Abstract

We propose the use of ultrasmall semiconductor quantum dots (USQDs) for specialized bio-imaging applications, and discuss methods for enhancing fluorescent signals from USQDs to be used for two-photon-absorption based deep tissue imaging. In particular, we report optimizing the excitation wavelength for two-photon absorption-induced fluorescence (TPAF) in CdSeZnS SQDs and demonstrate a 68-fold enhancement in the fluorescence signal when the TPAF excitation wavelength is changed from 900nmto780nm.

© 2009 Optical Society of America

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  1. W. Denk, J. H. Strickler, and W. W. Webb, “Two-photon laser scanning fluorescence microscopy,” Science 248, 73-76 (1990).
    [CrossRef] [PubMed]
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    [CrossRef]
  3. R. M. Williams, W. R. Zipfel, and W. W. Webb, “Multiphoton microscopy in biological research,” Curr. Opin. Chem. Biol. 5, 603-608 (2001).
    [CrossRef] [PubMed]
  4. D. R. Larson, W. R. Zipfel, R. M. Williams, S. W. Clark, M. P. Bruchez, F. W. Wise, and W. W. Webb, “Water-soluble quantum dots for multiphoton fluorescence imaging in vivo,” Science 300, 1434-1436 (2003).
    [CrossRef] [PubMed]
  5. J. M. Squirrell, D. L. Wokosin, J. G. White, and B. D. Bavister, “Long-term two-photon fluorescence imaging of mammalian embryos without compromising viability,” Nat. Biotechnol. 17, 763-767 (1999).
    [CrossRef] [PubMed]
  6. E. B. Brown, R. B. Campbell, Y. Tsuzuki, L. Xu, P. Carmeliet, D. Fukumura, and R. K. Jain, “In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy,” Nat. Med. 7, 864-868 (2001).
    [CrossRef] [PubMed]
  7. K. Svoboda, W. Denk, D. Kleinfeld, and D. W. Tank, “In vivo dendritic calcium dynamics in neocortical pyramidal neurons,” Nature 385, 161-165 (1997).
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  8. B. E. Chen, B. Lendvai, E. A. Nimchinsky, B. Burbach, K. Fox, and K. Svoboda, “Imaging high-resolution structure of GFP-expressing neurons in neocortex in vivo,” Learn. Memory 7, 433-441 (2000).
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  9. K. W. Dunn, R. M. Sandoval, K. J. Kelly, P. C. Dagher, G. A. Tanner, S. J. Atkinson, R. L. Bacallao, and B. A. Molitoris, “Functional studies of the kidney of living animals using multicolor two-photon microscopy,” Am. J. Physiol.: Cell Physiol. 283, C905-C916 (2002).
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  12. L. Sacconi, R. P. O'Connor, A. Jasaitis, A. Masi, M. Buffelli, and F. S. Pavone, “In vivo multiphoton nanosurgery on cortical neurons,” J. Biomed. Opt. 12, 050502 (2007).
    [CrossRef] [PubMed]
  13. M. Bruchez, Jr., M. Moronne, P. Gin, S. Weiss, and A. P. Alivisatos, “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998).
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  14. W. C. W. Chan and S. Nie, “Quantum dot bioconjugates for ultrasensitive nonisotopic detection,” Science 281, 2016-2018 (1998).
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  17. C. B. Murray, D. J. Norris, and M. G. Bawendi, “Synthesis and characterization of nearly monodisperse CdE (E=sulfur, selenium, tellurium) semiconductor nanocrystallites,” J. Am. Chem. Soc. 115, 8706-8715 (1993).
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  18. P. T. Tran, E. R. Goldman, G. P. Anderson, J. M. Mauro, and H. Matroussi, Use of Luminescent CdSe-ZnS Nanocrystal Bioconjugates in Quantum Dot-based Nanosensors (Wiley-VCH, 2002), pp. 427-432.
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  22. W. Guo, J. J. Li, Y. A. Wang, and X. Peng, “Conjugation chemistry and bioapplications of semiconductor box nanocrystals prepared via dendrimer bridging,” Chem. Mater. 15, 3125-3133 (2003).
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    [CrossRef] [PubMed]
  25. M. J. Levene, D. A. Dombeck, K. A. Kasischke, R. P. Molloy, and W. W. Webb, “In vivo multiphoton microscopy of deep brain tissue,” J. Neurophysiol. 91, 1908-1912 (2004).
    [CrossRef]
  26. F. Chen and D. Gerion, “Fluorescent CdSe/ZnS nanocrystal-peptide conjugates for long-term, nontoxic imaging and nuclear targeting in living cells,” Nano Lett. 4, 1827-1832 (2004).
    [CrossRef]
  27. J. G. D. Foley and J. B. L. Bard, “Apoptosis in the cortex of the developing mouse kidney,” J. Anat. 201, 477-484 (2002).
    [CrossRef] [PubMed]
  28. W. Jiang, A. Singhal, J. Zheng, C. Wang, and W. C. W. Chan, “Optimizing the synthesis of red- to near-IR-emitting CdS-capped CdTexSe1−x alloyed quantum dots for biomedical imaging,” Chem. Mater. 18, 4845-4854 (2006).
    [CrossRef]
  29. I. Nabiev, S. Mitchell, A. Davies, Y. Williams, D. Kelleher, R. Moore, Y. K. Gun'ko, S. Byrne, Y. P. Rakovich, J. F. Donegan, A. Sukhanova, J. Conroy, D. Cottell, N. Gaponik, A. Rogach, and Y. Volkov, “Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments,” Nano Lett. 7, 3452-3461 (2007).
    [CrossRef] [PubMed]
  30. Y. Xu, Q. Wang, P. He, Q. Dong, F. Liu, Y. Liu, L. Lin, H. Yan, and X. Zhao, “Cell nucleus penetration by quantum dots induced by nuclear staining organic fluorophore and UV-irradiation,” Adv. Mater. 20, 3468-3473 (2008).
    [CrossRef]
  31. K.-T. Yong, I. Roy, H. E. Pudavar, E. J. Bergey, K. M. Tramposch, M. T. Swihart, and P. N. Prasad, “Multiplex imaging of pancreatic cancer cells by using functionalized quantum rods,” Adv. Mater. 20, 1412-1417 (2008).
    [CrossRef]
  32. L. Wang, D. Ancukiewicz, J. Y. Chen, and R. K. Jain, “Surface-plasmon enhanced fluorescence in CdSe/ZnS semiconductor quantum dots,” Paper # CTu07, presented at the Conference on Lasers and Electro-Optics Conference (CLEO/IQEC 2009), Baltimore, Maryland, 31 May, 2009.
  33. All the SQD samples described here were purchased from Evident Technologies; the “2 nm” USQD samples used in this study are their “Blue” product with a specified CdSe core diameter of 1.9 nm(+/−5%) and a peak emission wavelength of 490 nm, consistent with our measurements reported here.
  34. Z. Tang, N. A. Kotov, and M. Giersig, “Spontaneous organization of single CdTe nanoparticles into luminescent nanowires,” Science 297, 237-240 (2002).
    [CrossRef] [PubMed]
  35. K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
    [CrossRef]
  36. M. E. Schmidt, S. A. Blanton, M. A. Hines, and P. Guyot-Sionnest, “Size-dependent two-photon excitation spectroscopy of CdSe nanocrystals,” Phys. Rev. B 53, 12629-12632 (1996).
    [CrossRef]
  37. A. L. Efros and M. Rosen, “Electronic structure of semiconductor nanocrystals,” Annu. Rev. Mater. Sci. 30, 475-521 (2000).
    [CrossRef]
  38. N. J. Durr, T. Larson, D. K. Smith, B. A. Korgel, K. Sokolov, and A. Ben-Yakar, “Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods,” Nano Lett. 7, 941-945 (2007).
    [CrossRef] [PubMed]
  39. B. I. Tarnowski, F. G. Spinale, and J. H. Nicholson, “DAPI as a useful stain for nuclear quantitation,” Biotech. Histochem. 66, 296-302 (1991).
    [CrossRef]
  40. H. M. Elsheikha and L. S. Mansfield, “Assessment of Sarcocystis neurona sporocyst viability and differentiation between viable and nonviable sporocysts using propidium iodide stain,” J. Parasitol. 90, 872-875 (2004).
    [CrossRef] [PubMed]
  41. C. Xu and W. W. Webb, “Measurement of two-photon excitation cross sections of molecular fluorophores with data from 690to1050 nm,” J. Opt. Soc. Am. B 13, 481-491 (1996).
    [CrossRef]

2008

Y. Xu, Q. Wang, P. He, Q. Dong, F. Liu, Y. Liu, L. Lin, H. Yan, and X. Zhao, “Cell nucleus penetration by quantum dots induced by nuclear staining organic fluorophore and UV-irradiation,” Adv. Mater. 20, 3468-3473 (2008).
[CrossRef]

K.-T. Yong, I. Roy, H. E. Pudavar, E. J. Bergey, K. M. Tramposch, M. T. Swihart, and P. N. Prasad, “Multiplex imaging of pancreatic cancer cells by using functionalized quantum rods,” Adv. Mater. 20, 1412-1417 (2008).
[CrossRef]

2007

I. Nabiev, S. Mitchell, A. Davies, Y. Williams, D. Kelleher, R. Moore, Y. K. Gun'ko, S. Byrne, Y. P. Rakovich, J. F. Donegan, A. Sukhanova, J. Conroy, D. Cottell, N. Gaponik, A. Rogach, and Y. Volkov, “Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments,” Nano Lett. 7, 3452-3461 (2007).
[CrossRef] [PubMed]

L. Sacconi, R. P. O'Connor, A. Jasaitis, A. Masi, M. Buffelli, and F. S. Pavone, “In vivo multiphoton nanosurgery on cortical neurons,” J. Biomed. Opt. 12, 050502 (2007).
[CrossRef] [PubMed]

N. J. Durr, T. Larson, D. K. Smith, B. A. Korgel, K. Sokolov, and A. Ben-Yakar, “Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods,” Nano Lett. 7, 941-945 (2007).
[CrossRef] [PubMed]

2006

W. Jiang, A. Singhal, J. Zheng, C. Wang, and W. C. W. Chan, “Optimizing the synthesis of red- to near-IR-emitting CdS-capped CdTexSe1−x alloyed quantum dots for biomedical imaging,” Chem. Mater. 18, 4845-4854 (2006).
[CrossRef]

S.-C. Pu, M.-J. Yang, C.-C. Hsu, C.-W. Lai, C.-C. Hsieh, S. H. Lin, Y.-M. Cheng, and P.-T. Chou, “The empirical correlation between size and two-photon absorption cross section of CdSe and CdTe quantum dots,” Small 2, 1308-1313 (2006).
[CrossRef] [PubMed]

2004

M. J. Levene, D. A. Dombeck, K. A. Kasischke, R. P. Molloy, and W. W. Webb, “In vivo multiphoton microscopy of deep brain tissue,” J. Neurophysiol. 91, 1908-1912 (2004).
[CrossRef]

F. Chen and D. Gerion, “Fluorescent CdSe/ZnS nanocrystal-peptide conjugates for long-term, nontoxic imaging and nuclear targeting in living cells,” Nano Lett. 4, 1827-1832 (2004).
[CrossRef]

H. M. Elsheikha and L. S. Mansfield, “Assessment of Sarcocystis neurona sporocyst viability and differentiation between viable and nonviable sporocysts using propidium iodide stain,” J. Parasitol. 90, 872-875 (2004).
[CrossRef] [PubMed]

2003

X. Deng and M. Gu, “Penetration depth of single-, two-, and three-photon fluorescence microscopic imaging through human cortex structures: Monte Carlo simulation,” Appl. Opt. 42, 3321-3329 (2003).
[CrossRef] [PubMed]

W. Guo, J. J. Li, Y. A. Wang, and X. Peng, “Conjugation chemistry and bioapplications of semiconductor box nanocrystals prepared via dendrimer bridging,” Chem. Mater. 15, 3125-3133 (2003).
[CrossRef]

D. R. Larson, W. R. Zipfel, R. M. Williams, S. W. Clark, M. P. Bruchez, F. W. Wise, and W. W. Webb, “Water-soluble quantum dots for multiphoton fluorescence imaging in vivo,” Science 300, 1434-1436 (2003).
[CrossRef] [PubMed]

2002

K. W. Dunn, R. M. Sandoval, K. J. Kelly, P. C. Dagher, G. A. Tanner, S. J. Atkinson, R. L. Bacallao, and B. A. Molitoris, “Functional studies of the kidney of living animals using multicolor two-photon microscopy,” Am. J. Physiol.: Cell Physiol. 283, C905-C916 (2002).

Z. Tang, N. A. Kotov, and M. Giersig, “Spontaneous organization of single CdTe nanoparticles into luminescent nanowires,” Science 297, 237-240 (2002).
[CrossRef] [PubMed]

W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
[CrossRef]

S. Wang, N. Mamedova, N. A. Kotov, W. Chen, andJ. Studer, “Antigen/antibody immunocomplex from CdTe nanoparticle bioconjugates,” Nano Lett. 2, 817-822 (2002).
[CrossRef]

J. G. D. Foley and J. B. L. Bard, “Apoptosis in the cortex of the developing mouse kidney,” J. Anat. 201, 477-484 (2002).
[CrossRef] [PubMed]

2001

D. Gerion, F. Pinaud, S. C. Williams, W. J. Parak, D. Zanchet, S. Weiss, and A. P. Alivisatos, “Synthesis and properties of biocompatible water-soluble silica-coated CdSe/ZnS semiconductor quantum dots,” J. Phys. Chem. B 105, 8861-8871 (2001).
[CrossRef]

E. B. Brown, R. B. Campbell, Y. Tsuzuki, L. Xu, P. Carmeliet, D. Fukumura, and R. K. Jain, “In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy,” Nat. Med. 7, 864-868 (2001).
[CrossRef] [PubMed]

R. M. Williams, W. R. Zipfel, and W. W. Webb, “Multiphoton microscopy in biological research,” Curr. Opin. Chem. Biol. 5, 603-608 (2001).
[CrossRef] [PubMed]

2000

B. E. Chen, B. Lendvai, E. A. Nimchinsky, B. Burbach, K. Fox, and K. Svoboda, “Imaging high-resolution structure of GFP-expressing neurons in neocortex in vivo,” Learn. Memory 7, 433-441 (2000).
[CrossRef]

A. L. Efros and M. Rosen, “Electronic structure of semiconductor nanocrystals,” Annu. Rev. Mater. Sci. 30, 475-521 (2000).
[CrossRef]

1999

J. M. Squirrell, D. L. Wokosin, J. G. White, and B. D. Bavister, “Long-term two-photon fluorescence imaging of mammalian embryos without compromising viability,” Nat. Biotechnol. 17, 763-767 (1999).
[CrossRef] [PubMed]

1998

B. R. Masters, P. T. C. So, and E. Gratton, “Optical biopsy of in vivo human skin: Multiphoton excitation microscopy,” Lasers Med. Sci. 13, 196-203 (1998).
[CrossRef]

V. E. Centonze and J. G. White, “Multiphoton excitation provides optical sections from deeper within scattering specimens than confocal imaging,” Biophys. J. 75, 2015-2024 (1998).
[CrossRef] [PubMed]

M. Bruchez, Jr., M. Moronne, P. Gin, S. Weiss, and A. P. Alivisatos, “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998).
[CrossRef] [PubMed]

W. C. W. Chan and S. Nie, “Quantum dot bioconjugates for ultrasensitive nonisotopic detection,” Science 281, 2016-2018 (1998).
[CrossRef] [PubMed]

1997

K. Svoboda, W. Denk, D. Kleinfeld, and D. W. Tank, “In vivo dendritic calcium dynamics in neocortical pyramidal neurons,” Nature 385, 161-165 (1997).
[CrossRef] [PubMed]

1996

M. Danek, K. F. Jensen, C. B. Murray, and M. G. Bawendi, “Synthesis of luminescent thin-film CdSe/ZnSe quantum dot composites using CdSe quantum dots passivated with an overlayer of ZnSe,” Chem. Mater. 8, 173-180 (1996).
[CrossRef]

M. E. Schmidt, S. A. Blanton, M. A. Hines, and P. Guyot-Sionnest, “Size-dependent two-photon excitation spectroscopy of CdSe nanocrystals,” Phys. Rev. B 53, 12629-12632 (1996).
[CrossRef]

C. Xu and W. W. Webb, “Measurement of two-photon excitation cross sections of molecular fluorophores with data from 690to1050 nm,” J. Opt. Soc. Am. B 13, 481-491 (1996).
[CrossRef]

1993

C. B. Murray, D. J. Norris, and M. G. Bawendi, “Synthesis and characterization of nearly monodisperse CdE (E=sulfur, selenium, tellurium) semiconductor nanocrystallites,” J. Am. Chem. Soc. 115, 8706-8715 (1993).
[CrossRef]

M. J. O'Donovan, S. Ho, G. Sholomenko, and W. Yee, “Real-time imaging of neurons retrogradely and anterogradely labelled with calcium-sensitive dyes,” J. Neurosci. Methods 46, 91-106 (1993).
[CrossRef] [PubMed]

1992

K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
[CrossRef]

1991

B. I. Tarnowski, F. G. Spinale, and J. H. Nicholson, “DAPI as a useful stain for nuclear quantitation,” Biotech. Histochem. 66, 296-302 (1991).
[CrossRef]

1990

W. Denk, J. H. Strickler, and W. W. Webb, “Two-photon laser scanning fluorescence microscopy,” Science 248, 73-76 (1990).
[CrossRef] [PubMed]

Alivisatos, A. P.

W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
[CrossRef]

D. Gerion, F. Pinaud, S. C. Williams, W. J. Parak, D. Zanchet, S. Weiss, and A. P. Alivisatos, “Synthesis and properties of biocompatible water-soluble silica-coated CdSe/ZnS semiconductor quantum dots,” J. Phys. Chem. B 105, 8861-8871 (2001).
[CrossRef]

M. Bruchez, Jr., M. Moronne, P. Gin, S. Weiss, and A. P. Alivisatos, “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998).
[CrossRef] [PubMed]

Ancukiewicz, D.

L. Wang, D. Ancukiewicz, J. Y. Chen, and R. K. Jain, “Surface-plasmon enhanced fluorescence in CdSe/ZnS semiconductor quantum dots,” Paper # CTu07, presented at the Conference on Lasers and Electro-Optics Conference (CLEO/IQEC 2009), Baltimore, Maryland, 31 May, 2009.

Anderson, G. P.

P. T. Tran, E. R. Goldman, G. P. Anderson, J. M. Mauro, and H. Matroussi, Use of Luminescent CdSe-ZnS Nanocrystal Bioconjugates in Quantum Dot-based Nanosensors (Wiley-VCH, 2002), pp. 427-432.

Atkinson, S. J.

K. W. Dunn, R. M. Sandoval, K. J. Kelly, P. C. Dagher, G. A. Tanner, S. J. Atkinson, R. L. Bacallao, and B. A. Molitoris, “Functional studies of the kidney of living animals using multicolor two-photon microscopy,” Am. J. Physiol.: Cell Physiol. 283, C905-C916 (2002).

Bacallao, R. L.

K. W. Dunn, R. M. Sandoval, K. J. Kelly, P. C. Dagher, G. A. Tanner, S. J. Atkinson, R. L. Bacallao, and B. A. Molitoris, “Functional studies of the kidney of living animals using multicolor two-photon microscopy,” Am. J. Physiol.: Cell Physiol. 283, C905-C916 (2002).

Bard, J. B. L.

J. G. D. Foley and J. B. L. Bard, “Apoptosis in the cortex of the developing mouse kidney,” J. Anat. 201, 477-484 (2002).
[CrossRef] [PubMed]

Bavister, B. D.

J. M. Squirrell, D. L. Wokosin, J. G. White, and B. D. Bavister, “Long-term two-photon fluorescence imaging of mammalian embryos without compromising viability,” Nat. Biotechnol. 17, 763-767 (1999).
[CrossRef] [PubMed]

Bawendi, M. G.

M. Danek, K. F. Jensen, C. B. Murray, and M. G. Bawendi, “Synthesis of luminescent thin-film CdSe/ZnSe quantum dot composites using CdSe quantum dots passivated with an overlayer of ZnSe,” Chem. Mater. 8, 173-180 (1996).
[CrossRef]

C. B. Murray, D. J. Norris, and M. G. Bawendi, “Synthesis and characterization of nearly monodisperse CdE (E=sulfur, selenium, tellurium) semiconductor nanocrystallites,” J. Am. Chem. Soc. 115, 8706-8715 (1993).
[CrossRef]

Ben-Yakar, A.

N. J. Durr, T. Larson, D. K. Smith, B. A. Korgel, K. Sokolov, and A. Ben-Yakar, “Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods,” Nano Lett. 7, 941-945 (2007).
[CrossRef] [PubMed]

Bergey, E. J.

K.-T. Yong, I. Roy, H. E. Pudavar, E. J. Bergey, K. M. Tramposch, M. T. Swihart, and P. N. Prasad, “Multiplex imaging of pancreatic cancer cells by using functionalized quantum rods,” Adv. Mater. 20, 1412-1417 (2008).
[CrossRef]

Bertozzi, C. R.

W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
[CrossRef]

Blanton, S. A.

M. E. Schmidt, S. A. Blanton, M. A. Hines, and P. Guyot-Sionnest, “Size-dependent two-photon excitation spectroscopy of CdSe nanocrystals,” Phys. Rev. B 53, 12629-12632 (1996).
[CrossRef]

Brown, E. B.

E. B. Brown, R. B. Campbell, Y. Tsuzuki, L. Xu, P. Carmeliet, D. Fukumura, and R. K. Jain, “In vivo measurement of gene expression, angiogenesis and physiological function in tumors using multiphoton laser scanning microscopy,” Nat. Med. 7, 864-868 (2001).
[CrossRef] [PubMed]

Bruchez, M.

M. Bruchez, Jr., M. Moronne, P. Gin, S. Weiss, and A. P. Alivisatos, “Semiconductor nanocrystals as fluorescent biological labels,” Science 281, 2013-2016 (1998).
[CrossRef] [PubMed]

Bruchez, M. P.

D. R. Larson, W. R. Zipfel, R. M. Williams, S. W. Clark, M. P. Bruchez, F. W. Wise, and W. W. Webb, “Water-soluble quantum dots for multiphoton fluorescence imaging in vivo,” Science 300, 1434-1436 (2003).
[CrossRef] [PubMed]

Bruehl, R. E.

W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
[CrossRef]

Bryant, Z.

W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
[CrossRef]

Buffelli, M.

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L. Sacconi, R. P. O'Connor, A. Jasaitis, A. Masi, M. Buffelli, and F. S. Pavone, “In vivo multiphoton nanosurgery on cortical neurons,” J. Biomed. Opt. 12, 050502 (2007).
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W. Jiang, A. Singhal, J. Zheng, C. Wang, and W. C. W. Chan, “Optimizing the synthesis of red- to near-IR-emitting CdS-capped CdTexSe1−x alloyed quantum dots for biomedical imaging,” Chem. Mater. 18, 4845-4854 (2006).
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K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
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I. Nabiev, S. Mitchell, A. Davies, Y. Williams, D. Kelleher, R. Moore, Y. K. Gun'ko, S. Byrne, Y. P. Rakovich, J. F. Donegan, A. Sukhanova, J. Conroy, D. Cottell, N. Gaponik, A. Rogach, and Y. Volkov, “Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments,” Nano Lett. 7, 3452-3461 (2007).
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K. W. Dunn, R. M. Sandoval, K. J. Kelly, P. C. Dagher, G. A. Tanner, S. J. Atkinson, R. L. Bacallao, and B. A. Molitoris, “Functional studies of the kidney of living animals using multicolor two-photon microscopy,” Am. J. Physiol.: Cell Physiol. 283, C905-C916 (2002).

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K. Svoboda, W. Denk, D. Kleinfeld, and D. W. Tank, “In vivo dendritic calcium dynamics in neocortical pyramidal neurons,” Nature 385, 161-165 (1997).
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K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
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N. J. Durr, T. Larson, D. K. Smith, B. A. Korgel, K. Sokolov, and A. Ben-Yakar, “Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods,” Nano Lett. 7, 941-945 (2007).
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Z. Tang, N. A. Kotov, and M. Giersig, “Spontaneous organization of single CdTe nanoparticles into luminescent nanowires,” Science 297, 237-240 (2002).
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S. Wang, N. Mamedova, N. A. Kotov, W. Chen, andJ. Studer, “Antigen/antibody immunocomplex from CdTe nanoparticle bioconjugates,” Nano Lett. 2, 817-822 (2002).
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S.-C. Pu, M.-J. Yang, C.-C. Hsu, C.-W. Lai, C.-C. Hsieh, S. H. Lin, Y.-M. Cheng, and P.-T. Chou, “The empirical correlation between size and two-photon absorption cross section of CdSe and CdTe quantum dots,” Small 2, 1308-1313 (2006).
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N. J. Durr, T. Larson, D. K. Smith, B. A. Korgel, K. Sokolov, and A. Ben-Yakar, “Two-photon luminescence imaging of cancer cells using molecularly targeted gold nanorods,” Nano Lett. 7, 941-945 (2007).
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B. E. Chen, B. Lendvai, E. A. Nimchinsky, B. Burbach, K. Fox, and K. Svoboda, “Imaging high-resolution structure of GFP-expressing neurons in neocortex in vivo,” Learn. Memory 7, 433-441 (2000).
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M. J. Levene, D. A. Dombeck, K. A. Kasischke, R. P. Molloy, and W. W. Webb, “In vivo multiphoton microscopy of deep brain tissue,” J. Neurophysiol. 91, 1908-1912 (2004).
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Li, J. J.

W. Guo, J. J. Li, Y. A. Wang, and X. Peng, “Conjugation chemistry and bioapplications of semiconductor box nanocrystals prepared via dendrimer bridging,” Chem. Mater. 15, 3125-3133 (2003).
[CrossRef]

Lin, L.

Y. Xu, Q. Wang, P. He, Q. Dong, F. Liu, Y. Liu, L. Lin, H. Yan, and X. Zhao, “Cell nucleus penetration by quantum dots induced by nuclear staining organic fluorophore and UV-irradiation,” Adv. Mater. 20, 3468-3473 (2008).
[CrossRef]

Lin, S. H.

S.-C. Pu, M.-J. Yang, C.-C. Hsu, C.-W. Lai, C.-C. Hsieh, S. H. Lin, Y.-M. Cheng, and P.-T. Chou, “The empirical correlation between size and two-photon absorption cross section of CdSe and CdTe quantum dots,” Small 2, 1308-1313 (2006).
[CrossRef] [PubMed]

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Y. Xu, Q. Wang, P. He, Q. Dong, F. Liu, Y. Liu, L. Lin, H. Yan, and X. Zhao, “Cell nucleus penetration by quantum dots induced by nuclear staining organic fluorophore and UV-irradiation,” Adv. Mater. 20, 3468-3473 (2008).
[CrossRef]

Liu, L. C.

K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
[CrossRef]

Liu, Y.

Y. Xu, Q. Wang, P. He, Q. Dong, F. Liu, Y. Liu, L. Lin, H. Yan, and X. Zhao, “Cell nucleus penetration by quantum dots induced by nuclear staining organic fluorophore and UV-irradiation,” Adv. Mater. 20, 3468-3473 (2008).
[CrossRef]

Mamedova, N.

S. Wang, N. Mamedova, N. A. Kotov, W. Chen, andJ. Studer, “Antigen/antibody immunocomplex from CdTe nanoparticle bioconjugates,” Nano Lett. 2, 817-822 (2002).
[CrossRef]

Mansfield, L. S.

H. M. Elsheikha and L. S. Mansfield, “Assessment of Sarcocystis neurona sporocyst viability and differentiation between viable and nonviable sporocysts using propidium iodide stain,” J. Parasitol. 90, 872-875 (2004).
[CrossRef] [PubMed]

Masi, A.

L. Sacconi, R. P. O'Connor, A. Jasaitis, A. Masi, M. Buffelli, and F. S. Pavone, “In vivo multiphoton nanosurgery on cortical neurons,” J. Biomed. Opt. 12, 050502 (2007).
[CrossRef] [PubMed]

Masters, B. R.

B. R. Masters, P. T. C. So, and E. Gratton, “Optical biopsy of in vivo human skin: Multiphoton excitation microscopy,” Lasers Med. Sci. 13, 196-203 (1998).
[CrossRef]

Matroussi, H.

P. T. Tran, E. R. Goldman, G. P. Anderson, J. M. Mauro, and H. Matroussi, Use of Luminescent CdSe-ZnS Nanocrystal Bioconjugates in Quantum Dot-based Nanosensors (Wiley-VCH, 2002), pp. 427-432.

Mauro, J. M.

P. T. Tran, E. R. Goldman, G. P. Anderson, J. M. Mauro, and H. Matroussi, Use of Luminescent CdSe-ZnS Nanocrystal Bioconjugates in Quantum Dot-based Nanosensors (Wiley-VCH, 2002), pp. 427-432.

McGinnis, B. P.

K. I. Kang, B. P. McGinnis, Sandalphon, Y. Z. Hu, S. W. Koch, N. Peyghambarian, L. C. Liu, and S. H. Risbud, “Confinement-induced valence-band mixing in CdS quantum dots observed by two-photon spectroscopy,” Phys. Rev. B 45, 3465-3468 (1992).
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W. J. Parak, D. Gerion, D. Zanchet, A. S. Woerz, T. Pellegrino, C. Micheel, S. C. Williams, M. Seitz, R. E. Bruehl, Z. Bryant, C. Bustamante, C. R. Bertozzi, and A. P. Alivisatos, “Conjugation of DNA to silanized colloidal semiconductor nanocrystalline quantum dots,” Chem. Mater. 14, 2113-2119 (2002).
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Mitchell, S.

I. Nabiev, S. Mitchell, A. Davies, Y. Williams, D. Kelleher, R. Moore, Y. K. Gun'ko, S. Byrne, Y. P. Rakovich, J. F. Donegan, A. Sukhanova, J. Conroy, D. Cottell, N. Gaponik, A. Rogach, and Y. Volkov, “Nonfunctionalized nanocrystals can exploit a cell's active transport machinery delivering them to specific nuclear and cytoplasmic compartments,” Nano Lett. 7, 3452-3461 (2007).
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All the SQD samples described here were purchased from Evident Technologies; the “2 nm” USQD samples used in this study are their “Blue” product with a specified CdSe core diameter of 1.9 nm(+/−5%) and a peak emission wavelength of 490 nm, consistent with our measurements reported here.

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Figures (7)

Fig. 1
Fig. 1

Experimental setup used to characterize TPAF signals from Cd Se Zn S USQDs.

Fig. 2
Fig. 2

(a) Linear absorption (peak at 460 nm and FWHM of 40 nm ) and fluorescence (peak at 496 nm and FWHM of 30 nm ) spectra of 2 nm Cd Se Zn S USQDs. The absorbance corresponds to a 2 mm path length solution at a concentration of 1.4 mg ml ; (b) a typical TEM image of the Cd Se Zn S USQDs used in this study. The darker dots that are predominantly in the right-hand area (at the right of the NE to SW diagonal) are the CdSe SQDs, whereas the finer “sub-nm” type of graininess in the image is due to an artifact of the TEM imaging setup.

Fig. 3
Fig. 3

Linear fluorescence from four different Cd Se Zn S SQD colloidal samples, corresponding to SQDs of distinct average sizes varying from 2 nm to 3.4 nm .

Fig. 4
Fig. 4

TPAF spectra for several distinct excitation wavelengths in the 810 nm 860 nm range, using a constant excitation intensity of 8 GW cm 2 . The vertical axis corresponds to the signals obtained with the lock-in amplifier when the PMT is located at the exit of the monochromator.

Fig. 5
Fig. 5

Power in the TPA-induced fluorescence as a function of the excitation intensity for excitation at 810 nm and 930 nm respectively. The vertical axis corresponds to the lock-in amplifier signal when the entire fluorescence spectrum (no monochromator) is focused on the PMT, and a value of 12 on the horizontal axis corresponds to an intensity of 8 GW cm 2 .

Fig. 6
Fig. 6

The wavelength dependence of the TPA-induced fluorescence outputs for the 2 nm Cd Se Zn S USQDs at two different concentrations ( 1.4 mg mL , triangles; 0.4 mg mL , squares).

Fig. 7
Fig. 7

Schematic of the electronic energy levels for Cd Se Zn S quantum dots of 2 nm diameter. (See Ref [37] for details).

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