Synthesis and characterization of air-stable Cu nanoparticles for conductive pattern drawing directly on paper substrates

Air-stable Cu nanoparticles (NPs) with an average diameter of 6.5 nm were synthesized under ambient conditions using polyvinylpyrrolidone and cetyltrimethylammonium bromide as a mixed capping agent, for preparing nano-Cu ink applicable for direct writing on photo paper using a roller pen. The size, morphology, and air-stability of the Cu NPs were characterized by TEM, SEM, XRD, etc. The mixed capping agent was effective in reducing the aggregation, size of the Cu NPs and improving their air-stability. The reduced size and enhanced air-stability of the Cu NPs resulted in an improved particle density upon sintering, which was mainly responsible for the increased conductivity of the Cu patterns. The resistivity of Cu patterns sintered at 160 °C for 2 h was 11 ± 0.8 μΩ cm, 6.40 times the bulk resistivity. A sample RFID antenna and a decorative logo were successfully made and the Cu patterns or lines exhibited excellent integrity and good conductivity, which were experimentally tested.