Polybenzimidazole-Benzophenone Composite Nanofiber Window Air Filter with Superb UV Resistance and High Chemical and Thermal Durability

Synergic Cellulose Nanofiber/Tourmaline Nanoparticle-Assembled Layered Piezoelectric Cryogels for High-Performance Airborne Particulate Filtration

Here, hybrid stimuli-responsive (exhibiting pyroelectricity and piezoelectricity) porous cryogels are engineered by embedding tourmaline nanoparticles (TNs) in a cellulose nanofiber (CNF) skeleton to generate high-performance CNF-TN-based airborne particulate matter (PM) filters. First, single-layer hybrid cryogels with varying TN contents (0-5% w v-1) are assembled, and the design principles for multilayered filters are established based on a novel sequential pre-freezing and freeze-drying technique. As observed, the embedded TNs transformed the CNF network into a more homogeneous, isotropic, and firm structure, thus improving the structural integrity and thermal stability of the assembled cryogels while maintaining their ultrahigh porosity and low density. The TN induced piezoelectric voltage in the cryogels during filtration significantly enhanced the filtration performance. Furthermore, the patterned surface texture of the cryogels notably improved quality factor (Qf) and the reusability of the layered filters overall. The explored hybrid cryogels, particularly those exhibiting multilayered configurations, can be deployed for high-performance airborne particulates filtration owing to the synergistic effect of their mechanical robustness, stability, and high filtration efficiency. As far as it is known that, the Qf values (>0.04) obtained by the three-layered cryogels are similar to or even higher than those of the reported best aerosol filters.

High-Performance and Durable Window-Type Air Filter Based on Embedded PVDF-TrFE Nanofibrous Membrane

Fine inhalable particulate matter (PM2.5) is a harmful airborne pollutant, with serious repercussions to public health worldwide. To prevent the influx of PM2.5 into the indoor living and working space, we conceived the design of a "filtration window" that exhibits efficient PM2.5 filtration capabilities while having sufficient transparency and physical durability. In this work, we demonstrate the successful fabrication of a transparent (∼80%) PM2.5 filter based on nanofibrous poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE), which captures PM2.5 by electrostatic mechanisms originating from the ferroelectric property of the copolymer. The embedded PVDF-TrFE-based nanofibrous filter exhibits a notable PM2.5 removal efficiency of 93%, which is on par with those of medical-grade face masks. Simultaneously, owing to its dense packing, the PVDF-TrFE nanofibrous filter is highly durable, allowing it to be cleaned with water for reuse, and withstands its structural integrity even under a wind flow of 15 m/s, altogether making it practically viable as a functional window unit.

Nanofiberous facemasks as protectives against pandemic respiratory viruses

INTRODUCTION

Wearing protective face masks and respirators has been a necessity to reduce the transmission rate of respiratory viruses since the outbreak of the coronavirus (COVID-19) disease. Nevertheless, the outbreak has revealed the need to develop efficient air filter materials and innovative anti-microbial protectives. Nanofibrous facemasks, either loaded with antiviral nanoparticles or not, are very promising personal protective equipment (PPE) against pandemic respiratory viruses.

AREAS COVERED

In this review, multiple types of face masks and respirators are discussed as well as filtration mechanisms of particulates. In this regard, the limitations of traditional face masks were summarized and the advancement of nanotechnology in developing nanofibrous masks and air filters was discussed. Different methods of preparing nanofibers were explained. The various approaches used for enhancing nanofibrous face masks were covered.

EXPERT OPINION

Although wearing conventional face masks can limit viral infection spread to some extent, the world is in great need for more protective face masks. Nanofibers can block viral particles efficiently and can be incorporated into face masks in order to enhance their filtration efficiency. Also, we believe that other modifications such as addition of antiviral nanoparticles can significantly increase the protection power of facemasks.

Bioinspired artificial spider silk photocatalyst for the high-efficiency capture and inactivation of bacteria aerosols

Bioaerosol can cause the spread of disease, and therefore, capture and inactivation of bioaerosols is desirable. However, filtration systems can easily become blocked, and are often unable to inactivate the bioaerosol once it is captured. Herein, we reported a bioinspired artificial spider silk (ASS) photocatalyst, consisting of a periodic spindle structure of TiO2 on nylon fiber that can efficiently capture and concentrate airborne bacteria, followed by photocatalytic inactivation in situ, without a power-supply exhaust system. The ASS photocatalyst exhibits a higher capture capacity than the nylon fiber substrate and a photocatalytic inactivation efficiency of 99.99% obtained under 4 h irradiation. We found that the capture capacity of the ASS photocatalyst can be mainly attributed to the synergistic effects of hydrophilicity, Laplace pressure differences caused by the size of the spindle knots and surface energy gradients induced by surface roughness. The bacteria captured by the ASS photocatalyst are inactivated by photocatalysis within droplets or at the air/photocatalyst interfaces. This strategy paves the way for constructing materials for bioaerosol purification.

Inorganic-organic nanofiber networks with antibacteria properties for enhanced particulate filtration: The critical role of amorphous titania

The demand for air filter media at indoor and outdoor is increasing tremendously due to air pollution and especially for problems related to airborne particulate matter (PM). To realize that, here a class nanofiber air filter media with strong antibacterial activity, hydrophobic nature, high filtration efficiency with low pressure drop is prepared. Novel organic-inorganic nanocomposite nanofibers used in this work benefited for the multifunctional performance. Amorphous titanium dioxide (mTiO₂) is utilized for air filtration application which exhibits excellent enhancement of PM_2.5 filtration properties and antibacterial activity. The unique Poly (vinylpyrrolidone) (PVP)-mTiO₂ nanofiber air filter media acquired hydrophobic nature with a large increase in water contact angle of 127° from 36°. The resulting free-standing nanofiber filters exhibit high PM_2.5 filtration efficiency of >99.9% and low pressure drop of 39 Pa. Antibacterial activity of nanofibrous membrane has been rationally engineered by titanium oxide as the barrier to bacterial ingression. A long term of 160 h filtration test has proved PVP-mTiO₂ nanofibers air filter media holds outstanding 99% filtration efficiency for PM_2.5. This work takes forward a significant lead in design and production of high performance and very low pressure drop air filter media with a wide range of functional properties.