Prepared by Dr. Mohammed M. Obeid and Dr. Salwan Obaid Waheed Khafaji
Mechanical Power Technology and Al-Mustaqbal Energy Research Center
"Carbon is one of the important elements in the periodic table and can be termed the "Magic Element" due to its involvement in many applications that touch our daily lives. Its ability to form various allotropes during the chemical bonding process of its atoms (sp, sp², sp³) under suitable manufacturing conditions of temperature and pressure is remarkable. One of the most practical examples is graphite (Graphite-sp²), which is used in pencils and the negative electrode of lithium batteries, as well as the diamond (Diamond-sp³) allotrope, which is used as a cutting tool and ornament. Graphite, a three-dimensional allotrope, is the most stable form and is widely found in nature, while diamond requires special conditions for its formation.
It is natural for readers to wonder: Are there other allotropes of carbon that differ in their dimensions?
To clarify the existence of additional dimensions of carbon, let’s start with the zero-dimensional allotrope. Fullerene (Fullerene C60-sp²) is the first ultra-small substance discovered and manufactured in the laboratory in 1985. Its discoverers were awarded the Nobel Prize in Chemistry in 1996. This substance consists of 12 pentagons and 20 hexagons (as shown in Figure 1), and it is primarily used for drug delivery and clean energy storage.
Following this incredible discovery of fullerene, carbon nanotubes (nanotubes-sp²) were produced as a one-dimensional allotrope by vaporizing graphite. Known as "Fibers of the Future," they are manufactured with specific diameters and lengths, ranging from 1-2 nanometers in diameter to lengths visible to the naked eye, and they vary in shape depending on the wrapping method. Not only are carbon nanotubes one-dimensional, but there are also strips of carbon hexagonal rings arranged in a coordinated atomic sequence, known as graphene nanoribbons. The properties of these nanotubes or ribbons vary based on the wrapping method and the edge shape, allowing for a wide range of applications in electronics and beyond (see Figure 1).
Graphene (Graphene-sp²), a two-dimensional allotrope, is one of the strangest and most important forms of carbon discovered today. Single layers of graphene were successfully created in the laboratory through simple mechanical exfoliation of three-dimensional graphite using adhesive tape. As a result, Andre Geim and Konstantin Novoselov, who led the discovery team, were awarded the Nobel Prize in Physics in 2010. Graphene is the thinnest known material today, with a thickness of 3.4 angstroms (as shown in Figure 1). It is 200 times stronger than steel, "to penetrate a layer of graphene, we would need the weight of an elephant balanced on a pencil," and it is an excellent conductor of heat and electricity while being semi-transparent. The discovery of graphene is one of the most significant scientific breakthroughs due to its various applications in electronics and medicine today.
Thus, we can quote, "Carbon is a simple element at its core, yet it reshapes itself like a great artist. Every atom is capable of painting a new world."
After observing the many allotropes of carbon across different dimensions, it is important to note that their manufacturing or discovery has relied for years on trial and error. Therefore, we should question the potential role of artificial intelligence in discovering new allotropes. Recently, the topic of artificial intelligence and its predictive capabilities in material discovery has won Nobel Prizes in Physics and Chemistry, making it one of the essential tools in our current age. Given the flexibility of carbon atoms to bond with each other and form various hybridizations, along with the structural defects and differences in crystal structures, we can say that using generative algorithms to create theoretical atomic configurations of carbon with extreme accuracy, based on quantum mechanics, is not far-fetched! There are many innumerable allotropes of carbon with different dimensions that have been designed and simulated for various applications such as batteries, reducing carbon footprints, hydrogen storage, solar cells, and electronic applications. The designed materials (some of which have been synthesized in the lab) possess unique chemical, physical, thermal, electrical, and mechanical properties not found in the aforementioned allotropes. This uniqueness arises from having more than one hybridization within the same structural framework of the designed allotropes, resulting in rare properties (as shown in Figure 1).
Thus, we can quote, "Artificial intelligence is our new telescope. It illuminates worlds of atoms we would not have seen if we continued to work with traditional methods," Ian Foster.
In conclusion, discovering carbon allotropes is no longer a matter of chance; it has become a data-driven science where scientists rely on artificial intelligence to accelerate these discoveries, mimicking atomic arrangements and predicting the properties of forms we have yet to see. This "infinity" of carbon configurations is the secret to its strength, making the combination of carbon and artificial intelligence a limitless world of possibilities to solve humanity's greatest challenges, from clean energy to advanced medicine, thus achieving many of the 17 Sustainable Development Goals."
### References
1. "The era of carbon allotropes," Nature, 2010, 9, 868-871. [1] A. Hirsch
2. G-H Lee et al. "High-Strength Chemical-Vapor–Deposited Graphene and Grain Boundaries," Science, 2013, 340, 1073-1076.
3. M. Obeid et al. "Design of Three-Dimensional Metallic Biphenylene Networks for Na-Ion Battery Anodes with a Record High Capacity," ACS Appl. Mater. Interfaces, 2022, 14, 32043−32055.
