Preparation of sub-micrometer Cu particles by green hydrothermal synthesis under air

Cu particles ranging in size from several micrometers to less than a micrometer were synthesized using an environmentally friendly hydrothermal process involving L-ascorbic acid as a reducing agent and gelatin. The size and synthetic yield of Cu particles was investigated at different gelatin additions and synthesis temperatures. With increasing gelatin content, the particle size decreased from 2.4 µm to 0.4 µm and the yield increased from 79.4% to 90.4%. With increasing synthesis temperature, the particle size changed significantly and the yield increased from 42.4% to 91.2%. The Cu particles synthesized at 85°C for 50 min with 12 g of gelatin showed the lowest average particle size of 0.4 µm and a yield of 90.4%. The FR-IR spectra indicated that coordinating bonds between the N in the gelatin and the Cu were formed, and a sequential reaction mechanism was proposed. It was determined that the gelatin addition not only prevents the Cu particles from agglomerating but also enhances the reduction of Cu ions.