Synthesis of recyclable SERS platform based on magnetic Fe3O4/mTiO2/Ag composites for photodegradation and identification of organic pollutants in different water samples

In this study, we coatedmagnetic Fe 3 O 4 nanospheres with a crystalline mesoporous TiO 2 (mTiO 2 ) layer with photocatalytic activity, followed by the deposition of Ag nanoparticles as an outer layer through in-situ reduction of AgNO 3 to obtain multifunctional Fe 3 O 4 /mTiO 2 /Ag core-shell-shell structured composites. By adjusting the amount of AgNO 3 , we were able to precisely control the size and coverage of the Ag nanoparticles. To evaluate the surface-enhanced Raman spectroscopy (SERS) activity of the Fe 3 O 4 /mTiO 2 /Ag composites, we employed 4-mercaptobenzoic acid (4-MBA) as a model Raman reporter. The limit of detection (LOD) of 4-MBA was down to 10 −10 M. Moreover, for practical applications, we successfully detected methylene blue (MB) in different water samples, such as tap water and industrial wastewater, and both of systems presented an ultralow LOD of 10 −9 M. Notably, a strong linear relationship (R 2 ≥ 0.95) between the SERS intensities and the logarithmic concentration of MB was observed, highlighting the excellent quantitative sensing capabilities of these substrates. The Fe 3 O 4 /mTiO 2 /Ag composites also exhibited remarkable signal reproducibility and exceptional stability during storage. Additionally, these composites demonstrated promising photocatalytic property. In five consecutive cycles, we were able to efficiently detect MB by utilizing the composites' photocatalytic removal ability under UV irradiation , which was facilitated by simple magnetic separation. These findings hold significant importance for environmental safety and pollutant removal applications.