Ion transport based structural description for in situ synthesized SBA-15 nanochannels in a sub-micropipette

Abstract

Construction of nanoporous arrays can greatly facilitate their development in the fields of sensing, energy conversion, and nanofluidic devices. It is important to characterize the structure and understand the ion transport behaviour of a nanoporous array, especially those prepared by in situ synthesis, which are difficult to be characterized by conventional methods. Herein, an inorganic and non-crystalline mesoporous silica SBA-15 is selected as a template, where a combination (GP-SBA-15) of a sub-micropipette and SBA-15 is constructed by in situ synthesis, and the multichannel array structure of GP-SBA-15 is illustrated by its ion transport properties from current–voltage responses. Experiments of linear scan voltammetry and chronoamperometry show a rapid accumulation and slow redistribution of ions in the surface-charged nanochannels, and the high/low currents originate from the accumulation/depletion of ions in the channels. The finite element simulation is introduced to calculate the effects of surface charge and pore size on ion rectification and ion concentration distribution. In addition, the short straight channels and long bending channels present in GP-SBA-15 are demonstrated by the voltage-independent resistance pulse signals in the translocation of BSA. This study shows that electrochemical means effectively provide insight into ion transport, achieve structural description and reveal the sensing potential of GP-SBA-15.