Synthesis of citrate-capped copper nanoparticles: A low temperature sintering approach for the fabrication of oxidation stable flexible conductive film

Abstract

Printable flexible electronics are gaining attention day by day over the last few years due to the increasing demand for wearable electronics. Copper-based conductive inks are the most promising material for printing flexible electronics due to their high conductivity and cost-effectiveness. However, high-temperature sintering under reductive environment, rapid oxidation in the air and poor bending stability are the big constrains in the widespread utilization of copper inks. Herein we describe a facile method for fabrication of flexible conductive PET film under ambient air using as-synthesized citrate-capped copper nanoparticles. Sodium alginate paste (made in hydrazine) was used as a sintering aid to make the film conductive at low heating temperature. The citric acid capping protects the particles from oxidation while esterification with sodium alginate contribute to mechanical stability. The achieved resistivity of 74.4 ± 9 × 10−2 μΩ m is way better than reported in literature considering ambient air sintering under 60 ○C with improved adhesion, to the best of our knowledge. Persistent current flow even after 2500 bending cycles (not reported before) shows the exceptional mechanical stability of our film against bending, while the utilization of facial screen-printing fabrication technology made the process commercially viable and cost-effective.