Carbon nanomaterials, for example, have become more and more common in recent years for their remarkable properties and ubiquity in electronics, materials science and biotechnology. The most studied and most useful carbons are carbon nanotubes (CNTs) and fullerenes. And while they have the same building block - carbon - they are very different in structure, composition and function.
Introduction to Carbon Nanotubes and Fullerenes
Carbon Nanotubes (CNTs): CNTs are cylinder nanotubes, formed by one sheet of graphene wrapped into a tube. They're also sometimes called single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs), depending on the layer of graphene. CNTs have great mechanical, electrical and thermal stability, and hence they are the ideal choice for just about any application.
Fullerenes: Fullerenes are closed hollow carbon molecules molecule types. Most well-known fullerene is C60, a soccer-ball (long icosahedron). Fullerenes are like carbon nanotubes made up of carbon atoms but are much more complex in shape: they are spherical or close to it.
Comparing Carbon Nanotubes and Fullerenes
Below is a detailed comparison of the key features of carbon nanotubes and fullerenes:
| Feature | Carbon Nanotubes (CNTs) | Fullerenes |
| Structure | Cylindrical, either single-walled (SWCNT) or multi-walled (MWCNT) | Spherical or nearly spherical, often referred to as C60 (football-like structure) |
| Shape | Tube-like, with a long aspect ratio (high length to diameter ratio) | Closed hollow structure (e.g., C60, C70) with a spherical shape |
| Electronic Properties | Can be metallic or semiconducting depending on chirality (twist) | Generally semiconducting; strong electron acceptor properties |
| Mechanical Properties | Extremely strong, lightweight, and flexible with high tensile strength | Mechanical strength is lower compared to CNTs, but stable under various conditions |
| Applications | Electronics, nanocomposites, energy storage, drug delivery, sensors | Drug delivery, photovoltaics, catalysis, lubrication, electronics |
| Synthesis Methods | Chemical vapor deposition (CVD), laser ablation, arc discharge | Arc discharge, laser ablation, chemical vapor deposition (CVD) |
| Chemical Reactivity | High reactivity, particularly at the tube ends and defects, suitable for functionalization | Can accept electrons, undergo addition reactions, often used for catalysis |
| Stability | Stable, but may be sensitive to environmental factors like temperature and chemicals | Generally stable, but can be affected by UV radiation and oxygen |
| Size | Diameter typically 1-100 nm, length can reach several micrometers or more | Typically 0.7-1 nm in diameter, varies depending on the fullerene type |
| Electronics | Excellent electrical conductivity, used in field-effect transistors (FETs), sensors | Used in organic solar cells, organic field-effect transistors (OFETs), and photonic devices |
How to Choose Between Carbon Nanotubes and Fullerenes?
In practical applications, the choice between carbon nanotubes (CNTs) and fullerenes depends on the material properties and the specific application requirements. Below are some factors to consider that can help in making the choice across different fields:
| Application Field | Carbon Nanotubes (CNTs) | Fullerenes |
| Mechanical Strength | Extremely high tensile strength and flexibility, suitable for high-strength applications | Lower mechanical strength, suitable for applications requiring high chemical stability |
| Electrical Properties | Tunable metallic or semiconducting properties, suitable for electronic devices and sensors | Primarily used as electron acceptors, suitable for photovoltaic materials, electron injection materials, etc. |
| Surface Functionalization | High reactivity, suitable for drug delivery, sensors, and composites | Suitable for electron addition reactions, commonly used in catalyst supports and drug delivery |
| Optical Applications | Suitable for optoelectronic devices, such as LEDs and lasers | Suitable for organic photovoltaic cells and photoconversion |
| Environmental Impact | Further research needed on environmental impact and biodegradability | More suitable for environmental protection and biodegradation applications |
| Cost Effectiveness | Lower cost, suitable for large-scale applications | Complex synthesis, higher cost, suitable for high-end and specialized applications |
Conclusion
To summarise, carbon nanotubes and fullerenes are similar amazing things, yet their structures, electronic structure, mechanical robustness and uses vary a great deal. Carbon nanotubes can be applied to applications where mechanical strength and electrical conductivity are important: they are good for electronics, energy storage, and sensors. In contrast, fullerenes better suit electron-accepting, catalytic and drug-delivery uses due to their spherical nature.
Both materials have enormous applications, and scientists are still coming up with new strategies for how they might be exploited in other technologies. CNTs versus fullerenes will likely depend more on the specific application: strength and compatibility of CNTs or electron-accepting ability of fullerenes.
