state some possible uses of fullerenes
Answers
Fullerenes can make excellent antioxidants, this property can be attributed to the large number of conjugated double bonds they possess and a very high electron affinity of these molecules (due to low energy of the unoccupied molecular orbital). Fullerenes can react with a number of radicals before being consumed. A single C60 molecule can interact with up to 34 methyl radicals before being used up. That is why, these molecules are also known as the 'world's most efficient radical scavengers' or 'radical sponge'. Perhaps, one of the major advantages of using these molecules as an antioxidant is that these can be localized within the cell.
Antiviral Agents
Fullerenes have grabbed quite a bit of attention due to their potential as antiviral agents. Perhaps the most exciting aspect of this may be their ability to suppress the replication of the human immunodeficiency virus (HIV), and thus, delay the onset of acquired immunodeficiency syndrome (AIDS). Dendrofullerene 1 and Derivative 2, trans isomer have been seen to inhibit the HIV protease, and thus, prevent replication of HIV 1. Bivalent metal derivatives of amino acid derivatives of fullerene, like C60-1-Ala, are also seen to be active against HIV and human cytomegalovirus replication. These molecules are usually inserted in the hydrophobic domains of proteins (binding site of protease in HIV).
Another target for amino acid derivative of fullerene is the reverse transcriptase in HIV, these molecules are seen to be more active than the non nucleoside analog inhibitors usually used. Cationic fullerene derivatives are antibacterial and antiproliferative in nature. Most fullerene derivatives can inhibit hepatitis C virus.
Drug Delivery and Gene Delivery
Drug delivery is the proper transportation of a pharmaceutical compound to its site of action, whereas gene delivery is the introduction of foreign DNA into cells to bring about a desired effect. It is therefore of utmost importance to deliver these molecules with safety and great efficacy. Fullerenes are a class of inorganic carriers, these molecules are preferred as they show good bio compatibility, greater selectivity, retain the biological activity, and are small enough to be diffused. DNA sequences are attached to the amino acid derivatives of fullerene. These sequences detach from their carrier with the loss or denaturation of the amino groups. Biochemical studies have shown greater protective abilities of these derivatives as compared to the traditional vector used.
Photosensitizers in Photodynamic Therapy
Photodynamic Therapy (PDT) is a form of therapy of using non-toxic light sensitive compound which, when exposed to light, becomes toxic. This is used to target altered and malignant cells. Fullerenes are usually used as these compounds. Fullerenes get excited upon irradiation, when these molecules return to ground state, they give off energy that splits the oxygen present to generate singlet oxygen, which can be cytotoxic in nature.
Solar Cells
A polymer-based organic photovoltaic cell may be the answer to finding an economical and lightweight medium for the conversion of solar energy. These solar cells basically work by transfer of electrons from a material that gets excited when irradiated with light (known as the donor). This electron in its excited state is taken by an acceptor molecule, which is transferred further to the electrode. Fullerenes, due to their high electron affinity and ability to transfer these electrons, make excellent acceptors. These organic photovoltaic cells are complexes of fullerenes and polymers, and are called bulk heterojunctions.
Phenyl-C61-butyric acid methyl ester (PCBM) is a common acceptor used in organic solar cells. It usually used in conjunction with the polymer polythiophene (P3HT) as an electron donor.