Abstracts are provided in the language submitted.

Metal nanoparticles exhibit selectivity and enhanced optical and electrical properties compared to bulk materials. Gold is often the metal of choice when fabricating plasmonic materials. The properties of gold nanoparticles are directly related to their shape and size, and many procedures to obtain specific forms of nanoparticles are available in the literature. Common methods for their making and isolation involve multiple steps: seeding, growth, and stabilization. These steps are usually done in separate, distinct reaction environments. We completed all these steps in the same reaction mixture by inducing nanoparticle formation at a liquid-liquid interface. The aqueous phase contains gold ions, and the organic phase contains a dithiafulvene derivative as the reducing agent. Once oxidized, the dithiafulvene dimerizes into tetrathiafulvalene, which then caps the gold nanoparticles. The nanoparticles remain in the aqueous solution, which can be isolated by simple liquid-liquid separation. By limiting the reaction to the interface, we hoped to create the conditions for controlled, organized growth of gold nanoparticles. Our results show that the reaction completes in two different scenarios: i) the reaction is left undisturbed; ii) the reaction is initially sonicated and then left undisturbed. These two scenarios give nanoparticles of different shapes and sizes. The sonication leads to smaller, berry-like shaped nanoparticles, while the undisturbed reaction leads to bigger hexagons and triangle shaped particles. In conclusion, we demonstrated the key-role of the interface in a liquid-liquid reaction system to obtain gold nanoparticles of distinct shapes and sizes.

Silvana Rodrigues Pereira