Morphological control of gold nanoparticles on exfoliated layers of layered double hydroxide: A reusable hybrid catalyst for the reduction of p-nitrophenol

We have developed a controllable method for high density of ultrafine gold nanoparticles (NP) and their uniform aggregates on exfoliated nanosheet of layered double hydroxide (LDH). The LDH nanosheet effectively supports the growth of ultrafine gold NP because the freshly exfoliated hydroxide prevents the formation of large and irregular aggregation of gold NP. We found that the reduction conditions allowed controlling the sizes and morphologies of gold NP during their growth on LDH layers. Additionally, pre-added ascorbic acid effectively induced a narrow distribution of gold NP during their reduction reactions by NaBH 4 or hydrazine hydrate. This hybrid material exhibited excellent durability and catalytic activity ( > 99% conversion efficiency) in the reduction of p-nitrophenol. The nanoscopic nature of exfoliated LDH nanosheets affects the catalytic performances of the hybrid catalyst, such as a high positive charge for strong binding to gold NP, and a fresh hydroxide surface for a good dispersion of the hybrid catalyst in reacting solutions. Our method can be very useful to make stable and reusable Au/LDH nanohybrids for a variety of applications.