Optical Trapping of Quantum Dots Based on Gap-Mode-Excitation of Localized Surface Plasmon

Abstract

One of the recent hot topics in the fields of plasmonics and related nanophotonics is optical trapping of nano/microparticles based on surface plasmon. Experimental demonstration of such trapping by gap-mode plasmon has hitherto been limited so far to a few reports in which submicrometer polymer beads were trapped with intense irradiation at MW/cm2, satisfying an energetic condition of U > kT. (U is the potential energy of the trap and kT is an averaged thermal background energy.) We demonstrate plasmon-based optical trapping of a luminescent quantum dot (Q dot, diameter ≥10 nm) with a very weak irradiation (0.5−10 kW/cm2). The most important discovery is that the Q dot trapping was clearly observed through luminescence detection even under an energetic condition of U < kT, on the basis of which we propose a novel concept that is peculiar to plasmon-based trapping at a nanogap.

Plasmon-Assisted Photoresponse in Ge-Coated Bowtie Nanojunctions

“…Optical antennas exploit the resonant behavior and large scattering cross section of plasmons in nanostructured metals for use in a wide variety of applications including surface-enhanced Raman spectroscopy (SERS) 1,2 , subwavelength optics 3,4 , plasmonic optical trapping [5][6][7][8] , and plasmon-assisted light harvesting [9][10][11][12][13][14][15][16][17] . Photosensitive devices utilizing plasmonic nanoantennas generate photocurrent through two dominant mechanisms:…”

Reversible Photoinduced Formation and Manipulation of a Two-Dimensional Closely Packed Assembly of Polystyrene Nanospheres on a Metallic Nanostructure

“…15−24 We also demonstrated the LSP-OT of semiconductor nanocrystals (quantum dots) and polystyrene nanospheres and by means of confocal fluorescence microspectroscopy. 22−24 Such LSP-OT has a great advantage with respect to incident light intensity: the laser intensity can be much decreased (to the order of kW/cm 2 ) and still achieve stable trapping, as compared to conventional optical tweezers (∼MW/cm 2 ). 25−29 Thus, LSP-OT could enable a new technique for manipulating not only nanoparticles but also smaller molecules such as polymer chains, 24 proteins, and DNA.…”

Optical trapping through the localized surface-plasmon resonance of engineered gold nanoblock pairs

“…In addition to optical gradients, coupling to the surface plasmon resonances can produce local heating in the metal and heat dissipation within the chamber, which results in convection. However, a local temperature elevation in the gold nanostructure for low incident intensity of 750 W/cm 2 is estimated to be less than 0.1 °C from some previous reports which experimentally and theoretically evaluate it [9,23]. Thus, the trapping contribution from plasmon-thermal fluid convection can be negligible.…”

“…The optical trapping of nanometer-sized objects by using plasmonic nanostructures has attracted considerable attention in recent years because it significantly improves the trapping performance compared with conventional optical tweezers that use a tightly focused laser beam [1][2][3][4][5][6][7][8][9]. Localized surface plasmons, i.e., resonant charge-density oscillations confined to metal nanostructures, can efficiently convert propagating light into nanoscale confined and strongly enhanced optical fields, which generate high-intensity gradients responsible for the trapping mechanism.…”

“…Among the huge variety of plasmonic nanostructures, a pair of metal nanoparticles separated by a nanometric gap produces an intense optical spot that is approximately two orders of magnitude smaller than the wavelength of the incident light [10][11][12], and it enables the optical trapping and confinement of dielectric nanoparticles such as polystyrene and living biological specimens with reduced laser intensity compared with conventional optical tweezers [6,7]. Furthermore, the nanogap structure was shown to trap metal and semiconductor nanoparticles with 10-nm dimensions [8,9]. The parallel trapping of micro-and nanoparticles has also demonstrated using patterned plasmonic nanostructures [7,13].…”