Balancing potency and durability: A new material for infection control

Door handles, train straps, and touchscreens at convenience stores—these are surfaces we touch every day. Invisible viruses may linger on them. Although regular disinfection helps, it is not easy to keep up continuously. Wouldn’t it be reassuring if there were a material that could weaken viruses simply by being there?

In recent years, inorganic materials such as photocatalysts, silver, and copper have attracted attention for antiviral applications. Among them, copper oxides have been studied extensively. In particular, cuprous oxide (Cu₂O) is known to have high antiviral activity—that is, a strong ability to inactivate viruses. However, Cu₂O has a major weakness. When exposed to moisture in the air, it gradually changes into a more stable but less active form called CuO. As a result, its antiviral performance can drop significantly within two weeks to a month.

Photocatalysts, on the other hand, work when exposed to light. But in real-life environments, light does not always reach every surface—for example, the back side of a doorknob or the corner of a room. This led researchers to consider oxides containing lanthanum (La) or yttrium (Y), which can show antiviral effects even in dark conditions. However, there had been little systematic evaluation of ternary oxides combining these elements with copper. Moreover, how such materials interact with viruses at the atomic level was not well understood.

To address this challenge, a research team led by Professor Akira Nakajima, Assistant Professor Yasuhide Mochizuki, and doctoral student Ryuju Kiribayashi (2nd year, PhD program) at Institute of Science Tokyo (Science Tokyo) investigated new ternary copper oxides, La₂CuO₄ and Y₂Cu₂O₅. They carefully examined both their antiviral performance and their underlying mechanisms using experiments and theoretical calculations.

The weakness of Cu₂O was already known. The real question was how to achieve both high antiviral activity and long-term durability. Overcoming this trade-off was the team’s biggest challenge.

Instead of modifying only the surface, Professor Nakajima and colleagues decided to redesign the crystal structure itself. A crystal structure describes how atoms are arranged inside a material. By carefully controlling this atomic arrangement, the researchers aimed to stabilize copper in its highly active state.

Their results showed that La₂CuO₄ and Y₂Cu₂O₅ exhibited stronger antiviral effects than single-component oxides against a type of non-enveloped virus, which can sometimes be resistant to alcohol-based disinfectants. The reason for this improved performance was supported by theoretical calculations. The surfaces of these ternary oxides tend to carry a positive charge, allowing them to attract viruses that carry a negative charge. In addition, copper on the surface remains in a special Cu⁺ state, which may help disrupt the structure of viral proteins and contribute to viral inactivation.

Perhaps most impressively, the material demonstrated remarkable durability. Even after one and a half years, La₂CuO₄ retained more than 70% of its initial antiviral activity—far longer than conventional Cu₂O.

The new material works even in dark and humid environments, and tests have confirmed that it does not show cellular toxicity. If applied as a coating on surfaces such as doorknobs, handrails, or medical equipment, it could help reduce viruses simply through everyday contact.

Furthermore, the idea of enhancing performance by designing materials at the level of crystal structure provides valuable insight for the development of next-generation antiviral materials.

Solid surfaces, viruses, and computational science may seem like unrelated fields at first glance. By connecting these three areas, we were able to reach a new understanding. The principles of natural science are always filled with mystery. The passion of the students and collaborators who worked together with me opened the door to uncovering that mystery.
（Akira Nakajima, Professor, School of Materials and Chemical Technology, Institute of Science Tokyo）

Nakajima-Isobe Laboratory

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