This set of Nanotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Heterofullerene”.
1. What happens when odd numbers of carbon atoms are replaced by other elements during formation of heterofullerenes?
a) Radical formation takes place
b) Lead to closed shell systems
c) Fragmentation of cages
d) Result in opened shell systems
View Answer
Explanation: In heterofullerenes, one or more carbon atoms are substituted by heteroatoms such as boron, oxygen, silicon, nitrogen etc. Replacement of an odd number of carbon atoms lead to radicals that are stabilized by dimerization. On the other hand, the replacement of an even number of carbon atoms result in closed shell systems.
2. The multiple functionalization of aza[60]fullerene is not possible.
a) True
b) False
View Answer
Explanation: Although multiple functionalization of heterofullerene is a challenging task, scientists have accomplished it. The first multiple functionalization of aza[60] fullerene with organic addends was accomplished via template mediated addition of malonates into octahedral [6,6] – bonds of the fullerene framework.
3. What are heterofullerenes with nitrogen atom in them called?
a) Fullerides
b) Azafullerenes
c) Fullerols
d) Borafullerenes
View Answer
Explanation: Heterofullerenes are a group of modified fullerenes in which one or more carbon atoms of the cage are replaced by another element. Now there exists the borafullerenes – substituted by boron, azafullerenes – substituted by nitrogen. Other elements known to form heterofullerenes are oxygen, phosphorus, germanium etc.
4. Which of the following methods lead to formation of heterofullerenes?
a) Krätschmer – Huffman vaporization of graphite in presence of BN
b) Hummer’s method of oxidation of graphene oxide
c) Cluster rearrangement within iminofullerenes
d) Sonication followed by centrifugation
View Answer
Explanation: All efforts to produce heterofullerenes via Krätschmer – Huffman vaporization of graphite in the presence of hetero-element containing compounds like boron nitride (BN) or cyanogen (CN)2, have failed. An alternative method that has considerable success in direct formation of heterofullerenes is cluster rearrangement within exohedral fullerene derivatives such as iminofullerenes and azafulleroids.
5. When was the first synthesis of heterofullerenes in bulk amounts accomplished?
a) 1992
b) 1990
c) 1993
d) 1995
View Answer
Explanation: Heterofullerenes were first synthesized in bulk quantities in 1995. Azafullerene C59N and its dimer (C59N)2 were the earliest heterofullerenes to be formed efficiently in the gas phase.
Sanfoundry Global Education & Learning Series – Nanotechnology.
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