Purposefully Designed Surfactants for Facile and Controllable Gold Colloidal Nanocrystal Synthesis

Three new cationic surfactants-N-cetyl-bis(2-dimethylaminoethyl)ether bromide (CBDEB), N-dodecyl-bis(2-dimethylaminoethyl)ether bromide (DBDEB), and N-hexyl-bis(2-dimethylaminoethyl)ether bromide (HBDEB)-have been designed herein using a simple and tailorable synthesis route. CBDEB and DBDEB, the 16- and 12-carbon chain surfactants, demonstrate facile, rapid, and controllable aqueous syntheses of gold nanoparticles (AuNPs) as dual-action reducing and capping agents. The synthesis strategy, using only surfactant and HAuCl4 salt, and 4 min of heating at 80 degrees C, results in spherical AuNPs (average diameters of 13.4 +/- 3.8 nm for CBDEB and 12.0 +/- 3.8 nm for DBDEB). Microwave irradiation was also investigated as a heating method and produces AuNPs in as little as 30 s. Control over the size and shape of AuNPs was proven to be feasible (toward populations of Euclidean shapes) by appropriately tuning reaction parameters, such as the molar ratio of surfactant to Au3+, temperature, incorporation of a time delay before heating, or shape control agents, such as Cu2+. Frustratingly, the cytotoxicity of CBDEB is similar to that of cetyltrimethylammonium bromide (CTAB), a popular 16-carbon chain cationic surfactant. Notably, while the shorter HBDEB (6-carbon chain) does not produce AuNPs under the applied conditions, it does appear to improve cell viability upon cytotoxicity evaluation and may be favorable as a new biological surfactant.

Automated summary

Three new cationic surfactants have been designed and used to synthesize gold nanoparticles. The synthesis method is simple and fast, and allows control over the size and shape of the nanoparticles. One of the surfactants shows promising results in terms of cell viability and may serve as a new biological surfactant.