[physics_student]

Hi!
I am a physics student and am doing a master in physics/chemistry and I have to make a presentation for an article, but there's something I don't understand...

When the author explains the preparation of a sol-gel solution, he gives the concentration as follows :

zinc acetate dihydrate (99.5% Zn(OAc)2, Riedel-deHaen) in
diethylene glycol (99.5% DEG, EDTA)

What does 99.5% mean? And Riedel-deHaen? Does this mean that there is 99.5% (weight?) and 0.5% of Riedel-deHaen, and what IS Riedel-deHaen?
Same thing for the one below... Is it 99.5% DEG and 0.5% EDTA? Weight or volume?

I suppose this must be standard for chemists, but I am not used to seeing these, and though I understand the general idea, I need to be 100% certain if I am to make a presentation explaining the procedure...

Thank you very much.

[Dan]

What does 99.5% mean? And Riedel-deHaen? Does this mean that there is 99.5% (weight?) and 0.5% of Riedel-deHaen, and what IS Riedel-deHaen?

According to google, Riedel-deHaen is a chemical supplier and I suspect that 99.5% is the purity of the zinc acetate supplied by that company. DEG = diethylene glycol, and again 99.5% is probably purity - not sure what the EDTA is doing there.

Can you give a reference to the article, it will be easier to help you if we know where to find it?

[physics_student]

Here is the reference :
K.F. Lin, H.M. Cheng, H.C. Hsu, L.J. Lin and W.F. Hsieh, Band gap variation of size-controlled ZnO quantum dots synthesized by sol–gel method, Chem. Phys. Lett. 409 (2005), p. 208

[Dan]

Ok so the method is to heat a solution of zinc acetate in DEG to get a suspension of ZnO [the procedure can be found in ref. 24, which you should read]. This is the centrifuged to separate "single crystalline ZnO QDs" from the "secondary ZnO clusters". The authors then go on to list the concentrations of starting solution as 0.04, 0.06, 0.08, 0.10, 0.16 and 0.32 M (= molar = mol/L) they have used to obtain ZnO QDs of different average sizes.

In both cases, 99.5% refers to the purity of the chemical used, Riedel-deHaen is a chemical supplier. The EDTA still is unclear to me. Maybe there's a supplier called EDTA, which is a very confusing name for a chemical supplier, not sure...

[physics_student]

Well thank you very much... As I said before, I did get the general idea but I just wondered if it meant anything particular, like something that was standard in chemistry...
In ref. 24, which I had read too, they used the same description of solvents, so that didn't help much for this particular questioning.

Anyway, that's all I wanted to know, so thanks a lot!

[democanarchis]

Ok so the method is to heat a solution of zinc acetate in DEG to get a suspension of ZnO [the procedure can be found in ref. 24, which you should read]. This is the centrifuged to separate "single crystalline ZnO QDs" from the "secondary ZnO clusters". The authors then go on to list the concentrations of starting solution as 0.04, 0.06, 0.08, 0.10, 0.16 and 0.32 M (= molar = mol/L) they have used to obtain ZnO QDs of different average sizes.

In both cases, 99.5% refers to the purity of the chemical used, Riedel-deHaen is a chemical supplier. The EDTA still is unclear to me. Maybe there's a supplier called EDTA, which is a very confusing name for a chemical supplier, not sure...

EDTA is ethylenediaminetetraacetic acid, I would assume its 99.5% diethylene glycol with 0.5% of EDTA as a process impurity

[dunno260]

I would imagine the EDTA is there to chelate the zinc and help get it into the solution, but that is a semi-wild guess.  I doubt the concentration of it is that high as a process impurity.

[democanarchis]

Ah, read it as two separate substances, the ZnOAc2 and the DEG. Still, I wouldn't be sure it was 0.5% EDTA if not stated, could be other impurities present. You'd need to look at a cert of analysis I guess.

plysics_student, you don't really get chemicals at 100% purity. Most reagents are 98-99.5% pure.