Nanoporous Atomically Thin Graphene Filters for Nanoscale Aerosols

Abstract

Filtering nanoparticulate aerosols from air streams is important for a wide range of personal protection equipment (PPE), including masks used for medical research, healthcare, law enforcement, first responders, and military applications. Conventional PPEs capable of filtering nanoparticles <300 nm are typically bulky and sacrifice breathability to maximize protection from exposure to harmful nanoparticulate aerosols including viruses ∼20–300 nm from air streams. Here, we show that nanopores introduced into centimeter-scale monolayer graphene supported on polycarbonate track-etched supports via a facile oxygen plasma etch can allow for filtration of aerosolized SiO2 nanoparticles of ∼5–20 nm from air steams while maintaining air permeance of ∼2.28–7.1 × 10–5 mol m–2 s–1 Pa–1. Furthermore, a systematic increase in oxygen plasma etch time allows for a tunable size-selective filtration of aerosolized nanoparticles. We demonstrate a new route to realize ultra-compact, lightweight, and conformal form-factor filters capable of blocking sub-20 nm aerosolized nanoparticles with particular relevance for biological/viral threat mitigation.

High‐Performance Hemofiltration via Molecular Sieving and Ultra‐Low Friction in Carbon Nanotube Capillary Membranes

“…A fiber optic dip probe (attached to an Agilent Cary 60 UV–vis Spectrophotometer) was immersed in the permeate side to record the absorbance spectra of organic molecules (B12, Lz, or BSA) in the range of 190 to 1100 nm every 15 s for 40 min. [ 52,68–71 ] Different UV–vis wavelengths were used for measuring the intensity changes of each species: 710 nm for DI water (reference wavelength), [ 52,68–71 ] 360 nm for B12, [ 52,68–71 ] 282 nm for Lz, [ 52,68–71 ] and 278 nm for BSA, [ 73,74 ] respectively. The flow rate of each solute was computed via the slope of concentration change in the permeate side; while the permeance was calculated using $$p = \frac{{V \times \frac{{dC}}{{dt}}}}{{\Delta C \times {A}_{{\mathrm{effective}}}}}$$, where V is the volume of solution (7 mL), dC/dt is the slope of concentration change in the permeate side, A effective is the effective area of CNT membrane subjected to diffusion test (5 mm diameter orifice area multiplied by 5% of CNT membrane porosity), and ΔC is the solute concentration difference across CNT membrane.…”

“…All the measurements were replicated three times to obtain average values and standard deviations. [ 52,68–71 ]…”

“…The diffusion-driven solute transport measurements across the fabricated CNT membrane were performed as previously reported in detail elsewhere. [52,[68][69][70][71][72] The setup used for diffusion measurements was a customized 7 mL Side-Bi-Side glass diffusion cell (PermeGear, Inc.) with a 5 mm orifice as shown in Figure S1, Supporting Information. The CNT membrane (≈1.6 cm diameter) was installed between two diffusion cells, followed by clamping the diffusion system.…”

“…[53] For measuring diffusion-driven KCl (Fisher Chemical, 7447-40-7) transport, KCl solution (0.5 mol L −1 in DI water) was filled into the left cell (feed side) and DI water was filled into the right cell (permeate side), with a conductivity meter probe (attached to a Mettler Toledo SevenCompact S230 conductivity benchtop meter) immersed in the permeate side to measure the conductivity every 15 s for 15 min. [52,[68][69][70][71] For measuring diffusiondriven B12 (Sigma-Aldrich, 68-19-9) or Lz (Bio-world, 12650-88-3) transport, the organic molecule solution (1 mmol L −1 in 0.5 mol L −1 KCl) was filled into the feed side and KCl solution (0.5 mol L −1 ) was filled into the permeate side. [52,[68][69][70][71] For measuring diffusion-driven BSA (Fisher Scientific, BP9703-100) transport, BSA solution (1 mmol L −1 in 1× PBS) was filled into the feed side and PBS solution (1×) was filled into the permeate side.…”

Differences in water and vapor transport through angstrom-scale pores in atomically thin membranes

“…Nanoporous graphene was synthesized on Cu foils at 900 °C using lowpressure chemical vapor deposition (LPCVD) as reported in detail elsewhere 32,42,43,51,[75][76][77][78][79][80] . First, the Cu foil (99.9% purity, 18 µm thick, JX Holding HA) was pre-cleaned in diluted nitric acid (20%) via sonication for 4 min to remove surface oxides and contaminants, followed by rinsing in deionized (DI) water for 2 min and drying in air 32,42,43,51,75,76 .…”