Fabrication of Silanized Nanopipette Probes

Schott glass capillaries (o.d. 1.5 mm, i.d. 1.0 mm, World Precision Instruments, Sarasota, FL) were cleaned by sonication in H₂O followed by ethanol, and dried at 60 °C for 1 h. Dried capillaries were pulled into pipets using a P-97 micropipette puller (Sutter Instrument Co., Novato, CA), and cut and fire polished using a MF-900 microforge (Narishige, East Meadow, NY) to an aperture i.d. of 15-20 μm. The pipet surface was cleaned with 1 M HNO₃ for 30 min, washed with H₂O and then dried at 110 °C for 1 h. Pipets were then silanized with PFDCS vapor for 10 min in a heated chamber.^{33 (link)} Modified pipets were sequentially washed with acetonitrile, acetone, H₂O and ethanol, then dried at 60 °C for 1 h prior to use.