抄録
We have recently reported photoluminescence (PL) oscillation in both water and nonpolar-solvent dispersions of nanocrystals (NCs). In this paper, we report on the characteristics of PL oscillation in NC suspensions to clarify the mechanism. We used 5.2-nm diameter CdSe/ZnS core/shell NCs, whose surfaces were capped with tri-n-octylphosphine oxide (TOPO). PL oscillation is observed in the NC/toluene suspension as well as in a water dispersion. The period of the oscillation is revealed to be about 100 s by Fourier analysis. Since the temperature dependence on PL oscillation is similar to the scenario to chaos in closed unstirred Belousov-Zhabotinsky (BZ) system, it may be caused by a similar chemical oscillation. It is also observed that the continuous irradiation promotes the rate of NC aggregation. From these experimental results, we propose a hypothetic model which is based on both autocatalytic TOPO molecules desorption and its re-adsorption (feedback process) in the process of NC aggregation.
