Facile One-Step Photochemical Fabrication and Characterization of an Ultrathin Gold-Decorated Single Glass Nanopipette

The inner surface of a conical glass nanopipette was modified with ultrathin gold film by a facile one-step photochemical approach, using HAuCl4 and ethanol as common reagents with the aid of UV irradiation. The method is simple, straightforward, time-saving, and environmentally friendly. The morphology and component of the as-prepared ultrathin gold film was thoroughly characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) analysis, and X-ray photoelectron spectroscopy (XPS). The mechanism of the gold film growth was briefly discussed. Other small photochemical reagents with a hydroxy group, e.g., ethylene glycol, methanol, and glucose, may also work but with a different rate of reaction. The facile ultrathin gold decoration of a single glass nanopipette renders the glass nanopipette-based nanopore platform very easy for surface chemical modifications and potential sensing applications. The success of the gold decoration on the inner surface of the glass nanopore was further confirmed electrochemically by surface modification of a small thiol molecule (cysteine), and the pH (surface charge)-dependent ionic current rectification behaviors through the nanopore were investigated. Due to its facile preparation, the method and the Au-decorated glass nanopore would find promising and extended applications in ultrasensitive detection and biosensing.