Au@Pd Core-Shell Nanoparticle Incorporated Alumina Sols and Coatings: Transformation of Au@Pd to Au-Pd Alloy Nanoparticles

摘要

Au@Pd nanoparticles (NPs) of size range 4.5-13 nm ( ≈ 7.2 nm) were generated inside the alumina matrix sol without using any additional reducing agent. Partially acetylacetonato (acac) complexed aluminum tri-sec-butoxide has been used to prepare the matrix alumina sol. First, Au NPs of size range 3-9 nm ( ≈ 5.3 nm) were generated in the alumina sol following our reported method (J. Mater. Chem. 2008, 18, 2816). The addition of Pd-acetate in this Au NPs containing sol resulted in formation of Pd shells onto the Au NPs. The previously formed Au NPs were acting as seeds and the mild reducing environment of the reaction medium (due to Al-alkoxide) reduced the Pd ions to form Pd shells onto the Au NPs. The strong plasmon band observed at 520 nm in the case of Au NPs containing sol has been significantly dampened due to the formation of Pd shells. Grazing incidence X-ray diffraction and transmission electron microscopy (including scanning TEM, EDS using nanoprobe, and HRTEM) analyses revealed the core-shell structure of the NPs. The above sol can be used to prepare Au@Pd core-shell NPs incorporated alumina coatings on glass substrates. The Au@Pd NPs were transformed to Au-Pd alloy NPs inside the film matrix after heat treatment at 500 °C in air.