# Highly Sensitive Non-Enzymatic Detection of Glucose at MWCNT-CuBTC Composite Electrode
## 4 Discussion  
Various types of copper-based electrode compositions (e.g., copper-copper oxide nanoparticles, nanocubes, nanowires, and MOF-derived) have been reported for the non-enzymatic determination of glucose [15, 16, 17, 23, 24]. In general, the electrode potential (V versus the SCE) for glucose detection ranged between +0.4 and +1.0 V versus the SCE, which corresponds to the involvement of Cu\({}^{+}\)/Cu\({}^{2+}\) and Cu\({}^{2+}\)/Cu\({}^{3+}\) redox systems that act as electrocatalysts toward glucose oxidation. The electrocatalytic \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Electrode Material** & \begin{tabular}{c} **Concentration** \\ **Range** \\ \end{tabular} & \
\begin{tabular}{c} **Sensitivity** \\ **(\(\mu\)Am\({}^{-1}\)cm\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Limit of Detection** \\ **(\(\mu\)M)** \\ \end{tabular} & **Reference** \\ \hline MOF-derived CuO architectures & 10–120 \(\mu\)M & 934.2 & 0.1 & [15] \\ \hline CuO/CuBi2O4 & 1 nM–100 mM & 330 & 0.7 & [17] \\ \hline CuS microflowers & 0.2–5.4 mM & 1007 & n.a. & [23] \\ \hline CuO nanospheres & 50 \(\mu\)M–5 mM & 404.53 & 1 & [24] \\ \hline Cu2O-c/SPCE & 31 nM–1.42 mM & 2376.7 & 0.003 & [35] \\ \hline Cu O nanowire & 0.40 \(\mu\)M–2 mM & 2450 & 0.049 & [36] \\ \hline MWCNT-CuBTC & 0.2–1 mM & 14,949 & 10 & This work \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the performances of the MWCNT-CuBTC composite electrode with other copper-based electrodes for the non-enzymatic sensing of glucose. Figure 7: Multiple pulse amperometry (MPA) recordings for three levels of the potential pulses of +1.25 V/SCE for 0.1 s (E1), +0.6 V/SCE for 0.05 s (E2), and \(-\)0.5 V/SCE for 0.1 s (E3) at the MWCNT-CuBTC composite electrode in 0.1 M of NaOH supporting electrolyte and in the presence of various glucose concentrations in the range of 0.2–1.4 mM. The inset shows the calibration plots of the current recorded at +0.6 V/SCE versus the glucose concentration. ability of glucose oxidation is responsible for the electroanalytical parameters for glucose detection. The operating variables related to the detection potential (i.e., the electrode potential at which glucose oxidation occurred) and the sensing parameters (i.e., the sensitivity and the lowest limit of detection) constitute the main highlights for the development of the glucose detection method. In comparison with other copper-based electrodes and MOF-based electrodes, the sensitivity that is given by the electron transfer is highly enhanced, which is probably directly linked to the electrode surface morphology and the electroactive centers. Moreover, very nice results for the sensitivity were achieved using MPA, which is a very useful method for practical application of glucose detection, allowing in situ renewing of the electrode surface, avoiding its fouling. A very interesting aspect that was found in our study was related to the possibility of glucose detection at the potential value of +0.27 V/SCE that had a lower detection overvoltage in comparison with the reports presented above. A lower overvoltage oxidation potential is preferred, due to an increase in electrode ability toward a more efficient oxidation of the target analyte and more effective detection due to the better probability to avoid interferences. This desired result was achieved using DPV and was due to the combination effect of the catalytic properties of the electrode composition and the characteristics of the DPV technique. This aspect will be further studied in order to get enhanced sensitivity at this lower electrode potential value. The interference study was achieved by using MPA techniques for ascorbic acid, uric acid, dopamine and sodium chloride, which normally coexist with glucose in human blood serum (but at concentration levels about 30 times lower than glucose), and no significant responses were found.