#24 - Specifics of fullerene C60 and C70 cluster formation in toluene /N-methyl-2-pyrrolidone solvent mixture.
CMR Posters
Poster author: Nagorna T.V.
Link to the poster: https://indico.jinr.ru/event/1165/attachments/8037/11891/Poster_Nagorna_Carbon_nanostructures.pdf
Avdeev Mikhail
Tetiana Nagorna
ak mi
1) Why does the <I> parameter increase with toluene addition (clusters are being destroyed, slide 6), when in the same time <I> increases with NMP addition (clusters formation, signal may be worse or not, slide 7) ?
2) Why do curves for C70 NMP+toluene (slide 8, 9) differ from equal curves for C60 (slide 10)? (with high fraction of NMP there should be curves with small, blurred peaks or smth like that, but one see quietly similar curves, except with 20% toluene). Also, why do we see something like hysteresis in both systems (in C70 and C60)? (curves corresponding to the same solution composition differ from each other)
3) How much time have you been waiting before the measurements (SANS, UV-vis spectrum) or you have used fresh solutions?
Tetiana Nagorna
Thank you for interesting questions!
1. Why does the <I> parameter increase with toluene addition (clusters are being destroyed, slide 6), when in the same time <I> increases with NMP addition (clusters formation, signal may be worse or not, slide 7) ?
Size of fullerene clusters C70 in the initial system C70 / NMP is above the range of sensitivity of the instrument and the signal from such systems stays at the background level. Addition of big fraction of toluene (70 and 80 vol.%) leads to destruction of big aggregates and just to signal detection of particles with the sizes less than D = 2π/qmin ≈ 70 nm.
At the same time, the spectrum of reverse system C70 / toluene is at the background level because of the difficulties in detecting fullerenes in their monomeric state. But the addition of NMP to the solution leads to the gradual rise in the scattering signal. I.e. with the increase of volume fraction of the polar solvent NMP the integral scattering intensity also starts to gradually rise
2. Why do curves for C70 NMP+toluene (slide 8, 9) differ from equal curves for C60 (slide 10)? (with high fraction of NMP there should be curves with small, blurred peaks or smth like that, but one see quietly similar curves, except with 20% toluene).
UV-vis spectra of fullerene solutions have their characteristic peaks. Thus, solutions with C60 fullerenes have a peak at 336 nm, while solutions with C70 fullerenes have a peaks at 315, 335, 366, 382, 472 nm. Absence of “blurry” peaks was achieved by taking measurements immediately after preparation.
Also, why do we see something like hysteresis in both systems (in C70 and C60)? (curves corresponding to the same solution composition differ from each other)
The inability to return to the original form of the spectra is associated with the temporary solvatochromic effect, and also the dependence of the form of the spectra on the method of preparing the system indicates a special interaction between fullerene and solvent molecules.
3. How much time have you been waiting before the measurements (SANS, UV-vis spectrum) or you have used fresh solutions?
The initial solutions were stored for 4weeks and the second solvent was added just before measurements.
4. Сan you explain the peaks broadening with toluene addition (slides 15-16)? (It seems that larger clusters appear in the system)
The broadening of the peaks is probably related to the technical features of detecting polydisperse particles. Thus, the intensity of scattering by bidisperse solutions is significantly lower than the intensity of scattering by monodisperse solutions.