Exact, no "solvents" exist, only strong acids for ZnO and preferably strong bases and hot for TiO2.

Alain

Exact, no "solvents" exist, only strong acids for ZnO and preferably strong bases and hot for TiO2.

Alain

You can use hot Aqua regia (nitro-hydrochloric acid). About 0.1 g of nanopowder per 10 cm3 of acid.

I assume you don't mean "dissolve", and if not, then also "suspend" is not the right term, biut shoul be "disperse". You want to make a colloidal dispersion, right?

Dissolution studies were conducted using Varian inductively coupled plasma optical emission spectrophotometer (ICP-OES) at room temperature (~25°C) at pH 7.5. This solution contained HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid). Dissolution at pH 7.5 was studied using seven ZnO samples of sizes 4, 7, 15, 17, 24, 47 and 130 nm with a solid loading of 0.5 g/L. ZnO and pH 7.5 buffer prepared in optima water were mixed in a 20 ml vial and then covered with aluminum foil to inhibit any photo-induced dissolution. This vial was then placed on a Cole-Parmer circular rotator for 24 hours. After completion of mixing, suspension pH was measured. From each reactor three aliquots (~ 1 ml each) were drawn out with a disposable syringe, passed through a 0.2 μm syringe-driven filter (Xpertek) into centrifugation vials, and centrifuged at 22000 rpm for 30 min to separate the solution from ZnO nanoparticles. Samples were analyzed using a Varian 720-ES inductively coupled plasma optical emission spectrophotometer (ICPOES) to quantify dissolved zinc. These centrifuged samples were diluted to 5 ml with 1 M HCl prior to analysis and the calibration was conducted with 5.0, 10.0, 25.0, 50.0 and 100 ppm Zn2+ standards prepared in 1 M HCl. The average and standard deviation of triplicate measures are reported for all dissolution measurements. Similar ICP-OES analysis of ca. 4 nm TiO2 nanoparticles has shown that filtration followed by centrifugation successfully remove all non-dissolved nanoparticles from the medium.

Read more on this thesis:

Dissolution and aggregation of zinc oxide nanoparticles at circumneutral pH; a study of size effects in the presence and absence of citric acid

R-A-Thilini Perera Rupasinghe

University of Iowa 2011

why would anyone try to "completely dissolve" nanoparticles, for what purpose? Please explain.

If I want to make a (true) solution ("solution" in the sense of a true chemical, physical solution, defined by thermodynamics what is characterizing a "solution"), then why I don't go in a shop, buy some ZnO and TiO2 and simply dissolve it? Why would I want to make nanoparticles first and then destroy them by dissolving?

What I still assume is that people in the field, als A. Ouerdane and R-A-Thilini Perera Rupasinghe with his thesis, still don't distinguish between "solution" and "(colloidal) dispersion".

I also somehow guess so when I read "successfully remove all non-dissolved nanoparticles from the medium."

It is extremely easy to dissolve ZnO and TiO2! no problem!

but when you try to make a colloidal dispersion of ZnO and or TiO2 nanoparticles, then you run into difficulties and you may find some particles don't want to be dispersed - but that is not a topic to be described by the term "solution".

You can find more about this in my RG pages.

The question I think is aimed towards forming a suspension of the particles, which has been clearly pointed out by all. However, still no exact answer :)

I too wish to know which organic/inorganic solvents can form a stable dispersion of ZnO.

We can only disperse ZnO and TiO2 in solvents.

Which, I mean? Water is a solvent, so are strong and weak acids !!

Both can dissolve in strong acid.  

please, I need to carryout U-V analysis on ZnO nanoparticle, which solvent can I use to form a solution of it.

I would take water containing a suitable surfactant.

we disperse ZnO in toluene, isopropanol and chlorobenzene for solar cell. you can use these solvents.