Multifunctional Electrospun Nanofiber Air Filters for Removing Particulate Matter and Sensing Formaldehyde Gas Simultaneously

Particulate matter (PM) and volatile organic compounds (VOCs) in contaminated air have harmed human health and the global biosphere. PM is defined as particles smaller than 10 µm in size and composed of ionic, metal, and carbon components. VOCs are invisible gases made up of dangerous CO, NO₂, and HCHO (formaldehyde). Many filters for treating PMs and VOCs, which cause a variety of ailments, have been developed, but people are still becoming exposed to these contaminants.<br/>Electrospinning has been explored with significant interest among many methods for fabricating air filters because of its unique ability to produce nanofibers with adjustable permeability and porosity. Various electrospun nanofiber filters with better PM removal performance and lower pressure drops than commercial filters have been developed. However, electrospun nanofiber filters were challenging to maintain their morphology due to weak mechanical properties and be uniformly deposited on non-conductive substrates by instability from the electrospinning process.<br/>Removing VOCs with adsorption frameworks is generally ineffective compared to PM removal. Meanwhile, colorimetric nanofiber membranes have been demonstrated for their rapid color changes induced by VOC reactions without the need for expensive equipment or a controlled environment. Still, these nanofiber membranes or mats have been revealed in treating one type of air pollutants, such as PM or VOCs.<br/>In this study, we proposed a fabrication process of electrospun nanofiber filters that remove PM while also detecting formaldehyde gas. By our methods, fabricated nanofiber filters were uniformly and directly deposited on non-conductive masks and showed self-assembled structures that could possess a high PM removal rate and moderate pressure drop compared to commercial filters. As a representative indoor VOC capable of causing underlying death even at low concentrations, formaldehyde was also colorimetrically detected by changing the color of nanofiber filters that can effectively remove PM. As a result, the fabrication of an electrospun nanofiber filter that can simultaneously perform PM capture and formaldehyde detection in complex air pollution was successfully demonstrated. We believed that this fabrication process is pioneering work for producing nanofiber filters for capturing PM and synchronously sensing VOCs and that it could provide new insight into the production of multifunctional electrospun nanofiber filters.<br/>This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1C1C100944311) and BK21 FOUR Program by Pusan National University Research Grant, 2021. Jin Yeong Song is grateful for financial support from Hyundai Motor Chung Mong-Koo Foundation.