Fabrication of Glass Nanopore Electrodes for Single-molecule Detection of β-Cyclodextrin

Nanopores are increasingly utilized as tools for single-molecule detection. We have developed a new and simple way for preparing nanopore electrodes by polishing the fused glass capillaries with sandpapers. The prepared nanopore electrodes can realize single β-cyclodextrin molecule detection with high signal-to-noise ratio, which were mechanically strong and easy to handle. Two clearly distinguishable current pulse amplitudes corresponding to the two orientations between β-cyclodextrin and pores were for the first time discovered. Pulse amplitude was closely related to size of the pore; in our case, 2–5 pA current pulse can be gained with (10 ± 5) nm electrode. The analysis of duration and amplitude of current pulse showed that the electroosmosis flow dictated by the values and direction of applied potential difference has significant effects on detections. When the direction of electroosmosis was opposite to the concentration gradient, the electrode can always produce excellent signals by adjusting potential difference from 100 mV to 600 mV. Moreover, we also observed that the amplitude of average current pulse increased first and then reached a maximum at the potential of around 300 mV, and it decreased again.