Exploring the Full Spectrum of UV-C Radiation: Analysis of Biocidal Potential from Far UV-C to UV-B Boundary Frequencies

Ultraviolet C (UV-C) radiation, particularly in the peak wavelength range of 260 to 265 nm, is remarkably effective in deactivating micro-organisms. This specific wavelength range causes the formation of genetic abnormalities known as thymine dimers and uracil dimers. These abnormalities disrupt replication and transcription processes, rendering the material non-functional. Mercury UV-C lamps have a long history of effective germicidal performance. They are widely used in healthcare and water treatment applications and have a proven track record. However, conventional mercury lamps, which emit UV-C light at 254 nm, possess limitations such as size, warm-up time and inherent risks to health and the environment. As an alternative, UV light-emitting diodes (UV-LEDs) have emerged as a viable option, offering instantaneous high-intensity light. UV-LEDs exhibit compactness, durability and economic feasibility. Furthermore, they do not contain mercury, ensuring a safer choice and maintaining a consistent output with low-temperature fluctuations. They can emit specific target wavelengths, such as the desired range of 260 to 265 nm, or very low frequencies, such as 232 nm (not too far from the 222 nm of excimer lamps), to effectively accomplish germicidal actions. Unfortunately, the more the wavelength decreases, the more the output power and efficiency of the LED falls. The main objective of this investigation was to compare the performance of four UV-C LEDs, each operating at distinct wavelength peaks, for the inactivation of three bacterial species.