Colleagues,
Sorry for long e-mail. These are questions for
those of you who worked with solid state NMR,
particularly with solid state NMR of conductive
samples.
One of our professors works with functionalized
carbon nanotubes . There are two properties that
make these samples "special" from NMR point of
veiw: (A) nanotubes are electric conductors; and
(B) the samples may contain a lot of
ferromagnetic metal particles (10-20% w/w) coming
from a catalyst used for synthesis (there may be
some other factors beside A and B which are
important, but I am not aware of them).
I tried to run solid state 13C NMR of his samples
but experienced some technical problems. I am not
a "solid-state" person, and I apologize if my
questions sound too trivial or naïve.
Here are the problems:
1) No wobble curve for pure samples is
observed. Only significant dilution by kaolin
makes the tuning possible.
2) Difficult (although possible) to spin
(more difficult than regular organic samples).
3) Arcing while running HP decoupling and CP
(no arcing for regular organic samples with the
same proton power levels; significant dilution by
kaolin eliminates the arcing).
I know that electric conductivity makes tuning
problematic. I understand that ferromagnetic
particles will broaden the spectra. Here are my
questions. Can conductivity of the sample
contribute to the two other problems? Can
ferromagnetic particles contribute to any of
these problems? Any tricks that may be useful
while working with this staff? Are these
problems sensitive to the instrument
configuration (we use a narrow bore Avance 500
with a CP-MAS 4 mm probe; this is the only "solid
state" NMR we have). Any input and relevant
references will be greatly appreciated. I can
tell the professor to get rid of most metal
particles (it is not easy to do but possible in
principle), but first I want to be sure that it
will help to solve at least some of the problems.
Best regards.
Alex Kitt
--
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Dr. Alex Kitaygorodskiy (Alex Kitt) Phone: 864-656-0611
Director, NMR Facility Lab: 864-656-3577
Chemistry Department Fax: 864-656-6613
Clemson University kkitayg_at_clemson.edu
Clemson, SC 29634-0973
http://chemistry.clemson.edu/chemdocs/faculty/kitaygorodskiy.html
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Received on Fri Sep 10 2004 - 18:22:45 MST