Table 1
Summary of circuit components.
Circuit component
Unit
Best fit Correlation coefficient square Trend with increasing ammonia conc.
Contact resistance, R1
Charge transfer resistance, R2
High frequency capacitance, C1
Low frequency Charge transfer resistance, R3
Low frequency capacitance, C2 K Ω
k Ω
pF
k Ω
µF Linear
Quadratic
Linear
Quadratic
Quadratic 0.9961
0.9925
0.9805
1
0.9981 Decreases
Decreases
Increases
Increases
Increases
3.6. Amperometric results
PANI is an inherently conducting polymer only in the presence of a donor. With ammonia diffusing into the system, a neutralization of the acid proton donor can be expected which gives rise to a change in the inherent conductivity of the polymer. At the same time there is formation of ammonium chloride which in turn also significantly affects the amperometric response.
PANI + HCl → PANIH+ + Cl-
PANIH + +Cl- + NH3→ PANI + NH4Cl
The suitable potential for amperometric study inferred from cyclic voltammetry was found to be 0.106 V. The amperometric response is very well linearly correlated in the range, 2.5–20 ppm with squared correlation coefficient of 0.9944 with the conduction, increasing with increasing ammonia concentration, as seen in Fig. 7. The % RSD value for the sensor was 1.89.
Fig. 6. (a) Contact resistance (R1), charge transfer resistance predominant at high frequencies (R2) and charge transfer resistance predominant at low frequencies (R3) as a function of ammonia concentration. Each data point reported is an average of at least 3 readings to ensure repeatability. The experimental data was well within the error limit of ±1.0%, the radii of the circles over each point adequately covering the errors. The squares of the correlation coefficients are presented for each fit in Table 1. (b) Capacitance predominant at high frequency (C1, pF) and low frequency (C1, µF) as a function of ammonia concentration. Each data point reported is an average of at least 3 readings to ensure repeatability. The experimental data was well within the error limit of ±1.0%, the radii of the circles over each point adequately covering the errors. The squares of the correlation coefficients are presented for each fit in Table 1.
Table 1
Summary of circuit components.
Circuit component
Unit
Best fit Correlation coefficient square Trend with increasing ammonia conc.
Contact resistance, R1
Charge transfer resistance, R2
High frequency capacitance, C1
Low frequency Charge transfer resistance, R3
Low frequency capacitance, C2 K Ω
k Ω
pF
k Ω
µF Linear
Quadratic
Linear
Quadratic
Quadratic 0.9961
0.9925
0.9805
1
0.9981 Decreases
Decreases
Increases
Increases
Increases
3.6. Amperometric results
PANI is an inherently conducting polymer only in the presence of a donor. With ammonia diffusing into the system, a neutralization of the acid proton donor can be expected which gives rise to a change in the inherent conductivity of the polymer. At the same time there is formation of ammonium chloride which in turn also significantly affects the amperometric response.
PANI + HCl → PANIH+ + Cl-
PANIH + +Cl- + NH3→ PANI + NH4Cl
The suitable potential for amperometric study inferred from cyclic voltammetry was found to be 0.106 V. The amperometric response is very well linearly correlated in the range, 2.5–20 ppm with squared correlation coefficient of 0.9944 with the conduction, increasing with increasing ammonia concentration, as seen in Fig. 7. The % RSD value for the sensor was 1.89.
Fig. 6. (a) Contact resistance (R1), charge transfer resistance predominant at high frequencies (R2) and charge transfer resistance predominant at low frequencies (R3) as a function of ammonia concentration. Each data point reported is an average of at least 3 readings to ensure repeatability. The experimental data was well within the error limit of ±1.0%, the radii of the circles over each point adequately covering the errors. The squares of the correlation coefficients are presented for each fit in Table 1. (b) Capacitance predominant at high frequency (C1, pF) and low frequency (C1, µF) as a function of ammonia concentration. Each data point reported is an average of at least 3 readings to ensure repeatability. The experimental data was well within the error limit of ±1.0%, the radii of the circles over each point adequately covering the errors. The squares of the correlation coefficients are presented for each fit in Table 1.
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