I'm using PVP and TiO2 nano particles. And i can't use ultrasonic bath, because i scare that the properties of nano particles will change in ultrasonic bath.

Mr mohammad Razzaghi, You can keep the solution under vacuum condition about 30 min or 60 min. I hope this will be useful for u. I am also using the same technique.

Sometimes the bubbles are made because of glass surface. I do not know how you clean your glass surface but if you even use the Kimwips, they remain some tiny particles on glass surface which cause bubbles when the doctor blade is moving on surface. The other possibility can be pipetting the casting solution on glass. It should be done, very slowly and patiently to reduce the possibility of bubble creation.

Before keeping solution in dark, you can apply slow stirring for longer..may be helpful..

If you can use of an ultrasonic bath you can remove bubbles from your solution rapidly and completely.

Pay attention during using ultrasonic the temperature of solution increase rapidly.

how can an ultrasonic bath change the properties of your nano particles?

After 24 h it should not be gas bubbles in dope solution. We always use rest time or 5 min ultrasonication to remove bubbles. If your membranes are pierced, that is not because of gas bubble. Check your glass plates and the knife. Also the temperature of the nonsolvent bath affects it.

TiO2 is a very stable nanoparticle therefore ultrasonication can not affected on TiO2

keep ur solution in freeze, but not in freezer. it will definitely help.  

Hi,

I've used Tio2 nano particles and PVP before. There is no problem with using Ultrasonic bath and the results was good.

So don't scare about that. Just do it.