Tuning Transport Selectivity of Ionic Species by Phosphoric Acid Gradient in Positively Charged Nanochannel Membranes

Abstract

The transport of ionic species through a nanochannel plays important roles in fundamental research and practical applications of the nanofluidic device. Here, we demonstrated that ionic transport selectivity of a positively charged nanochannel membrane can be tuned under a phosphoric acid gradient. When phosphoric acid solution and analyte solution were connected by the positively charged nanochannel membrane, the faster-moving analyte through the positively charged nanochannel membrane was the positively charged dye (methylviologen, MV(2+)) instead of the negatively charged dye (1,5-naphthalene disulfonate, NDS(2-)). In other words, a reversed ion selectivity of the nanochannel membranes can be found. It can be explained as a result of the combination of diffusion, induced electroosmosis, and induced electrophoresis. In addition, the influencing factors of transport selectivity, including concentration of phosphoric acid, penetration time, and volume of feed solution, were also investigated. The results showed that the transport selectivity can further be tuned by adjusting these factors. As a method of tuning ionic transport selectivity by establishing phosphoric acid gradient, it will be conducive to improving the separation of ionic species.

Self-assembled membrane composed of amyloid-like proteins for efficient size-selective molecular separation and dialysis

“…16f). With the same anion in the draw solution (Cl − ), this order was consistent with the increase in cationic radius, i.e., K + (0.331 nm) < Na + (0.358 nm) < Ca 2+ (0.412 nm) < Cu 2+ (0.419 nm) < Mg 2+ (0.428 nm), and thus attributed to a slower transfer rate for larger cations across the membrane 47,48 . This osmotic pressure-driven permeation allowed the PTL membrane to be operated in an FO mode with low energy consumption and fouling propensity compared to reverse osmosis membrane technology 13,45 .…”

Salt-Gradient Approach for Regulating Capture-to-Translocation Dynamics of DNA with Nanochannel Sensors

“…Recently by imposing different concentrations of salt to the two ends of charged nanochannels, a bunch of interesting transport phenomena have been reported. − As shown in Figure b, due to the larger concentration C max in the left chamber ( z < − L /2) the counterions at that end of the channel are more densely piled up, while at the opposite C min end the layer of screening ions is much thicker. Hence a nonuniformity of ion distribution along the channel axis arises.…”

“…However, the experiments showed much more complicated behaviors. ,, One central discovery is the transition of fluidics from osmosis to the reverse one with increasing salt gradient. Yang et al , showed a four-stage variation of EOF: at first an osmotic flow was boosted given small LiCl concentration bias C max / C min across the channel (region I in Figure b); as the imposed salt gradient was enhanced, the osmotic flow first increased and then switched to decrease (region II in Figure b); when the salt gradient became larger than a critical value, the fluidics shifted to reverse osmosis (RO, region III in Figure b); if the salt gradient still kept increasing, once again the magnitude of RO began to decrease (region IV in Figure b) In summary, rather than monotonic increasing there existed a transition of osmotic flow to the reversed one. Furthermore, within either osmosis or reverse osmosis there was U-turn-like dependence of the fluidics on the imposed salt gradient.…”

Ion Selective Nanochannels: From Critical Principles to Sensing and Biosensing Applications

“…However, the dehydration effect governs the ionic trans port in a low number of negatively surface charges, and thereby nanochannel affinity switched to Li + ions at small surface charge densities. [204] Razmjou and et al fabricated an efficient 2D negatively charged vermiculite (VCT)based nanochannel for separation of Li + ions in aquatic environments. The sche matic and microscopy images of fabricated VCT nanosheets are displayed in Figure 6Aa,b.…”