Supercritical Hydrothermal Synthesis of Polyacrylic Acid-Capped Copper Nanoparticles and Their Feasibility as Conductive Nanoinks.

Polyacrylic acid (PAA) applied as surface modifier of zero-valent copper nanoparticles (CuNPs) for electronic printing inks has great potential to replace presently used polymers, because of its favorable technical, environmental and biodegradability characteristics. Continuous synthesis (400°C, 30 MPa) of nanoparticles in supercritical water with short reaction times (1.1 s) was used to form PAA-surface-modified zero-valent (34–46 nm) CuNPs. CuNP particle sizes decreased with an increase in PAA molecular mass (5000, 250,000) and were stable as dispersions in methanol and 1-propanol, respectively. The resistivity of conductive films prepared with CuNPs decreased with an increase in heating temperature. The minimum resistivity of the PAA-modified CuNPs was 1.4 × 10⁻⁵ Ω cm at 320°C (PAA25000) and 4.2 × 10⁻⁴ Ω cm at 350°C (PAA5000), demonstrating the feasibility of PAA as a dispersant and surface modifier for CuNPs. Polyacrylic acid is thus effective as a surface modifier for zero-valent metal nanoparticles and expands the possible applications in sustainable printed electronics. [ABSTRACT FROM AUTHOR]