Bidirectional Optical Sorting of Gold Nanoparticles

• Published in: Nano letters Vol. 12; no. 4; pp. 1923 - 1927
• Main Authors: Ploschner, M, Čižmár, T, Mazilu, M, Di Falco, A, Dholakia, K
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11-04-2012
• Subjects: Bidirectional; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Evanescent waves; Exact sciences and technology; Gold; Materials science; Nanocrystalline materials; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Physics; Plasmons; Sorting; Surface and interface electron states; Wavelengths; plasmon resonance; counter-propagating geometry; evanescent field; Gold nanoparticle; optical manipulation; optical sorting; Nanoparticles; Gold; Plasmons; Resonance; Optical forces; Nanostructured materials
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl204378r

We present a generic technique allowing size-based all-optical sorting of gold nanoparticles. Optical forces acting on metallic nanoparticles are substantially enhanced when they are illuminated at a wavelength near the plasmon resonance, as determined by the particle’s geometry. Exploiting these resonances, we realize sorting in a system of two counter-propagating evanescent waves, each at different wavelengths that selectively guide nanoparticles of different sizes in opposite directions. We validate this concept by demonstrating bidirectional sorting of gold nanoparticles of either 150 or 130 nm in diameter from those of 100 nm in diameter within a mixture.