Convert blue light to ultraviolet light in an environmentally friendly way
Receiving the right amount and type of UV light is beneficial to us. Beyond that, ultraviolet radiation can cause skin burns and cause other problems.
Ultraviolet light is subdivided into three types based on wavelength: A, B, and C.
Ultraviolet-B light has many applications today, but conventional methods of producing it require toxic substances.The new system causes blue light from LEDs to be transformed into ultraviolet-B light without having to use these substances. (Image: Kyushu University)
Ultraviolet-A (UVA) contains the long-wavelength ultraviolet light that reaches the Earth’s surface, while the shorter-wavelength ultraviolet-B (UVB) and ultraviolet-C (UVC) are absorbed in its mostly by the ozone layer.
It was discovered some time ago that artificially produced ultraviolet-B and ultraviolet-C light here on the Earth’s surface are useful in applications such as disinfection.
Specifically, ultraviolet-B light has been applied in processes that include photochemical reactions, deactivation of pollutants, and wastewater treatment.
It is used in the medical field as part of treatments for skin disorders like eczema and vitiligo.
However, the generation of ultraviolet-B light currently requires sources such as mercury lamps, whose efficiency leaves much to be desired and which are also toxic to the environment if disposed of improperly at the end of their useful life.
One way to generate ultraviolet-B light without all that trouble is to do it by “up-converting” photons of light produced by LEDs.
Upconversion is a method in which a material absorbs two lower-energy photons of light and combines their energy to emit a higher-energy photon of light. This method is used with several special organic materials.
For several years two research teams have been working together to evaluate various compounds capable of transforming blue light from LEDs into ultraviolet light in the manner described.
One such team is the one led by Nobuhiro Yanai from Kyushu University in Japan. The other is led by Christoph Kerzig of the Johannes Gutenberg University of Mainz in Germany.
Finally, they have managed to carry out the transformation of blue light from LEDs into ultraviolet-B light using alternative chemical substances without having to resort to the use of heavy metals as traditional methods do.
Now, the new process needs to be perfected to increase its efficiency.
Yanai, Kerzig, and their colleagues discuss the technical details of their new process in the academic journal Angewandte Chemie under the title “Blue-to-UVB Upconversion, Solvent Sensitization and Challenging Bond Activation Enabled by a Benzene-Based Annihilator.”