Stable Gold Nanoparticle Colloids for Inkjet Printing Conductive Films

ABSTRACT A water‐soluble gold ink was prepared in this study after synthesizing gold nanoparticles (AuNPs) of different sizes. By systematically modifying ink composition using a polymeric capping agent, a stable colloidal ink was formulated. With an average nanoparticle diameter of 5.6 nm and narrow size distribution, the synthesized nanoparticles allowed for the formulation of long‐term and clog‐free inks. Both printability and shape resolution of printed patterns were greatly impacted by the ink solvent composition. Thermal‐sintered films with low sheet resistance (< 2 Ω/sq) were obtained. Surface characterization of printed films revealed percolation of charges and sintering of nanoparticles to be the root cause of observed variation in the sheet resistance. Heterogeneous film thickness was observed after printing and thermal annealing, and it was reasoned that a combination of particle aggregation and heterogeneous dissolution/aggregation dynamics occurred during layer‐by‐layer printing. This study has demonstrated the size control of AuNPs and stable ink formulation, even after weeks of storage in ambient conditions and at >10 wt/wt% capped nanoparticles, for fabricating conductive traces.