Since their discovery in 1985, fullerenes—a unique class of carbon allotropes—have fascinated scientists and engineers. Named after architect Buckminster Fuller, due to their resemblance to geodesic domes, these spherical molecules are composed entirely of carbon atoms arranged in hexagonal and pentagonal rings.

The two most studied forms are:

• C60, also known as Buckminsterfullerene, a 60-carbon spherical structure resembling a soccer ball.

• C70, an elongated cage-shaped molecule with 70 carbon atoms.

Both molecules are part of the broader nanocarbon family (which includes graphene, nanotubes, and nanodiamonds), but they stand out due to their unique 3D cage structure, electron affinity, redox activity, and photophysical properties.

Today, C60 and C70 are used across nanotechnology, biomedicine, energy storage, coatings, and optoelectronics. This blog provides a detailed 4000+ word guide covering their history, properties, synthesis, applications, current research, and future directions—plus a comparative table for quick reference.

1. Structural Basics of Fullerenes

1.1 C60 Fullerene

• Consists of 60 carbon atoms.

• Geometry: Truncated icosahedron (like a soccer ball).

• 12 pentagons + 20 hexagons.

• Diameter: ~0.7 nm.

• Symmetry: Exceptional, leading to unique electronic and optical behavior.

1.2 C70 Fullerene

• Consists of 70 carbon atoms.

• Geometry: Ellipsoidal cage structure.

• 12 pentagons + 25 hexagons.

• Diameter: ~0.71 nm × ~0.79 nm (slightly elongated).

• Less symmetric than C60, giving different energy levels and reactivity.

2. Synthesis and Production

2.1 Common Methods

• Arc Discharge Method: Vaporizing graphite rods in inert gas → soot contains fullerenes.

• Laser Ablation of Graphite.

• Combustion Methods: Hydrocarbon combustion in controlled conditions.

2.2 Separation

• Mixtures of C60, C70, and higher fullerenes are separated via:

  • High-Performance Liquid Chromatography (HPLC).

  • Solvent extraction (toluene, xylene, CS₂).

2.3 Commercial Availability

• C60 is easier to produce in bulk → more widely used.

• C70 is harder to isolate but offers superior performance in specific optoelectronic and photovoltaic applications.

3. Properties

3.1 Electronic and Optical

• Both are electron acceptors (excellent n-type materials).

• Exhibit multiple redox states.

• High electron affinity, making them useful in organic photovoltaics.

• Absorb strongly in UV-visible spectrum.

3.2 Mechanical

• Extremely stable cage-like structure.

• High resilience against pressure.

3.3 Thermal

• Stable up to ~400 °C in inert atmosphere.

• Decompose above 600 °C in air.

3.4 Chemical

• Hydrophobic, soluble in aromatic solvents.

• Easily functionalized (hydroxylation, carboxylation, fluorination).

• Functionalized derivatives improve water solubility for biomedical use.

4. Applications of Fullerene C60

4.1 Energy and Electronics

• Organic Photovoltaics (OPVs):

  • C60 derivatives (e.g., PCBM) are classic electron acceptors in polymer solar cells.

  • High efficiency and stability.

• Organic Field-Effect Transistors (OFETs):

  • Used as n-type semiconductors.

• Superconductors:

  • Alkali-metal-doped C60 (A₃C60) shows superconductivity above 30 K.

4.2 Biomedicine

• Antioxidants: Scavenge free radicals due to high electron affinity.

• Drug delivery: Functionalized C60 can carry drugs across membranes.

• Photodynamic therapy (PDT): Generates reactive oxygen species (ROS) under light, useful for cancer treatment.

• Neuroprotection: Studied for diseases like Parkinson’s.

4.3 Coatings and Materials

• Lubricants: Reduce friction and wear.

• UV protection: C60 absorbs UV light, useful in cosmetics and coatings.

5. Applications of Fullerene C70

5.1 Energy and Electronics

• Photovoltaics:

  • C70 absorbs broader spectrum than C60 (especially in visible range).

  • Used in organic solar cells for higher efficiency.

• Photodetectors:

  • High sensitivity due to elongated shape.

• Nonlinear optics:

  • Strong third-order nonlinear susceptibility.

5.2 Biomedicine

• ROS generation: More efficient than C60 in photodynamic therapy.

• Drug carriers: Functionalized C70 derivatives exhibit improved bioactivity.

5.3 Advanced Materials

• Sensors: Gas sensing with higher sensitivity.

• Nanocomposites: Improves mechanical and electronic properties of polymers.

6. Current Research

6.1 C60

• Next-gen OPVs with non-fullerene acceptors replacing C60—but C60 derivatives remain reference materials.

• Cancer therapy using water-soluble C60 derivatives.

• Hybrid materials with graphene and nanotubes.

6.2 C70

• Improved performance in solar cells, especially tandem structures.

• Research into C70 nanocrystals for perovskite solar cells.

• Biocompatibility and safety studies for medical applications.

7. Challenges

• Cost: Especially for C70 due to difficult separation.

• Stability: Both oxidize under UV exposure without protection.

• Scalability: Large-scale, cost-effective production remains limited.

• Toxicology: Long-term health/environmental impact still under study.

8. Comparative Overview

9. Future Outlook

• Energy: C60 and C70 will remain central in organic photovoltaics until non-fullerene acceptors dominate.

• Biomedicine: Functionalized derivatives will expand into drug delivery, antioxidant therapies, and cancer treatment.

• Electronics: Continued role in sensors, OFETs, and photodetectors.

• Hybrid nanomaterials: Integration with graphene, nanotubes, and perovskites for multifunctional devices.

The combination of unique structure, versatile chemistry, and proven performance ensures that fullerenes remain vital nanocarbons for years to come.

Conclusion

Fullerene C60 and C70 represent two of the most iconic nanomaterials, bridging the gap between fundamental science and applied technology. From solar cells to cancer therapies, coatings to superconductors, they continue to inspire research and commercialization.

While C60 is more common and commercially available, C70 offers superior optical absorption and biomedical potential—making them complementary rather than competing nanomaterials.

As synthesis scales up and functionalization improves, expect both fullerenes to be indispensable tools in energy, medicine, and advanced electronics.