X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic analysis of RuO2-Ta2O5 thick film pH sensors.
The paper reports on investigation of the pH sensing mechanism of thick film RuO2-Ta2O5 sensors by using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Interdigitated conductimetric pH sensors were screen printed on alumina substrates. The microstructure and elemental composition of the films were examined by scanning electron microscopy and energy dispersive spectroscopy. The XPS studies revealed the presence of Ru ions at different oxidation states and the surface hydroxylation of the sensing layer increasing with increasing pH. The EIS analysis carried out in the frequency range 10 Hz-2 MHz showed that the electrical parameters of the sensitive electrodes in the low frequency range were distinctly dependent on pH. The charge transfer and ionic exchange occurring at metal oxide-solution interface were indicated as processes responsible for the sensing mechanism of thick film RuO2-Ta2O5 pH sensors.
Institute of Electron Technology, Krakow Division, 30-701 Kraków, Zabłocie 39, Poland.
Libu
L
Manjakkal
Institute of Electron Technology, Krakow Division, 30-701 Kraków, Zabłocie 39, Poland.
Katarina
K
Cvejin
Institute of Electron Technology, Krakow Division, 30-701 Kraków, Zabłocie 39, Poland.
Jan
J
Kulawik
Institute of Electron Technology, Krakow Division, 30-701 Kraków, Zabłocie 39, Poland.
Krzysztof
K
Zaraska
Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Kraków, Poland.
Robert P
RP
Socha
Institute of Electron Technology, Krakow Division, 30-701 Kraków, Zabłocie 39, Poland. Electronic address: dszwagi@ite.waw.pl.
Dorota
D
Szwagierczak
Conductimetric pH sensor; Impedance spectroscopy; Ion sensitive electrode; RuO(2)-Ta(2)O(5); Screen printing; X-ray photoelectron spectroscopy