Understanding and reducing photo-thermal forces for the fabrication of Au nanoparticle dimers by optical printing

GARGIULO, JULIAN; BRICK, THOMAS; VIOLI, IANINA L.; HERRERA, FACUNDO C.; SHIBANUMA, TOSHIHIKO; ALBELLA, PABLO; CORTES, EMILIANO; REQUEJO, FELIX G.; MAIER, STEFAN A.; STEFANI, FERNANDO D

NANO LETTERS (PRINT)

AMER CHEMICAL SOC

Lugar: Washington; Año: 2017

1530-6984

Optical printing holds great potential to enable the use of the vast variety of colloidal nanoparticles (NPs) in nano- and micro- devices and circuits. By means of optical forces, it enables the direct assembly of NPs, one by one, onto specific positions of solid surfaces with great flexibility of pattern design and no need of previous surface patterning. However, for unclear causes it was not possible to print NPs closer to each other than 300 nm. Here, we show that the repulsion restricting the optical printing of close by NPs arises from light absorption by the printed NPs and consequent local heating. By optimizing heat dissipation, it is possible to reduce the minimum separation between NPs. Using a reduced graphene oxide layer onto a sapphire substrate, we demonstrate for the first time the optical printing of Au-Au NP dimers. Modelling the experiments considering optical, thermophoretic and thermo-osmotic forces we obtain a detailed understanding and a clear pathway for the optical printing fabrication of complex nano structures and circuits based on connected colloidal NPs.