Fabrication of chitosan nanofiber composite copper thin film with high electrical conductivity using copper formate complex ink

A chitosan nanofiber composite copper thin film was synthesized using a copper formate–octylamine complex ink and chitosan nanofibers to enhance electrical conductivity. The interaction between the amino groups of the chitosan nanofibers and copper formate was proposed to form a coordination bond, leading to the deposition of copper on the nanofiber surfaces. This resulted in the formation of conductive pathways composed of copper-coated fibers and surrounding copper particles. To maintain nanofiber dispersion during calcination, water in the chitosan nanofiber suspension was replaced with ethylene glycol, which has a higher boiling point. The fabricated copper thin film containing 2 wt% chitosan nanofibers exhibited a low volume resistivity of 6 μΩ cm, approximately three times that of bulk copper (1.7 μΩ cm). Energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of thin copper layers (∼4 nm thick) on the nanofiber surfaces, consistent with observations of nanofiber width. Copper particles were also observed in proximity to the nanofibers. The formation of thin copper layers on the nanofibers was attributed to the coordination between amino groups and the copper formate ligand, thereby contributing to the enhanced electrical conductivity. • High electrical copper thin films with were prepared by adding chitosan nanofibers. • Optimum concentration of chitosan nanofiber was 2 wt%. • Copper layer covered on chitosan nanofibers and copper particles were observed. • High electrical conductivity was due to formation of copper layer on nanofibers.