Hi
Im functionalising gold nanoparticles with thiolated oligos. Part of all (Or all that Im aware) protocols require spinning the final solution down at 13,300 rpm for 20 minute cycles to seperate any remaining unattached oligos. It seems like large amounts of the gold aggregate in this method even after 1 spin cycle. When the final product is examined under atomic force microscope this seems to be confirmed as there are large aggregates in solution and no smaller structures visible.
Does anyone have any experience with this method or advice?
Thank you so much Vasily and Cordula! Thats very helpful and informative. I have experienced a lot of frustration with these functionalisations and I will begin using your suggestions immediately.
If your nano particles was covered completely you will get the result from your current procedure. but if you looking or more easier process you should try centrifuge tube, Just like our previous paper.
http://www.tandfonline.com/doi/abs/10.1080/21691401.2017.1373656
You need to increase the concentration of oliges in order to prevent any chance for aggregation. in addition that try to monitor the absorption AuNps after the addition as well as try to check the speed of your centrifuge
Regards
Alaa is right, if particles agglomerate upon concentration they are not sufficiently stabilized, i.e. would agglomerate sooner or later anyway. You can calculate time necessary to separate the particles at given acceleration for a given size according to Stokes law. Given rotation speed may mean different acceleration according to given centrifuge geometry.
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