A Filter for Light-based Airborne Microbe Sterilization
The National Research Foundation of Korea announced on March 8 that Korea Institute of Industrial Technology senior researcher Choi Dong-yoon and Sejong University mechanical engineering professor Jung Jae-hee have proposed a filter for visible light-based airborne microbe sterilization.
At present, antibacterial filters using inorganic antibacterial substances such as silver, copper oxide and zinc oxide and those using natural organic substances such as chitosan are available for microbial sterilization. However, these require a direct microbial contact with a treated fiber surface and their performance tends to decline with time due to particular matter deposition.
In this regard, the research team aimed to devise a filter capable of affecting nearby microorganisms on the surface of the filter. To this end, it produced titanium dioxide-organic dye composite nanoparticles generating active oxygen in response to visible light and improved the surface in terms of moisture resistance and photochemical sterilization.
Titanium dioxide as a well-known photocatalyst generates active oxygen for microbial sterilization by reacting to oxygen and water when it absorbs ultraviolet rays. However, the rays are rather limited in terms of everyday use. Researchers are focusing on visible light-based photocatalyst activation as an alternative, but the complexity of the process is hindering the research.
The research team simplified the manufacturing process by using an organic dye reacting to visible light on titanium dioxide nanoparticles after hydrophobic surface modification and formed a three-dimensional nanostructure in the filter with a complex fiber structure by the single-particle aerosol technique. As a result, the efficiency of active oxygen generation was improved along with the performance of particulate matter removal and moisture stability.
The team conducted an experiment with the filter and staphylococcus epidermidis and the filter showed an antibacterial performance of 99.9 percent in four hours in an indoor lighting environment of 2.9 mW/cm2 and 99.98 percent in one hour under the light of the sun (18 mW/cm2 to 21 mW/cm2). Still, the team is yet to reach commercialization and the goal requires additional research on the optimization of active oxygen generation linked to nanoparticle attachment stability enhancement and human safety evaluation depending on active oxygen concentration. Details of the research are available in the Feb. 24 edition of Nano Letters.