Electrospun PAN-HNTs composite nanofiber membranes for efficient electrostatic capture of particulate matters.

The fine particulate matter (PM) pollution has become a serious concern to public health. As the core part of PM air filters, high-performance electrostatic nanofiber membranes are urgently needed. However, the existing air filters remain challenging to further decrease the pressure drop to improve the wearer comfort. On the other hand, the rapidly disappearing static electricity of the existing electrostatic nanofiber inevitably gives rise to a relatively short service life. Here, we demonstrate a novel and enhanced electrostatic nanofiber membrane by introducing the halloysite nanotubes (HNTs) to the traditional electrospun PAN nanofiber membrane. The optimal PAN-HNTs nanofiber membrane shows a high removal efficiency of 99.54%, a low pressure drop of 39 Pa, and a high quality factor of 0.89 Pa-1. This greatly improved filtration performance can be attributed to the increased surface area and diameter of nanofiber after introducing the HNTs as additives with suitable doping concentrations. More importantly, compared with the pure PAN nanofiber membrane, the electrostatic capacity of the PAN-HNTs nanofiber membrane is significantly enhanced, which is confirmed by the leaf electroscope. After introducing the HNTs as additives, the surface of the PAN-HNTs nanofiber membrane becomes hydrophilic, which benefits for preventing foulants from attaching to the surface. We anticipate that the PAN-HNTs nanofibers as high-performance membrane air filters will bring great benefits to public health.

Laminated polyacrylonitrile nanofiber membrane codoped with boehmite nanoparticles for efficient electrostatic capture of particulate matters.

Particulate matters (PMs) air pollution is identified as the major threat to public health and climate. High-performance air filter technology based on various electrospun nanofibers is considered as an effective strategy to eliminate the effects of PMs air pollution. However, to date, nearly all the existing micro-/nanofibers are hard to meet both requirements of high PMs removal efficiency and long service life. In this work, we reported the production of laminated polyacrylonitrile(PAN)-boehmite nanoparticles (BNPs) nanofiber structured membrane by the electrospinning process. The dimension of PAN-BNPs nanofiber can be tunable from (0.09 ± 0.03)µm to (0.81 ± 0.11)µm by controlling the PAN and BNPs concentrations in precursors. The optimized PAN-BNPs nanofiber air filter with a basis weight of 1 g m-2demonstrates the attractive attributes of high PM2.5removal efficiency up to 99.962% and low pressure drop of 58 Pa. Most importantly, after introducing the BNPs as electret, the removal efficiency is very stable under the air flow rate of 6 l min-1. This PAN-BNPs nanofiber with a long electrostatic duration time offers an approach for fabricating future high-performance air filters.

Investigation of energy transfer mechanisms in rare-earth doped amorphous silica films embedded with tin oxide nanocrystals.

Three different types of rare earth (RE3+) ions-doped silica thin films are fabricated by a soft chemistry-based method. By introducing tin oxide (SnO2) nanocrystals with larger cross-sections as sensitizers, the characteristic emission intensity of RE3+ ions in amorphous silica thin films can be enhanced by more than two orders of magnitude via the energy transfer process. The possible energy transfer processes under different local environment are revealed by using Eu3+ ions as an optical probe. Quantitative studies of PL decay lifetime and temperature-dependence PL spectra suggest that the partial incorporation of RE3+ ions into SnO2 sites gives rises to the change of crystal-field symmetry and the significant enhancement of energy transfer efficiency. Further, typical analytical energy dispersive X-ray spectroscopy (EDS) mapping results prove that part of Eu3+ ions doped into the SnO2 sites after annealing at 1000 °C. We anticipate that our results would shed light on the future research on the energy transfer mechanisms under different local structures of RE3+ ions.

Transparent thermoplastic polyurethane air filters for efficient electrostatic capture of particulate matter pollutants.

Particulate matter (PM) air pollution has been established as a significant threat to public health and a destructive factor to the climate and eco-systems. In order to eliminate the effects of PM air pollution, various air filtering strategies based on electrospun nanofibers have recently been developed. However, to date, almost none of the existing nanofibers based air filters can meet the requirements of high-performance air PM filtering, including high PM removal efficiency, low resistance to airflow, and long service life, etc. For the first time, we report a fabrication process using the electrospinning method for air filters based on thermoplastic polyurethane (TPU) nanofibers. The average diameters of TPU nanofibers are tunable from 0.14 ± 0.06 µm to 0.82 ± 0.22 µm by changing the TPU concentrations in polymeric solutions. The optimized TPU nanofibers based air filters demonstrate the attractive attributes of high PM2.5 removal efficiency up to 98.92%, good optical transparency of ∼60%, low pressure drop of ∼10 Pa, high quality factor of 0.45 Pa-1, and long service life under the flow rate of 200 ml min-1, which is ground-breaking compared with the existing nanofibers based air filters. These TPU nanofibers based air filters, with the excellent filtration performance and light transmittance, will shed light on the future research of nanofibers for various filtration applications and greatly benefit the public health by reducing the effects of PM air pollution.