Scientists achieved a chemical-physical process to transform infrared radiation into visible light, which could then be used to accelerate reactions of specific interest. The result can now be used in various applications ranging from therapies for some types of cancer to solar panels.
This chemical-physical process is designed by researchers at Columbia University in New York and Harvard University.
The study is part of a broad field of research called "Photoredox catalysis", with the goal of exploiting the energy of light to accelerate a chemical reaction by shifting a single electron. In recent years, photoredox catalysis has achieved promising results, using stimuli in the visible spectrum or ultraviolet as input.
A new process to convert infrared into visible light
The new photochemical process is carried out by a compound that can be thought as a myriad of molecular-sized bulbs that absorb infrared light from one side and re-emit visible light to the other side. As an intermediate step, this new process paves the way for producing a photoredox catalysis activated by the infrared.
Hence the authors' idea of exploiting the radiation that lies beyond the upper limit of visible wavelengths, where the infrared spectrum is found, which has a greater capacity to penetrate biological tissues. It is a chain of processes that joins two photons - the light quanta - of infrared radiation in a single visible photon.
"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 Tomislav Rovis, professor of chemistry at Columbia and co-author of the study.
This method, used to treat certain types of cancer, uses a special chemical compound, called photosensitizer, which is triggered by light to produce a highly reactive form of oxygen, capable of killing cancer cells or inhibiting their growth. In its current form, photodynamic therapy is limited to the treatment of superficial bladder cancer tumors. But things could soon change with the new photochemical process, which could act as an intermediate step: absorb infrared and emit visible light to activate a photosensitizer.
Other possible applications concern technologies that can only capture visible light. For example, photovoltaic panels waste the rest of the solar spectrum. In this case, the approach developed by Rovis and colleagues can collect low energy infrared light and convert it into light that can be absorbed.
"With this technology, we were able to fine-tune infrared light to the necessary, longer wavelengths needed to non-invasively pass through a wide range of barriers, such as paper, plastic molds, blood, and biological tissues," concluded Luis Campos, associate professor of chemistry at Columbia and co-author of the article.
Other possible uses include remote supervision of chemical storage, solar power production, and data storage, drug development, sensors, food safety methods, moldable bone-mimic composites, and microelectromechanical systems.