SODl-CNT-PPy-Pt electrodes

The effect of CNT on the current response due to NO2 is shown in F ire 3.35. It exhibits a remarkable increase in the amperometric response from the modified electrode consisting of CNT when compared to that without CNT. Furthermore, with N02 (500 pM), the increase in the anodic oxidation current observed at the SODl-CNT-PPy-Pt electrode was fivefold greater than that of the CNT free... 

Figure 3.35 Influence of CNT on the amperometric response of (a) SODl-PPy-Pt and (b) SODl-CNT-PPy-Pt electrodes to 500 pM NOz solution in 0.1 M PBS (pH 7.0) containing 100 pM DTPA at scan rate of 50 mVs ...

The SODl-CNT-PPy-Pt electrodes were further electrochemicaUy characterized and exhibited a quasireversible peak at the potential of +0.06 V versus Ag/AgCl (Figure 3.38). This observed quasireversible peak is attributed to the Cu /Cu redox... 

Further, the influence of scan rate on the performance of the SODl-CNT-PPy-Pt electrode in 0.1 M PBS containing 100 pM of NO solution was also investigated (Figure 3.40). It was observed that the anodic peak currents negatively increased hneady with increasing the scan rate of 50 to 300 mV s and also that the characteristic CV remains unchanged. This indicates the favorable orientation of SODl at the CNT-PPy-Pt electrode leading to a facilitated electron transfer of SOD 1, and the linear variation of anodic peak currents (IP) with scan rate (y) indicate that the electrochemical process is diffusion controlled. 

The stability of the bienzymatic NaR-SODl-CNT-PPy-Pt electrode was evaluated by monitoring the current response three times a day in the presence of 100 nM nitrite and 300 nM nitrate over four weeks, and the rest of the time it was stored at 4 °C. The SODl and NaR were quite stable, as inferred from their electrocatalytical activity of 92% and 89.6%, respectively, after one month of storage and 83% and 76%, respectively, after two months of storage. RepeatabiHty of the bienzymatic biosensor was tested by... 

Figure 3.16 displays the electrochemical responses obtained for the SODl-PPy-Pt and SOD-CNT-PPy-Pt electrodes in the absence (curves a and b) and presence (curves c and d) of 200 pM N02 at a scan rate of 50 mV s in 0.1 M PBS (pH 7.0). Before the addition of N02, no change was observed in the current response. However, after the addition of 200 pMN02, SOD-PPy-Pt and SOD-CNT-PPy-Pt electrodes exhibited significant increases in current anodicaUy at the potential, +0.8 V. These increases are ascribed to the electrochemical oxidation of N02 to NOs via a cyclic redox reaction of SOD active site Cu(I/II) moiety. The electrochemical responses of the NaR-SOD-CNT-PPy-Pt electrode in 0.1 M PBS (control) and various N02 concentrations using the same scan rate are shown in Figure 3.17. As the concentration increases, the anodic current response also increases linearly at +0.8 V. The observed anodic peak currents versus N02 concentrations were plotted as shown in the inset of Figure 3.17. The calibration curve thus obtained exhibits a linear range of response...

SODl-PPy-Pt electrode (Figure 3.35). It is clearly evident that the CNT-PPy nanocomposite facilitated the direct electron transfer between SODl and the base electrode (Madasamy et ah, 2014a,b). 

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