This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Since the COVID-19 pandemic, developing surfaces that can inactivate viruses upon contact has become an important goal in public health care. Ideally, such surfaces would work on their own without requiring chemical disinfectants, so they could offer consistent protection in hospitals, public transportation and other shared spaces.
This has driven scientists worldwide to search for durable antiviral materials that can be used in everyday surfaces. Although several options have already been developed and studied, they come with important limitations. Antiviral materials based on silver or copper are effective; however, they suffer from discoloration and performance degradation over time, and silver is also costly.
Meanwhile, those based on rare-earth elements pose supply and cost risks because the necessary raw materials are unevenly distributed around the world. Thus far, reports of inexpensive yet highly effective materials made from earth-abundant elements have been few and far between. To address this challenge, a research team led by professor Akira Nakajima and graduate student Kotaro Miyazaki from the Department of Materials Science and Engineering, School of Materials and Chemical Technology, Institute of Science Tokyo (Science Tokyo), Japan, investigated whether a simple mechanochemical treatment could improve the antiviral performance of manganese (Mn)-based complex oxides.
Their study, published online in RSC Mechanochemistry, was conducted in collaboration with the Next-Generation Life Science Technology Development Project at the Kanagawa Institute of Industrial Science and Technology (KISTEC), Japan. The team first prepared four Mn oxides, each paired with a different common element: zinc, copper, yttrium and bismuth, obtaining ZnMn2O4, CuMn2O4, YMnO3 and BiMn2O5, respectively. Each material was then ground in a ball mill together with ethanol, a process that breaks particles into much smaller pieces and reshapes their surfaces.
The researchers tested how well the milled and pristine materials could inactivate a bacteriophage called Φ6, a virus with an outer envelope similar to those of influenza and SARS-CoV-2. Milling boosted antiviral performance in every material tested, far beyond what could be explained by the increase in surface area alone. The copper-containing oxide stood out, as Nakajima says, "CuMn2O4 exhibited an extraordinary increase in antiviral activity per unit surface area, exceeding 5,000 times that of the untreated material." Detailed analysis showed that milling created new chemically reactive spots on the particle surfaces called Lewis acid sites.
These sites are believed to capture viruses by binding to their outer structures, allowing Mn-driven oxidation reactions to more efficiently damage viral surface lipids and proteins. In the case of CuMn2O4, the researchers also found that surface ethoxy groups formed during milling in ethanol further enhanced antiviral performance. Because Mn is inexpensive and widely available, this approach could support the development of affordable antiviral coatings.
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