Figure 1.

Opto-thermoelectric trapping of single particles on single nanoantennas. (a) Dispersion of a positively charged nanoparticle and multiple ions in solvent surrounding the Au nanoantenna when the laser is off. (b) Thermophoresis-induced redistribution of the solutes in the solvent when the laser is on. The temperature gradient from the optical heating of the nanoantenna generates thermoelectric force (F) that traps the nanoparticle at the center of the nanoantenna. (c) Three-dimensional view of opto-thermoelectric trapping of a nanoparticle (NP) on the AuNR. The incident laser beam is normal to the substrate with its polarization along the y direction. (d) Scanning electron micrographs (SEM) of Au nanorod arrays (left) and a single nanorod (right) on a glass substrate. The scale bars: 300 nm (left) and 100 nm (right), respectively. (e) Simulated and (f) experimental temperature profiles at the AuNR–substrate interface upon the illumination of 780 nm laser beam with a power density of 0.6 mW/μm². The black dotted rectangular boxes outline the AuNRs. Scale bars were 1 μm. (g) Dark-field optical images of 100 nm AgNS, 200 nm AgNS, 100 nm AuNS, and 200 nm AuNS trapped at single AuNRs centered in the nanorod arrays, respectively. The red circle highlights the size of the laser spot. Scale bars were 500 nm. (h) Trapping stiffness along the y axis (see Figure 1d) for 200 nm PS sphere as a function of optical power density and the maximum AuNR temperature as a function of optical power density. The inset is an optical image of a 200 nm fluorescence particle being trapped at an AuNR. The scale bar in the optical image is 500 nm.