Views: 0 Author: Site Editor Publish Time: 2022-08-03 Origin: Site
2. Comparison of UV light sources
In the process of inactivating microorganisms, mainly ultraviolet rays in the 240-260 nm band play a role. Common UV disinfection products are mainly based on UV light output from low-pressure mercury lamps. With the continuous development of nitride material technology, UV LEDs based on nitrides with high Al composition have attracted attention. By comparing the characteristics of the two light sources, it is helpful to understand the performance differences between solid-state light sources and UV mercury lamps in the field of disinfection.
The efficiency of UV disinfection technology is mainly affected by the output wavelength of the light source and the dose of UV radiation. In 2011, a research team from the Technical University of Berlin designed and fabricated UV LED light source modules based on 269 nm and 282 nm, and used these two different wavelengths of UV solid-state light sources to inactivate Bacillus subtilis in water. The results showed that under the same UV irradiation dose, the inactivation effect of 269 nm on Bacillus subtilis was more thorough. In 2016, a research team from Seoul National University in South Korea studied the inactivation efficiency of UV LEDs and low-pressure mercury lamps on Escherichia coli and Salmonella. The results show that under the same irradiation dose conditions, the UV LED with a peak wavelength of 266 nm has a significantly better killing rate of the two bacteria than the low-pressure mercury lamp. The above experimental results show that there is a wavelength with the highest efficiency for the inactivation of a specific microorganism by ultraviolet rays.
The output wavelength of the UV LED can be set by adjusting the composition of the material in the active region, and the half-peak width is narrow, around 10 nm. Therefore, the output wavelength of UV LED can be adjusted arbitrarily between 200 and 365 nm, covering the range from UVA to UVC. For UV mercury lamps, the spectral range of this light source is very wide and cannot be adjusted. For example, low-pressure UV mercury lamps mainly output ultraviolet rays around 253.7 nm. The wavelengths and irradiation doses required for the inactivation of different microorganisms are quite different. Therefore, in the actual research of ultraviolet disinfection, it is difficult to use mercury lamps to identify and distinguish which specific wavelength has the best inactivation of a certain microorganism. efficiency. In addition to more flexibility in output wavelengths, compared with UV mercury lamps, UV LEDs are smaller in size and can easily prepare light source modules containing multiple wavelengths through integrated packaging, helping researchers to develop efficient disinfection light sources in a targeted manner.
The dose of ultraviolet radiation is mainly determined by the irradiation intensity and irradiation time of the light source. The researchers found that using ultraviolet rays with an irradiation intensity greater than 90 μW/cm2 for 30 minutes can effectively kill the SARS virus. This dose is the effective dose for the SARS virus. The new coronavirus is also an RNA virus. In theory, ultraviolet light can effectively kill the coronavirus. In practice, the deep ultraviolet inactivation dose of the new coronavirus needs further experiments by relevant departments and institutions to be clear. At present, the general reference is the inactivation dose for the SARS virus. Restricted by factors such as crystal quality, doping efficiency, and light extraction efficiency, the quantum efficiency and output optical power of UVC LEDs need to be improved. Under the condition of the same irradiation distance, the UV radiation intensity of UV LED cannot reach the level of UV mercury lamp temporarily. Therefore, in actual use, it is necessary to appropriately increase the working time of the UV LED and shorten the distance between the light source and the irradiated surface, so as to ensure an effective disinfection dose.
In addition to the freedom of output wavelength and the difference in output optical power, UV LEDs and UV mercury lamps are also different in terms of volume, turn-on speed, power consumption, reliability and safety. Compared with LEDs, UV mercury lamps are larger in size, take longer to start and warm up, cannot be used immediately, have high energy consumption, are fragile , and contain mercury, which poses a threat to the environment and human health. With the official implementation of the "Minamata Convention on Mercury", it is a general trend to replace traditional mercury-containing light sources with cleaner and more efficient UV LED light sources. With the characteristics of UV LED, technical application scenarios that cannot be realized by traditional UV mercury lamps will also be realized. For example, UV disinfection technology based on UV LED light source can be combined with personal electronic equipment to develop portable UV disinfection products.
