A Magnetic Four Component Nanocomposite: Biosynthesis Using Melissa officinalis Leaves Extract, Application in High-Performance Naked-Eye Sensing of Mercury(II) and Efficient Catalytic Reduction of Para-nitrophenol

In the present research, we aimed to develop a simple and green approach to producing a very versatile Ag@AgCl/Fe 3 O 4 @kaolinite bionanocomposite with the aid of the aqueous extract of Melissa officinalis . In fact, the Ag@AgCl sample, biosynthesized using the extract, was upgraded with imprinting on kaolinite to produce the Ag@AgCl/kaolinite bionanocomposite. Likewise, we synthesized the four-component Ag@AgCl/Fe 3 O 4 @kaolinite for promoting the properties and applications of the as-made nanocomposites. The products were characterized using various techniques such as UV–Vis, FT-IR, XRD, FE-SEM, EDX and XPS. Moreover, they were utilized not only as the efficient heterogeneous catalysts for the reduction of para-nitrophenol to para-aminophenol, but also as the useful biosensors for the detection of Hg 2+ in the aqueous media. The resulting heterogeneous catalysts, thus, featured valuable advantages like easier work-up, better stability, and greater separation ability using an external magnet.