Study of size effect on the conductivity of nano-silver colloids

Two nano-silver particles, 22 nm and 120 nm, were prepared by the polyol method where silver nitride was as the silver source and polyvinylpyrrolidone (PVP) was added to prevent the as-synthesized nanoparticles from agglomeration. After that, the particles in the colloid form were coated separately, where photo paper was the substrate. It is found that the resistances of the two coatings are strongly depending on the particle sizes. Through heating process, the 22 nm silver coating shows excellent conductivity which the sheet resistance can decrease to 0.39 Ω/□ when it was heating for 10 min, 200 °C. Meanwhile, the 120 nm silver coating showed high resistance. UV-vis spectrum was used to characteristic the nano Ag colloids, the resistivity variation and microstructure of the Ag coating were using a four-point probe and scanning electron microscopy (SEM). The good conductivity of the 22 nm Ag colloid coating shows us a bright future which can be used as the conductive ink of printing electronics.