Hollow bimetallic nanoparticles generated in situ inside a polymer thin film: fabrication and catalytic application of silver–palladium–poly(vinyl alcohol)

Hollow bimetallic nanoparticles of silver–palladium (Ag–Pd) are generated in situ inside poly(vinyl alcohol) (PVA) thin films by a two-stage process. In the first stage, Ag–PVA is fabricated by mild thermal treatment of a spin-coated thin film, with the polymer functioning as the reducing agent for the embedded metal precursor ions as well as the stabilizer for the generated nanoparticles. In the second stage, an aqueous solution of potassium palladium chloride (K₂PdCl₄) is spread on this film under ambient conditions, whereupon Pd gets deposited on the Ag nanoparticles through a Galvanic displacement reaction and alloys with it. A crucial requirement of relatively large Ag nanoparticles that can act as the sacrificial template in the second stage is met by the addition of catalytic amounts of cupric ions in the first stage. A gradual variation of the concentration of K₂PdCl₄ solution used in the in situ process allowed a systematic demonstration of the evolution of the bimetallic nanoparticles with the eventual formation of hollow particles with Ag–Pd alloy walls. The high catalytic efficiency of the Ag–Pd hollow nanoparticle-embedded PVA thin film is demonstrated by its application in the Suzuki–Miyaura reaction