Nano-Ag particles, with dodecylamine (DDA) and dodecanethiol (DDT) as the protective agent, were prepared and studied in order to investigate the effect of protective agent in the post heat-treatment of nano-Ag films. Results of electrical resistivity, micro-structural evolution and thermal analysis showed that the Ag-DDA films require a lower treatment temperature to convert into conductive materials compared to that of the Ag-DDT films. And the Ag-DDA films also have lower final electrical resistivity as well as more uniform and dense microstructure in comparison with the Ag-DDT films. Further study indicated that Ag-DDA films are thermodynamically unstable and the sinter of Ag-DDA particles could occur spontaneously even at room temperature. FT-IR, H-1 NMR and X-ray diffraction determinations revealed that both DDA and DDT molecules coordinate to the surface of nano-Ag particles through their head-groups. The bonding energy of Ag-S is higher than that of Ag-N and the alkyl chains ordering of chemisorbed DDT is also higher than that of chemisorbed DDA. It is implied that the post heat-treatment temperature and final resistivity of nano-Ag films are associated with the bonding energy and configuration of different capping molecules. Finally the conductive ink was prepared with well dispersed Ag-DDA nanoparticles and the ink-jet printed patterns on PI films show a sheet resistance of 166m Omega/square after heat-treating at 140 degrees C for 60 min. (C) 2011 Elsevier B. V. All rights reserved.