Expanding the Optical Trapping Range of Gold Nanoparticles

Hansen, P.M.T.; Bhatia, Vikram; Harrit, Niels; Oddershede, Lene B.

doi:10.1021/nl051289r

Cited by 417 publications

(434 citation statements)

References 27 publications

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“…[1][2][3][4][5][6][7][8][9] This paper investigates the laser induced optical forces of metallic nanoparticle clusters when their localized surface plasmons ͑SPs͒ are excited. Such forces are important because they may affect the signal of surface enhanced Raman spectroscopy 10,11 or promote controllable aggregation of nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Electrodynamics study of plasmonic bonding and antibonding forces in a bisphere

Tang

Chan

2008

Phys. Rev. B

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Light excitation of surface plasmons in metallic nanoparticle clusters can induce huge forces. We study such forces by using an electrodynamics approach, which fully incorporates the retardation effect. As two particles approach each other, the single-particle plasmons hybridize and split into attractive bonding modes and repulsive antibonding modes, which eventually evolve into an attractive band and a repulsive band. At an intensity of about 0.05 W / m 2 , the force can reach nano-Newtons and, hence, can dominate over other relevant interactions.

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Section: Introductionmentioning

confidence: 99%

Electrodynamics study of plasmonic bonding and antibonding forces in a bisphere

Tang

Chan

2008

Phys. Rev. B

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“…Metallic nanoparticles with dimensions down to 10 nm have been proven individually manipulated. [5][6][7][8][9] Aggregates of QDs have been trapped with pulsed high power lasers 10 and even individual QDs were trapped with CW infrared optical tweezers. 11 This is very useful, as a single QD can serve both for visualization and as a handle for controlled force transduction.…”

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confidence: 99%

Two-Photon Quantum Dot Excitation during Optical Trapping

Jauffred

Oddershede

2010

Nano Lett.

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A single CW infrared laser beam can simultaneously trap and excite an individual colloidal quantum dot. Though the laser light is relatively weak, the excitation occurs through two-photon absorption. This finding eliminates the demand for an excitation light source in addition to a trapping laser in nanoscale experiments with simultaneous force-manipulation and quantum dot visualization. Also, we demonstrate that optical trapping efficiencies of individual quantum dots do not correlate with their emission wavelength or physical size.

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“…After approximately 25 min the photodiode signal shown in Figure 1 broadened, after an additional 10 min it broadened even further, and at later times the broadening continues. Previous experience from trapping gold nanoparticles 9 suggests that the broadening of the photodiode signal is a result of additional particles entering the trap. Hence, in a typical experiment we would have a single QD at least 10 min before more QDs entered the trap.…”

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confidence: 99%

Three-Dimensional Optical Control of Individual Quantum Dots

2008

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We show that individual colloidal CdSe-core quantum dots can be optically trapped and manipulated in three dimensions by an infrared continuous wave laser operated at low laser powers. This makes possible utilizing quantum dots not only for visualization but also for manipulation, an important advantage for single molecule experiments. Moreover, we provide quantitative information about the magnitude of forces applicable to a single quantum dot and of the polarizability of an individual quantum dot.Colloidal quantum dots (QDs) are fluorescent semiconductor nanocrystals.1 They are bright and photostable with a broad excitation spectrum and a narrow emission spectrum, normally distributed around a specific wavelength, dependent on the size of the QD. Absorption of any photons with wavelengths above this specific wavelength causes the formation of an electron-hole pair, the recombination of which results in photon emission. The fluorescent blinking of nanocrystal quantum dots is the result of a bistability between an emitting state where the quantum dot is described as on and the nonemitting off state.2 The extreme brightness and photostability of QDs make them excellent choices as markers to visualize biological systems. For instance they have been used to mark individual receptors in cell membranes 3 or to label living embryos at different stages. 4 It has long been a goal to optically trap or otherwise control quantum dots 5 to establish a combined visualization and optical manipulation technique. Optical trapping of aggregates of colloidal quantum dots in two dimensions was recently proved possible 6 using a pulsed YLF laser, and it was claimed that to trap quantum dots with a continuous wave (CW) laser one would need extremely high powers on the order of 20 W. In this Letter, we prove that optical trapping of individual quantum dots using a CW infrared laser operated at only 0.5 W is, in fact, possible. By observing the Brownian motion of the trapped quantum dots, we deduced the strength of the optical trap and thus found the magnitude of the optical forces acting on a single quantum dot. We used two independent approaches to render probable that it was indeed a single quantum dot in the trap and not an aggregate.An inducible dipole in an inhomogeneous field experiences a force in the direction of the field gradient, the gradient force, F b grad . A particle with an induced dipole moment will be forced toward the laser focus by this three-dimensional restoring force. Hence, the existence of an induced QD dipole moment is essential for optical trapping. Opposing the gradient force are the scattering force, F b scat , and the absorption force, F b abs , which are proportional to the scattering and absorption cross sections, respectively. If infrared laser light, with a wavelength that exceeds the maximum emitted wavelength of the QDs by far, is used for trapping and if the QDs are physically very small in comparison to the focus area of the trapping laser light, then the scattering and absorption forces ...

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Expanding the Optical Trapping Range of Gold Nanoparticles

Cited by 417 publications

References 27 publications

Electrodynamics study of plasmonic bonding and antibonding forces in a bisphere

Electrodynamics study of plasmonic bonding and antibonding forces in a bisphere

Two-Photon Quantum Dot Excitation during Optical Trapping

Three-Dimensional Optical Control of Individual Quantum Dots

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