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

Abstract

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.