Ion-current-rectification-based customizable pH response in glass nanopipettes via silanization

This study shows that it is possible to customize the ion-current-rectification (ICR)-based pH response in glass nanopipettes by adjusting the ratio of 3-aminopropyldimethylethoxysilane (APTES) and (3-triethoxysilylpropyl) succinic acid anhydride (TESP-SA) used in silanization. The silanization time and concentration were optimized by investigating the rectification ratio of the nanopipettes. For each APTES/TESP-SA silane ratio, analysis of variance (ANOVA) tests indicated that the rectification ratio of the nanopipette had good linearity in the pH range 3-8. Moreover, nanopipettes silanized with equal concentrations of amino and carboxylic groups gave the highest pH response of 1.06 × 10−4 pH −1. This method for customizing the ICR-based pH response in nanopipettes has the potential and versatility to be used in applications such as mimicking biological ion channels and developing nanosized pH sensing devices.