Electric Field-Controlled Ion Transport In TiO2 Nanochannel

Fabrication and Applications of Solid-State Nanopores

Nanopores fabricated from synthetic materials (solid-state nanopores), platforms for characterizing biological molecules, have been widely studied among researchers. Compared with biological nanopores, solid-state nanopores are mechanically robust and durable with a tunable pore size and geometry. Solid-state nanopores with sizes as small as 1.3 nm have been fabricated in various films using engraving techniques, such as focused ion beam (FIB) and focused electron beam (FEB) drilling methods. With the demand of massively parallel sensing, many scalable fabrication strategies have been proposed. In this review, typical fabrication technologies for solid-state nanopores reported to date are summarized, with the advantages and limitations of each technology discussed in detail. Advanced shrinking strategies to prepare nanopores with desired shapes and sizes down to sub-1 nm are concluded. Finally, applications of solid-state nanopores in DNA sequencing, single molecule detection, ion-selective transport, and nanopatterning are outlined.

Low-voltage efficient electroosmotic pumps with ultrathin silica nanoporous membrane

In this work, an efficient electroosmotic pump (EOP) based on the ultrathin silica nanoporous membrane (u-SNM), which can drive the motion of fluid under the operating voltage as low as 0.2 V, has been fabricated. Thanks to the ultrathin thickness of u-SNM (∼75 nm), the effective electric field strength across u-SNM could be as high as 8.27 × 10⁵ V m^-1 in 0.4 M KCl when 1.0 V of voltage was applied. The maximum normalized electroosmotic flow (EOF) rate was as high as 172.90 mL/min/cm² /V, which was larger than most of other nanoporous membrane based EOPs. In addition to the ultrathin thickness, the high porosity of this membrane (with a pore density of 4 × 10¹² cm^-2 , corresponding to a porosity of 16.7%) also contribute to such a high EOF rate. Moreover, the EOF rate was found to be proportional to both the applied voltage and the electrolyte concentration. Because of small electrokinetic radius of u-SNM arising from its ultrasmall pore size (ca. 2.3 nm in diameter), the EOF rate increased with increasing the electrolyte concentration and reached the maximum at a concentration of 0.4 M. This dependence was rationalized by the variations of both zeta potential and electrokinetic radius with the electrolyte concentration.

Ion transport through a nanoporous C2N membrane: the effect of electric field and layer number

Using all-atom molecular dynamic simulations, we show that a monolayer C₂N membrane possesses higher permeability and excellent ion selectivity, and that multilayer C₂N membranes have promising potential for water desalination.

Balancing Osmotic Pressure of Electrolytes for Nanoporous Membrane Vanadium Redox Flow Battery with a Draw Solute

Vanadium redox flow batteries with nanoporous membranes (VRFBNM) have been demonstrated to be good energy storage devices. Yet the capacity decay due to permeation of vanadium and water makes their commercialization very difficult. Inspired by the forward osmosis (FO) mechanism, the VRFBNM battery capacity decrease was alleviated by adding a soluble draw solute (e.g., 2-methylimidazole) into the catholyte, which can counterbalance the osmotic pressure between the positive and negative half-cell. No change of the electrolyte volume has been observed after VRFBNM being operated for 55 h, revealing that the permeation of water and vanadium ions was effectively limited. Consequently, the Coulombic efficiency (CE) of nanoporous TiO₂ vanadium redox flow battery (VRFB) was enhanced from 93.5% to 95.3%, meanwhile, its capacity decay was significantly suppressed from 60.7% to 27.5% upon the addition of soluble draw solute. Moreover, the energy capacity of the VRFBNM was noticeably improved from 297.0 to 406.4 mAh remarkably. These results indicate balancing the osmotic pressure via the addition of draw solute can restrict pressure-dependent vanadium permeation and it can be established as a promising method for up-scaling VRFBNM application.