## 3 Results & Discussion
### Electrochemical Characterization  
The electroactive surface area for each stage of the PANI@CNT/CNC SPME MNs development was evaluated by performing CV at different scan rates (0.025 to 0.20 V/s) in 5.0 mM K\({}_{3}\)FeCN\({}_{6}\) (in 0.10 M KCl) and invoking the Randles-Sevcik equation [30]. Figure 4a,b show the difference in CV response, the relationship between the cathodic peak current (i\({}_{\text{p}}\)), and the square root of the scan rate for CNT/CNC and PANI@CNT/CNC SPME MNs, respectively. The calculated electroactive surface areas for the PANI@CNT/CNC and CNT/CNC SPME MNs are shown in Table 1. The increase in the electroactive surface area of the PANI@CNT/CNC SPME MN relative to the CNT/CNC coated MN (Table 1) is indicative of the enhanced conductivity and porosity afforded by the PANI layer. The determined electroactive surface area of 0.0215 cm\({}^{2}\) was statistically identical to a similar PANI-based MN coated platform reported earlier for a different application, which confirms excellent reproducibility in the fabrication process [26].  
The PANI@CNT/CNC SPME MN was then characterized by EIS during the various stages of its LbL assembly using 25 mM K\({}_{3}\)FeCN\({}_{6}\) (in 0.10 M KCl) as a standard redox probe. Nyquist plots and equivalent circuit fittings for the silylated MN, CNT/CNC, and PANI@CNT/CNC SPME MNs are shown in Figure 5 and Figure S1, respectively. A low electron transfer resistance (R\({}_{\text{ct}}\)) value is desirable, as it is indicative of greater signal transducing capabilities and electrical conductivity [25]. R\({}_{\text{ct}}\) values for the PANI@CNT/CNC SPME MNs, CNT/CNC coated MN, and silylated MNs were extracted from the circuit fittings (Figure S1) and are shown in Table 1. There was a decrease in the R\({}_{\text{ct}}\) value after integration of CNT/CNC into the silylated MN, attributed to the increased electroactive surface area afforded by the conductive CNT/CNC composite film. The R\({}_{\text{ct}}\) further decreased upon addition of PANI to the CNT/CNC coated MN. When composited with  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Electroactive Surface Area (cm\({}^{2}\))** & **R\({}_{\text{ct}}\) (k\(\Omega\))** \\ \hline PANI@CNT/CNC SPME MN & 0.0215 \(\pm\) 0.0005 & 1.06 \(\pm\) 0.01 \\ \hline CNT/CNC coated MN & 0.0070 \(\pm\) 0.0004 & 6.0 \(\pm\) 0.2 \\ \hline Silylated MN & - & 10.0 \(\pm\) 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Electroactive surface area and electron transfer resistance (R\({}_{\text{ct}}\)) values for PANI@CNT/CNC SPME MN, CNT/CNC coated MN, and silylated MN.  
Figure 4: (**a**) Representative CV scans taken at 0.10 V/s and (**b**) Overlapped linear plot of peak cathodic current (i\({}_{\text{p}}\)) vs. square root of scan rate for PANI@CNT/CNC SPME MN and CNT/CNC coated MN acquired in 5.0 mM K\({}_{3}\)FeCN\({}_{6}\) (in 0.1 M KCl).  
PANI, the CNT nanostructures act synergistically with PANI, forming conductive bridges between their emeraldine salt domains, and thus increasing the electrical conductivity of the PANI@CNT/CNC SPME MN [25; 31]. These values bear similarities to those earlier-reported in a similar MN platform [26].