Field-Assisted Efficient\nCapturing and Analysis of\nAirborne Nanoparticulate Matter Using a Multifunctional Nanoporous\nMembrane

As the potential adverse health and environmental effects\nof nanoscale\npollutants have garnered significant attention, the demand for monitoring\nand capturing ultrafine particulate matter has been growing. With\nthe rise in ultrafine dust emissions, this issue has become increasingly\nimportant. However, submicron particles require advanced strategies\nto be captured because of their limited inertial effect. For example,\nelectrostatic air filters have been investigated for their improved\nperformance in the fine particle regime. On the other hand, Raman\nspectroscopy was proposed as a promising analytical strategy for aerosol\nparticles because it can be used to conveniently detect analytes in\na label-free manner. Thus, the synergistic integration of these strategies\ncan open new applications for addressing environment-related challenges.\nThis study presents a multifunctional approach for achieving both\nair filtration and surface-enhanced Raman scattering (SERS) for analyte\nidentification. We propose a nanoporous membrane composed of a thin\ngold layer, copper, and copper oxide to provide the desired functions.\nThe structures are produced by performing scalable electrodeposition\nand subsequent electron-beam evaporation, attaining an excellent filtration\nefficiency of 95.9% with an applied voltage of 5 kV for 300 nm KCl\nparticles and a pressure drop of 121 Pa. Raman intensity measurements\nconfirm that the nanodendritic surface of the membrane intensifies\nthe Raman signals and allows for the detection of 10 μL of nanoplastic\nparticle dispersion with a concentration of 50 μg/mL. Rhodamine\n6G aerosol stream with an approximate particle deposition rate of\n0.040 × 10<sup>6</sup> mm<sup>–2</sup>·min<sup>–1</sup> is also identified in a minimum detectable time of 50 s. The membrane\nis shown to be recyclable owing to its structural robustness in organic\nsolvents. In addition, the fatigue resistance of the structure is\nevaluated through 22,000 iterative loading cycles at a pressure of\n177 kPa. No performance degradation is observed after the fatigue\nloading.