High-concentration silver colloid stabilized by a cationic gemini surfactant

Silver nanoparticles have been intensively investigated in recent years due to their unique physical and chemical properties. However, the low concentration and poor stability of silver nanoparticles in aqueous solution limit their wide applications. In this work, the cationic gemini surfactant dimethylene-1,2-bis(dodecyl dimethylammonium bromide) (12-2-12) was employed to prepare and stabilize high-concentration silver nanoparticle, in comparison with its monomeric counterpart, dodecyl trimethyl ammonium bromide (DTAB). The size, size distribution and long-term stability of silver nanoparticles were examined by means of transmission electron microscopy and UV–vis spectrophotometry. It was found that when using 12-2-12 as the stabilizer, the concentration of silver nanoparticles in aqueous solution can reach 44.6 mM, and the average size was 11 ± 3 nm, much higher concentration and much narrower size distribution than those (35.7 mM, 15 ± 10 nm) with DTAB as the stabilizer. Silver nanoparticles stabilized by 12-2-12 show better long-term stability that those stabilized by DTAB. Negative staining TEM observation proved the 12-2-12 molecule had more stable and more efficient capping ability to stabilize silver nanoparticles than DTAB due to its double-head architecture and high charge density. The as-obtained nanoparticles stabilized by 12-2-12 also displayed good catalytic activity for the reduction of 4-nitrophenol.