###### Abstract
Among them, organic dye molecules are highly colored. A trace amount below 1 ppm of dye is clearly visible and can influence the water environment considerably. Therefore, removal of dye molecules from wastewater by using sensitive techniques is important. Combining the strong local surface plasmon resonance (LSPR) between noble metal and nanostructures of ZnO via an active charge transport layer of a conducting PDA to create a substrate that exhibits strong SERS activity and is photocatalytic can provide a substrate that is ideally suited for both detection and remediation of organic pollutants. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**SERS Substrate Based on ZnO** & **SERS Reporters** & **EF** & **Ref.** \\ \hline Ag/ZnO nano arrays & benzenethiol, Rhodamine 6 G, adenine & \(10^{10}\)–\(10^{11}\) & [19] \\ Au/ZnO Nano Rods/Graphite & Rhodamine 6 G & \(2.3\times 10^{6}\) & [20] \\ Si/ZnO nanotrees & Rhodamine 6 G & \(10^{6}\) & [21] \\ Ag@ZnO Nanorods & Rhodamine 6 G & \(1.6\times 10^{6}\) & [22] \\ Ag/ZnO/Si & Rhodamine 6 G & \(8.7\times 10^{7}\) & [23] \\ Au/ZnO & phenanthrene & \(10^{6}\) & [24] \\ Ag/ZnO-nanorods & 4-aminotinophenol & \(3.5\times 10^{7}\) & [25] \\ ZnO/graphene/Ag & Rhodamine 6 G & \(0.95\times 10^{12}\) & [26] \\ Mg/ZnO heterostructure & 4-MPY & \(1.36\times 10^{7}\) & [27] \\ Au/ZnO nanorods & Dopamine & \(1.2\times 10^{4}\) & [28] \\ ZnO/ZnS/MoS\({}_{2}\) & Rhodamine 6 G & \(1.4\times 10^{8}\) & [29] \\ ZnO/Au Nanoarrays & Rhodamine 6 G & \(1.2\times 10^{7}\) & [30] \\ \hline Ag/PDA/ZnO@GMF & Rhodamine B & \(10^{10}\) & Our substrate \\ \hline \hline \end{tabular}
\end{table} 
Table 1: ZnO based SERS substrates developed in the past few years. In this scenario, we constructed a multicomponent Ag/PDA/ZnO@GMF SERS substrate by introducing a facile charge transport channel of PDA in between AgNPs and ZnO nanorods. Additionally, the ZnO nanostructures formed multibranched clusters which increased active site density and thereby further improved the SERS effects and photocatalytic activity. The main advantages of PDA in our system are summarized as follows: (1) A large number of PDA functional groups, including catechol, amine, and imine, served as both reducing agent and as the anchor for homogeneous and controlled distribution of grown AgNPs onto ZnO nanostructures: (2) The excellent stability of PDA conferred durability as well as excellent biocompatibility to the substrate; (3) The remarkable mechanical reinforcement of PDA, as strong adhesion prevented leakage of AgNPs and ZnO segments and thus excellent recyclability of the substrate was observed; (4) Efficient charge redistribution between Ag and ZnO through the plentiful \(\pi\) electrons of PDA improved the SERS effect. Overall, these factors and a mode of easy charge transport between Ag and ZnO played an essential role in achieving an improved plasmon sensitivity (EF: 10\({}^{10}\)) for a model organic pollutant dye (Rhodamine B, RhB) molecule. The substrate possesses high stability and UV light-induced self-cleaning and further can be reused even after six cycles. Due to the enhanced SERS sensitivity and to the other stated advantages that this hybrid SERS system demonstrates, this model may provide new strategies for developing highly sensitive and stable SERS technology.