Optical detection of the kinetics of phase transition in a water drop with eosin and silver nanoparticles

ABSTRACT

The intensity of delayed fluorescence and kinetics processes of eosin molecules in a hanging drop of water solution with ablative silver nanoparticles and without them during phase change have been investigated in this work. Basing on the fluorescence data the obtained times of the initial stage of water-ice phase transitions were amount to 0.04 s and 0.067 s in solutions with and without nanoparticles respectively. It has been established that in the presence of silver nanoparticles in the drop, crystallization process is described by nonlinear low. The femtosecond laser probing technique (λ = 1.03 µm) was used to estimate the thickness of the frozen spherical shell of the drop after 200 ms freezing. At a constant heat removal capacity during cooling, the thickness of the ice shell was 0.1 mm. Numerical modeling of phase transitions in the drop with and without silver nanoparticles was also carried out. The authors solved a boundary value problem of heat conduction for a sphere to obtain the parameters of thermal processes.

KEYWORDS:

• Water drop
• phase transition
• optical detection
• delayed fluorescence
• ablative silver nanoparticles
• eosin molecules
• numerical modeling