Title : Design of ion current and fluorescence dual-signal nanochannel sensors for effective and reliable detection
Abstract:
Nanochannel sensors show high sensitivity and are promising for the detection of toxic substance, biomolecules, and other analytes. However, ion current may be affected by many other factors, leading to false-positive signals. In contrast to the conventional passive reaction to analytes, here, we create a series of ion current and fluorescence dual-signal nanochannels for reliable detection. The spatially resolved fluorescence signal combined with ion current signal significantly improve the reliability of the sensing. Inspired by biological aquaporins, we developed an effective strategy to regulate the hydrophilic/hydrophobic balance by the controllable in situ assembly of coordination polymers (CPs) using BDC-NH2 on anodic aluminum oxide (AAO) nanochannels to promote HCHO detection. We found that the hydrophobic/hydrophilic balance in CP/AAO heterosomes plays significant roles in the effective detection of HCHO. The hydrophobic AAO barrier layer is necessary to support the confinement effect, while the hydrophilic CP surface is favorable for HCHO to access the channels and then condense with the responsive amine to generate a new imine. The optimized CP/AAO Janus device shows excellent performance in the quantitative analysis of HCHO over a wide range from 100 pM to 1 mM by monitoring the rectified ionic current. Inspired by light-activatable biological channelrhodopsin-2, photochromic spiropyran/anodic aluminium oxide nanochannel sensors are constructed to realize a light-controlled inert/active-switchable response to SO2 by ionic transport behaviour. We find that light can finely regulate the reactivity of spiropyran/anodic aluminium oxide nanochannels for the on-demand detection of SO2. After ultraviolet irradiation of the nanochannels, spiropyran isomerizes to merocyanine with a carbon?carbon double bond nucleophilic site, which can react with SO2 to generate a new hydrophilic adduct. Benefiting from increasing asymmetric wettability, the proposed spiropyran/anodic aluminium oxide nanochannel device exhibits a robust photoactivated detection performance in SO2 detection in the range from 10 nM to 1 mM achieved by monitoring the rectified current.
