Figure 4.

Opto-thermoelectric trapping with femtosecond laser heating. Temperature profiles at the AuNR–substrate interface irradiated with (a) CW and (b) femtosecond laser beams of 0.3 mW/μm², respectively. Scale bars in panels a and b are 200 nm. Measured position distributions of a single 500 nm PS particle along with histograms of the particle displacement along the y axis for (c) CW and (d) femtosecond laser heating. Scale bars in panels a and b are 200 nm. (e) Schematic of the emission lifetime measurement for the AuNR antennas and quantum dots (QDs). AuNRs have blue-green second harmonic emission (peak wavelength: 490 nm), while QDs have red emission (peak wavelength: 615 nm). The inset is the fluorescence image of a CdSe/CdS trapped QD. Scale bar in panel e is 200 nm. (f) Tracking of fluorescence intensity of the trapped QD and estimated number of trapped QDs as a function of time. The single QD region is highlighted as a gray region. (g) Time-evolved fluorescence lifetime of single QDs that underwent free motion, trapping at the nanoantenna, and release to free motion from the laser-on to the laser-off time period. (h) Fluorescence lifetimes of free and trapped QDs under the variable CTAC concentrations.