Highly conductive nanosilver ink treated at mild temperatures by reducing the amount of PVP

Silver nanoparticles colloid was obtained by reducing the high molar concentration of AgNO3 (up to 3.92 M) with the hydrazine hydrate (H4N2 · H2O) as reductant in the presence of polyethylene pyrrole (PVP) as the protectant. It was well known that the polymer protective agent capped on the surface of silver nanoparticles could control the particles growth and stabilize the nanosilver suspension. Meanwhile, the insulative PVP capped on the surface of nanosilver could prevent the transfer of electrons, resulting in the conductivity decreasing of the corresponding nanosilver films. Thus, the amount of PVP should be reduced in order to improve its conductivity. The silver nanoparticles was treated by the chemical sedimentation, which is the most widely used solid-liquid separation method in the preparation of nanosilver conductive printing ink, for its low costing and without destroying the structure of the silver nanoparticles. It was found that the treatment can effectively reduce the amount of PVP. Good dispersion and electrical conductivity nanosilver ink can be obtained by acetone sedimentation for three times. The average size of the particles after sedimentation is 120.3 nm, while the initial size is 92 nm and no precipitation was observed even after aging for 15 days. Surface resistance of the silver layer coated on PET can be reduced to 226.4 mΩ/□ after heating at 100°C for 30s, and the conductive ink with these properties can be widely used in preparation of transparent conductive film and RFID antennas.