NaOH etching will remove Al2O3, and may not effect SnO2..

see this: DOI: 10.1039/b714904b

Can't say about ZnO though.

NaOH etching will remove Al2O3, and may not effect SnO2..

see this: DOI: 10.1039/b714904b

Can't say about ZnO though.

Hi Marta ..these materials are ceramic materials and are not soluble in any of the solvents. The maximum you can do is make a suspension out of these materials (by size reduction). Even the hydrooxides are not soluble in any of the solvents.

Boiling H2SO4 Dissolve Al2O3 but i don't know it dissolve SnO2 or Not!

Sridhar, thank you, it realy help me. I will try with 5% NaOH and I have hope that will work.

Subhendu, I know that this is ceramic materials, but it's no problem. In my experiment, Al2O3 is the AAO template. It can be successfully dissolve by 5% NaOH or 5% H3PO4. Unfortunately, I didn't know how would behave in these conditions SnO2 and / or ZnO. Now I know that with the SnO2 is likely to succeed with NaOH.

There is still a valid question about ZnO.

Dear Marta: An alternative to alkaline dissolution is by using controlled acid attack: First you should verify which alumina phase is contained in the composite. The more stable and resistance to chemical attack is the so called alfa-alumina (British nomenclature). In this case you can try a buffer solution with pH between 4 and 5 (e.g acetic acid-sodium acetate/ or citric acid- sodium dihydrogenphosphate) to dissolve the alumina phase statically, at a temperature of about 150 C for about 8 h, autogeneously pressured. Experimental runs to test solubility of SnO2 and ZnO under the same conditions should also be carried out.

All these 3 oxides are amphoteric oxides that means that can be react with both bases and acids. Up to my knowledge ZnO reacts more easily than Al2O3 (depents the type α-, β-, γ-, δ-, η-, θ-, and χ-) and SnO2 with acids and bases. If you are lucky and have a type of Al2O3 that reacts more easily than ZnO with acids and bases you can try the controled reaction with with acids or bases. There is also something else to try. Both ZnO & SnO2 are heavier than Al2O3. You can start with centrification of dispersions of these materials, collect always the fraction close to the bottom and diluted with water then centrification and so on. Theoritically the fraction close to the bottom after every centrification it will be reacher in SnO2 and/or ZnO.

Your question is not clear. Did you use Al2O3 as a template to synthesize ZnO or SnO2 nanostructures? then you want to remove template? Is this what you mean? If so, it is not difficult to find the way to do it from a lot of literature.

if you have good experience in Organic Chemistry I will advise to use so called piranha solution, mixture of hot H2SO4 and H2O2 (70/30). You have to be extremely careful with this solution. I used it for etching of Al2O3

In nmp

65-75 % H3PO4 can dissolve the Al2O3

How about this ? at pH 12 ?

http://pubs.acs.org/doi/abs/10.1021/am501912q

I am asking about any solvent for SnO2 or ZnO to be prepare solution for Optical measurements? 

if we use NAOH very low molarity below 0.01M at 60 Celsius for 1-hr..but if need more care to avoid any damage decrease the temp as well as time . 

Hi 

Please find the attached file that discussed the dissolution in molten cryolite