Optical Nanoparticle Sorting Elucidates Synthesis of Plasmonic Nanotriangles

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• 作者：María Ana Huergo ; Christoph Matthias Maier ; Marcos Federico Castez ; Carolina Vericat ; Spas Nedev ; Roberto C. Salvarezza ; Alexander S. Urban ; Jochen Feldmann
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：March 22, 2016
• 年：2016
• 卷：10
• 期：3
• 页码：3614-3621
• 全文大小：426K
• ISSN：1936-086X

文摘

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.