Optical Gating of Photosensitive Synthetic Ion Channels

Abstract

4‐oxo‐4‐(pyren‐4‐ylmethoxy) butanoic acid is used as a photolabile protecting group to show the optical gating of nanofluidic devices based on synthetic ion channels. The inner surface of the channels is decorated with monolayers of photolabile hydrophobic molecules that can be removed by irradiation, which leads to the generation of hydrophilic groups. This process can be exploited in the UV‐light‐triggered permselective transport of ionic species in aqueous solution through the channels. The optical gating of a single conical nanochannel and multichannel polymeric membranes is characterised experimentally and theoretically by means of current–voltage and selective permeation measurements, respectively. It is anticipated that the integration of nanostructures into multifunctional devices is feasible and can readily find applications in light‐induced controlled release, sensing, and information processing.

Nernst-Planck model of photo-triggered, pH–tunable ionic transport through nanopores functionalized with “caged” lysine chains

“…45,46,67 We have described the transport properties of asymmetric nanopores functionalized with photosensitive amphoteric lysine groups. The experiments concern the I-V curves of polymer samples containing the as-prepared single asymmetric nanopore with carboxylate groups acting as fixed charges, the I-V curves of the single nanopore functionalized with "caged" and "uncaged" lysine groups, and the fluxes of divalent positive and negative analytes through multipore membranes.…”

“…45,46 The pores use photo-labile protecting groups (PPGs) or photosensitive active groups, initially in hydrophobic state, that switch to a hydrophilic form after UV light irradiation. UV light constitutes a facile way to change the pore functionalities externally, without causing further damage to the active groups attached to the pore wall.…”

Net currents obtained from zero-average potentials in single amphoteric nanopores

“…While a clear understanding of the pore response to external stimuli (voltage, temperature, pH and UV light) has already been achieved [14,[20][21][22][23][24][25][26], practical applications are still emerging. We demonstrate here that a pH-controlled net current can be obtained with a single asymmetric nanopore functionalized with amphoteric lysine groups in the case of zero-average timedependent potentials, suggesting some practical applications of the concept.…”

Mimicking how plants control CO2 influx: CO2 activation of ion current rectification in nanochannels

“…The interior surface of the nanochannels was modified with DEPBA or DEDA using a three-step coupling reaction. 37 EDA was covalently coupled to the surface to introduce -NH 2 functional groups after activation with EDC·HCl and PFP. Subsequently, the interior surface of the nanochannels was modified by DEPBA or DEDA.…”