A group of researchers has succeeded in developing a chemical process to convert infrared into visible light. The technology, described in the journal Nature, could have far-reaching impact: infrared light therapy may be instrumental in treating a number of diseases and conditions, including traumatic brain injury, damaged nerves and spinal cords, hearing loss, as well as cancer; other potential applications include remote management of chemical storage solar power production and data storage, drug development, sensors, food safety methods, moldable bone-mimic composites and processing microelectronic components.
Infrared lamp. Image credit: Bernd Marczak.
“The findings are exciting because we were able to perform a series of complex chemical transformations that usually require high-energy, visible light using a noninvasive, infrared light source,” said study co-lead author Professor Tomislav Rovis, a researcher in the Department of Chemistry at Columbia University.
“One can imagine many potential applications where barriers are in the way to controlling matter. For example, the research holds promise for enhancing the reach and effectiveness of photodynamic therapy, whose full potential for managing cancer has yet to be realized.”
Professor Rovis and his colleagues carried out a series of experiments using small quantities of a novel compound that, when stimulated by light, can mediate the transfer of electrons between molecules that otherwise would react more slowly or not at all.
Known as triplet fusion upconversion, their approach involves a chain of processes that essentially fuses two infrared photons into a single visible light photon.
Most technologies only capture visible light, meaning the rest of the solar spectrum goes to waste.
Triplet fusion upconversion can harvest low-energy infrared light and convert it to light that is then absorbed by the solar panels.
Visible light is also easily reflected by many surfaces, whereas infrared light has longer wavelengths that can penetrate dense materials.
“With this technology, we were able to fine-tune infrared light to the necessary, longer wavelengths that allowed us to noninvasively pass through a wide range of barriers, such as paper, plastic molds, blood and tissue,” said study co-lead author Dr. Luis Campos, also from Columbia University.
Scientists have long tried to solve the problem of how to get visible light to penetrate skin and blood without damaging internal organs or healthy tissue.
Photodynamic therapy (PDT), used to treat some cancers, employs a special drug, called a photosensitizer, that is triggered by light to produce a highly reactive form of oxygen that is able to kill or inhibit the growth of cancer cells.
Current PDT is limited to the treatment of localized or surface cancers.
“This new technology could bring PDT into areas of the body that were previously inaccessible,” Professor Rovis said.
“Rather than poisoning the entire body with a drug that causes the death of malignant cells and healthy cells, a nontoxic drug combined with infrared light could selectively target the tumor site and irradiate cancer cells.”
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Benjamin D. Ravetz et al. 2019. Photoredox catalysis using infrared light via triplet fusion upconversion. Nature 565: 343-346; doi: 10.1038/s41586-018-0835-2
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