Integrated pH Sensors Based on RuO 2 /GO Nanocomposites Fabricated Using the Aerosol Jet Printing Method.

An aerosol jet printing (AJP) process for depositing ruthenium dioxide (RuO 2 ) as a promising material for pH sensing is reported. Graphene oxide (GO) with a large surface area was used for the in situ sol-gel deposition of RuO 2 nanoparticles on its surface. The cosolvent ratio and solid loading of the solution are adjusted to form a printable and stable ink. The monodispersed aerosol was atomized on the surface of the screen-printed carbon electrode in order to develop an integrated pH sensor. The RuO 2 -GO pH sensor demonstrates excellent performance, with a rapid response time of less than 5 s and high sensitivity in the pH range of 4-10. Compared to traditional carbon electrodes, the RuO 2 -GO sensor shows up to four times higher sensitivity. The increased sensitivity is a result of the consistent attachment of small-crystallized RuO 2 nanoparticles onto the surface of GO sheets, leading to a synergistic effect. Thanks to the AJP method as a facile and cost-effective integration technique, the fabricated electrodes can serve as an alternative to traditional rigid pH electrodes for accurate pH measurement.