A novel core-shell heterostructure of zinc oxide/metal-organic frameworks anchored silver nanoparticles for enhanced SERS and photocatalytic performance

Here, a novel well-ordered ZnO rod-flower/zeolitic imidazolate framework-M (ZIF-M, using 5-mercapto-1-methyltetrazole as ligand) core-shell heterostructure (Al/ZnO/ZIF-M, AZZ*) is induced by aluminum (Al) sheet. Subsequently, Ag nanoparticles (AgNPs) are tightly attached to the ZIF-M layer in AZZ* through the strong Ag-N and Ag-S bonds, and a portable bifunctional substrate of Al/ZnO/ZIF-M/Ag (AZZ*Ag) is constructed. The finite difference time domain (FDTD) analysis shows that the AZZ*Ag substrate generates the stronger electromagnetic field intensity than the AZAg. Also, there is a strong synergistic effect among Al, ZnO, ZIF-M and Ag which can effectively facilitate the electron transfer. Importantly, the AZZ*Ag substrate exhibits outstanding SERS response with high sensitivity and selectivity for crystal violet (CV) molecules. The low detection limit (LOD) of CV molecule is 2.81 × 10-11 mol·L-1 with high analysis enhancement factor (AEF) of 1.93 × 106. In addition, AZZ*Ag substrate shows good photocatalytic performance for CV molecules with high degradation efficiency of 97.35% within 105 minutes, which is 4.72 times that of AZAg. Importantly, the SERS and photocatalytic performance of AZZ*Ag are 4.4 times and 3.09 times those of the Al/ZnO/ZIF-8/Ag (AZZ#Ag, using 2-methylimidazole as ligand), respectively. Moreover, the AZZ*Ag substrate displays excellent stability, good reproducibility, recyclability and uniformity. Thus, the designed portable bifunctional composite exhibits great potential for SERS detection and photocatalytic degradation of other pollutants in environmental wastewater.