A wide-range solid state potentiometric pH sensor based on poly-dopamine coated carbon nano-onion electrodes

A novel potentiometric pH sensor based on polydopamine films coated on a carbon nano-onion conducive surface is introduced. Glassy carbon electrodes containing a carbon nano-onion layer were modified by electropolymerization and self-polymerization of dopamine. The modified surfaces were characterized by ESEM, RAMAN spectroscopy and cyclic voltammetry. The modified electrodes displayed an almost Nernstian potentiometric response over the pH range 2-10. Furthermore, the pH sensors exhibit a fast and reversible behavior toward variations of pH and negligible interference effects from monovalent cations. The sensors showed an excellent correspondence between the pH values obtained using the GCE/CNO/PDA electrodes and those measured with glass electrodes and were applied to the analysis of real samples covering a wide pH range from 2.2 to 8.3. The analytical performance is comparable to other reported devices based on electropolymerized amines over graphite and noble metal electrodes. Their reproducible and stable response and their ease of fabrication is very promising for the miniaturization and integration of pH sensors in (bio)analytical devices.