Two-photon fluorescence-guided laser tweezers for study of cluster growth and gelation process

Laser tweezers trapping technology has been used to monitor the bulk solution viscosity during the sol-gel gelation process at different depths from an interface. The gelation rate is the same in depth ranges 2–20 μm from the bounding surface. Simultaneously with the laser tweezers study, a microviscosity kinetic measurement of the sol-gel process was performed by fluorescent anisotropy and quantum yield methods. The large differences found between the bulk and microviscosities obtained in the experiment reflect the intrinsic differences in solution environment sensed by the laser tweezers on the macro level and by other optical techniques on the microlevels.

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