Lower-cost, more reliable diagnostic testing could be a light at the end of the nanophotonic tunnel … or barrel, in this case. A barrel-shaped molecular container called cucurbituril (CB) that acts as a mini test tube has been developed by a team at the University of Cambridge, in collaboration with the school’s Melville Laboratory for Polymer Synthesis, as well as researchers in Spain and France. It allows single molecules to enter and effectively isolates them. Now, the researchers have discovered that by using and manipulating light — and adding particles of gold a few thousand atoms across that self-assemble with the nanobarrels at room temperature — they can detect what is in the barrel. Light can be manipulated at the nanoscale, allowing researchers to detect and study molecules inside a barrel-shaped container. Courtesy of Gen Kamita and Jeremy Baumberg, University of Cambridge. “Shining light onto this gold-barrel mixture focuses and enhances the light waves into tiny volumes of space exactly where the molecules are located,” said Dr. Jeremy Baumberg, a professor of nanophotonics in Cambridge’s physics department. “By looking at the colors of the scattered light, we can work out which molecules are present and what they are doing, and with very high sensitivity.” The prospect of observing individual or small numbers of molecules “in a sea of others” is something that has long appealed to scientists, he added. The new technology could also work as a low-cost, rapid, plasmonic sensor. The researchers have begun developing such a diagnostic sensor, which could be used in testing biological fluids, as well as detecting neurotransmitters in the brain. “We’re starting to learn how we can make materials that respond optically to the presence of individual molecules in biological fluids,” Baumberg said, adding that this could make doctor visits and clinical testing more efficient because patients would not have to send samples to a lab. Eventually, this technology will allow real-time observation of molecules, the researchers expect. “We want to understand how we can go further with the technology, from controlling chemical reactions happening inside the barrel, to making captured molecules inside flex themselves,” Baumberg said. “At the moment, we are capable of assembling new structures with different optical properties in a highly controlled way. Eventually, though, we will be able to build things with light itself.” The work was funded in part by the European Union and the Engineering and Physical Sciences Research Council. For more information, visit www.cam.ac.uk.