Discrete intensity jumps and intramolecular electronic energy transfer in the spectroscopy of single conjugated polymer molecules

Science

Volumn 277, Issue 5329, 1997, Pages 1074-1077

  Vanden Bout, David A ^a   Yip, Wai Tak ^a   Hu, Dehong ^a   Fu, Dian Kui ^b   Swager, Timothy M ^b   Barbara, Paul F ^a  

^a University of Minnesota ^*  (United States)

^b MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BLEACHING; ELECTRON EMISSION; ELECTRON TRANSPORT PROPERTIES; ENERGY TRANSFER; FLUORESCENCE; MOLECULAR DYNAMICS; MOLECULAR SPECTROSCOPY; PHOTOCHEMICAL REACTIONS; QUANTUM OPTICS;

DISCRETE INTENSITY JUMPS; FLUORESCENCE QUENCHING POLYMER DEFECT; INTRAMOLECULAR ELECTRONIC ENERGY TRANSFER; PHOTOBLEACHING KINETICS;

ORGANIC POLYMERS;

ARTICLE; CHROMATOPHORE; ENERGY TRANSFER; FLUORESCENCE; LIGHT EMITTING DIODE; NONHUMAN; PRIORITY JOURNAL; QUANTUM MECHANICS; SPECTROSCOPY;

EID: 1842407820     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.277.5329.1074     Document Type: Article

References (36)

1. E. Betzig and R. J. Chichester, Science 262, 1422 (1993).
2. S. Nie, D. T. Chiu, R. N. Zare, ibid. 266, 1018 (1994).
3. X. S. Xie and R. C. Dunn, ibid. 265, 361 (1994).
4. J. J. Macklin, J. K. Trautman, T. D. Harris, L. E. Brus, ibid. 272, 255 (1996).
5. W. P. Ambrose, P. M. Goodwin, J. C. Martin, R. A. Keller, ibid. 265, 364 (1994).
6. J. K. Trautman, J. J. Macklin, L. E. Brus, E. Betzig, Nature 369, 40 (1994).
7. R. M. Dickson, D. J. Morris, Y.-L. Tzeng, W. E. Moerner, Science 274, 966 (1996).
8. X. S. Xie, Acc. Chem. Res. 29, 598 (1996).
9. T. Ha et al., Proc. Natl. Acad. Sci. U.S.A. 93, 6264 (1996).
10. T. Ha, T. Enderle, D. S. Chemla, P. R. Selvin, S. Weiss, Phys. Rev. Lett. 77, 3979 (1996).
11. T. Funatsu, Y. Harada, M. Tokunaga, K. Saito, T. Yanagida, Nature 374, 555 (1995).
12. T. Schmidt, G. J. Schültz, W. Baumgartner, H. J. Gruber, H. Schindler, Proc. Natl. Acad. Sci. U.S.A. 93, 2926 (1996).
13. W. E. Moerner, Science 265, 46 (1994).
14. H. P. Lu and X. S. Xie, J. Phys. Chem. B 101, 2753 (1997).
15. _, Nature 385, 143 (1997).
16. J. H. Burroughes et al., ibid. 347, 539 (1990).
17. G. Gustafsson et al., ibid. 357, 477 (1992).
18. N. T. Harrison, D. R. Baigent, I. D. W. Samuel, R. H. Friend, Phys. Rev. B 53, 15815 (1996).
19. T. M. Swager, C. J. Gil, M. S. Wrighton, J. Phys. Chem. 99, 4886 (1995).
20. H. S. Woo et al., Synth. Met. 59, 13 (1993). For the polymer studies here, a molecular weight of 20,000 would correspond to ∼80 phenyl-vinyl units.
21. -1 of the polystyrene (molecular weight ∼50,000). The resulting film is ∼20 nm thick.
22. The sample scanning confocal microscope consisted of an inverted Zeiss optical microscope (Axiovert 135TV) and an X-Y sample scanning stage (Newport 462) driven by electrostrictive actuator micrometers (Newport). The laser excitation was delivered to the epi-illumination port of the microscope with a single-mode optical fiber and collimating lens and reflected up to the sample by a dichroic beam splitter (Omega). The size of the beam was chosen to slightly overfill the back focal plane of the objective (Zeiss, Achrostigmat 100x oil immersion 1.25 N.A.). The fluorescence signal was taken out of the bottom port of the microscope and focused onto a 200-μm aperture in the first image plane. The fluorescence spot was reimaged onto a 100-μm pinhole and then onto an avalanche photodiode detector (EG&G Canada SPCM). Between the aperture and pinhole, a notch filter at the excitation wavelength (Kaiser Notch-plus) and a colored-glass long-pass filter (OG530) removed residual excitation light. Spectra were taken by reimaging the fluorescence spot after the initial aperture onto the 100-μm slits of a polychrometer (Acton Spectrapro 150) equipped with a front-illuminated liquid nitrogen-cooled charge-coupled device camera (Princeton Instruments).
23. -2. The density is seen to vary linearly with the concentration of the original solution over two orders of magnitude.
24. M. Wu, P. M. Goodwin, W. P. Ambrose, R. A. Keller, J. Phys. Chem. 100, 17406 (1996).
25. The broad spectra are in strong contrast to the extremely narrow spectra of single emitting excitons imaged at low temperature [H. F. Hess, E. Betzig, T. D. Harris, L. N. Pfeiffer, K. W. West, Science 264, 1740 (1994)].
26. M. Van, L. J. Rothberg, F. Papadimitrakopoulos, M. E. Galvin, T. M. Miller, Phys. Rev. Lett. 73, 744 (1994).
27. Simultaneous transients at two wavelengths were recorded by coupling two laser wavelengths into the optical fiber source of the microscope. The sample was alternately illuminated for 10 ms by each color. The two beams were modulated with two acoustooptic modulators (IntraAction). The final 100-ms dwell transients were reconstructed by binning five points for each excitation wavelength. Because of chromatic aberrations in the optical path, the beams were collimated to a smaller diameter and focused to a larger spot size (500 μm). This procedure caused a slight increase in the background, but it ensured that both wavelengths would focus in the same spot on the sample.
28. -1 of the polystyrene. Several layers of the film were cast on top of each other to make a sample ∼1 μm thick.
29. At long times, the 457-nm transients occasionally showed intensity, whereas the 514-nm transients remained at the background. This result indicates that there may be some chemistry that was driving the spectrum of the polymer to the blue at long times. Apparent red shifts in the spectrum were never seen.
30. R. W. Wagner, J. S. Lindsey, J. Seth, V. Palaniappan, D. F. Bocian, J. Am. Chem. Soc. 118, 3996 (1996).
31. A. J. Epstein et al., Synth. Met. 78, 253 (1996).
32. R. J. Cook and H. J. Kimble, Phys. Rev. Lett. 54, 1023 (1985).
33. M. Nirmal et al., Nature 383, 802 (1996).
34. Gel permeation chromatography (GPC) showed the polymer to have a molecular weight of ∼20,000 (versus polystyrene standards) with a polydispersity near 2. The polymer was separated into low, medium, and high molecular weight fractions by GPC. All three fractions yielded molecules that had the same qualitative behavior.
35. D. A. Vanden Bout, W.-T. Yip, D. Hu, D.-K. Fu, T. A. Swager, P. F. Barbara, unpublished results.
36. Supported by grants from the U.S. Office of Naval Research and the NSF. D.A.V.B. thanks the NSF for a postdoctoral fellowship. We thank J. Kerimo for his help with initial near field scanning optical microscopy studies, Th. Basché and S. Xie for insightful discussions, and C. Orr and J. Cernohou for their help with the GPC fractionation and characterization.