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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 5 — Mar. 2, 2009
  • pp: 3291–3298
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Temperature mapping near plasmonic nanostructures using fluorescence polarization anisotropy

G. Baffou, M.P. Kreuzer, F. Kulzer, and R. Quidant  »View Author Affiliations


Optics Express, Vol. 17, Issue 5, pp. 3291-3298 (2009)
http://dx.doi.org/10.1364/OE.17.003291


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Abstract

We report on a thermal imaging technique based on fluorescence polarization anisotropy measurements, which enables mapping the local temperature near nanometer-sized heat sources with 300 nm spatial resolution and a typical accuracy of 0.1 °C. The principle is demonstrated by mapping the temperature landscape around plasmonic nano-structures heated by near-infrared light. By assessing directly the molecules’ Brownian dynamics, it is shown that fluorescence polarization anisotropy is a robust and reliable method which overcomes the limitations of previous thermal imaging techniques. It opens new perspectives in medicine, nanoelectronics and nanofluidics where a control of temperature of a few degrees at the nanoscale is required.

© 2009 Optical Society of America

Efforts to measure and control temperature at the nanoscale are no longer motivated only by fundamental interest, but are increasingly becoming important in many areas of nanotechnology including photothermal therapeutic medicine [1

1. A. M. Gobin, M. H. Lee, N. J. Halas, W. D. James, R. A. Drezek, and J. L. West, “Near-Infrared Resonant Nanoshells for Combined Optical Imaging and Photothermal Cancer Therapy,” Nano Lett. 7, 1929–1934 (2007). [CrossRef] [PubMed]

, 2

2. P. K. Jain, I. H. El-Sayed, and M. A. El-Sayed, “Au nanoparticles target cancer,” Nano Today 2, 18 (2007). [CrossRef]

, 3

3. D. Pissuwana, S. M. Valenzuelaa, and M. B. Cortie, “Therapeutic possibilities of plasmonically heated gold nanoparticles,” Trends Biotechnol. 24, 62 (2006). [CrossRef]

, 4

4. G. Han, P. Ghosh, M. De, and V.M. Rotello, “Drug and Gene Delivery using Gold Nanoparticles,” NanoBioTech-nology 3, 40 (2007). [CrossRef]

, 5

5. A. G. Skirtach, C. Dejugnat, D. Braun, A. S. Susha, A. L. Rogach, W. J. Parak, H. Möhwald, and G. B. Sukho-rukov, “The Role of Metal Nanoparticles in Remote Release of Encapsulated Materials,” Nano Lett. 5, 1371 (2005). [CrossRef] [PubMed]

], nanoscale catalysis [6

6. L. Cao, D. Barsic, A. Guichard, and M. Brongersma, “Plasmon-assisted local temperature control to pattern individual semiconductor nanowires and carbon nanotubes,” Nano Lett. 7, 3523–3527 (2007). [CrossRef] [PubMed]

], nanofluidics [7

7. G. L. Liu, J. Kim, L. Y., and L. P. Pee, “Optofluidic control using photothermal nanoparticles,” Nat. Mater. 5, 27 (2006). [CrossRef]

, 8

8. D. Ross, M. Gaitan, and L. E. Locascio, “Temperature Measurement in Microfluidic Systems Using a Temperature-Dependent Fluorescent Dye,” Anal. Chem. 73, 4117 (2001). [CrossRef] [PubMed]

, 9

9. M. Righini, A. S. Zelenina, C. Girard, and R. Quidant, “Parallel and selective trapping in a patterned plasmonic landscape,” Nat. Phys. 3, 477 (2007). [CrossRef]

, 10

10. V. Garces-Chavez, R. Quidant, P. J. Reece, G. Badenes, L. Torner, and K. Dholakia, “Extended organization of colloidal microparticles by surface plasmon polariton excitation,” Phys. Rev. B 73, 085417 (pages 5) (2006). [CrossRef]

], micro and nanoelectronics [11

11. A. Bar-Cohen, P. Wang, and E. Rahim, “Thermal management of high heat flux nanoelectronic chips,” Micro-gravity Sci. Technol. 19, 48 (2007).

] and photothermal imaging [12

12. D. Boyer, P. Tamarat, A. Maali, B. Lounis, and M. Orrit, “Photothermal Imaging of Nanometer-Sized Metal Particles Among Scatterers,” Science 297, 1160 (2002). [CrossRef] [PubMed]

], spectroscopy [13

13. M. A. van Dijk, A. L. Tchebotareva, M. Orrit, M. Lippitz, S. Berciaud, D. Lasne, L. Cognet, and B. Lounis, “Absorption and scattering microscopy of single metal nanoparticles,” Phys. Chem. Chem. Phys. 8, 3486 (2006). [CrossRef] [PubMed]

] and nanoparticle tracking [14

14. D. Lasne, G. A. Blab, S. Berciaud, M. Heine, L. Groc, D. Choquet, L. Cognet, and B. Lounis, “Single NanoParticle Photothermal Tracking (SNaPT) of 5 nm gold beads in live cells,” Biophys. J. 91, 4598 (2006). [CrossRef] [PubMed]

]. Along with the need of understanding thermal processes at the micro and nanoscale, several techniques aiming at high resolution temperature mapping have been proposed. Scanning Thermal Microscopy (SThM) uses a composite sharp tip to directly probe the temperature of the sample surface [15

15. H. M. Pollock and A. Hammiche, “Micro-thermal analysis: techniques and applications,” J. Phys. D-Appl. Phys. 34, R23 (2001). [CrossRef]

]. Although it allows a spatial resolution lower than 100 nm, this technique is only suited for surface science investigations and is known to remain slow and invasive. More recently, a collection of optical-based temperature probing techniques have been proposed based on the temperature dependence of either Raman spectra [16

16. J. W. Pomeroy, M. Kuball, D. J. Wallis, A. M. Keir, K. P. Hilton, R. S. Balmer, M. J. Uren, T. Martin, and P. J. Heard, “Thermal mapping of defects in AlGaN/GaN heterostructure field-effect transistors using micro-Raman spectroscopy,” Appl. Phys. Lett. 87, 103,508 (2005). [CrossRef]

, 17

17. K. K. Liu, K. L. Davis, and M. D. Morris, “Raman spectroscopic measurement of spatial and temporal gradients in operating electrophoresis capillaries,” Anal. Chem. 66, 3744 (1994). [CrossRef] [PubMed]

], fluorescence intensity/spectra/time correlation [8

8. D. Ross, M. Gaitan, and L. E. Locascio, “Temperature Measurement in Microfluidic Systems Using a Temperature-Dependent Fluorescent Dye,” Anal. Chem. 73, 4117 (2001). [CrossRef] [PubMed]

, 18

18. P. Löw, B. Kim, N. Takama, and C. Bergaud, “High-spatial-resolution surface-temperature mapping using fluorescent thermometry,” Small 4, 908 (2008). [CrossRef] [PubMed]

, 19

19. G. A. Robinson, R. P. Lucht, and M. Laurendeau, “Two-color planar laser-induced fluorescence thermometry in aqueous solutions,” Appl. Opt. 47, 2852 (2008). [CrossRef] [PubMed]

, 20

20. B. Samson, L. Aigouy, P. Löw, C. Bergaud, B. J. Kim, and M. Mortier, “ac thermal imaging of nanoheaters using a scanning fluorescent probe,” Appl. Phys. Lett. 92, 023,101 (2008). [CrossRef]

] or infrared spectra. However, none of these techniques combines the advantages of reliability, fast readout rate and high-resolution making them prohibitive for temperature imaging in Nanotechnology.

r=III2I
(1)

1r=1r0(1+τFτR)
(2)

where τ R is the rotational correlation time and τ F the fluorescence life time. This equation means that substantial molecular rotation (induced by its Brownian dynamics) during the lifetime of the excited state leads to a fluorescence depolarization, i.e., a lower value of r. The key point of the technique is that an increase of the temperature contributes to lower the FPA r since it gives rise to a faster rotation of the molecules, i.e., a lower value of τ R. This happens according to the Debye-Stokes-Einstein equation [21

21. B. Valeur, Molecular Fluorescence: Principles and Applications (Wiley-VCH, 2002). Chap. 5.

, 22

22. A. Kawski, “Fluorescence anisotropy: Theory and applications of rotational polarization,” Crit. Rev. Anal. Chem. 23, 459 (1993). [CrossRef]

]:

τR=(T)kBT
(3)

where T is the temperature, η(T) the dynamic viscosity of the medium, V the hydrodynamic molecular volume and k B the Boltzmann constant. The maximum temperature sensitivity of r is achieved when τ R is of the order of magnitude of the fluorescence lifetime τ F (Eq. (2)). The sensitivity of the method can be enhanced if the fluid furthermore experiences substantial variations of its viscosity η(T) within the temperature range of interest.

In the present experiment, we consider two kinds of gold nanostructures acting as nanometer-sized heat sources: lithographic nanowires and colloidal nanorods. In both cases, the nanostruc-tures lie onto a glass substrate and are embedded in a 30 μm thick layer of a glycerol-water (4:1) mixture containing fluorescein molecules (c = 1.4×10-4M). A glass coverslip is placed on top of the solution layer to avoid water exchange with the surrounding air, which could affect the glycerol-water ratio and hence the fluid viscosity. The viscosity of glycerol decreases by more than one order of magnitude from 20 to 50 °C, which makes FPA measurements in glycerol highly temperature sensitive. Fluorescein is a xanthene-type chromophore (see inset Fig. 2), characterized by a high photostability and a fluorescence quantum efficiency close to 100%. Fluorescein in pure glycerol exhibits a rotational correlation time τ R around 150 ns at 20 °C, while its fluorescence life time τ F is about 4 ns. Consequently, we use a glycerol-water (4:1) mixture to reduce the viscosity from 1400 to 60 mPa·s and the rotational correlation time to τ R = 6 ns. This results in a much stronger variation of the polarization anisotropy between 20 and 50 °C, our window of interest.

Fig. 1. Schematic of the experimental configuration and procedure. Two laser beams (for heating in the NIR and for probing at 473 nm) are overlapped prior to entering the objective of a confocal microscope. The sample is scanned through the focus to obtain an image. The collected fluorescence light is divided by a polarizing cube and sent to two avalanche photodiodes (APDs) measuring parallel and perpendicular polarizations. From these two maps, the FPA map is calculated using Eq. (1) and the temperature map is obtained using the calibration curve presented in Fig. 2. To illustrate the technique, a measurement on dispersed nanorods over a 30μm×30μm area is presented.

The experimental configuration and processing is sketched in Fig. 1. Using a confocal microscope, the fluorescein molecules are excited by a linearly polarized 473 nm laser beam while the parallel and orthogonal components of the collected fluorescence are separated by a polarizing cube and sent to two avalanche photodiodes (APDs). In all the experiments, the power applied for fluorescence excitation was around 0.1 μW right before the objective entrance. Heating of gold nanostructures is performed using a CW near-infrared (NIR) laser beam from a Ti:sapphire laser, coincident with the blue excitation light. To maximize the temperature increase due to absorption of the metal, the wavelength is tuned to the localized plasmon band of the nanos-tructures. Both the blue and the NIR beams are focused and overlapped on the sample through the objective of the confocal microscope (100 ×, NA 1.25) and scanned across the sample plane for simultaneous local heating and temperature measurement.

Fig. 2. Fluorescence polarization anisotropy calibration. Theoretical curve (solid green line) of fluorescence polarization anisotropy as a function of the temperature for fluorescein dissolved in a glycerol-water (4:1) mixture, showing a good agreement with the experimental measurements (green diamonds) along with the calculated corrected curve (red solid line) associated to our high-NA objective. The chemical structure of fluorescein is represented in the inset.

In order to explain in detail the image acquisition and data processing, we first describe results obtained on single 250 nm wide and 30 nm thick gold nanowires prepared by conventional e-beam lithography combined with lift off. Figure 3 shows two sets of measurements, one without heating Figs. 3(b)–(e) and the other one while heating Figs. 3(f)–(i) with a 775 nm laser light linearly polarized perpendicularly to the nanowire axis. The scan proceeds upward, line by line and from left to right.

Fig. 3. (a), Scanning Electron Microscopy (SEM) image (3μm×3μm) of a 200 nm wide and 40 nm thick gold nanowire, corresponding to the area of interest. (b), (c), maps of the fluorescence intensities with parallel and perpendicular polarizations with respect to the incident light, no heating is performed in this first case. (d) fluorescence polarization anisotropy map calculated from images b and c using Eq. (1). (e) associated temperature distribution. (f), (g), maps of the fluorescence intensities with parallel and perpendicular polarizations while heating. (h), associated fluorescence polarization anisotropy map and (i) temperature distribution.

Figures 3(f) and (g) show the fluorescence intensity maps while heating with NIR light. Two effects are responsible for the contrast variation on these images: (i) due to the temperature increase, the depolarization effect tends to increase the orthogonal fluorescence intensity I and decrease (twice as much) the parallel fluorescence intensity I , (ii) the temperature increase is also responsible of an overall reduction of the fluorescence intensity associated to an increase of the molecular population in the dark state. However, since this latter side-effect affects equally both polarization intensities, this has no consequences on the FPA calculation (see Eq. (1)) and temperature measurement. Similarly, any unwanted fluorescence intensities variations resulting from e.g. mechanical noise, photobleaching or uncontrolled variation of the pump laser intensity, would not affect the temperature acquisition. Due to heating, a substantial decrease of the FPA along the wire is observed (Fig. 3(h)) which corresponds to an increase of the metal temperature (Fig. 3(i)) of a few degrees. In order to study the heating dynamics of the nanowire, a series of temperature measurements was performed as a function of the NIR laser power entering the objective. The results plotted in Fig. 4 verify that the temperature follows a linear dependency, as is expected for a linear absorption process. This remains true for a temperature increase of about 10 °C, without hysteresis. At higher temperature, the system may eventually get modified, especially for very small structures, presumably due to temperature-induced fluid convection which tends to move the nanostructures a couple of micrometers away.

Fig. 4. Average temperature of the gold nanowire as a function of the power of the heating NIR light showing an expected linearity.

Fig. 5. Temperature mapping near dispersed gold nanorods. (a), Optical image (30μm×30 μm) of dispersed and agglomerated nanorods (NRs). (b), Fluorescence polarization anisot-ropy of the fluorescein molecules surrounding the gold nanorods and sensing the temperature variations. (c), Temperature map calculated from image (b).

In conclusion, we have introduced the use of fluorescence polarization anisotropy (FPA) to measure and map the temperature increase near nano-sized heat sources. The data demonstrate a typical temperature accuracy of a tenth of a degree and a spatial resolution of 300 nm. Because FPA is directly sensitive to fluorophore Brownian dynamics, it naturally provides a direct and reliable measurement of the actual local temperature. In particular, the method is non sensitive to side effects like photobleaching or thermal damage of the fluorophores. This feature makes the technique particularly robust and reliable. The applicability of the method has been successfully demonstrated on plasmonic gold nanostructures heated by coupling with NIR light to their plasmon resonance, but can be extended to any kind of heat source and geometry.

Acknowledgments

This research has been funded by the Spanish Ministry of Sciences through grants no. TEC2007-60186/MIC and no. CSD2007-046-NanoLight.es and by the fundació CELLEX. M. P. K. and F. K. acknowledge support from the Ramón y Cajal program.

References and links

1.

A. M. Gobin, M. H. Lee, N. J. Halas, W. D. James, R. A. Drezek, and J. L. West, “Near-Infrared Resonant Nanoshells for Combined Optical Imaging and Photothermal Cancer Therapy,” Nano Lett. 7, 1929–1934 (2007). [CrossRef] [PubMed]

2.

P. K. Jain, I. H. El-Sayed, and M. A. El-Sayed, “Au nanoparticles target cancer,” Nano Today 2, 18 (2007). [CrossRef]

3.

D. Pissuwana, S. M. Valenzuelaa, and M. B. Cortie, “Therapeutic possibilities of plasmonically heated gold nanoparticles,” Trends Biotechnol. 24, 62 (2006). [CrossRef]

4.

G. Han, P. Ghosh, M. De, and V.M. Rotello, “Drug and Gene Delivery using Gold Nanoparticles,” NanoBioTech-nology 3, 40 (2007). [CrossRef]

5.

A. G. Skirtach, C. Dejugnat, D. Braun, A. S. Susha, A. L. Rogach, W. J. Parak, H. Möhwald, and G. B. Sukho-rukov, “The Role of Metal Nanoparticles in Remote Release of Encapsulated Materials,” Nano Lett. 5, 1371 (2005). [CrossRef] [PubMed]

6.

L. Cao, D. Barsic, A. Guichard, and M. Brongersma, “Plasmon-assisted local temperature control to pattern individual semiconductor nanowires and carbon nanotubes,” Nano Lett. 7, 3523–3527 (2007). [CrossRef] [PubMed]

7.

G. L. Liu, J. Kim, L. Y., and L. P. Pee, “Optofluidic control using photothermal nanoparticles,” Nat. Mater. 5, 27 (2006). [CrossRef]

8.

D. Ross, M. Gaitan, and L. E. Locascio, “Temperature Measurement in Microfluidic Systems Using a Temperature-Dependent Fluorescent Dye,” Anal. Chem. 73, 4117 (2001). [CrossRef] [PubMed]

9.

M. Righini, A. S. Zelenina, C. Girard, and R. Quidant, “Parallel and selective trapping in a patterned plasmonic landscape,” Nat. Phys. 3, 477 (2007). [CrossRef]

10.

V. Garces-Chavez, R. Quidant, P. J. Reece, G. Badenes, L. Torner, and K. Dholakia, “Extended organization of colloidal microparticles by surface plasmon polariton excitation,” Phys. Rev. B 73, 085417 (pages 5) (2006). [CrossRef]

11.

A. Bar-Cohen, P. Wang, and E. Rahim, “Thermal management of high heat flux nanoelectronic chips,” Micro-gravity Sci. Technol. 19, 48 (2007).

12.

D. Boyer, P. Tamarat, A. Maali, B. Lounis, and M. Orrit, “Photothermal Imaging of Nanometer-Sized Metal Particles Among Scatterers,” Science 297, 1160 (2002). [CrossRef] [PubMed]

13.

M. A. van Dijk, A. L. Tchebotareva, M. Orrit, M. Lippitz, S. Berciaud, D. Lasne, L. Cognet, and B. Lounis, “Absorption and scattering microscopy of single metal nanoparticles,” Phys. Chem. Chem. Phys. 8, 3486 (2006). [CrossRef] [PubMed]

14.

D. Lasne, G. A. Blab, S. Berciaud, M. Heine, L. Groc, D. Choquet, L. Cognet, and B. Lounis, “Single NanoParticle Photothermal Tracking (SNaPT) of 5 nm gold beads in live cells,” Biophys. J. 91, 4598 (2006). [CrossRef] [PubMed]

15.

H. M. Pollock and A. Hammiche, “Micro-thermal analysis: techniques and applications,” J. Phys. D-Appl. Phys. 34, R23 (2001). [CrossRef]

16.

J. W. Pomeroy, M. Kuball, D. J. Wallis, A. M. Keir, K. P. Hilton, R. S. Balmer, M. J. Uren, T. Martin, and P. J. Heard, “Thermal mapping of defects in AlGaN/GaN heterostructure field-effect transistors using micro-Raman spectroscopy,” Appl. Phys. Lett. 87, 103,508 (2005). [CrossRef]

17.

K. K. Liu, K. L. Davis, and M. D. Morris, “Raman spectroscopic measurement of spatial and temporal gradients in operating electrophoresis capillaries,” Anal. Chem. 66, 3744 (1994). [CrossRef] [PubMed]

18.

P. Löw, B. Kim, N. Takama, and C. Bergaud, “High-spatial-resolution surface-temperature mapping using fluorescent thermometry,” Small 4, 908 (2008). [CrossRef] [PubMed]

19.

G. A. Robinson, R. P. Lucht, and M. Laurendeau, “Two-color planar laser-induced fluorescence thermometry in aqueous solutions,” Appl. Opt. 47, 2852 (2008). [CrossRef] [PubMed]

20.

B. Samson, L. Aigouy, P. Löw, C. Bergaud, B. J. Kim, and M. Mortier, “ac thermal imaging of nanoheaters using a scanning fluorescent probe,” Appl. Phys. Lett. 92, 023,101 (2008). [CrossRef]

21.

B. Valeur, Molecular Fluorescence: Principles and Applications (Wiley-VCH, 2002). Chap. 5.

22.

A. Kawski, “Fluorescence anisotropy: Theory and applications of rotational polarization,” Crit. Rev. Anal. Chem. 23, 459 (1993). [CrossRef]

23.

R. Zondervan, F. Kulzer, H. van der Meer, J. A. J. M. Disselhorst, and M. Orrit, “Laser-Driven Microsecond Temperature Cycles Analyzed by Fluorescence Polarization Microscopy,” Biophys. J. 90, 2958 (2006). [CrossRef] [PubMed]

24.

G. W., “Polarization of the fluorescence of macromolecules. 1. Theory and experiment method,” Biochem J. 51, 145 (1952).

25.

A. H. A. Clayton, Q. S. Hanley, D. J. Arndt-Jovin, V. Subramaniam, and T. M. Jovin, “Dynamic fluorescence anisotropy imaging microscopy in the frequency domain (rFLIM),” Biophys. J. 83, 1631–1649 (2002). [CrossRef] [PubMed]

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R. F. Chen and R. L. Bowman, “Fluorescence polarization - measurement with ultraviolet-polarizing filters in a spectrophotofluorometer,” Science 147(3659), 729–732 (1965). [CrossRef] [PubMed]

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N. S. Cheng, “Formula for the viscosity of a glycerol-water mixture,” Ind. Eng. Chem. Res. 47, 3285 (2008). [CrossRef]

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30.

F. X. Gu, R. Karnik, A. Z. Wang, F. Alexis, E. Levy-Nissenbaum, S. Hong, R. S. Langer, and O. C. Farokhzad, “Targeted nanoparticles for cancer therapy,” Nano Today 2, 14 (2007). [CrossRef]

31.

K. Maier-Hauff, R. Rothe, R. Scholz, U. Gneveckow, P. Wust, B. Thiesen, A. Freussner, A. von Deimling, N. Waldoefner, R. Felix, and A. Jordan, “Intracranial thermotherapy using magnetic nanoparticles combined with external beam radiotherapy: Results of a feasibility study on patients with glioblastoma multiforme,” J. Neuro-Oncol. 81, 53 (2007). [CrossRef]

32.

B. Nikoobakht and M. A. El-Sayed, “Preparation and growth mechanism of gold nanorods (NRs) using seed-mediated growth method,” Chem. Mat. 15, 1957 (2003). [CrossRef]

OCIS Codes
(120.6810) Instrumentation, measurement, and metrology : Thermal effects
(180.2520) Microscopy : Fluorescence microscopy
(250.5403) Optoelectronics : Plasmonics

ToC Category:
Instrumentation, Measurement, and Metrology

History
Original Manuscript: December 17, 2008
Revised Manuscript: January 30, 2009
Manuscript Accepted: January 30, 2009
Published: February 17, 2009

Virtual Issues
Vol. 4, Iss. 5 Virtual Journal for Biomedical Optics

Citation
G. Baffou, M. P. Kreuzer, F. Kulzer, and R. Quidant, "Temperature mapping near plasmonic nanostructures using fluorescence polarization anisotropy," Opt. Express 17, 3291-3298 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-5-3291


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References

  1. A. M. Gobin, M. H. Lee, N. J. Halas, W. D. James, R. A. Drezek, and J. L. West, "Near-Infrared Resonant Nanoshells for Combined Optical Imaging and Photothermal Cancer Therapy," Nano Lett. 7, 1929-1934 (2007). [CrossRef] [PubMed]
  2. P. K. Jain, I. H. El-Sayed, and M. A. El-Sayed, "Au nanoparticles target cancer," Nano Today 2, 18 (2007). [CrossRef]
  3. D. Pissuwana, S. M. Valenzuelaa, and M. B. Cortie, "Therapeutic possibilities of plasmonically heated gold nanoparticles," Trends Biotechnol. 24, 62 (2006). [CrossRef]
  4. G. Han, P. Ghosh, M. De, and V. M. Rotello, "Drug and Gene Delivery using Gold Nanoparticles," NanoBioTechnology 3, 40 (2007). [CrossRef]
  5. A. G. Skirtach, C. Dejugnat, D. Braun, A. S. Susha, A. L. Rogach, W. J. Parak, H. Mohwald, and G. B. Sukhorukov, "The Role of Metal Nanoparticles in Remote Release of Encapsulated Materials," Nano Lett. 5, 1371 (2005). [CrossRef] [PubMed]
  6. L. Cao, D. Barsic, A. Guichard, and M. Brongersma, "Plasmon-assisted local temperature control to pattern individual semiconductor nanowires and carbon nanotubes," Nano Lett. 7, 3523-3527 (2007). [CrossRef] [PubMed]
  7. G. L. Liu, J. Kim, L. Y. and L. P. Pee, "Optofluidic control using photothermal nanoparticles," Nat. Mater. 5, 27 (2006). [CrossRef]
  8. D. Ross, M. Gaitan, and L. E. Locascio, "Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye," Anal. Chem. 73, 4117 (2001). [CrossRef] [PubMed]
  9. M. Righini, A. S. Zelenina, C. Girard, and R. Quidant, "Parallel and selective trapping in a patterned plasmonic landscape," Nat. Phys. 3, 477 (2007). [CrossRef]
  10. V. Garces-Chavez, R. Quidant, P. J. Reece, G. Badenes, L. Torner, and K. Dholakia, "Extended organization of colloidal microparticles by surface plasmon polariton excitation," Phys. Rev. B 73, 085417 (2006). [CrossRef]
  11. A. Bar-Cohen, P. Wang, and E. Rahim, "Thermal management of high heat flux nanoelectronic chips," Microgravity Sci. Technol. 19, 48 (2007).
  12. D. Boyer, P. Tamarat, A. Maali, and B. Lounis, M. Orrit, "Photothermal Imaging of Nanometer-Sized Metal Particles Among Scatterers," Science 297, 1160 (2002). [CrossRef] [PubMed]
  13. M. A. van Dijk, A. L. Tchebotareva, M. Orrit, M. Lippitz, S. Berciaud, D. Lasne, L. Cognet, and B. Lounis, "Absorption and scattering microscopy of single metal nanoparticles," Phys. Chem. Chem. Phys. 8, 3486 (2006). [CrossRef] [PubMed]
  14. D. Lasne, G. A. Blab, S. Berciaud, M. Heine, L. Groc, D. Choquet, L. Cognet, and B. Lounis, "Single NanoParticle Photothermal Tracking (SNaPT) of 5 nm gold beads in live cells," Biophys. J. 91, 4598 (2006). [CrossRef] [PubMed]
  15. H. M. Pollock and A. Hammiche, "Micro-thermal analysis: techniques and applications," J. Phys. D-Appl. Phys. 34, R23 (2001). [CrossRef]
  16. J. W. Pomeroy, M. Kuball, D. J. Wallis, A. M. Keir, K. P. Hilton, R. S. Balmer, M. J. Uren, T. Martin, and P. J. Heard, "Thermal mapping of defects in AlGaN/GaN heterostructure field-effect transistors using micro-Raman spectroscopy," Appl. Phys. Lett. 87, 103,508 (2005). [CrossRef]
  17. K. K. Liu, K. L. Davis, and M. D. Morris, "Raman spectroscopic measurement of spatial and temporal gradients in operating electrophoresis capillaries," Anal. Chem. 66, 3744 (1994). [CrossRef] [PubMed]
  18. P. L¨ow, B. Kim, N. Takama, and C. Bergaud, "High-spatial-resolution surface-temperature mapping using fluorescent thermometry," Small 4, 908 (2008). [CrossRef] [PubMed]
  19. G. A. Robinson, R. P. Lucht, and M. Laurendeau, "Two-color planar laser-induced fluorescence thermometry in aqueous solutions," Appl. Opt. 47, 2852 (2008). [CrossRef] [PubMed]
  20. B. Samson, L. Aigouy, P. L¨ow, C. Bergaud, B. J. Kim, and M. Mortier, "ac thermal imaging of nanoheaters using a scanning fluorescent probe," Appl. Phys. Lett. 92, 023,101 (2008). [CrossRef]
  21. B. Valeur, Molecular Fluorescence: Principles and Applications (Wiley-VCH, 2002). Chap. 5.
  22. A. Kawski, "Fluorescence anisotropy: Theory and applications of rotational polarization," Crit. Rev. Anal. Chem. 23, 459 (1993). [CrossRef]
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