Observation of the surface and volume nucleation phenomena in undercooled sucrose solution droplets

We present the direct observation of surface-activated ice nucleation in undercooled sucrose solution droplets. Video images of freezing sucrose solution droplets while suspended at the junction of a thermocouple show two distinctive nucleation mechanisms for a droplet. These are at the surface and in the volume of the droplet. Analysis of the temperature-dependent nucleation data support the conclusion that they are separate nucleation mechanisms. Increased sucrose concentration caused surface nucleation to become less favorable. The results are not entirely described by either the two-dimensional or the capillary theories of surface nucleation but do suggest that surface-activated nucleation is a pseudo-heterogeneous process.