I am investigating laser ablation in water with TiO2 nanoparticles, Usually I get a homogeneous blue colour afterwards, as expected. But sometimes the particles turn grey and aggregate compeltely at the bottom of he suspension. Has anybody experienced something similar?
The aggregation is a stability/stabilization issue. See:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
and earlier presentations references therein. The (faint) blue color is small TiO2 (probably 200 - 300 nm) . The grey/white color is sub- and post micron aggregated material. TiO2 has a high density (4.2 g/cm3) and it needs to be small to keep in suspension. A good idea is to carry out a Stokes Law calculation.
The optimum concentration of phosphate should help you stabilize the system.
Thanks a lot, Sir. This is very helpful to me.
Do you think there are problems for the application in solar cells after aggregation?
Actually I have also performed SEM measurements and did not find any differences.
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