Probing slow dynamics by ultrafast process: Sol-gel transition detected by transient absorption spectroscopy of quantum dots

► For the first time quantum dots have been used as sensors of gelation process. ► We have shown that exciton lifetimes in PbS quantum dots increase during sol-gel transition. ► Using percolation theory we described the dependence of exciton decay rate on the number of bonds in gel network. ► We have found the method to establish the gel point and appropriate universal critical exponents.