Amperometric Nitric Oxide Microsensor Based on Nanopore-Platinized Platinum: The Application for Imaging NO Concentrations

This paper reports an amperometric nitric oxide (NO) microsensor based on a cone-shaped nanopore-platinized Pt working electrode. The senor was fabricated using the following procedure: (1) a parent nanodisk electrode was prepared by polishing an etched Pit wire (radius = 12.5 pm; dimension of etched tip end point <10 nm) embedded in a glass capillary, (2) the nanodisk Pit was further etched to produce a nanopore (pore opening radius < 1 pm; pore depth similar to 30 pm), (3) the Pt base surface in the nanopore electrode was platinized electrochemically to improve the sensor sensitivity, and (4) silanization and further modification with the electropolymerized polymeric film [poly(5-amino-1-naphthol)] on the nanoporeplatinized Pt electrode were carried out to obtain the sensor selectivity to NO. The analytical performance of the sensor was characterized. For example, a sensor with a pore opening radius of 797 nm exhibited a decent linear dynamic range (at least for 0.2-1.8 mu M), detection limit of < similar to 32 nM, response time (t(90%)) of < similar to 5 s, and sensitivity of 6.5 +/- 0.02 pA/nM. This sensor was used successfully as a NO-selective probe tip in scanning electrochemical microscopy (SECM) to obtain a two-dimensional image of the local NO concentrations for an inlaid NO-emitting microdisk film (radius = 12.5 mu m) on a glass substrate.