## 4 Conclusions  
A new electrochemical sensor based on a biomimetic ion-imprinted polymer for the detection of mercury (II) traces was prepared on a gold electrode with a strategy based on the combination of the surface modification with a diazonium salt and the growth of ZnO nanorods followed by electropolymerization of the pyrrole in the presence of the template (Hg\({}^{2+}\)) and L-cysteine as crosslinker. These two steps (diazonium salt and ZnO nanorods) permitted us to increase the performance of the final sensor (Au-diazo-ZnO/IIP) in terms of selectivity and limit of detection (LOD), which is in the picomolar range. This is proven by investigating the performance of an IIP prepared directly on a bare gold electrode, without any surface modification and in the absence of any ZnO nanorods. The fit of the electrochemical results obtained by the one site/Hill model allowed us to determine the dissociation constants [\(K_{d1}\) = (7.89 \(\pm\) 3.63) mM and \(K_{d2}\) = (38.10 \(\pm\) 9.22) pM] as well as the sensitivity, which was equal to 0.692 \(\pm\) 0.034 \(\mu\)A.pM\({}^{-1}\). The competitivity and selectivity tests were undertaken using several ions such as Cu\({}^{2+}\), Pb\({}^{2+}\) and Cd\({}^{2+}\), taking into account the ionic radius and their concentration in an aqueous medium. IIP showed excellent ability to distinguish between mercury and different competitive ions even at \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Electrode** & **Analytical Method** & **Electrolyte** & **LOD** & **Ref** \\ \hline Glassy carbon electrode & Difference pulse voltammetry (DPV) & PBS (pH 7.0) & 0.42 nM & [88] \\ \hline Carbon-paste electrode (CPE) & Electrochemical Impedance Spectroscopy (EIS) & Nitrate solution & 1.95 nM & [89] \\ \hline Commercial screen-printed carbon electrode (SPCE) & Differential pulse voltammetry (DPV) & KNO\({}_{3}\)/HNO\({}_{3}\) solution (pH 2.7) & 0.104 nM & [90] \\ \hline Glassy carbon electrode & Square wave anodic stripping voltammetry (SWASV) & K\({}_{3}\)[Fe(CN)\({}_{6}\)] solution & 0.1 nM & [91] \\ \hline Carbon paste electrode (CPE) & Square wave anodic stripping voltammetry (SWASV) & HCl solution & 18 pM & [92] \\ \hline Glassy carbon electrode (GCE) & Differential pulse voltammetry (DPV) & PBS (pH 7.0) & 0.2 \(\mu\)M & [93] \\ \hline Carbon nanomaterials/AuNPs & Anodic stripping voltammetry (ASV) & KCl solution & 0.03 \(\mu\)M & [94] \\ \hline Mechanical Pencil Lead-NiS/Reduced Graphene Oxide & Anodic stripping voltammetry & PBS 1 mg/mL & 0.8 nM & [95] \\ \hline Platinum/(D) moderate decorated modified glassy carbon electrode (GCE) & Cyclic voltammetry (CV) & KCl solution & 3.4 nM & [96] \\ \hline Gold/polyethylene (GCE) & Differential pulse voltammetry & HNO\({}_{3}\)/KCl & 2.49 nM & [97] \\ \hline Zincophosphate NPs (NTOU4 nano)/polyaniline (PANI) & Differential pulse voltammetry & PBS (pH 7.0) & 3.49.10\({}^{-11}\) M & [98] \\ \hline Zinc oxide nanorods grafted on a Gold electrode & Square Wave voltammetry (SWV) & KCl solution & 1 pM & This work \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._low concentrations. Au-diazo-ZnO/IIP can therefore be used for environmental applications to detect mercury in the laboratory or for field analysis using a portable potensiostat. Conceptualization of the research work by [PERSON], [PERSON], C.Z. ; Methodology by [PERSON], [PERSON], C.Z., M.M.C. ; Validation by [PERSON], N.F., C.Z., R.T., M.M.C. ; Formal Analysis by [PERSON], [PERSON], N.F., C.Z., N.M., N.Y., M.M.C. ; Writing of Original Draft was done by [PERSON], N.F., C.Z., M.M.C. ; Writing: Review and Editing by [PERSON], H.E.E.Y.S., N.F., C.Z., N.M., N.Y., R.T., M.M.C. ; Supervision: N.F., C.Z., R.T., M.M.C. ; Funding Acquisition: N.F., C.Z., N.M., N.Y., R.T. All authors have read and agreed to the published version of the manuscript. This research was funded by La Region Pays de Loire, grant No LMAC/MEMSAW (recipient: N.Y) and by the Algerian Ministry of Higher Education and Scientific Research, grant number PNE 474 (recipient: H.E.E.Y.S.).