Simple and Versatile Detection of Viruses Using Anodized Alumina Membranes

A simple sensor for viral particles based on ionic conductivity through anodized alumina membranes was demonstrated using MS2 bacteriophage as an example. A facile two-point measuring scheme is geared toward realization using a computer’s sound card input/output capabilities suitable for a fast and inexpensive point of care testing. The lowest detection concentration down to ∼7 pfu/mL and a large dynamic range up to ∼2000 pfu/mL were obtained due to physical optimization that included proper length and diameter for the pores, removing the oxide layer at the electrode, as well as the chemical optimization of covalent binding of antibodies to the pore’s walls

Ionic Conductance through Graphene: Assessing Its Applicability as a Proton Selective Membrane

Inspired by recent reports on possible proton conductance through graphene, we have investigated the behavior of pristine graphene and defect engineered graphene membranes for ionic conductance and selectivity with the goal of evaluating a possibility of its application as a proton selective membrane. The averaged conductance for pristine chemical vapor deposited (CVD) graphene at pH1 is ∼4 mS/cm2 but varies strongly due to contributions from the unavoidable defects in our CVD graphene. From the variations in the conductance with electrolyte strength and pH, we can conclude that pristine graphene is fairly selective and the conductance is mainly due to protons. Engineering of the defects with ion beam (He+, Ga+) irradiation and plasma (N2 and H2) treatment showed improved areal conductance with high proton selectivity mostly for He-ion beam and H2 plasma treatments, which agrees with primarily vacancy-free type of defects produced in these cases confirmed by Raman analysis

Kinetic Control of Angstrom-Scale Porosity in 2D Lattices for Direct Scalable Synthesis of Atomically Thin Proton Exchange Membranes

Angstrom-scale pores introduced into atomically thin 2D materials offer transformative advances for proton exchange membranes in several energy applications. Here, we show that facile kinetic control of scalable chemical vapor deposition (CVD) can allow for direct formation of angstrom-scale proton-selective pores in monolayer graphene with significant hindrance to even small, hydrated ions (K+ diameter ∼6.6 Å) and gas molecules (H2 kinetic diameter ∼2.9 Å). We demonstrate centimeter-scale Nafion|Graphene|Nafion membranes with proton conductance ∼3.3–3.8 S cm–2 (graphene ∼12.7–24.6 S cm–2) and H+/K+ selectivity ∼6.2–44.2 with liquid electrolytes. The same membranes show proton conductance ∼4.6–4.8 S cm–2 (graphene ∼39.9–57.5 S cm–2) and extremely low H2 crossover ∼1.7 × 10–1 – 2.2 × 10–1 mA cm–2 (∼0.4 V, ∼25 °C) with H2 gas feed. We rationalize our findings via a resistance-based transport model and introduce a stacking approach that leverages combinatorial effects of interdefect distance and interlayer transport to allow for Nafion|Graphene|Graphene|Nafion membranes with H+/K+ selectivity ∼86.1 (at 1 M) and record low H2 crossover current density ∼2.5 × 10–2 mA cm–2, up to ∼90% lower than state-of-the-art ionomer Nafion membranes ∼2.7 × 10–1 mA cm–2 under identical conditions, while still maintaining proton conductance ∼4.2 S cm–2 (graphene stack ∼20.8 S cm–2) comparable to that for Nafion of ∼5.2 S cm–2. Our experimental insights enable functional atomically thin high flux proton exchange membranes with minimal crossover