Ultraviolet-A (UV-A) and blue light (wavelength 365-405 nm) has been reported to exhibit photobactericidal activity. However, their lights, being of lower energy than UV-C, exhibit lower photobactericidal activity. In recent years, a more versatile UV source has been provided by the development of light-emitting diodes (LEDs), which yield constant illumination at a specific wavelength and do not contain mercury. UV-A and blue LEDs outperform UV-C LEDs in output power, irradiance, phototransformation efficiency, price, and non-hazardous to humans. Therefore, LEDs with their wavelengths hold promise for engineering uses. To increase the sterilization efficiency of UV-A and blue lights, we have been investigating the synergistic bactericidal activity of the combination of their lights and photoreactive substrates.​
1. Improvement of photobactericidal activity by the combination of phenolic acids and their derivatives.​
2. Development of the photo technology for disinfection in medical and food industries.