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How soft interactions promote the welding of gold nanoparticles ?

In collaboration with S. Laza and B. Palpant (LPQM, Ecole Centrale Paris) and C. Sicard-Roselli (LCP, Université Paris Sud), we report the formation of micrometric length gold nanowires by selective self-organization and cold welding of gold nanorods in water induced by poly(ethylene oxide-st-propylene oxide) copolymers.
By monitoring the fast kinetics of UV-vis spectrum, we have put in evidence the end-to-end assembling of gold nanorods in water induced by the addition of the copolymer solution (figure 1). Figure 2 shows HR-TEM details of the junctions between the gold nanorods forming the micrometric nanowires. It appears that the assembled gold nanorods are not only in contact one with the other, but they are welded together.
Taking in account the results of UV-vis, HR-TEM, FTIR and SERS, we suggest the scenario shown in Figure 3 which goes along with a selective surface cleaning of the gold nanorod tips by interaction between CTAB and copolymers. This strategy is an easy way to produce micrometric metallic nanowires (up to several microns) by nanoscale cold welding. This is anticipated to be a possible future microfabrication technique with applications in the construction of interconnects for extremely dense logic circuits and flexible electronics, as well as 3D scaffolds for tissue engineering.


Figure 1 : Kinetics of the optical absorbance spectrum of gold nanorod assembly


Figure 2 : High-resolution transmission electron microscopy of twined and perfect end-to-end welding


Figure 3 : Scenario for the copolymer-induced cold welding of gold nanorods


Reference : S. Laza*, N. Sanson*, C. Sicard-Roselli, A. Aghedu and B. Palpant, Particle and Particle Systems Characterization 2013, DOI:10.1002/ppsc.201300026.