publication detail

First Experimental Evidence of Anti-Stokes Laser-Induced Fluorescence Emission in Microdroplets and Microfluidic Systems Driven by Low Thermal Conductivity of Fluorocarbon Carrier Oil

AUTHORS

  • Hayat Zain
  • El Abed Abdel

KEYWORDS

  • Droplets microfluidics LIF laser-induced fluorescence SF stokes fluorescence ASF anti-stokes fluorescence thermal sensitivity low thermal conductivity TICT twisted intermolecular charge transfer
  • Droplets
  • Microfluidics
  • LIF laser-induced fluorescence
  • SF stokes fluorescence
  • ASF anti-stokes fluorescence
  • Thermal sensitivity
  • Low thermal conductivity
  • TICT twisted intermolecular charge transfer
  • Document type

    Journal articles

    Résumé

    With the advent of many optofluidic and droplet microfluidic applications using laserinduced fluorescence (LIF), the need for a better understanding of the heating effect induced by pump laser excitation sources and good monitoring of temperature inside such confined microsystems started to emerge. We developed a broadband highly sensitive optofluidic detection system, which enabled us to show for the first time that Rhodamine-B dye molecules can exhibit standard photoluminescence as well as blue-shifted photoluminescence. We demonstrate that this phenomenon originates from the interaction between the pump laser beam and dye molecules when surrounded by the low thermal conductive fluorocarbon oil, generally used as a carrier medium in droplet microfluidics. We also show that when the temperature is increased, both Stokes and anti-Stokes fluorescence intensities remain practically constant until a temperature transition is reached, above which the fluorescence intensity starts to decrease linearly with a thermal sensitivity of about-0.4%/ • C for Stokes emission or-0.2%/ • C for anti-Stokes emission. For an excitation power of 3.5 mW, the temperature transition was found to be about 25 • C, whereas for a smaller excitation power (0.5 mW), the transition temperature was found to be about 36 • C.

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