simultaneously with the disappearance of the radical signal. This allows the identification of one of the coordinating sites in the internal dendrimer structure. Heating of the 6.5 and 7.5 G-SBD at high pH causes decomposition of the dendrimers, whereas lower generation dendrimers show good thermal stability. The evaluation of the Cu(I1) bonding parameters, a2, d2, and 8lz, indicates substantial covalency of the in-plane bonds, with the covalent character increasing respectively for the species corresponding to signal C, signal A, and signal B.