ECD of metals in thin gap geometry has been widely used over the last twenty years to study the foundation of pattern formation and self organization in open systems far from equilibrium. A great variety of macroscopic patterns (morphologies) are formed as a function of several control parameters: applied voltage, initial concentration, chemical composition of the solutions, its viscosity etc.

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Sub-micron hot (900) source powder is dropped into RF-irradiated water kept below the anomaly temperature. The process leads to the formation of spherical particles

Source powder

The effect of Rf-irradiation on ECD –A manifestation of induced long range order?The effect of Rf-irradiation on ECD –A manifestation of induced long range order? Y.Katsir(1)(2)(*)($), L.Miller(3)(*), Y.Aharonov(1), E.Ben-Jacob(1)

(1) Y. Katsir*, L. Miller*, Y. Aharonov and E. Ben-Jacob, The effect of rf-irradiation on electrochemical deposition and its stabilization by nanoparticle doping J. Electrochemical Society (accepted 2007). (*) these authors have equal contributions.

(2) For definition of water formatics see “Exploring water complexity” in: http://star.tau.ac.il/~eshel/

(3) M. Colic and D. Morse, Physical Review Letters, 80, 2465 (1998)(4) P. Attard, Advanced in Colloid and Interface Science, 104, 75 (2003).(5) The NPD-water is NeowaterTM provided by Do-coop Technologies Ltd.

(1)School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel (2) Current address: Department of Chemistry Bar Ilan University, Ramat Gan 52900, Israel

(3) Department of Materials Engineering, Technion, Haifa 3200, Israel(*) These authors have equal contributions ($) Presenting author

Direct observations of nanobubbles on hydrophobic surfaces using liquid atomic force microscopy in high resolution tapping mode (4). The observations revealed that once formed, the nanobubbles can be stable for hours. (Picture is thanks to P. Attard ref(4 ))

Control Rf-treated solutesNPD-water

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Testing the New paradigm Affiliations

References

The experimental findings

The New paradigm Nanobubbles stability – Experimental proof using AFM

The processed particles

HR SEM TEM

Dendrites

DBM

The circular ECD cell The typical Morphology Diagram

Electro-Chemical-Deposition in Circular Cells

Measurements on all scales from micro-level structures (using electron microscopy and X-rays) to the macro-level patterns played a crucial role in establishing the theoretical framework about the micro-macro singular interplay reflected in the morphology selection and morphology transitions. In this regard the ECD process provides a probe of micro-level effects.

Micro-Macro interplay and Morphology Selection in ECD:Micro-Macro interplay and Morphology Selection in ECD:

Nano Particle Doped water (NPD-water)

Bubble-Bubble Exchange Interactions

Formation of Nanobubble Networks

The effect of Nano particle doping

Bubble Particle

Nanobubbles Nanobubbles

The NPD-water used here is the Neowater (5) that has about 1012 particles per 1ml

As a step in this direction, we used Isothermal Titration Calorimetry (ITC) to test the effect of injecting solutions made with the NPD-water into control solutions and vice versa. The preliminary results show an endothermic peak in the former case, implying that the NPD-water solutions have lower free energy, which is consistent with the hypothesis about induced long range order (1).

It has been proposed before that

(1) The nanobubbles have long-term stability (hours);

(2) The gas-water interface of the nanobubbles is hydrophobic and therefore the water molecules form clathrate shells with an “ice-like” structure around the gas nanobubbles;

(3) The ordered shells can induce order in the water molecules surrounding the nanobubbles that extends up to a micron in range.

We propose that:

1. The induced order around each of the nanobubbles mediates bubble-bubble exchange interactions.

2. The exchange interactions lead to the formation of nanobubblenetworks with hierarchical organization. With larger bubblesbeing the hubs of the network.

3 .The networks induce long range order .

4 .In NPD-water nanoparticles act as the hubs leading to stabilization of the nanobubble

networks .

The effects of RF-irradiation of water

During the past two decades, much effort has been devoted to study the long term (hours) effects of rf-treatment on the properties of water and aqueous solutions (1-3). The following are some examples of well documented effects: 1. Formation of stable gas nanobubbles.2. A decrease in surface tension from 72 to 68 dyn/cm. 3. Increase in the intensity of all three infra-red (IR) spectroscopy frequency bands. 4. Increase in the concentration of atomic hydrogen. 5. Modifications in the spectra of dissolved hydrophobic fluorescent molecules. 6. Changes in the zeta potential.

It was proposed that the effects are due to water ordering induced by the gas bubbles. Here we test this hypothesis by study of the effect of RF-treatment on Electro-Chemical-Deposition (ECD) (1) .

The protocol

1. We performed ECD experiments in control solutions, solutions that where treated by RF-irradiation before the ECD process and in solutions made from NPD-water.

2. We monitored the pattern on the macro-scale and used HR SEM and SEM to study the micron-level organization of the deposits.

3. The RF-irradiation was at 915 MHZ , for about 20 minutes and about 10W power while keeping the water at fixed temperature.

Induced Morphology Diagram: For some growth conditions that dendrites are grown in the control solution, DBM morphology is generated in the RF-treated solutions and in the solutions made from NPD-water.

SEM observations of the effect on the DBM: These results are at lower voltages (8V) .

The effect on Dendritic growth: These results are at higher voltages (13V) .

We propose that our findings together with the previously reported anomalous effects of RF-treatment hint the existence of new physical phenomenon – The formation of Nanobubble Networks