I used ethanol and water for sample preparation but in both case my material agglomerated at the bottom. Can you suggest me a proper solution for particle size analysis?
It depends on the particle size, the nanometer size range TiO2 powders will disperse very well in aqueous medium. If you try to ultrasonicate the TiO2 particles, the structural morphology will not change. But Ag particles are bit different. The ultrasonication would result either large aggregate or collapse it shape, size and structure. So properly choose the dispersion medium, and try a short - low frequency sonication. I would recommend using an organic solvent as a dispersion medium to prevent any oxidation of Ag particles. Take a precaution that the Ag nano particles are highly sensitive to light, so try to conduct the experiment in dark or shadow place. Good luck.
Did you vortex the mixture thoroughly to ensure the nanoparticles are polydisperse in the solution, this may help tackle the agglomeration.
No i haven't tried ultrasonic vortex. May be it is suitable for TiO2 , but i'm afraid of aggregating my sample. But at least i may try it.
Both are well dispersible in water. You should avoid drying as an intermediate step.
It seems your particles are already highly agglomerated.
Thanks Titus as you said i managed to disperse both of my materials in the water. I found some data in an article related to ultrasonic mixing values.
Hi Yusuf, TiO2 will aggregate at neutral pH (its isoelectric point is around pH 4-5), try redispersing them in acidified (pH 2) ethanol/water mix that should help. But just out of curiosity, how do you synthesise your nanoparticles and how do you remove them from the synthetic medium prior to redispersion?
As Titus wrote, try not to dry your sample after the synthesis. After the synthesis make at least 3 washes with water (if you use centrifuge) and then prepare your sample for DLS.
I thank you all for your help but i do not synthesise the particles, i asked just for analysis.
Usually 10mM NaCl (or other buffer) aqueous solution it's ok. If you use a mixture of sovents (eg. water/alcohol) then the viscosity and refractive index (for a certain temp.) of the mixture should me known.
If the particles agglomerate try to sonicate the sample solution before measuring.
It depends on the particle size, the nanometer size range TiO2 powders will disperse very well in aqueous medium. If you try to ultrasonicate the TiO2 particles, the structural morphology will not change. But Ag particles are bit different. The ultrasonication would result either large aggregate or collapse it shape, size and structure. So properly choose the dispersion medium, and try a short - low frequency sonication. I would recommend using an organic solvent as a dispersion medium to prevent any oxidation of Ag particles. Take a precaution that the Ag nano particles are highly sensitive to light, so try to conduct the experiment in dark or shadow place. Good luck.
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