Frequently asked questions
How do you determine the purity of fullerene derivatives?
The purity of our fullerene derivatives is generally determined by HPLC and 1H NMR analysis. In this way, we check for the purity of the fullerene compound (HPLC), for the correct structure (NMR and HPLC), and for residual solvent residues (NMR).
For our products, we have strict rules regarding their purity, and how this is to be determined. The analytical data of a specific compound/batch are always available upon request. Just send us an e-mail and we can send you further information.
Why is the color of my new PCBM different from that of a previous batch?
This is a normal phenomenom, and nothing to worry about. The color of solid fullerene derivatives sometimes varies, because of small differences between batches in for example the particle size and powder density. As a result, the color of the PCBM can vary between brown and black.
Do you have fullerene derivatives with a different LUMO level than PCBM?
Yes, we do. The LUMO level varies with the type of fullerene derivative, and it is therefore possible to change it.
Derivatives that have LUMO levels above that of PCBM are, for example, IPH, bisPCBM, and ICBA. These compounds have LUMO levels that are 30-150 mV above that of PCBM. It is possible to go even further. Derivatives of C60-fullerene with a LUMO level below that of PCBM are quite rare, but we sell KLOC-6, which has a LUMO level approximately 150 mV below that of PCBM.
Why are most fullerene derivatives listed as 99% purity only?
This is common practice for fullerenes. We could easily label all our materials as 100% pure by HPLC, but we don’t. Why? Well, first of all small solvent residues are often present. Second, for C60 fullerene it is easy to get >99.5% purity by HPLC. However, upon derivatization, such a high purity becomes more complicated to reach. The HPLC will often give a single peak, thus suggesting 100% purity, but evidently the side-products are difficult to separate from the main product because of the small differences between the compounds.
What kind of impurities are present in fullerene derivatives?
Common impurities are isomers of the main compound (e.g. ethyl ester instead of methyl ester in PCBM), as well as small amounts of oxidized fullerenes.