Distinct pH-regulated conductance behaviors of PEI-coated PET and silica nanochannels

Polyethyleneimine (PEI)-functionalized nanochannels have been extensively exploited in ion gating and biosensing. It is of great significance to explore their conductance determining ion-surface interaction and ionic transport at the nanoscale. Here, pH-regulated conductance of PEI-coated nanochannels is theoretically studied. The results suggest that coating PEI may improve nanochannel conductance in different ways depending on the surface charge of nanochannels. The conductance of a PEI-coated PET nanochannel whose surface charge is assumed to be constant for simplicity is weakly changed and then decreased to that of a non-PEI-coated PET nanochannel with increasing pH, which is consistent with the reported experimental results. The conductance of a PEI-coated silica nanochannel, whose surface charge largely depends on pH, ion concentration, and nanochannel radius, is significantly increased and, subsequently, decreased to that of a non-PEI-coated silica nanochannel as pH rises, which is rarely reported in experiments. This work provides a fundamental framework to investigate the conductance of PEI-coated nanochannels, and the PEI-coated silica nanochannels with unique pH-dependent conductance may be explored in the construction of mesoporous silica thin films for biomedical analytical applications.