UVC radiation
Effective tool for disinfection
The recent COVID-19 pandemic has emphasized the need for developing effective and convenient methods to disinfect surfaces in hospitals, workplaces, and other public areas. Furthermore, the growing threat of antibiotic resistance of bacteria has become an urgent, global concern. Addressing this problem requires a multidimensional approach, emphasizing not only the development of new antibiotics but also prioritizing the prevention of bacterial and viral infections. Effective cleaning and disinfection methods are essential to achieve this. Utilizing ultraviolet C (UVC) radiation for microbial inactivation has emerged as a common strategy to address this challenge.
UVC light is the radiation of the wavelength between 100 and 280 nm. Since the 1930s, it has been known that UVC radiation possesses germicidal properties. Wells [1] demonstrated the effectiveness of 254 nm radiation on aerosolized B. coli, proving that airborne infectious organisms could be eliminated in a short amount of time. The peak germicidal effectiveness occurs around 260–265 nm, which closely matches the absorption maximum of nucleic acids, particularly DNA and RNA. When microorganisms are exposed to UVC light, the radiation is absorbed by their nucleic acids, leading to the formation of thymine dimers and other photochemical lesions [2]. These structural changes inhibit DNA replication and transcription, ultimately rendering the microorganism inactive or unable to reproduce. This mechanism makes UVC radiation highly effective against a broad spectrum of pathogens, including bacteria, viruses, and fungi. Because it works without the need for chemical agents or high temperatures, UVC is widely used in applications such as water and air purification, surface sterilization, and medical equipment disinfection.
The first devices used for disinfection purposes were mercury lamps [3], which are still commonly used today due to their high effectiveness in microbial inactivation. However, they have several drawbacks, such as the toxicity of mercury, high energy consumption, long warm-up times, and undesirably large size. Light-emitting diodes (LEDs) can also serve this purpose; however, their practical application is limited by a low external quantum yield that decreases rapidly at wavelengths below 375 nm [4]. Therefore, there is an urgent need to develop new UVC light sources that are highly efficient in luminescence, free of toxic materials, and environmentally friendly. We are confident that the material developed through our project will support the advancement of novel and innovative UVC radiation sources.
It is also worth mentioning that the potential of visible-to-UVC upconverters extends beyond disinfection. Since UVC light is invisible to the human eye, Pr3+-doped upconversion materials hold significant potential for static and dynamic labeling, as well as information encryption under sunlight excitation [5]. Additionally, Vis-to-UVC upconverters have been used to enhance photocatalytic reactions by pairing UC luminescence agents with UV-responsive photocatalysts [6].
Bibliography:
[1] Wells, W.F.; Fair, G.M. Viability of B. Coli Exposed to Ultra-Violet Radiation in Air. Science (1979) 1935, 82, 280–281, doi:10.1126/science.82.2125.280.b.
[2] Besaratinia, A.; Yoon, J.; Schroeder, C.; Bradforth, S. E.; Cockburn, M.; Pfeifer, G. P. Wavelength Dependence of Ultraviolet Radiation‐induced DNA Damage as Determined by Laser Irradiation Suggests That Cyclobutane Pyrimidine Dimers Are the Principal DNA Lesions Produced by Terrestrial Sunlight. The FASEB Journal 2011, 25 (9), 3079–3091, doi: https://doi.org/10.1096/fj.11-187336.
[3] Hart M. D., D. Sterilization of The Air In The Operating Room by Special Bactericidal Radiant Energy: Results of Its Use in Extrapleural Thoracoplasties. J Thorac Surg 1936, 6, 45–81, doi:https://doi.org/10.1016/S0096-5588(20)32445-4.
[4] M. Kneissl, T.-Y. Seong, J. Han, H. Amano, The emergence and prospects of deep-ultraviolet light-emitting diode technologies, Nat Photonics 2019, 13, 233-244, doi: https://doi.org/10.1038/s41566-019-0359-9.
[5] Zi, L.; Li, L.; Wang, C.; Yang, F.; Feng, S.; Lv, P.; Yang, Y. Triple‐Responsive Visible‐To‐Ultraviolet‐C Upconverted Photons for Multifunctional Applications. Adv Opt Mater 2024, 12 (6), 2301881, doi: https://doi.org/10.1002/adom.202301881.
[6] Du, Y.; Jin, Z.; Li, Z.; Sun, T.; Meng, H.; Jiang, X.; Wang, Y.; Peng, D.; Li, J.; Wang, A.; Zou, H.; Rao, F.; Wang, F.; Chen, X. Tuning the 5d State of Pr3+ in Oxyhalides for Efficient Deep Ultraviolet Upconversion. Adv Opt Mater 2024, 12(30), 2400971, doi: https://doi.org/10.1002/adom.202400971.