I want to get individual single-walled carbon nanotube (CVD) in water by using 1wt%SDS. I have tried the most powerful experimental methods in my lab including 200W tip-type sonicator for 3 h as well as ultracentrifuge (200,000g) for 2h. But the UV-vis spectra never show any small peaks in the range from 300 nm to 1100 nm. Only an absorption peak at 256 nm was observed. I am thinking that whether UV is sensitive enough for my measurement. In case of the detection of individual single wall carbon nanotube, is PL or Raman measurement more sensitive than UV?
The OD of my tubes is 1-2 nm. Can the absence of (6,5) and (7,6) SWCNT absorption peaks result from very low content of (6,5) and (7,6) SWCNT?
There could be a number of reasons for that... I don't think it's bad individualisation, but u may want to try sodium cholate as surfactant as this usually exfoliates better. Probably the composition of your starting material is different so the absorbance spectrum will be different as well. You can have a look in the Hersam DGU paper (Sorting carbon nanotubes by electronic structure using density differentiation. Nature Nanotechnology 1, 60-65, (2006).) there are some spectra of other tubes species as well. Another reason may be that the tubes are defectous and then the excitonic transisitions (both abs and PL) are quenched, So you should measure Raman to make sure this is not the case. In terms of technique, Raman will not easily tell u whether the tubes are individualised. PL usually only makes sense when u see nice transitions in the abs spectra as well. If u don't see anything there, u will not see ath in PL either
Raman spectroscopy. Look at the paper "Raman Spectroscopy of Carbon Nanotubes" by MS Dresselhaus.
Thanks a lot for your kind suggestion, Claudia! I think the possibility of the second cause associated with defects induced by sonication is very low. Since in the first one hour of sonication, I measured the UV spectra in every 10 mins. If there are some individualizations of (6,5) and (7,6) SWCNT, I should see some adsorption peaks.
Maybe your tubes are intrinsically defectous... Have u measured Raman on the pristine powder? What was your D/G?
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