Enhanced Stability and Controllability of an Ionic Diode Based on Funnel‐Shaped Nanochannels with an Extended Critical Region

Abstract

The enhanced stability and controllability of an ionic diode system based on funnel-shaped nanochannels with a much longer critical region is reported. The polarity of ion transport switching from anion/cation-selective to ambipolar can be controlled by tuning the length and charge of the critical region. This nanofluidic structure anticipates potential applications in single-molecule biosensing, water resource monitoring, and healthcare.

Wettability and Applications of Nanochannels

“…Such phenomena demonstrate that the ultrafast transport conducts in a quantum way with single ionic or molecular chain, so we have proposed a concept of QSF to understand this ultrafast fluid . Besides biological ionic channels, the QSF phenomena also exist in the artificial ionic channels with an increased critical cylindrical region, which show tremendous rectification (Figure c) . Electrochemical storage with ultrafast ionic transport in confined systems can rapidly charge and discharge, also indicating QSF feature of the ions .…”

Nanofluidic Ion Transport and Energy Conversion through Ultrathin Free‐Standing Polymeric Carbon Nitride Membranes

“…In general, the conductivity of bulk KCl solution is proportional to its concentration. [16] At both pH 5.8 and 10, the UFSCNM is negative charged because of the incomplete polymerization or condensation with electron rich -NH terminal group (Figure 3b), therefore conductivity becomes independent of the nominal ionic concentrations because of the cation selectivity at low concentrations. However,t his conductivity begins to deviate from bulk behavior at about 10 À3 m and gradually plateaus at lower concentrations for pH 5.8 and 10 ( Figure 3a).…”

“…This is the signature of surface charge controlled ions transportation properties. [16] At both pH 5.8 and 10, the UFSCNM is negative charged because of the incomplete polymerization or condensation with electron rich -NH terminal group (Figure 3b), therefore conductivity becomes independent of the nominal ionic concentrations because of the cation selectivity at low concentrations.…”

Biomimetic Peptide‐Gated Nanoporous Membrane for On‐Demand Molecule Transport

“…As asophisticated molecule-transport platform, the range of molecules transported by nano-gating can be tuned to match the practical applications including various therapeutic windows by changing the composition and geometry of the nanoporous membrane (e.g.,t hickness,p orosity,s urface charge,c hannel shape). [14,18] Of further importance is that the nano-gating can be assembled into portable or wearable controllable drug-release platforms because of the flexibility and stability of nanoporous membrane. [15,19] In summary,w er ealized an ano-gating system for ondemand molecule transport with sustained release based on an anoporous membrane.T he principle of nano-gating was attributed to the conformation transition of peptides in the channel in the presence of dissolved oxygen in an electrolyte solution.…”

“…Then anoporous membrane used in this work was acommercial poly(ethylene terephthalate) (PET) membrane with ap ore density of 10 7 pores cm À2 ,i nw hich asymmetric conical-shaped nanochannels can be generated by the welldeveloped asymmetric track-etching technique ( Figure 1d and Figure S1 in the Supporting Information). [14] Then anogating can be realized mainly because the effective pore diameter of the nanochannels,especially the pore diameter on the tip side,could be manipulated effectively,which benefited from the conformational transformations of the peptides.I n all samples,t he initial base and tip diameters were approximately 510 AE 30 nm and 22 AE 4nm, respectively.After modification with peptides,t he effective base diameters had no obvious change while the effective tip diameter decreased ( Figure 1e). Then anoporous membranes before and after modification also could be confirmed by X-ray photoelectron spectroscopy (XPS,F igure 1f).…”