I am working on the liquid 29Si NMR test, but I only got a big peak around -110 ppm.
The original solution is H2O+TEOS+TPAOH, after 2 h, I took the water layer and do the extraction with octane to remove the potential TEOS in the water layer. Then the water layer sample was diluted with D20as the NMR sample. (the result in the attached)
The NMR sittings are just normal.
Is something special I should do in order to get the liquid 29Si NMR peaks?
Thanks in advance.
What are you expecting to see. Are you creating Nanoparticles? The signal you observe might be the NMR tube. NMR tubes are made from boro-silicate glass. Nanoparticles might be too large to give sharp lines and are silicates as well. They might be difficult to distinguish from glass.
I agree entirely with Clemens diagnosis.
The following reference may be useful:
Article An overview of the fundamentals of the chemistry of silica w...
Using a PTFE-FEP tube liner may be a useful option (and removing most of the lower part of the glass NMR tube - check with your local NMR expert before proceeding!)
Dear Clemens,
Thanks for your reply.
The NMR tube is the PTFE tube and NO silicon.
I am looking for the silica species by the NMR peaks, which would lead to the formation of zeolites.
I am following this paper:
Article Identification of precursor species in the formation of MFI ...
If the tube is not the source of the signals the peak might well be your nanoparticles. Try to measure a sample without silicon. There is always the possibility that the probe also has a small Si background. There are glass and ceramic parts in probes. Completely Si free probes are special constructuions.
Dear Clemens,
Thanks for your further response.
According to your suggestion, I did try to test the tube only and found that the same peak appeared.
I cleaned it again and don't have a chance to test again.
I planned to test the Si precursors during my zeolite synthesis (the mother solution include TEOS, NAAlO2, NaOH, ionic liquid (IL)and DI water)but no peaks beside that big one. Then I tried the solution only has TEOS, TPAOH (the same role of IL)and DI water, the result was in the picture.
According to the literature, I could get some peak:
Article Identification of precursor species in the formation of MFI ...
Could you please give comments about this?
Cheers,
Xuemin
Dear Xuemin, cleaning the tube will not help. The Silicon is in the glass. The tube is made from borosilicate glass. This will give a signal.
Unfortunately I can not get the full text of the paper you mention.
Clemens
Dear Xuemin,
if you want to be sure on the origin you should take a spectrum of the empty probe...for this line-width you simply can do it without lock.
Good luck
Alfred
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