Hello,I have prepared the ZnO suspension in ethanol following a solution method. However, having filtered by a 0.22μm pore size nylon membrane, the ZnO (whose size is within 10nm theoretically) was all missing. Could anyone tell me whether it is caused by cluster effect? How could I avoid it? Thanks.
You have filtered off all your material as all of it is aggregated > 220 nm. See:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
November 3rd, 2015 Adhesion and cohesion http://tinyurl.com/zwb2wlh
I suggest centrifugation to wash the particles.
Article Synthesis and testing of ZnO nanoparticles for photo-initiat...
We use these filters to remove ZnO nano and micro clusters during water experiments because the particles agglomerate and they tend to be attracted to the filters (likely static attraction). I would suggest centrifuging to wash particles, and a zeta potential and/or TEM measurement of non-filtered sample to check your true size vs. agglomeration. If you want to avoid agglomeration you can to look into a capping agent with appropriate pKa, and even then, it's not perfect.
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