I have Ni-CdSe and CdSe Nanowires grown via electrodeposition in AAO templates with Ag film on the back, after dissolving the templates I'm left with the wires stuck to the Ag film.
I have tried sonication (with times suggested in literature and much longer), didn't work well. Does anyone know what is the optimum time for doing so?
Also etching away Silver with Nitric Acid before dissolving the template didn't work (CdSe was etched too).
Wow, usually people would be very happy with keeping their nanowires stuck to the substrate instead of having them breaking at the bottom and falling down... What are the dimensions of your wires? Maybe the aspect ratio is too small for breaking them from the substrate... Otherwise, could you please tell me your trick for keeping the nanowires standing on the substrates?
Hi Wouter.
I'd like them in a suspension because my next step would be making contacts to a single wire for measurements. Diameters are around 200 nm (found that pores of AAO are sometimes bigger than the 200 specified) and height around few microns.
Actually I haven't done anything special! I just thermally evaporated a film of Silver to the template, did the electrodeposition, dissolved the AAO template and after viewing the Silver film under SEM, the wires appeared coming out from silver film and some was also broken on the top as expected. I just need them free for dropcasting later and making devices. Do you know a way of doing that?
Then the dimensions shouldn't be the problem. A solution I could think of is to make the Ag layer thinner (100-200 nm should be enough for the electrodeposition) so that it will break apart during ultrasonication and release the NWs. I hope this will help...
Do you have to dissolve the AAO template? Just try to wipe your nanowires off the substrate. You should be able to have some nanowires you can perform your measurements on. Alternatively, use a drop of polymer, e.g. PMMA. When it dries you can remove it from your substrate - hopefully with some nanowires. Dissolve PMMA in e.g. anisole. Centrifuge nanowire solution few times purging with fresh anisole till you have a clean suspension of your nanowires. Another option would be to use adhesive tape instead of PMMA.
Just scratch with a scalpel or something similar, then pour drops of solvent along the cutting edge. Collect the drops and sonicate to avoid agglomeration of NW. I've prepared several nanowire samples for TEM this way and it works just fine.
Usually is a matter of sonication power. (better a sonication probe than a sonication bath) If you have a sonicator strong enough I guess you can remove wires with such aspect ratio.
http://www.hielscher.com/cascatrode-sonication-probe.htm
If you have access to liquid nitrogen, try dropping your sample in it, with the idea of the difference in thermal expansion coefficients doing the work of releasing the semiconductor nanowires from the metal surface.
If you will be making the samples again, use some other (more reactive, easier to dissolve) metal instead of Ag.
Dear Mirette
What is the ideal time for sonication that you found in literature to transferr the NWs from its substrate?
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