Imagine a world where we can design and assemble materials from the ground up, atom by atom, much like how a house is built brick by brick. In such a world, researchers are free to customise the properties of materials to meet exact needs, from strength to durability to conductivity to optical properties.
This is the world of atomic-level engineering of materials—a relatively new field but one that has seen significant progress in recent years. When contrasted with nano-level engineering, the atomic approach offers even greater potential for control and precision. Nanomaterials often exhibit properties that are different from their bulkier counterparts. However, there is still a limit to the amount of control that can be achieved at the nano-level. At the atomic level, on the other hand, scientists can have complete control over the arrangement of atoms, which allows them to create materials with unique and exotic properties.
“This ability to modify materials at the atomic scale would be a tremendous boon for sustainability, where the overarching goal is to do more with less,” said Professor Konstantin Sergeevich Novoselov, Director of the National University of Singapore (NUS) Institute for Functional Intelligent Materials (I-FIM). “While such materials might be expensive and complex to produce, we only need a very small amount of them, and the transformative potential is so huge that it would be both economically and practically viable.”
Two primary applications currently underpin the field of single-atom modification: single-atom catalysis and coloured centres.
Catalysts, essential in modern industry, accelerate the speed of reactions without being consumed during the process. Nevertheless, they still degrade over time due to factors like contamination. Furthermore, the production of many catalysts often involves the use of costly noble metals.
By introducing a single atom of an element into a foreign crystal, researchers discovered that catalysts can be made more efficient. “This is a very good example of synergy and sustainability: taking two relatively inexpensive materials and combining them to achieve enhanced catalytic performance,” added Prof Novoselov.
The art of introducing impurities such as single atoms into crystals to alter their properties is not unique to modern science—nature has long practised this technique. For example, chromium impurities lend rubies their vibrant red, while vanadium bestows a mesmerising purple upon sapphires. Absent these specific atoms, what remains is the uncoloured corundum, or aluminium oxide.
Building upon this principle, researchers are exploring the use of single atomic impurities to create structures for single photon emitters, which are crucial for quantum applications such as quantum computing and telecommunication. One efficient method, compatible with modern electronics, involves creating quantum dots by incorporating foreign atoms into specific crystals. By understanding and controlling these atomic impurities precisely, there’s a huge potential to unlock expansive possibilities in the domain of quantum technology.
While the idea of engineering materials at the atomic scale is alluring, significant challenges persist. For instance, current technologies enable global modifications rather than targeted atomic replacements. What’s more, predicting the properties of atomic defects and devising methods for their synthesis require intensive number crunching that considers quantum effects.
“Machine learning offers some hope as we have now created vast databases detailing defects across various materials,” said Prof Novoselov. “Neural networks can be trained to grasp the nuances of quantum mechanics, which allows us to predict the properties of particular atomic impurities rapidly and accurately.”
The efficacy of machine learning hinges on the volume and veracity of data it receives. Curating databases for materials, especially those with impurities and defects, demands enormous efforts and collaboration. Research groups must implement coherent settings for their experiments and calculations.
From more efficient, cost-effective catalysts that transform a panoply of green-energy processes such as hydrogen production, to ushering in the quantum revolution with advancements in devices such as sensors, the atomistic control of materials aligns closely with the ethos of sustainability: doing more with less.