Why do oyu want to *dissolve* the TiO2 nanoparticles, if you do, then they are gone!

If you want to prepare a *colloidal dispersion* (I do not like the term "colloidal solution", because a colloidal system is not a solution! it is a dispersion! Solutions and dispersions are completely different systems, they are as different as day and night, plus and minus, cold and hot, or thermodynamically spoken: equilibrium systems (solutions) and non-equilibrium systems (dispersions).

- you can find some basic publications about this in my RG pages.

For a colloidal dispersion, you can easily find enough references in the web, like

http://pubs.acs.org/doi/abs/10.1021/la026252q

To dissolve? I think you can treat with dil acids. if you want to make colloidal solution or dispersion try surfactants in non polar organic solvents.

You can use different base fluids such as water , oil etc..but the most difficult thing is that to disperese it ..I mean stability of nanofluids.As I am practically working with various types of nanofluids ,I have found that if you use surfactant lyk PVP ,oleic acid etc.. according to your base fluids.. But application of surfactants can also bring about some cahnges on the surface properties in nanosuspension...So be careful about your preparation regarding your area of study...

Why do oyu want to *dissolve* the TiO2 nanoparticles, if you do, then they are gone!

If you want to prepare a *colloidal dispersion* (I do not like the term "colloidal solution", because a colloidal system is not a solution! it is a dispersion! Solutions and dispersions are completely different systems, they are as different as day and night, plus and minus, cold and hot, or thermodynamically spoken: equilibrium systems (solutions) and non-equilibrium systems (dispersions).

- you can find some basic publications about this in my RG pages.

For a colloidal dispersion, you can easily find enough references in the web, like

http://pubs.acs.org/doi/abs/10.1021/la026252q

I am totally agree with you sir! its dispersion!

Colloidal dispersion is not a true solution.

I have used m-cresol to dissolve TiO2 and I have found it a better solvent for TiO2

why you all still use the term "dissolve"? If you *dissolve* TiO2 nanoparticles, tehre are no nanoparticles any more, you have TiO2 molecules individually solvated (surrounded) by the solvent molecule. Not only m-cresol can not do that, also you don't want it to happen because then the nanoparticles are gone.

You want to DISPERSE these nanoparticles!

What is wrong with using the correct term? "dissolving" and "dispersing" are terms for processes which can't be more difefrent, it is like plus and minus, day and night, right and left, 180 and 360 degrees, equilibrium and nonequilibrium.

If you say "it does not matter, we know what we want to say", then I tell you: ok then "electron and positron are also the same, doesn't matter, also Plus and minus - no meaning!"

In fact, solvatation and dispersion are (thermodynamically spoken) totally different, after dissolution, the system is in thermodynamical equilibrum, after dispersion, it is a non-equlibrium system with many very characteristic properties, especially so-calld dissipative structures. I have made a lot of publications about it, you can search here in RG, I have also theoretically described these non-equilibrium system (based on my experimental work)

Dear Prof. Bernhard Wessling,

In CVD method for thin film preparation, solvent is must used to dissolve or disperese. Can you give more tips for nanoparticles (SnO2, ZnO) to make a thin films. 

Q1: Which solvent i want to use ? Why ?

Q2: If you completely dissolved nano-particles. Whether it shows any problem in magnetism ? 

(I am not a professor, just a researcher / scientist)

Q1: I am not familiar with SnO2, ZnO nanoparticle dispersion, but usually, one would take solvents whose solubility parameter is close to the one of the nanoparticles you want to disperse, close, but not identical, and not too far away (no rules how close); or, if a bigger distance, then moderated by tensides

Q2: if you dissolve magnetic nanoparticles, their magnetism will be gone (1 single Fe atom is not magnetic!)

Dear Selvarajan Ethiraj

The nanoparticles of TiO2 are insoluble in polar and non-polar solvents. The correct term is dispersion. You can check the following manuscript:

Article Ultrasonic Dispersion of TiO2 Nanoparticles in Aqueous Suspension

dear Selvarajan,

Yes, its true that they dont get dissolve in any of the polar or non polar solvents except strong acids. they appear like dispersions in solvents other than strong acids.