Airborne transmission of SARS-CoV-2 plays a critical role in spreading COVID-19. To
protect public health, we designed and fabricated electrospun nanofibrous air filters
that hold promise for applications in personal protective equipment (PPE) and the indoor
environment. Due to ultrafine nanofibers (∼300 nm), the electrospun air filters
had a much smaller pore size in comparison to the surgical mask and cloth masks (a
couple of micrometers versus tens to hundreds of micrometers). A coronavirus strain
served as a SARS-CoV-2 surrogate and was used to generate aerosols for filtration
efficiency tests, which can better represent SARS-CoV-2 in comparison to other agents
used for aerosol generation in previous studies. The electrospun air filters showed
excellent performance by capturing up to 99.9% of coronavirus aerosols, which
outperformed many commercial face masks. In addition, we observed that the same
electrospun air filter or face mask removed NaCl aerosols equivalently or less
effectively in comparison to the coronavirus aerosols when both aerosols were generated
from the same system. Our work paves a new avenue for advancing air filtration by
developing electrospun nanofibrous air filters for controlling SARS-CoV-2 airborne
transmission.
Understanding the transformation
of graphitic carbon nitride (g-C3N4) is essential
to assess nanomaterial robustness
and environmental risks. Using an integrated experimental and simulation
approach, our work has demonstrated that the photoinduced hole (h+) on g-C3N4 nanosheets significantly
enhances nanomaterial decomposition under •OH attack.
Two g-C3N4 nanosheet samples D and M2 were synthesized,
among which M2 had more pores, defects, and edges, and they were subjected
to treatments with •OH alone and both •OH and h+. Both D and M2 were oxidized and released nitrate
and soluble organic fragments, and M2 was more susceptible to oxidation.
Particularly, h+ increased the nitrate release rate by
3.37–6.33 times even though the steady-state concentration
of •OH was similar. Molecular simulations highlighted
that •OH only attacked a limited number of edge-site
heptazines on g-C3N4 nanosheets and resulted
in peripheral etching and slow degradation, whereas h+ decreased
the activation energy barrier of C–N bond breaking between
heptazines, shifted the degradation pathway to bulk fragmentation,
and thus led to much faster degradation. This discovery not only sheds
light on the unique environmental transformation of emerging photoreactive
nanomaterials but also provides guidelines for designing robust nanomaterials
for engineering applications.
Biofilms are a cluster of bacteria embedded in extracellular polymeric substances (EPS) that contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to interrogate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Moreover, biofilms are viscoelastic, and their time-dependent mechanical behavior is difficult to capture. Herein, we developed a powerful technique that combines the high spatial resolution of the atomic force microscope (AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy in combination with an appropriate viscoelastic framework, we highlight the intensive amount of time-dependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental raw data. The detailed localization of mechanical properties in space and in time-frequency domain provides insights on the understanding of biofilm stability, cohesiveness, dispersal, and control.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.