Self-assisted optothermal trapping of gold nanorods under two-photon excitation

Hongtao Chen, Enrico Gratton, Michelle A. Digman

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We report a self-assisted optothermal trapping and patterning of gold nanorods (GNRs) on glass surfaces with a femtosecond laser. We show that GNRs are not only the trapping targets, but also can enhance the optothermal trapping of other particles. This trapping phenomenon is the net result of thermophoresis and a convective flow caused by localized heating. The heating is due to the conversion of absorbed photons into heat at GNR's longitudinal surface plasmon resonance (LSPR) wavelength. First, we investigated the optothermal trapping of GNRs at their LSPR wavelength on the glass surface with as low as 0.5 mW laser power. The trapping range was observed to be larger than a typical field of view, e.g. 210 μm × 210 μm here. Second, by adjusting the distance between the laser focus and the glass surface, ring patterns of GNRs on the glass surface were obtained. These patterns could be controlled by the laser power and the numerical aperture of the microscope objective. Moreover, we examined the spectral emission of GNRs under different trapping conditions using the spectral phasor approach to reveal the temperature and association status of GNRs. Our study will help understanding manipulation of flows in solution and in biological systems that can be applied in future investigations of GNR-induced heating and flows.

Original languageEnglish (US)
Article number035003
JournalMethods and Applications in Fluorescence
Issue number3
StatePublished - Sep 2016


  • Convective flow
  • Gold nanorods
  • Longitudinal surface plasmon resonance (LSPR)
  • Optothermal trapping
  • Spectral phasor analysis
  • Thermophoresis
  • Two-photon excitation

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Materials Science(all)
  • Spectroscopy

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