1. Three-Dimensional Optical Control of Individual Quantum Dots Liselotte Jauffred, Andrew C. Richardson, and Lene B. Oddershede Nano Lett. 2008, 10, 3376-3380 KAWAI Ryoichi Ashida Lab.

2.  Abstract / Motivation  Introduction What is Quantum Dots? Radiation Force  Experiment / Results  Summary / Future work  My work /Future plan Contents

3. Abstract / Motivation ３次元空間中で、低パワーでの赤外連続レーザー光による個々の CdSe-core 量子 ドットの光トラップ、および光操作が可能であることを示す。これにより、量子 ドットが可視化だけでなく操作に利用することが可能となり、単一分子実験に非 常に有益となる。さらに、我々は単一量子ドットに適用できる光誘起力の大きさ、 個々の量子ドットの分極率の大きさの定量的な値を示す。 Motivation: Optically trapping a single QDs using a CW infrared laser at low power. Deducing the strength of the optical trap and finding the magnitude of the optical force.

4. Introduction – Quantum dots (QDs) Fluorescent semiconductor nanocrystals Narrow emission spectrum …its wavelength is dependent on the size of QDs Broad excitation spectrum Fluorescence blinking…on/off ⇧ Quantum Dots (http://www.evidenttech.com/technology) Application: Markers to visualize biological systems (for instance, receptors in cell membranes, living embryos, and so on…)

5. Introduction – Radiation Force Gradient force( 勾配力 ) Dissipative force( 散逸力 ) Scattering force( 散乱力 ) Absorption force( 吸収力 ) Optical axis Trap region Colloidal QD Gradient force Dissipative force (Scat.+Abs. force) Lens

6. Experimental set up / Sample_1 Ref: Andrew C. Richardson Development of optical trapping techniques for in vivo investigations

7. Sample Quantum dots (Invitrogen) CdSe/ZnS(core-shell) -Water soluble -Emission wavelength: 655nm Experimental set up / Sample_2 Vacuum grease Colloidal QDs Quadrant photodiode Oil immersion objective -NA=1.4, ×100 Nd:YVO₄ laser (5W(max) Spectra Physics Millenia,λ=1064[nm], TEM₀₀) Cover slips CdSe ZnS shell core set up 3µm

8. Results – the 1 st experiment (blue)……1 QD in the trap (red)……..2 QDs in the trap (purple)…3 QDs in the trap (gray)…….4 QDs in the trap The full lines are Gaussian fits To the distributions. Trapping only a single QD for at least 10 min.

9. Results – the 2 nd experiment a)Before a QD is trapped b)After attaches the QD to a biotinylated surface Luminescence measurement A clear blinking behavior of the QD The individuality of the QD in the optical trap

10. Analysis Corner frequency / Trap stiffness_1 Harmonic force Langevin equation Fourier transformation Trapped nanoparticle The trap stiffness κ can be found.

11. Analysis Corner frequency / Trap stiffness_2 Power spectrum of the positions of a QD (1 lateral dimension) Fitting by Lorentzian function Trapped nanoparticle

12. Analysis Polarizability of one QD by σ …Gaussian beam

13. Clausius-Mossotti relation The two different ways of finding the polarizability of a single QD.

14. They succeeded in three dimensional optical control of QDs using an infrared CW laser at low power. They showed that only a single QD was in the trap. They calculated the optical forces applicable on a trapped QD and the absolute polarization of it. Summary

15. They will address the issue of how the interaction with the electric field and QDs changes when changing the size of the QDs and the trapping laser wavelength. Future work

16. My work / My future plan I succeeded in trapping a single QD or some QDs in the air. This is photoluminescence spectrum of the trapped QD(s). Sample CdSe/ZnS Particle size: 6.3nm(average) emission central wavelength: 640nm