Light-induced Polarization-directed Growth of Optically Printed Gold Nanoparticles

VIOLI, IANINA L.; CORTÉS, EMILIANO; VON BILDERLING, CATALINA; GARGIULO, JULIÁN; STEFANI, FERNANDO D.

Porquerolles

Workshop; PHOTOTHERMAL EFFECTS IN PLASMONICS; 2018

Optical printing has been proved a versatile and simple method to fabricate arbitrary arrays of colloidal NPs on substrates. Here we show that is also a powerful tool for studying chemical reactions at the single NP level. We demonstrate that 60 nm gold NPs immobilized by optical printing can be used as seeds to obtain larger NPs by plasmon-assisted reduction of aqueous HAuCl4. The final size of each NP is simply controlled by the irradiation time. Moreover, we show conditions for which the growth occurs preferentially in the direction of light polarization, enabling the in-situ anisotropic reshaping of the NPs in pre-determined orientations. Individual Au NPs on an array were grown in a controlled fashion to different final sizes by illumination at their surface plasmon resonance in presence of a HAuCl4 aqueous solution. As they grow, the NPs reshape their morphology from nearly spherical to spheroidal with their major axis parallel to the polarization of the light used to induce the reaction