The reduction of silver nitrate to metallic silver inside polyaniline nanotubes and on oligoaniline microspheres

Polyaniline (PANI) reduces silver nitrate to metallic silver. Composites based on conducting polymer and silver have been prepared with equimolar proportions of reactants. Polyaniline bases having different morphologies - granular or nanotubular - and oligoaniline microspheres have been left to react with silver nitrate in acidic, neutral, and alkaline media. The content of silver, typically 20-30 wt.%, was determined by thermogravimetric analysis. Clusters of 40-80 nm silver particles are produced in the granular form of PANI. The formation of silver inside PANI nanotubes has been observed. With oligoaniline microspheres, silver was produced on their surface, and on PANI agglomerates accompanying them. The highest conductivity, 943 S cm(-1), was found with silver reduced by nanotubular PANI base in 0.1 M nitric acid at 17.3 wt.% silver content. The standard granular PANI, used as a reference material, yielded a composite having a much lower conductivity of 8.3 x 10(-5) S cm(-1) at 24.3 wt.% Ag. There is no simple correlation between the conductivity and silver content. Infrared and Raman spectroscopies have been used to study the changes in the molecular structure of the PANI bases of various morphologies before and after reaction with silver nitrate. (C) 2010 Elsevier B.V. All rights reserved.