Electroactive and breathable protective membranes by surface engineering of dielectric nanohybrids at poly(lactic acid) nanofibers with excellent self-sterilization and photothermal properties

Biodegradable poly (lactic acid) (PLA) nanofibrous membranes (NFMs) are appealing to address the increasing air pollution and outbreak of epidemic diseases, as well as the drastic accumulation of plastic and microplastic pollutions. Central to the development of high-performance PLA membrane filters are the promotion of electroactivity, polarization and electret properties, which has been a roadblock toward efficient capturing of airborne particulate matters (PMs) and bacterial pathogens. Herein, we proposed a microwave-assisted synthetic approach to enable direct growth of ZIF-8 nanocrystals at carbon nanotubes (CNT@ZIF-8 nanohybrids), which were spontaneously embedded into PLA nanofibers by a combined electrospinning-electrospray technology. With uniform and affinitive anchoring of CNT@ZIF-8 (8, 10 and 12 wt%), the PLA NFMs were characterized by largely increased surface potential (up to 1.78 kV), nearly doubled dielectric constant, and excellent triboelectric properties (output voltage of 12.7 V at 10 N, 0.5 Hz). The highly electroactive PLA/CNT@ZIF-8 NFMs exhibited excellent air filtration properties (98.7 % and 99.8 % removal of PM0.3 and PM2.5, 206.9 Pa) even at the highest airflow capacity of 85 L/min, in clear contrast to the pure PLA counterpart (81.2 % and 84.1 %, 465.2 Pa). This was accompanied by 100 % perfect inhibition of both E. coli and S. aureus regardless of the CNT@ZIF-8 loadings, arising mainly from the elevated surface activity, facilitated generation of reactive oxygen species, and gradual release of zinc ions. Moreover, remarkable photothermal properties were demonstrated by temperature elevation of nearly 16 degrees C under near-infrared irradiation for only 20 s. The proposed methodology affords an exceptional combination of excellent air filtration, self-sterilization and photothermal properties, which may motivate development of ecofriendly and functional protective membranes for personal healthcare.