PUBLICATIONS

49. S. Lee, K. M. Mayer, J. H. Hafner,"Improved Localized Surface Plasmon Resonance Immunoassay with Gold Bipyramid Substrates", Analytical Chemistry 81, 4450-4455 (2009).

Gold nanoparticles bound to substrates exhibit localized surface plasmon resonance (LSPR) in their optical extinction spectra at visible and near-infrared wavelengths. The LSPR wavelength is sensitive to the surrounding refractive index, enabling a simple, label-free immunoassay when capture antibodies are bound to the nanoparticles. Gold bipyramids are nanoparticles with a penta-twinned crystal structure, which have a sharp LSPR due to their high monodispersity. Bipyramid substrates were found to have a refractive index sensitivity ranging from 288 to 381 nm/RIU (-0.62 to -0.68 eV/RIU), increasing with the nanoparticle size and aspect ratio. In an immunoassay, the bipyramid substrates yielded higher sensitivity than nanorods and nanospheres. An immunoassay sensitivity constant which depends on both the optical properties of the nanoparticle and conjugation chemistry was found to be KLSPR = 0.01 nm-m^2 for gold bipyramids.

48. E. Y. Hleb, Y. Hu, R. A. Drezek, J. H. Hafner, D. O. Lapotko, "Photothermal bubbles as optical scattering probes for imaging living cells", Nanomedicine 3, 797-812 (2008).

Aims: We propose and have experimentally studied a new method with improved sensitivity and specificity of imaging of living cells. Method: Intracellular photothermal bubbles generated around gold nanoparticles (NPs) and their clusters were proposed as optical scattering probes for the amplification of scattered light. Results: Microbubbles generated around gold spheres and shells with 10-ns 532-nm laser pulses in individual living cells (leukemia cells, lung and squamous carcinoma cancer cells) have amplified optical side scattering up to 1800-times relative to that of intracellular gold NPs, and without detectable damage to host cells. We explain the discovered optical amplification by the endocytosis-mediated clustering of NPs in cells, and by the selective generation of microbubbles (that do not disrupt the host cell) around these clusters at minimal levels of laser pulse fluence. Conclusions: Photothermal bubbles generated around laser-activated gold NPs may significantly improve the sensitivity and specificity of cell imaging, and can be considered as a new type of optical cellular probes.

47. Y. Yang, K. M. Mayer, N. S. Wickremasinghe, J. H. Hafner, "Probing the Lipid Membrane Dipole Potential by Atomic Force Microscopy", Biophysical Journal 95, 5193-5199 (2008).

The electrostatic properties of biological membranes can be described by three parameters: the transmembrane potential, the membrane surface potential, and the membrane dipole potential. The first two are well characterized in terms of their magnitudes and biological effects. The dipole potential, however, is not well characterized. Various methods to measure the membrane dipole potential indirectly yield different values, and there is not even agreement on the source of the membrane dipole moment. This ambiguity impedes investigations into the biological effects of the membrane dipole moment, which should be substantial considering the large interfacial fields with which it is associated. Electrostatic analysis of phosphatidylcholine lipid membranes with the atomic force microscope reveals a repulsive force between the negatively charged probe tips and the zwitterionic lipids. This unexpected interaction has been analyzed quantitatively to reveal that the repulsion is due to a weak external field created by the internal membrane dipole potential. The analysis yields a dipole moment of 1.5 Debye per lipid with a dipole potential of +275 mV for supported phosphatidylcholine membranes. This new ability to quantitatively measure the membrane dipole moment in a noninvasive manner with nanometer scale spatial resolution will be useful in identifying the biological effects of the dipole potential.

46. E. Y. Hleb, J. H. Hafner, J. N. Myers, E. Y. Hanna, B. C. Rostro, S. A. Zhdanok, D. O. Lapotko, "LANTCET: elimination of solid tumor cells with photothermal bubbles generated around clusters of gold nanoparticles", Nanomedicine 3, 647-667 (2008).

Background: We have developed a method, termed laser-activated nano-thermolysis as a cell elimination technology (LANTCET), for the selective detection and destruction of individual tumor cells by the generation of intracellular photothermal bubbles around clusters of gold nanoparticles. Method: Bare nanoparticles and their conjugates to C225 tumor-specific monoclonal antibodies were applied in vitro to C225-positive squamous carcinoma cells and in vivo to an experimental tumor in a rat in order to form intracellular clusters of nanoparticles. Results: Single 10 ns laser pulses generated intracellular photothermal microbubbles at a near-infrared and visible wavelengths. The cells with the clusters yielded an almost 100-fold decrease in the laser fluence threshold for bubble generation and cell damage relative to that for the cells without clusters. Cell damage had a mechanical origin and single cell selectivity. Three LANTCET processes (cell detection, damage and optical guidance) were realized as a microsecond sequence and with the one device.

45. C. L. Nehl, J. H. Hafner, "Shape-dependent Plasmon Resonances of Gold Nanoparticles", Journal of Materials Chemistry 8, 2415-2419 (2008).

Localized surface plasmon resonances in noble metal nanoparticles cause enhanced optical absorption and scattering that is tunable through the visible and near-infrared. Furthermore, these resonances create large local electric field enhancements at the nanoparticle surfaces, essentially focussing light at the nanometer scale. These properties suggest a range of applications, including biomedical imaging, therapeutics, and molecular sensing. Here we review some recent advances regarding shape-dependent optical properties of two specific nanoparticle geometries: gold nanorods and branched gold nanoparticles.

44. K. M. Mayer, S. Lee, H. Liao, B. C. Rostro, A. Fuentes, P. T. Scully, C. L. Nehl, J. H. Hafner, "A Label-Free Immunoassay Based Upon Localized Surface Plasmon Resonance of Gold Nanorods", ACS Nano 2, 687-692 (2008).

43. J. N. Lassiter, J. Aizpurua, L. I. Hernandez, D. W. Brandl, I. Romero, S. Lal, J. H. Hafner, P. Nordlander, N. J. Halas, "Close Encounters between Two Nanoshells", Nano Letters 8, 1212-1218 (2008).

42. F. Hao, C. L. Nehl, J. H. Hafner, P. Nordlander, "Plasmon Resonances of a gold Nanostar, Nano Letters 7, 729-732 (2007).

41. Y. Yang, K. Mayer, J. H. Hafner, "Quantitative membrane electrostatics with the atomic force microscope", Biophysical Journal 92, 1966-1974 (2007).

40. H. Liao, C. L. Nehl, J. H. Hafner, "Biomedical Applications of Plasmon Resonant Metal Nanoparticles", Nanomedicine 1, 201-208 (2006).

39. A. Gulati, H. Liao, J. H. Hafner, "Monitoring Gold Nanorod Synthesis by Localized Surface Plasmon Resonance", Journal of Physical Chemistry B, 110, 22323-22327 (2006).

38. H. Wang, Y. Wu, B. Lassiter, C. L. Nehl, J. H. Hafner, P. Nordlander, N. J. Halas, "Symmetry breaking in individual plasmonic nanoparticles", Proceedings of the National Academy of Science (USA) 103, 10856-10860 (2006).

37. C. L. Nehl, H. Liao, J. H. Hafner, "Plasmon Resonant Molecular Sensing with Single Gold Nanostars", Proceedings of the SPIE 6323 (2006).

36.  C. L. Nehl, H. Liao, J. H. Hafner, "Synthesis and Optical Properties of Star-shaped Gold Nanoparticles", Nano Letters 6, 683-688 (2006).

35. A. Conjusteau, S. A. Ermilov, D. Lapotko, H. Liao, J. H. Hafner, M. Eghtedari, M. Motamedi, N. Kotov, A. A. Oraevsky, "Metallic nanoparticles as optoacoustic contrast agents for medical sensing", Proc. SPIE 6086 (2006).

34. J. H. Hafner, "Plasmonics - Metal Nanoparticles Shaped for Effect", Laser Focus World 4 (2006).

33.  N. Wickremasinghe, J. H. Hafner, "Protein Crystal as Scanned Probes", Nano Letters 5, 2418-2421 (2005).

32.  H. Liao, J. H. Hafner, "Gold Nanorod Bioconjugates", Chemistry of Materials 17, 4636-4641 (2005).

31.  C. L. Nehl, N. K. Grady, G. P. Goodrich, F. Tam, N. J. Halas, J. H. Hafner, "Scattering Spectra of Single Gold Nanoshells", Nano Letters 4, 2355-2359 (2004).

30. H. Liao, J. H. Hafner, "Monitoring Gold Nanorod Growth on Surfaces.", Journal of Physical Chemistry B 108, 19276-19280 (2004).

29. H. Liao, J. H. Hafner, "Low-Temperature Single-Wall Carbon Nanotube Synthesis by Thermal Chemical Vapor Deposition." Journal of Physical Chemistry B 108, 6941-6943 (2004).

28. A. S. Johnson, C. L. Nehl, M. G. Mason, J. H. Hafner, "Fluid electric force microscopy for charge density mapping in biological systems", Langmuir 19, 10007-10010 (2003).

27. D. Bozovic, M. Bockrath, J. H. Hafner, C. M. Lieber, H. Park, M. Tinkham, “Plastic deformations in mechanically strained single-wall carbon nanotubes” Physical Review B 67, 033407 (2003).

26. A. Jorio, F. M. Matinaga, A. Righi, M. S. S. Dantas, M. A. Pimenta, A. G. Souza, J. Mendes, J. H. Hafner, C. M. Lieber, R. Saito, G. Dresselhaus, M. S. Dresselhaus, “Resonance Raman scattering: Nondestructive and noninvasive technique for structural and electronic characterization of isolated single-wall carbon nanotubes” Brazilian Journal of Physics 32, 921-924 (2002).

25. A. Jorio, A.G. Souza, G. Dresselhaus, M.S. Dresselhaus, A.K. Swan, M.S. Unlu, B.B. Goldberg, M.A. Pimenta, J.H. Hafner, C.M. Lieber, R. Saito, “G-band resonant Raman study of 62 isolated single-wall carbon nanotubes” Physical Review B 65, 155412 (2002).

24. A. Jorio, A.G Souza, V.W. Brar, A.K. Swan, M.S. Unlu, B.B. Goldberg, A. Righi, J.H. Hafner, C.M. Lieber, R. Saito, G. Dresselhaus, M.S. Dresselhaus, “Polarized resonant Raman study of single-wall carbon nanotubes:  Symmetry selection rules, dipolar and multipolar antenna effects” Physical Review B 65, 121402 (2002).

23. A.G. Souza, A. Jorio, G.G. Samsonidze, G. Dresselhaus, M.S. Dresselhaus, A.K. Swan, M.S. Unlu, B.B. Goldberg, R. Saito, J.H. Hafner, C.M. Lieber, M.A. Pimenta, “Probing the electronic trigonal warping effect in individual single-wall carbon nanotubes using phonon spectra” Chemical Physics Letters 354, 62-68 (2002).

22. A.G. Souza, A. Jorio, A.K. Swan, M.S. Unlu, B.B. Goldberg, R. Saito, J.H. Hafner, C.M. Lieber, M.A. Pimenta, G. Dresselhaus, M.S. Dresselhaus, “Anomalous two-peak G’-band Raman effect in one isolated single-wall carbon nanotube” Physical Review B 65, 085417 (2002).

21. A.G. Souza, A. Jorio, G. Dresselhaus, M.S. Dresselhaus, R. Saito, A.K. Swan, M.S. Unlu, B.B. Goldberg, J.H. Hafner, C.M. Lieber, M.A. Pimenta, “Effect of quantized electronic states on the dispersive Raman features in individual single-wall carbon nanotubes” Physical Review B 65, 035404 (2002).

20. G. R. Schnitzler, C.L. Cheung, J.H. Hafner, A.J. Saurin, R.E. Kingston, C.M. Lieber, "Direct imaging of hSWI/SNF remodeled mono- and polynucleosomes by atomic force microscopy employing carbon nanotube tips", Molecular and Cellular Biology 21, 8504-8511 (2001).

19. M. A. Pimenta, A. Jorio, S. D. M. Brown, A. G. Souza, G. Dresselhaus, J. H. Hafner, C. M. Lieber, R. Saito, M. S. Dresselhaus, "Diameter dependence of the Raman D-band in isolated single-wall carbon nanotubes," Physical Review B 64, 041401 (2001).

18. R. Saito, A. Jorio, J. H. Hafner, C. M. Lieber, M. Hunter, T. McClure, G. Dresselhaus, M. S. Dresselhaus, "Chirality Dependent G-band Raman Intensity of Carbon Nanotubes," Physical Review B 64, 085312 (2001).

17. W. Liang, M. Bockrath, D. Bozovic, J. H. Hafner, M. Tinkham, H. Park, "Fabry-Perot Interference in a Nanotube Electron Waveguide," Nature 411, 665-669 (2001).

16. A.G. Souza Filho, A. Jorio, J.H. Hafner, C.M. Lieber, R. Saito, M.A. Pimenta, G. Dresselhaus, M.S. Dresselhaus, "Electronic transition energy Eii for an isolated (n,m) single-wall carbon nanotube obtained by anti-Stokes/Stokes resonant Raman intensity ratio", Physical Review B 63, 241404 (2001).

15. A. Jorio, A.G. Souza Filho, G. Dresselhaus, M.S. Dresselhaus, R. Saito, J.H. Hafner, C.M. Lieber, F.M. Matinage, M.S.S. Dantas, M.A. Pimenta "Joint density of electronic states for one isolated single-walled carbon nanotube studied by resonant Raman scattering", Physical Review B 63, 245416 (2001).

14. D. Bozovic, M. Bockrath, J. H. Hafner, C. M. Lieber, H. Park, M. Tinkham, "Electronic Properties of Mechanically Induced Kinks in Single-Walled Carbon Nanotubes," Applied Physics Letters 78, 3693- (2001).

13. A. Jorio, R. Saito, J. H. Hafner, C. M. Lieber, G. Dresselhaus, M. S. Dresselhaus, "Structural (n,m) determination of isolated single walled carbon nanotubes by resonant Raman scattering," Physical Review Letters 86, 1118-1121 (2001).

12. J. H. Hafner, C.L. Cheung, T. H. Oosterkamp, C. M. Lieber, "High-yield fabrication of individual single-walled nanotube probe tips for atomic force microscopy," Journal of Physical Chemistry B 105, 743-746 (2001).

11. M. Bockrath, W. Liang, D. Bozovic, J. H. Hafner, C. M. Lieber, M. Tinkham, H. Park, "Resonant Electron Scattering by Defects in Single-Walled Carbon Nanotubes," Science 291, 283-285 (2001).

10. C. L. Cheung, J. H. Hafner, T. W. Odom, K. Kim, C. M. Lieber, "Growth and fabrication with single-walled carbon nanotube probe microscopy tips," Applied Physics Letters 76, 3136 (2000).

9. C. L. Cheung, J. H. Hafner, C. M. Lieber, "Carbon nanotube atomic force microscopy tips: Direct growth by chemical vapor deposition and application to high-resolution imaging," Proceedings of the National Academy of Sciences of the United States of America 97, 3809 (2000).

8. J. H. Hafner, C. L. Cheung, and C. M. Lieber, "Direct Growth of Single-Walled Carbon Nanotube Scanning Probe Microscopy Tips," Journal of the American Chemical Society 121, 9750 (1999).

7. J. H. Hafner, C. L. Cheung, and C. M. Lieber, "Growth of Nanotubes as Probe Microscopy Tips," Nature 398, 761 (1999).

6. J. H. Hafner, M. J. Bronikowski, B. R. Azamian, P. Nikolaev, A. G. Rinzler, D. T. Colbert, K. A. Smith, and R. E. Smalley, "Catalytic Growth of Single Wall Carbon Nanotubes from Metal Particles," Chemical Physics Letters 296, 195 (1998).

5. J. Liu, A. G. Rinzler, H. Dai, J. H. Hafner, R. K. Bradley, A. Lu, K. Shelimov, C.B. Huffman, F. Rodriguez-Macias, P. Boul, T. Iverson, D. T. Colbert, and R. E. Smalley, "Fullerene Pipes," Science 280, 1253 (1998).

4. J. Liu, H. Dai, J. H. Hafner, D. T. Colbert, S. J. Tans, C. Dekker, and R. E. Smalley, "Fullerene Crop Circles," Nature 385, 780 (1997).

3. H. Dai, J. H. Hafner, A. G. Rinzler, D. T. Colbert, and R. E. Smalley, "Nanotubes as Nanoprobes in Scanning Probe Microscopy," Nature 384, 147 (1996).

2. A. G .Rinzler, J. H. Hafner, P. Nikolaev, L. Lou, S. G. Kim, D. Tomanek, P. Nordlander, D. T. Colbert, and R. E. Smalley, "Unraveling Nanotubes: Field Emission from an Atomic Wire," Science 269, 1550 (1995).

1. D. T. Colbert, J. Zhang, S. M. McClure, P. Nikolaev, Z. Chen, J. H. Hafner, D. W. Owens, P. G. Kotula, C. B. Carter, J. H. Weaver, A. G. Rinzler, and R. E. Smalley, "Growth and Sintering of Fullerene Nanotubes," Science 266, 1218 (1994).