1. Fabrication of glass/ITO/PANI-LS Electrodes
Evaluation and comparison of the potentiometric responses of glass/ITO
and glass/ITO/PANI-LS electrodes in pH
Measurement
J. A. Somoza1, S. Pavoni1, E. M. Rodríguez1, J. E. Eirez2, R. A. Bistel1,
1 Universidad Tecnológica de La Habana José Antonio Echeverría (UTH-CUJAE), Cuba.
2 Escola Politécnica da Universidade de São Paulo (EPUSP), SP, Brazil.
ABSTRACT
Nowadays, numerous investigations are focused on the search of new materials for the manufacture of sensors of diverse types. These materials change their properties in the presence of different chemical agents. Polyaniline (PANI) and ITO can be used as sensitive materials to detect concentrations of various ions [1][2]. In this work, glass/ ITO/ PANI-LS and glass/ ITO working electrodes were constructed for the measurement of pH with dimensions of 2.5 cm x 1.5 cm and 2.5 cm x 2.5 cm. The deposition of the PANI-LS layers was performed using the Layer by Layer technique. A potentiometric measurement system for pH measurement was designed, based on the use of Virtual Instrumentation techniques. The results showed that the glass/ ITO/ PANI-LS and glass/ ITO electrodes had potentiometric responses close to Nernstian in a pH measurement range of 3 to 11 units. In this measurement range there was a linear relationship between the difference in voltage and pH, which is evidenced with coefficients of linear regression and correlation higher than 0.9. The results obtained experimentally are similar to those reported in the literature with other materials [3].
EXPERIMENTAL DESIGN
It was ensured that the selected data represented the stabilized response of each of the electrodes and the mean and standard deviation were calculated using the OriginPro SRI software (Table I).
For theAcquisition experiments were used INA116 (Fig. 1), a DC source (±15 V), a glass beaker, Data Target (USB TI 6212) and a Personal Computer. There were used buffer solutions of pH 3, 4, 7, 10 and 11. The buffer solutions were prepared using different concentrations of Acetic Acid and NaOH.
Fig. 3 Experimental results. Electrochemical cell potencial vs pH values.
Fig. 1 Figure shows the main parts of the measurement system
Electrode
Slope r R2
Value (mV/pH)
Standard deviation
(mV/pH)
Glass/ITO/PANI-LS
2,0 cm x 1,5 cm
-55,17
±3,43
-0,9942
0,98
2,0 cm x 2,5 cm
-56,57
±1,32
-0,9991
0,997
Glass/ITO
-53,50
±1,44
-0,9933
0,991
-56,63
±2,32
-0,9971
0,99
Fabrication of glass/ITO/PANI-LS Electrodes
Glass/ITO/PANI-LS electrodes were constructed using Layer by Layer (LbL) technique. Also, was used LS for adding PANI into the Glass/ITO interface.
RESULTS
After the experiments, the Fig. 2 shows the temporal response of the potentiometric curves obtained with the Glass/ITO/PANI-LS electrodes. The potentiometric curves were characterized by an initial transient response followed by a tendency to reach a stable potential value.
CONCLUSIONS
It was experimentally verified that with the devices and the measurement procedures used, it is possible to carry out the potentiometric measurement of pH of liquid solutions under laboratory conditions. This is demonstrated by the linear dependence obtained between the potential of the electrochemical cell and the pH values in a range of 3 to 11.
Glass/ITO/PANI-LS electrodes and Glass/ITO electrodes showed potentiometric responses that can be classified as close to Nernstian.
The results obtained experimentally show that it is possible to use glass/ITO/PANI-LS and glass/ITO electrodes to construct electrochemical cells for pH measurement.
ACKNOWLEDGMENT
Thanks to Brazilian funding agencies CAPES (project CAPES-MES Cuba 134/11.
REFERENCES
[1]: Lambrechts, M. and Sansen, W. Biosensors: Microelectrochemical Devices. Institute of Physics Publishing, Bristol, UK. ISBN:
[2]: Somoza Chuay, J. A et al. Construcción y caracterización de electrodos de Vidrio/ITO/PANI para la medición de pH. RIELAC, Vol.XXXV 3/2014 p
ISSN:
[3]: Al-Obeidi, A., et al. ITO/Poly (Aniline)/Sol-Gel Glass: An Optically Transparent, pH-Responsive Substrate for Supported Lipid Bilayers. Hindawi Publishing Corporation Journal of Materials. Article ID:
Fig. 2 Figure shows the main parts of the measurement system
Calibration curves of the Glass/ITO/PANI-LS electrodes and the glass/ITO electrodes were obtained (Fig. 3). Data were extracted from the experimental measurements performed. Of the 300 samples contained in each of the potentiometric curves the last 150 values were taken, when the signal had reached the steady state.