Explicit Dual Effects on Monovalent Ion Transport in 2D Functionalized Nanochannels for Ultrasensitive Sensing.

2D nanochannels have drawn significant interest as a means to develop nanofluidic devices with great potential for future sensing. Target recognition in the 2D nanochannels of a sensing system has been verified to change the ionic passageways to obtain high sensitivity, but until recently, the signal mechanisms have rarely been investigated. Here, explicit hydrophobic interactions and charge effects on target-induced ionic signals are demonstrated by using hydrophobic 2D nanochannels and hydrophilic negatively charged DNA complex-functionalized nanochannels. The comparison of the signals from two types of lithium salts with different anions (TfN and Cl have similar dehydrated sizes, whereas Cl has larger hydration shells) in these functionalized 2D nanochannels reveals mechanisms of ion transport: 1) the hydrophobic interactions govern the selection of incident ions to allow the transport of ions with small hydration shells; 2) the charge effect enhances ion transport rates. On the basis of ion transport mechanisms, this strategy for target recognition has achieved detection of target DNA with a sensitivity of 1 aM. The results provide new avenues for studying the effects of target recognition on ionic signals, which is important for advancements in nanoscale sensing, nanofluidics, iontronics, and other related technologies.