General Surface Modification Method for Nanospheres via Tannic Acid-Fe Layer-by-Layer Deposition: Preparation of a Magnetic Nanocatalyst

In this paper, a tannic acid-Fe layer-by-layer (TA-Fe LbL) modification process was developed to modify the highly curved surfaces of nanospheres. In contrast to the traditional TA-Fe one-step assembly method, TA-Fe coordination complexes were uniformly coated onto the surface of Fe3O4@SiO2 nanospheres by the TA-Fe LbL modification process with no TA-Fe aggregates forming on the nanospheres or in the reaction solution. By virtue of the reduction capability and effective immobilizing effect of TA, Ag nanoparticles (NPs) with small sizes (2–10 nm in diameter) and a narrow size distribution were formed in situ on the surface of the modified nanospheres. The resultant nanocomposites exhibited excellent catalytic performance and good stability for the reduction of 4-nitrophenol. This strategy can be extended to modify various highly curved surfaces to fabricate a variety of functional nanocomposites.