Generation of Catalytically Active Gold Nanocrystals in Water Induced with Ferrocene Carboxylate

The fabrication and properties of anisotropic gold nanoparticles (AuNPs) are of great interest from fundamental and application standpoints. Whereas various neutral ferrocene derivatives have been shown to reduce Au-III to Au(0)NPs owing to slightly exergonic electron transfer in biphasic systems, the question remained open for water soluble ferrocenes containing electron withdrawing substituents increasing the Fe-III/Fe-II oxidation potential. Here, it is shown that reaction of sodium ferrocene carboxylate, NaFcCO(2), alone, does not reduce H[(AuCl4)-Cl-III] to stable AuNPs under ambient conditions in water. On the other hand, reaction between NaFcCO(2) and H[(AuCl4)-Cl-III] in water in the presence of poly (vinyl pyrrolidone) (PVP), citrate or other 1,2,3-triazole (trz)-containing stabilizers is shown to produce catalytically active Au nanocrystals with various shapes. EDX results confirm the fixation of the ferrocenyl carboxylate ligand onto the AuNP surface. 4-nitrophenol reduction to 4-aminophenol by Na[BH4] in water proceeds in the presence of the various stabilizers, without induction time in most cases, which confirms the weakness of the ferrocenyl carboxylate ligand bonded to the AuNP surface and the favorable role of ferrocenyl carboxylate ligand for catalysis at the AuNP surface.

Automated summary

The study explores the effects of water-soluble ferrocene derivatives on gold nanoparticles, showing that under appropriate conditions, catalytically active gold nanocrystals can be produced.