Synthesis of Ag-PVA and Ag-PVA/PET-s20 composites by supercritical CO2 method and study of silver nanoparticle growth

Rafael Silva,Eduardo Radovanovic,Marcos H Kunita,Emerson M Girotto,Gizilene M Carvalho,Edvani C Muniz,Adley F Rubira

doi:10.1590/s0103-50532008000600025

Rafael Silva, Eduardo Radovanovic + Show 5 more

Open Access

https://doi.org/10.1590/s0103-50532008000600025

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Abstract

Supercritical CO2 has been used to prepare silver polymer composites, silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/sulfonated poly(ethylene terephthalate) through impregnation of a silver precursor in solid-state polymeric matrices followed by thermal reduction of the silver precursor. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, thermogravimetric analysis and UV/vis spectroscopy indicate that synthesis conditions and polymeric matrix composition affect silver particle size, shape and distribution in polymeric matrices. Silver particles are smaller, have a more uniform shape and present narrower size distribution in PVA-rich than in PETs-rich composites.

Highlights

The use of supercritical fluids offers the benefit of high diffusivity besides its ecological advantages, and the solvation power of supercritical CO2, which may be used as a swelling agent, as reported by Kunita et al.[23]
Ag‐poly(vinyl alcohol) (PVA) composites present interesting spectral characteristics depending on the impregnation and thermal treatment conditions
The polymer chain mobility increases during the thermal treatment; the silver particles have mobility in the composite bulk phase and the silver particles agglomerate, since their movement toward the surface is irreversible

Summary

Introduction

Nanostructured silver particles in zero oxidation state have been object of great interest for decades due to their use in catalysis, photography, photonics, electronics, information storage, labeling, imaging, sensing, and surface-enhanced Raman scattering (SERS).[1,2,3,4,5,6] In the several works with different preparation methods reported, the silver precursor, a silver salt, is reduced in solution in the presence of a capping agent.[7,8,9,10,11,12,13,14] The polyol process has been known for decades as a generic route for the synthesis of metal colloids.[12,13,14] It concerns the preparation of metallic powders, essentially of cobalt, nickel, copper, and precious metals, by reduction of inorganic compounds in liquid polyol, which acts both as a solvent and a reducing agent, as stated by Blin et al.[15]. Supercritical fluids have been applied to obtaining new materials.[18] Supercritical state has been studied and reported in literature since its discovery in the early 19th century by Baron La Tour.[19] Supercritical fluids allow controlling particle shape and size to produce highly uniform nanometric materials. The use of supercritical fluids offers the benefit of high diffusivity besides its ecological advantages, and the solvation power of supercritical CO2, which may be used as a swelling agent, as reported by Kunita et al.[23]

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