Solvent and stabilizer free growth of Ag and Pd nanoparticles using metallic salts/cyclotriphosphazenes mixtures

Cyclotriphosphazene is used as a sacrificial solid-state template to synthesize a range of Ag and Pd nanoparticles with diverse geometries by thermal treatment using MLn/N₃P₃(O₂C ₁₂H₈)₃ mixtures. The Pd and Ag nanoparticles are synthesized by solid-state pyrolysis of AgPPh₃[CF ₃SO₃]/N₃P₃(O₂C ₁₂H₈)₃ and PdCl₂/N₃P ₃(O₂C₁₂H₈)₃ mixtures with molar relationships of 1:1, 1:5 and 1:10 respectively, in air and at 800 C. The morphology of the as-prepared nanoparticles is found to depend on the molar ratio of the precursor mixture, the preparation method and of the nature of the metal. Ag and Pd, microcrystals were thermally grown on Si from the respective 1:1 precursors while that metal foams were grown from 1:5 ratios precursors on SiO₂ wafers. High resolution transmission electron microscopy investigations reveal in most cases small crystals of Pd. HRSTEM measurements indicate that the formation of the Pd and Ag nanoparticles occurs through a phase demixing and dewetting mechanism. This approach has potential to be a useful and facile method to prepare metallic nanoparticles without requiring solutions or surfactants for application in electronic, catalytic and sensor materials and devices.