Publication
This work presents the application of ZnO and ZnFe2O4 for electrochemical pH sensing. ZnO and ZnFe2O4 are synthesized by auto combustion synthesis method. FESEM images revealed that ZnO particles have pyramid and spherical shaped morphology with micrometer dimensions while ZnFe2O4 particles have spherical shape at the nanoscale. The surface modified screen-printed electrodes with ZnO and ZnFe2O4 particles are initially characterized by the ferri/ferrocyanide redox couple. Significant improvement in sensitivity (bare carbon: 6.3 ± 0.4 μA/mM, ZnO: 8.5 ± 0.3 μA/mM, ZnFe2O4: 8.9 ± 0.5 μA/mM) and rate constant (bare carbon: 10 ± 1 ms-1, ZnO: 46 ± 4 ms-1, ZnFe2O4: 42 ± 3 ms-1) is observed with the surface modified sensors. Chronopotentiometric pH response of the sensors showed hysteresis behavior with pH loop. No interference effects are observed, and the pH sensitivity of the bare carbon sensor (23.9 ± 1.4 mV/pH) is increased by the introduction of ZnO (38.1 ± 1.3 mV/pH) and ZnFe2O4 (37.2 ± 1.1 mV/pH) particles. Stability of the pH response is discussed and ways for its improvement are proposed.