Wet-Chemical Routes without Surfactants

Apparently, the simplest solution-based approach to produce copper colloids is the direct reduction of a precursor in an appropriate aqueous solution. Most frequently, an alkaline medium and complexing additives are employed this is necessary in order to sequester Cu ions and to prevent the undesired formation of insoluble CuP hydroxides, eventually evolving into CU2O or CuO NPs. In contrast, the formation of cuprate ions or other soluble Cu complexes makes possible the synthesis of Cu NPs, due to the following reaction scheme [99]  

Many studies have used a modified version of this aqueous route to Cu NPs [100-111] the key aspects of the different approaches are shown schematically in Table 1.1. 

Wet-Chemical Routes Based on Surfactants and Low-Molecular-Weight Capping Agents 

---