Green synthesis and response surface methodology optimization research of copper nanoparticles in supercritical ethanol

In this study, we employed the Box-Behnken design in Response Surface Methodology (RSM) to systematically optimize the process of continuous solvothermal synthesis of copper nanoparticles in supercritical ethanol. Through comprehensive analysis of four key operational parameters - reaction temperature, system pressure, reactor length, and precursor concentration- mathematical models were established to correlate these variables with critical product attributes including crystalline phase purity, grain size, and apparent particle size distribution. Among the investigated parameters, precursor concentration emerged as the most influential factor, demonstrating remarkable control over both morphological evolution and final particle dimensions. The study revealed that low precursor concentrations (0.01 mol·L⁻¹) preferentially yield cubic nanostructures, while higher concentrations promote the formation of spherical particles. Temperature and pressure were identified as primary regulators of crystalline phase purity and grain dimensions, while reactor length exhibited coupled effects with pressure in determining final particle size characteristics. Under the optimized conditions (300°C, 13 MPa, 27.5 cm reactor length, and 0.06 mol·L⁻¹ Cu²⁺ concentration), high-quality copper nanoparticles were successfully synthesized, exhibiting pure phase composition, spherical morphology, excellent dispersion stability, and a remarkably small average particle size of 19.79 nm. This work demonstrates RSM's efficacy for precise process optimization towards green, efficient production.