title: Optical Nanoparticle Sorting Elucidates Synthesis of Plasmonic Nanotriangles.
abstract: We investigate the optical and morphological properties of gold nanoparticles grown by reducing a gold salt with Na2S. Lasers are tuned to the observed plasmon resonances, and the optical forces exerted on the nanoparticles are used to selectively print individual nanoparticles onto a substrate. This enables us to combine dark-field spectroscopy and scanning electron microscopy to compare the optical properties of single nanoparticles with their morphology. By arresting the synthesis at different times, we are able to investigate which type of nanoparticle is responsible for the respective resonances. We find that thin Au nanotriangles are the source of the observed near infrared (NIR) resonance. The initial lateral growth of these triangles causes the plasmon resonance to redshift into the NIR, whereas a subsequent thickening of the triangles and a concomitant truncation lead to a blueshift of the resonance. Furthermore, we find that the nanotriangles produced have extremely narrow line widths (187 ± 23 meV), show nearly isotropic scattering, and are stable for long periods of time. This shows their vast potential for applications such as in vivo imaging and bio(chemical) sensing. The method used here is generally applicable to other syntheses, and shows how complex nanostructures can be built up on substrates by selectively printing NPs of varying plasmonic resonances.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET , Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina.|Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , Amalienstraße 54, 80799 Munich, Germany.|Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 Munich, Germany.
authors.forename: María Ana
authors.initials: MA
authors.lastname: Huergo
authors.affiliation: Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , Amalienstraße 54, 80799 Munich, Germany.|Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 Munich, Germany.
authors.forename: Christoph Matthias
authors.initials: CM
authors.lastname: Maier
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET , Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina.
authors.forename: Marcos Federico
authors.initials: MF
authors.lastname: Castez
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET , Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina.
authors.forename: Carolina
authors.initials: C
authors.lastname: Vericat
authors.affiliation: Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , Amalienstraße 54, 80799 Munich, Germany.|Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 Munich, Germany.
authors.forename: Spas
authors.initials: S
authors.lastname: Nedev
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET , Sucursal 4 Casilla de Correo 16, 1900 La Plata, Argentina.
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Salvarezza
authors.affiliation: Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , Amalienstraße 54, 80799 Munich, Germany.|Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 Munich, Germany.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Urban
authors.affiliation: Chair for Photonics and Optoelectronics, Department of Physics and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München , Amalienstraße 54, 80799 Munich, Germany.|Nanosystems Initiative Munich (NIM), Schellingstraße 4, 80799 Munich, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Feldmann
keywords: cancer therapy; gold nanoparticles; nanoparticle sorting; nanoshells; optical printing; plasmon