Tuning the morphology of metal deposits at liquid-liquid interfaces: nanoparticles, nanowires and super smooth films
Physikalische Chemie von Festkörpern und Oberflächen, Materialcharakterisierung
Zusammenfassung der Projektergebnisse
The project was aimed at synthesizing metal particles, wires and films at liquid|liquid interfaces (aqueous|non-aqueous interface) by a reduction of metal ions dissolved in the aqueous phase by an organic reductant dissolved in the organic phase. It was the aim to understand the rules which govern the morphology of the metal deposits. The main motivation was the elucidation of the scientific fundamentals. The reason for the growth of single crystal silver wires could be shown to be the growth mechanism which is explainable on the base of the microelectrode behavior of the silver wires. That growth mechanism could be mathematically modeled and a very good agreement between model and experiments has been observed for the first half of growing time. Another basic result of the project is that we could show that the orientation of silver seed crystals at the liquid|liquid interface is crucial for achieving wire growth: the seed crystals have been chemically modified to possess one hydrophobic and one hydrophilic side, which obviously oriented them at the liquid|liquid interface in such way that both phases have chemical access to the silver crystals. The vast number of experiments clearly showed that the nucleation at the normally extremely clean liquid|liquid interface is a process which is enormously difficult to control. Nucleation, and especially the nature of active sites, is still a research area with large white fields. This project also lead to the development of a chemical model of nucleation, were nucleation is understood as a chemical reaction of active sites with the nucleating species. The results of this project shine new light on nucleation, and it is expected that they will support researchers to find the right direction for further studies. Nucleation of a new phase is of paramount importance almost everywhere, e.g., cloud formation, raining, snowing, hale formation, boiling, melting, precipitation (crystallization), metal corrosion, metal plating, etc. So far, nucleation of a new phase at an active center was discussed only on the bases of interfacial tension, rarely including adsorption. We believe from our experimental results and model theory that chemical reactions may play a very important role in decreasing the free energy barrier which must be overcome during the initial stages of nucleation.
Projektbezogene Publikationen (Auswahl)
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The growth of single crystal silver wires at the nitrobenzene|water interface. Phys. Chem. Chem. Phys., 2011
Ulrich Hasse, Gottfried J. Palm, Winfried Hinrichs, Jan Schäfer, Fritz Scholz
