ZIF-8 derived TiO2/ZnO heterostructure decorated with AgNPs as SERS sensor for sensitive identification of trace pesticides

Pesticides are still abused and overused in agricultural production. Food safety monitoring in terms of reliable detection and quantification of pesticide residues is an ever increasing need. Surface-Enhanced Raman Scattering (SERS)-based chemical sensors and adsorption materials crafted for specific pesticide should provide high sensitivity and selectivity. Herein, zeolitic imidazolate framework (ZIF-8) derived TiO2/ZnO three-dimensional (3D) heterostructures were constructed on FTO substrate and were utilized to assemble silver nanoparticles (AgNPs) to create electromagnetic hot spots. The formation of TiO2/ZnO heterostructure greatly improve the SERS performance of the substrate. The calculated enhancement factor (EF) of the TiO2/ZnO/Ag is 39-fold higher than the TiO2/Ag substrates. Furthermore, the substrate shows high signal sensitivity and reproducibility for rapid detection of multiple pesticides. Even with a portable Raman device, the substrate was found to be highly efficient for model molecules of crystal violet (CV) and 4-mercaptobenzoic acid (4-MBA), and the limit of detection (LOD) for both of 10−9 M was demonstrated. Importantly, real life detection of multiple pesticides residues can be achieved with the TiO2/ZnO/Ag sensor, which was demonstrated by the detection of three common pesticides, thiram, acephate and phoxim at trace concentrations.