Abstract

Widespread applications of ZnO nanoparticles (NP) in sun-blocking cosmetic products have raised safety concerns related to their potential transdermal penetration and resultant cytotoxicity. Nonlinear optical microscopy provides means for high-contrast imaging of ZnO NPs lending in vitro and in vivo assessment of the nanoparticle uptake in skin, provided their nonlinear optical properties are characterized. We report on this characterization using ZnO NP commercial product, Zinclear, mean-sized 21 nm. Two-photon action cross-section of this bandgap material (Ebg = 3.37 eV, λbg = 370 nm) measured by two techniques yielded consistent results of ηZnOσZnO(2ph) = 6.2 ± 0.8 μGM at 795 nm, and 32 ± 6 μGM at 770 nm per unit ZnO crystal cell, with the quantum efficiency of ηZnO = (0.9 ± 0.2) %. In order to demonstrate the quantitative imaging, nonlinear optical microscopy images of the excised human skin topically treated with Zinclear were acquired and processed using σZnO(2ph) and ηZnOvalues yielding nanoparticle concentration map in skin. Accumulations of Zinclear ZnO nanoparticles were detected only on the skin surface and in skin folds reaching concentrations of 800 NPs per μm3.

© 2011 OSA

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    [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  38. T. M. Stachelek, T. A. Pazoha, W. M. McClain, and R. P. Drucker, ““Detection and assignment of the “phantom” photochemical singlet of trans-stilbene by two-photon excitation,” J. Chem. Phys.66(10), 4540–4543 (1977).
    [CrossRef]
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2011 (1)

L. L. Lin, J. E. Grice, M. K. Butler, A. V. Zvyagin, W. Becker, T. A. Robertson, H. P. Soyer, M. S. Roberts, and T. W. Prow, “Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin,” Pharm. Res.28(11), 2920–2930 (2011).
[CrossRef] [PubMed]

2010 (6)

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

A. P. Popov, A. V. Zvyagin, J. Lademann, M. S. Roberts, W. Sanchez, A. V. Priezzhev, and R. Myllylä, “Designing inorganic light-protective skin nanotechnology products,” J Biomed Nanotechnol6(5), 432–451 (2010).
[CrossRef] [PubMed]

B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

M. J. Osmond and M. J. McCall, “Zinc oxide nanoparticles in modern sunscreens: an analysis of potential exposure and hazard,” Nanotoxicology4(1), 15–41 (2010).
[CrossRef] [PubMed]

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

M. G. Vivas, T. Shih, T. Voss, E. Mazur, and C. R. Mendonca, “Nonlinear spectra of ZnO: reverse saturable, two- and three-photon absorption,” Opt. Express18(9), 9628–9633 (2010).
[CrossRef] [PubMed]

2009 (1)

C. Hanley, A. Thurber, C. Hanna, A. Punnoose, J. H. Zhang, and D. G. Wingett, “The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction,” Nanoscale Res. Lett.4(12), 1409–1420 (2009).
[CrossRef] [PubMed]

2008 (7)

A. V. Zvyagin, X. Zhao, A. Gierden, W. H. Sanchez, J. A. Ross, and M. S. Roberts, “Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo,” J. Biomed. Opt.13(6), 064031 (2008).
[CrossRef] [PubMed]

M. S. Roberts, M. J. Roberts, T. A. Robertson, W. Sanchez, C. Thörling, Y. Zou, X. Zhao, W. Becker, and A. V. Zvyagin, “In vitro and in vivo imaging of xenobiotic transport in human skin and in the rat liver,” J Biophotonics1(6), 478–493 (2008).
[CrossRef] [PubMed]

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Y. B. Zhang, W. Chen, S. P. Wang, Y. F. Liu, and C. Pope, “Phototoxicity of zinc oxide nanoparticle conjugates in human ovarian cancer NIH: OVCAR-3 cells,” J. Biomed. Nanotechnol.4(4), 432–438 (2008).
[CrossRef]

L. Irimpan, V. P. N. Nampoori, P. Radhakrishnan, B. Krishnan, and A. Deepthy, “Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO,” J. Appl. Phys.103(3), 033105 (2008).
[CrossRef]

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

M. H. Majles Ara, Z. Dehghani, and S. Saievar Iranizad, “Synthesis, characterization and single-beam Z-scan measurement of the third-order optical nonlinearities of ZnO nano-particles,” Int. J. Mod. Phys. B22(18 & 19), 3165–3171 (2008).
[CrossRef]

2007 (5)

Z.-W. Dong, C.-F. Zhang, G.-J. You, X.-Q. Qiu, K.-J. Liu, Y.-L. Yan, and S.-X. Qian, “Multi-photon excitation UV emission by femtosecond pulses and nonlinearity in ZnO single crystal,” J. Phys. Condens. Matter19(21), 216202 (2007).
[CrossRef]

J. A. Palero, H. S. de Bruijn, A. van der Ploeg van den Heuvel, H. J. Sterenborg, and H. C. Gerritsen, “Spectrally resolved multiphoton imaging of in vivo and excised mouse skin tissues,” Biophys. J.93(3), 992–1007 (2007).
[CrossRef] [PubMed]

S. E. Cross, B. Innes, M. S. Roberts, T. Tsuzuki, T. A. Robertson, and P. McCormick, “Human skin penetration of sunscreen nanoparticles: in-vitro assessment of a novel micronized zinc oxide formulation,” Skin Pharmacol. Physiol.20(3), 148–154 (2007).
[CrossRef] [PubMed]

R. M. Williams, A. Flesken-Nikitin, A. Y. Nikitin, and W. R. Zipfel, “Multiphoton microscopy of intrinsic tissue emissions for cancer research,” FASEB J.21, A601 (2007).

B. Nanda and R. S. R. Murthy, “Preparation and characterization of chitosan lactate nanoparticles for the nasal delivery of enalaprilat,” J. Biomed. Nanotech.3(1), 45–51 (2007).
[CrossRef]

2006 (1)

2005 (4)

A. P. Popov, J. Lademann, A. V. Priezzhev, and R. Myllylä, “Effect of size of TiO2 nanoparticles embedded into stratum corneum on ultraviolet-A and ultraviolet-B sun-blocking properties of the skin,” J. Biomed. Opt.10(6), 064037 (2005).
[CrossRef] [PubMed]

C. G. J. Hayden, S. E. Cross, C. Anderson, N. A. Saunders, and M. S. Roberts, “Sunscreen penetration of human skin and related keratinocyte toxicity after topical application,” Skin Pharmacol. Physiol.18(4), 170–174 (2005).
[CrossRef] [PubMed]

D. C. Dai, S. J. Xu, S. L. Shi, M. H. Xie, and C. M. Che, “Efficient multiphoton-absorption-induced luminescence in single-crystalline ZnO at room temperature,” Opt. Lett.30(24), 3377–3379 (2005).
[CrossRef] [PubMed]

J. H. Lin, Y. J. Chen, H. Y. Lin, and W. F. Hsieh, “Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films,” J. Appl. Phys.97(3), 033526 (2005).
[CrossRef]

2004 (1)

C. Y. Liu, B. P. Zhang, N. T. Binh, and Y. Segawa, “Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition,” Opt. Commun.237(1-3), 65–70 (2004).
[CrossRef]

2003 (2)

W. R. Zipfel, R. M. Williams, R. Christie, A. Y. Nikitin, B. T. Hyman, and W. W. Webb, “Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation,” Proc. Natl. Acad. Sci. U.S.A.100(12), 7075–7080 (2003).
[CrossRef] [PubMed]

W. R. Zipfel, R. M. Williams, and W. W. Webb, “Nonlinear magic: multiphoton microscopy in the biosciences,” Nat. Biotechnol.21(11), 1369–1377 (2003).
[CrossRef] [PubMed]

2001 (3)

F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
[CrossRef] [PubMed]

B. R. Masters and P. T. C. So, “Confocal microscopy and multi-photon excitation microscopy of human skin in vivo,” Opt. Express8(1), 2–10 (2001).
[CrossRef] [PubMed]

T. Tsuzuki and P. G. McCormick, “ZnO nanoparticles synthesised by mechanochemical processing,” Scr. Mater.44(8-9), 1731–1734 (2001).
[CrossRef]

2000 (1)

L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
[CrossRef]

1999 (2)

B. R. Masters and P. T. C. So, “Multi-photon excitation microscopy and confocal microscopy imaging of in vivo human skin: A comparison,” Microsc. Microanal.5(4), 282–289 (1999).
[PubMed]

J. Lademann, H. J. Weigmann, C. Rickmeyer, H. Barthelmes, H. Schaefer, G. Mueller, and W. Sterry, “Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice,” Skin Pharmacol. Appl. Skin Physiol.12(5), 247–256 (1999).
[CrossRef] [PubMed]

1998 (2)

Z. K. Tang, G. K. L. Wong, P. Yu, M. Kawasaki, A. Ohtomo, H. Koinuma, and Y. Segawa, “Room-temperature ultraviolet laser emission from self-assembled ZnO microcrystallite thin films,” Appl. Phys. Lett.72(25), 3270–3272 (1998).
[CrossRef]

M. A. Albota, C. Xu, and W. W. Webb, “Two-photon fluorescence excitation cross sections of biomolecular probes from 690 to 960 nm,” Appl. Opt.37(31), 7352–7356 (1998).
[CrossRef] [PubMed]

1997 (2)

X. J. Zhang, W. Ji, and S. H. Tang, “Determination of optical nonlinearities and carrier lifetime in ZnO,” J. Opt. Soc. Am. B14(8), 1951–1955 (1997).
[CrossRef]

M. Schubnell, I. Kamber, and P. Beaud, “Photochemistry at high temperatures - Potential of ZnO as a high temperature photocatalyst,” Appl. Phys., A Mater. Sci. Process.64(1), 109–113 (1997).
[CrossRef]

1977 (1)

T. M. Stachelek, T. A. Pazoha, W. M. McClain, and R. P. Drucker, ““Detection and assignment of the “phantom” photochemical singlet of trans-stilbene by two-photon excitation,” J. Chem. Phys.66(10), 4540–4543 (1977).
[CrossRef]

Albota, M. A.

Anderson, C.

C. G. J. Hayden, S. E. Cross, C. Anderson, N. A. Saunders, and M. S. Roberts, “Sunscreen penetration of human skin and related keratinocyte toxicity after topical application,” Skin Pharmacol. Physiol.18(4), 170–174 (2005).
[CrossRef] [PubMed]

Barthelmes, H.

J. Lademann, H. J. Weigmann, C. Rickmeyer, H. Barthelmes, H. Schaefer, G. Mueller, and W. Sterry, “Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice,” Skin Pharmacol. Appl. Skin Physiol.12(5), 247–256 (1999).
[CrossRef] [PubMed]

Beaud, P.

M. Schubnell, I. Kamber, and P. Beaud, “Photochemistry at high temperatures - Potential of ZnO as a high temperature photocatalyst,” Appl. Phys., A Mater. Sci. Process.64(1), 109–113 (1997).
[CrossRef]

Becker, W.

L. L. Lin, J. E. Grice, M. K. Butler, A. V. Zvyagin, W. Becker, T. A. Robertson, H. P. Soyer, M. S. Roberts, and T. W. Prow, “Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin,” Pharm. Res.28(11), 2920–2930 (2011).
[CrossRef] [PubMed]

M. S. Roberts, M. J. Roberts, T. A. Robertson, W. Sanchez, C. Thörling, Y. Zou, X. Zhao, W. Becker, and A. V. Zvyagin, “In vitro and in vivo imaging of xenobiotic transport in human skin and in the rat liver,” J Biophotonics1(6), 478–493 (2008).
[CrossRef] [PubMed]

Binh, N. T.

C. Y. Liu, B. P. Zhang, N. T. Binh, and Y. Segawa, “Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition,” Opt. Commun.237(1-3), 65–70 (2004).
[CrossRef]

Biswas, M.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Bock, M.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Boey, F. Y.-C.

B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

Breusing, M.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Butler, M. K.

L. L. Lin, J. E. Grice, M. K. Butler, A. V. Zvyagin, W. Becker, T. A. Robertson, H. P. Soyer, M. S. Roberts, and T. W. Prow, “Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin,” Pharm. Res.28(11), 2920–2930 (2011).
[CrossRef] [PubMed]

Byrne, D.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Casey, P.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Che, C. M.

Chen, W.

Y. B. Zhang, W. Chen, S. P. Wang, Y. F. Liu, and C. Pope, “Phototoxicity of zinc oxide nanoparticle conjugates in human ovarian cancer NIH: OVCAR-3 cells,” J. Biomed. Nanotechnol.4(4), 432–438 (2008).
[CrossRef]

Chen, Y. J.

J. H. Lin, Y. J. Chen, H. Y. Lin, and W. F. Hsieh, “Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films,” J. Appl. Phys.97(3), 033526 (2005).
[CrossRef]

Christie, R.

W. R. Zipfel, R. M. Williams, R. Christie, A. Y. Nikitin, B. T. Hyman, and W. W. Webb, “Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation,” Proc. Natl. Acad. Sci. U.S.A.100(12), 7075–7080 (2003).
[CrossRef] [PubMed]

Cross, S. E.

S. E. Cross, B. Innes, M. S. Roberts, T. Tsuzuki, T. A. Robertson, and P. McCormick, “Human skin penetration of sunscreen nanoparticles: in-vitro assessment of a novel micronized zinc oxide formulation,” Skin Pharmacol. Physiol.20(3), 148–154 (2007).
[CrossRef] [PubMed]

C. G. J. Hayden, S. E. Cross, C. Anderson, N. A. Saunders, and M. S. Roberts, “Sunscreen penetration of human skin and related keratinocyte toxicity after topical application,” Skin Pharmacol. Physiol.18(4), 170–174 (2005).
[CrossRef] [PubMed]

Dai, D. C.

Das, S. K.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

de Bruijn, H. S.

J. A. Palero, H. S. de Bruijn, A. van der Ploeg van den Heuvel, H. J. Sterenborg, and H. C. Gerritsen, “Spectrally resolved multiphoton imaging of in vivo and excised mouse skin tissues,” Biophys. J.93(3), 992–1007 (2007).
[CrossRef] [PubMed]

Deepthy, A.

L. Irimpan, V. P. N. Nampoori, P. Radhakrishnan, B. Krishnan, and A. Deepthy, “Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO,” J. Appl. Phys.103(3), 033105 (2008).
[CrossRef]

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

Dehghani, Z.

M. H. Majles Ara, Z. Dehghani, and S. Saievar Iranizad, “Synthesis, characterization and single-beam Z-scan measurement of the third-order optical nonlinearities of ZnO nano-particles,” Int. J. Mod. Phys. B22(18 & 19), 3165–3171 (2008).
[CrossRef]

Dong, Z.-W.

Z.-W. Dong, C.-F. Zhang, G.-J. You, X.-Q. Qiu, K.-J. Liu, Y.-L. Yan, and S.-X. Qian, “Multi-photon excitation UV emission by femtosecond pulses and nonlinearity in ZnO single crystal,” J. Phys. Condens. Matter19(21), 216202 (2007).
[CrossRef]

Drucker, R. P.

T. M. Stachelek, T. A. Pazoha, W. M. McClain, and R. P. Drucker, ““Detection and assignment of the “phantom” photochemical singlet of trans-stilbene by two-photon excitation,” J. Chem. Phys.66(10), 4540–4543 (1977).
[CrossRef]

Flesken-Nikitin, A.

R. M. Williams, A. Flesken-Nikitin, A. Y. Nikitin, and W. R. Zipfel, “Multiphoton microscopy of intrinsic tissue emissions for cancer research,” FASEB J.21, A601 (2007).

Frenz, M.

Gärtner, E.

F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
[CrossRef] [PubMed]

Ge, W. K.

L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
[CrossRef]

Gerritsen, H. C.

J. A. Palero, H. S. de Bruijn, A. van der Ploeg van den Heuvel, H. J. Sterenborg, and H. C. Gerritsen, “Spectrally resolved multiphoton imaging of in vivo and excised mouse skin tissues,” Biophys. J.93(3), 992–1007 (2007).
[CrossRef] [PubMed]

Gers-Barlag, H.

F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
[CrossRef] [PubMed]

Gierden, A.

A. V. Zvyagin, X. Zhao, A. Gierden, W. H. Sanchez, J. A. Ross, and M. S. Roberts, “Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo,” J. Biomed. Opt.13(6), 064031 (2008).
[CrossRef] [PubMed]

Gilbert, B.

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Gomez, L.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Greenoak, G.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Grice, J. E.

L. L. Lin, J. E. Grice, M. K. Butler, A. V. Zvyagin, W. Becker, T. A. Robertson, H. P. Soyer, M. S. Roberts, and T. W. Prow, “Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin,” Pharm. Res.28(11), 2920–2930 (2011).
[CrossRef] [PubMed]

Grunwald, R.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Gulson, B.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Guo, L.

L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
[CrossRef]

Hanley, C.

C. Hanley, A. Thurber, C. Hanna, A. Punnoose, J. H. Zhang, and D. G. Wingett, “The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction,” Nanoscale Res. Lett.4(12), 1409–1420 (2009).
[CrossRef] [PubMed]

Hanna, C.

C. Hanley, A. Thurber, C. Hanna, A. Punnoose, J. H. Zhang, and D. G. Wingett, “The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction,” Nanoscale Res. Lett.4(12), 1409–1420 (2009).
[CrossRef] [PubMed]

Hayden, C. G. J.

C. G. J. Hayden, S. E. Cross, C. Anderson, N. A. Saunders, and M. S. Roberts, “Sunscreen penetration of human skin and related keratinocyte toxicity after topical application,” Skin Pharmacol. Physiol.18(4), 170–174 (2005).
[CrossRef] [PubMed]

Heng, B. C.

B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

Hohenberg, H.

F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
[CrossRef] [PubMed]

Hsieh, W. F.

J. H. Lin, Y. J. Chen, H. Y. Lin, and W. F. Hsieh, “Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films,” J. Appl. Phys.97(3), 033526 (2005).
[CrossRef]

Hyman, B. T.

W. R. Zipfel, R. M. Williams, R. Christie, A. Y. Nikitin, B. T. Hyman, and W. W. Webb, “Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation,” Proc. Natl. Acad. Sci. U.S.A.100(12), 7075–7080 (2003).
[CrossRef] [PubMed]

Innes, B.

S. E. Cross, B. Innes, M. S. Roberts, T. Tsuzuki, T. A. Robertson, and P. McCormick, “Human skin penetration of sunscreen nanoparticles: in-vitro assessment of a novel micronized zinc oxide formulation,” Skin Pharmacol. Physiol.20(3), 148–154 (2007).
[CrossRef] [PubMed]

Irimpan, L.

L. Irimpan, V. P. N. Nampoori, P. Radhakrishnan, B. Krishnan, and A. Deepthy, “Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO,” J. Appl. Phys.103(3), 033105 (2008).
[CrossRef]

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

Ji, W.

Kamber, I.

M. Schubnell, I. Kamber, and P. Beaud, “Photochemistry at high temperatures - Potential of ZnO as a high temperature photocatalyst,” Appl. Phys., A Mater. Sci. Process.64(1), 109–113 (1997).
[CrossRef]

Kauert, M.

Kawasaki, M.

Z. K. Tang, G. K. L. Wong, P. Yu, M. Kawasaki, A. Ohtomo, H. Koinuma, and Y. Segawa, “Room-temperature ultraviolet laser emission from self-assembled ZnO microcrystallite thin films,” Appl. Phys. Lett.72(25), 3270–3272 (1998).
[CrossRef]

Kinsley, L.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Koinuma, H.

Z. K. Tang, G. K. L. Wong, P. Yu, M. Kawasaki, A. Ohtomo, H. Koinuma, and Y. Segawa, “Room-temperature ultraviolet laser emission from self-assembled ZnO microcrystallite thin films,” Appl. Phys. Lett.72(25), 3270–3272 (1998).
[CrossRef]

Korsch, M.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Kovochich, M.

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Krishnan, B.

L. Irimpan, V. P. N. Nampoori, P. Radhakrishnan, B. Krishnan, and A. Deepthy, “Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO,” J. Appl. Phys.103(3), 033105 (2008).
[CrossRef]

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

Kukreja, L. M.

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

Lademann, J.

A. P. Popov, A. V. Zvyagin, J. Lademann, M. S. Roberts, W. Sanchez, A. V. Priezzhev, and R. Myllylä, “Designing inorganic light-protective skin nanotechnology products,” J Biomed Nanotechnol6(5), 432–451 (2010).
[CrossRef] [PubMed]

A. P. Popov, J. Lademann, A. V. Priezzhev, and R. Myllylä, “Effect of size of TiO2 nanoparticles embedded into stratum corneum on ultraviolet-A and ultraviolet-B sun-blocking properties of the skin,” J. Biomed. Opt.10(6), 064037 (2005).
[CrossRef] [PubMed]

J. Lademann, H. J. Weigmann, C. Rickmeyer, H. Barthelmes, H. Schaefer, G. Mueller, and W. Sterry, “Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice,” Skin Pharmacol. Appl. Skin Physiol.12(5), 247–256 (1999).
[CrossRef] [PubMed]

Lin, H. Y.

J. H. Lin, Y. J. Chen, H. Y. Lin, and W. F. Hsieh, “Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films,” J. Appl. Phys.97(3), 033526 (2005).
[CrossRef]

Lin, J. H.

J. H. Lin, Y. J. Chen, H. Y. Lin, and W. F. Hsieh, “Two-photon resonance assisted huge nonlinear refraction and absorption in ZnO thin films,” J. Appl. Phys.97(3), 033526 (2005).
[CrossRef]

Lin, L. L.

L. L. Lin, J. E. Grice, M. K. Butler, A. V. Zvyagin, W. Becker, T. A. Robertson, H. P. Soyer, M. S. Roberts, and T. W. Prow, “Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin,” Pharm. Res.28(11), 2920–2930 (2011).
[CrossRef] [PubMed]

Liong, M.

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Liu, C. Y.

C. Y. Liu, B. P. Zhang, N. T. Binh, and Y. Segawa, “Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition,” Opt. Commun.237(1-3), 65–70 (2004).
[CrossRef]

Liu, K.-J.

Z.-W. Dong, C.-F. Zhang, G.-J. You, X.-Q. Qiu, K.-J. Liu, Y.-L. Yan, and S.-X. Qian, “Multi-photon excitation UV emission by femtosecond pulses and nonlinearity in ZnO single crystal,” J. Phys. Condens. Matter19(21), 216202 (2007).
[CrossRef]

Liu, Y. F.

Y. B. Zhang, W. Chen, S. P. Wang, Y. F. Liu, and C. Pope, “Phototoxicity of zinc oxide nanoparticle conjugates in human ovarian cancer NIH: OVCAR-3 cells,” J. Biomed. Nanotechnol.4(4), 432–438 (2008).
[CrossRef]

Loo, J. S.-C.

B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

Mädler, L.

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Majles Ara, M. H.

M. H. Majles Ara, Z. Dehghani, and S. Saievar Iranizad, “Synthesis, characterization and single-beam Z-scan measurement of the third-order optical nonlinearities of ZnO nano-particles,” Int. J. Mod. Phys. B22(18 & 19), 3165–3171 (2008).
[CrossRef]

Masters, B. R.

B. R. Masters and P. T. C. So, “Confocal microscopy and multi-photon excitation microscopy of human skin in vivo,” Opt. Express8(1), 2–10 (2001).
[CrossRef] [PubMed]

B. R. Masters and P. T. C. So, “Multi-photon excitation microscopy and confocal microscopy imaging of in vivo human skin: A comparison,” Microsc. Microanal.5(4), 282–289 (1999).
[PubMed]

Mazur, E.

McCall, M.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

McCall, M. J.

M. J. Osmond and M. J. McCall, “Zinc oxide nanoparticles in modern sunscreens: an analysis of potential exposure and hazard,” Nanotoxicology4(1), 15–41 (2010).
[CrossRef] [PubMed]

McClain, W. M.

T. M. Stachelek, T. A. Pazoha, W. M. McClain, and R. P. Drucker, ““Detection and assignment of the “phantom” photochemical singlet of trans-stilbene by two-photon excitation,” J. Chem. Phys.66(10), 4540–4543 (1977).
[CrossRef]

McCormick, P.

S. E. Cross, B. Innes, M. S. Roberts, T. Tsuzuki, T. A. Robertson, and P. McCormick, “Human skin penetration of sunscreen nanoparticles: in-vitro assessment of a novel micronized zinc oxide formulation,” Skin Pharmacol. Physiol.20(3), 148–154 (2007).
[CrossRef] [PubMed]

McCormick, P. G.

T. Tsuzuki and P. G. McCormick, “ZnO nanoparticles synthesised by mechanochemical processing,” Scr. Mater.44(8-9), 1731–1734 (2001).
[CrossRef]

McCulloch, M.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

McGlynn, E.

S. K. Das, M. Biswas, D. Byrne, M. Bock, E. McGlynn, M. Breusing, and R. Grunwald, “Multiphoton-absorption induced ultraviolet luminescence of ZnO nanorods using low-energy femtosecond pulses,” J. Appl. Phys.108(4), 043107–043112 (2010).
[CrossRef]

Mendonca, C. R.

Mueller, G.

J. Lademann, H. J. Weigmann, C. Rickmeyer, H. Barthelmes, H. Schaefer, G. Mueller, and W. Sterry, “Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice,” Skin Pharmacol. Appl. Skin Physiol.12(5), 247–256 (1999).
[CrossRef] [PubMed]

Murthy, R. S. R.

B. Nanda and R. S. R. Murthy, “Preparation and characterization of chitosan lactate nanoparticles for the nasal delivery of enalaprilat,” J. Biomed. Nanotech.3(1), 45–51 (2007).
[CrossRef]

Myllylä, R.

A. P. Popov, A. V. Zvyagin, J. Lademann, M. S. Roberts, W. Sanchez, A. V. Priezzhev, and R. Myllylä, “Designing inorganic light-protective skin nanotechnology products,” J Biomed Nanotechnol6(5), 432–451 (2010).
[CrossRef] [PubMed]

A. P. Popov, J. Lademann, A. V. Priezzhev, and R. Myllylä, “Effect of size of TiO2 nanoparticles embedded into stratum corneum on ultraviolet-A and ultraviolet-B sun-blocking properties of the skin,” J. Biomed. Opt.10(6), 064037 (2005).
[CrossRef] [PubMed]

Nampoori, V. P. N.

L. Irimpan, V. P. N. Nampoori, P. Radhakrishnan, B. Krishnan, and A. Deepthy, “Size-dependent enhancement of nonlinear optical properties in nanocolloids of ZnO,” J. Appl. Phys.103(3), 033105 (2008).
[CrossRef]

L. Irimpan, A. Deepthy, B. Krishnan, L. M. Kukreja, V. P. N. Nampoori, and P. Radhakrishnan, “Effect of self assembly on the nonlinear optical characteristics of ZnO thin films,” Opt. Commun.281(10), 2938–2943 (2008).
[CrossRef]

Nanda, B.

B. Nanda and R. S. R. Murthy, “Preparation and characterization of chitosan lactate nanoparticles for the nasal delivery of enalaprilat,” J. Biomed. Nanotech.3(1), 45–51 (2007).
[CrossRef]

Nel, A. E.

T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

Ng, K. W.

B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

Nikitin, A. Y.

R. M. Williams, A. Flesken-Nikitin, A. Y. Nikitin, and W. R. Zipfel, “Multiphoton microscopy of intrinsic tissue emissions for cancer research,” FASEB J.21, A601 (2007).

W. R. Zipfel, R. M. Williams, R. Christie, A. Y. Nikitin, B. T. Hyman, and W. W. Webb, “Live tissue intrinsic emission microscopy using multiphoton-excited native fluorescence and second harmonic generation,” Proc. Natl. Acad. Sci. U.S.A.100(12), 7075–7080 (2003).
[CrossRef] [PubMed]

Ohtomo, A.

Z. K. Tang, G. K. L. Wong, P. Yu, M. Kawasaki, A. Ohtomo, H. Koinuma, and Y. Segawa, “Room-temperature ultraviolet laser emission from self-assembled ZnO microcrystallite thin films,” Appl. Phys. Lett.72(25), 3270–3272 (1998).
[CrossRef]

Osmond, M. J.

M. J. Osmond and M. J. McCall, “Zinc oxide nanoparticles in modern sunscreens: an analysis of potential exposure and hazard,” Nanotoxicology4(1), 15–41 (2010).
[CrossRef] [PubMed]

Oytam, Y.

B. Gulson, M. McCall, M. Korsch, L. Gomez, P. Casey, Y. Oytam, A. Taylor, M. McCulloch, J. Trotter, L. Kinsley, and G. Greenoak, “Small amounts of zinc from zinc oxide particles in sunscreens applied outdoors are absorbed through human skin,” Toxicol. Sci.118(1), 140–149 (2010).
[CrossRef] [PubMed]

Palero, J. A.

J. A. Palero, H. S. de Bruijn, A. van der Ploeg van den Heuvel, H. J. Sterenborg, and H. C. Gerritsen, “Spectrally resolved multiphoton imaging of in vivo and excised mouse skin tissues,” Biophys. J.93(3), 992–1007 (2007).
[CrossRef] [PubMed]

Pazoha, T. A.

T. M. Stachelek, T. A. Pazoha, W. M. McClain, and R. P. Drucker, ““Detection and assignment of the “phantom” photochemical singlet of trans-stilbene by two-photon excitation,” J. Chem. Phys.66(10), 4540–4543 (1977).
[CrossRef]

Pfeiffer, S.

F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
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Pflücker, F.

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F. Pflücker, V. Wendel, H. Hohenberg, E. Gärtner, T. Will, S. Pfeiffer, R. Wepf, and H. Gers-Barlag, “The human stratum corneum layer: an effective barrier against dermal uptake of different forms of topically applied micronised titanium dioxide,” Skin Pharmacol. Appl. Skin Physiol.14(Suppl 1), 92–97 (2001).
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Xiong, S. J.

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Xu, S. J.

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L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
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L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
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T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
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Z.-W. Dong, C.-F. Zhang, G.-J. You, X.-Q. Qiu, K.-J. Liu, Y.-L. Yan, and S.-X. Qian, “Multi-photon excitation UV emission by femtosecond pulses and nonlinearity in ZnO single crystal,” J. Phys. Condens. Matter19(21), 216202 (2007).
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L. Guo, S. H. Yang, C. L. Yang, P. Yu, J. N. Wang, W. K. Ge, and G. K. L. Wong, “Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties,” Appl. Phys. Lett.76(20), 2901–2903 (2000).
[CrossRef]

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C. Y. Liu, B. P. Zhang, N. T. Binh, and Y. Segawa, “Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition,” Opt. Commun.237(1-3), 65–70 (2004).
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Z.-W. Dong, C.-F. Zhang, G.-J. You, X.-Q. Qiu, K.-J. Liu, Y.-L. Yan, and S.-X. Qian, “Multi-photon excitation UV emission by femtosecond pulses and nonlinearity in ZnO single crystal,” J. Phys. Condens. Matter19(21), 216202 (2007).
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C. Hanley, A. Thurber, C. Hanna, A. Punnoose, J. H. Zhang, and D. G. Wingett, “The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction,” Nanoscale Res. Lett.4(12), 1409–1420 (2009).
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Zhang, X. J.

Zhang, Y. B.

Y. B. Zhang, W. Chen, S. P. Wang, Y. F. Liu, and C. Pope, “Phototoxicity of zinc oxide nanoparticle conjugates in human ovarian cancer NIH: OVCAR-3 cells,” J. Biomed. Nanotechnol.4(4), 432–438 (2008).
[CrossRef]

Zhao, X.

A. V. Zvyagin, X. Zhao, A. Gierden, W. H. Sanchez, J. A. Ross, and M. S. Roberts, “Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo,” J. Biomed. Opt.13(6), 064031 (2008).
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M. S. Roberts, M. J. Roberts, T. A. Robertson, W. Sanchez, C. Thörling, Y. Zou, X. Zhao, W. Becker, and A. V. Zvyagin, “In vitro and in vivo imaging of xenobiotic transport in human skin and in the rat liver,” J Biophotonics1(6), 478–493 (2008).
[CrossRef] [PubMed]

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B. C. Heng, X. X. Zhao, S. J. Xiong, K. W. Ng, F. Y.-C. Boey, and J. S.-C. Loo, “Toxicity of zinc oxide (ZnO) nanoparticles on human bronchial epithelial cells (BEAS-2B) is accentuated by oxidative stress,” Food Chem. Toxicol.48(6), 1762–1766 (2010).
[CrossRef] [PubMed]

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T. Xia, M. Kovochich, M. Liong, L. Mädler, B. Gilbert, H. B. Shi, J. I. Yeh, J. I. Zink, and A. E. Nel, “Comparison of the mechanism of toxicity of zinc oxide and cerium oxide nanoparticles based on dissolution and oxidative stress properties,” ACS Nano2(10), 2121–2134 (2008).
[CrossRef] [PubMed]

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R. M. Williams, A. Flesken-Nikitin, A. Y. Nikitin, and W. R. Zipfel, “Multiphoton microscopy of intrinsic tissue emissions for cancer research,” FASEB J.21, A601 (2007).

W. R. Zipfel, R. M. Williams, and W. W. Webb, “Nonlinear magic: multiphoton microscopy in the biosciences,” Nat. Biotechnol.21(11), 1369–1377 (2003).
[CrossRef] [PubMed]

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[CrossRef] [PubMed]

Zou, Y.

M. S. Roberts, M. J. Roberts, T. A. Robertson, W. Sanchez, C. Thörling, Y. Zou, X. Zhao, W. Becker, and A. V. Zvyagin, “In vitro and in vivo imaging of xenobiotic transport in human skin and in the rat liver,” J Biophotonics1(6), 478–493 (2008).
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