Formation of Bimetallic Copper–Gold Alloy Nanoparticles Probed by in Situ X‐ray Absorption Fine Structure Spectroscopy

摘要

> Advanced studies of the formation and growth processes of metal alloy nanoparticles are of great importance and provide a better understanding for the fine tuning of their properties for the desired applications. In this work, we followed the synthesis of Au _{1– x} Cu _x colloidal nanoparticles by in situ time‐resolved X‐ray absorption fine structure (XAFS) spectroscopy. The particles were synthesized by a one‐pot approach with a homemade reactor adapted to the XAFS measurements. The colloidal nanoparticles were also characterized by complementary ex situ techniques. Analyses at the Cu‐ K edge and Au‐ L ₃ edge confirmed that the initial reduction of the Au species occurs at low temperatures (100 °C) to form Au seeds that are subsequently enriched with Cu to form Au _0.75 Cu _0.25 alloy nanoparticles at 225 °C. An important finding was the temporary formation of a Cu ₂ O‐type phase during the colloidal synthesis. This phase was consumed with the concomitant formation of the Au _{1– x} Cu _x alloy nanoparticles. These results directly confirm the previous proposal that the alloy formation occurs through a digestive‐ripening‐like process of an amorphous Cu‐enriched phase.