Gold nanoparticles play an important role in the development of metamaterials, and are used in numerous optical applications, including medical imaging, environmental sensing, and therapeutics. Yet these nanoparticles are only effective in strengthening optical signals when they are arranged in a precise pattern on a specially prepared surface. This arrangement and patterning process requires harsh chemicals and tightly controlled lab conditions. A discovery made by a team at McGill University could provide a simple, eco-friendly way to arrange gold nanoparticles into ultrathin sheets, strengthening the particles’ optical properties, and ultimately resulting in cheaper, more sustainable optical materials. The researchers developed a method to organize gold nanoparticles into precise patterns using affordable, ecological plant-virus proteins as scaffolding. They developed plasmonic nanostructures templated by tobacco mosaic virus coat protein (TMVP). Biotemplates like the one developed by the McGill team could increase the sustainability and lower the costs of developing materials for solar panels, sensors, cameras, microscopes, and other optical devices. “This is about using nature’s building blocks to make technology cleaner, cheaper and smarter,” professor Amy Blum said. The team modified the protein by tagging it with a short chain of histidine. Essentially, the histidine acts like tiny hooks that latch onto the gold nanoparticles and guide the proteins to self-assemble into ultrathin sheets. The TMVP assembles into disks, which further assemble into extended nanostructures, forming large, ultrathin sheets with either hexagonal or square packing and core-shell nanorods. Gold nanoparticles are attached to the disks within each nanostructure to form assemblies of nanoparticle rings. Without the histidine tagging, the protein exhibited a tendency to clump. Weaker interactions, in contrast, encouraged the proteins to lay flat. “We rely on a large number of very weak interactions,” Blum said. “If I have one, it definitely won’t hold together. If I have 15, it’ll hold it very, very rigidly.” The modifications made by the team enabled the TMVP to self-assemble into sheets in water and at room temperature, with gold nanoparticles appropriately spaced to optimize their effectiveness. “If you just chuck these nanoparticles on a surface, some fraction of them will randomly cause enhancement,” Blum said. “But if you can get them to be at a fixed, good distance, then the whole surface is active.” To ensure safety, the researchers did not use the active virus to build the template. “We just use the shell, which contains no genetic material,” Blum said. The researchers found that, under certain conditions, the large, ultrathin sheets demonstrated the ability to roll up into nanoscale tubes. Future investigations could provide insight into whether these nanotubes have the potential to function like nanoscopic fiber optic cables. Biotemplating is one way to organize nanoscale components with high precision, and several biological nanomaterials have been used for templating metal nanostructures. Depending on the template, advantages can include customizability, scalability, sustainability, low cost, and high spatial precision. With biotemplates, the nanomaterials used to enhance optical properties in diverse applications can be made at lower cost and with less environmental impact. Designing a diverse library of viral templates could enhance materials processing, by providing a way to develop a range of advanced nanomaterials under mild conditions, with nm precision, for optical applications ranging from lenses, to nanoantennas, to solar panels. The research was published in Small (www.doi.org/10.1002/smll.202507076).