Optical Properties of Amorphous ZnO, CdO, and PbO Nanoclusters in Solution

We prepared ZnO, CdO, and PbO rock salt-coordinated and ZnO wurtzite-coordinated nanoclusters with a microemulsion method in the AOT reverse micelle. X-ray and electron beam diffraction techniques indicate that all have amorphous structures. The similarity of the UV−visible absorption and photoluminescence spectra at room temperature for ZnO, CdO, and PbO rock salt-coordinated nanoclusters indicates that they are all similar in electronic structure. All prepared nanosystems show strong emission in the visible region, and the emission features depend on the wavelength of the excitation. This phenomenon is considered as a result of localization of the electronic state due to the amorphous structure of nanocluster and surface capping. Time-resolved photoluminescence studies on ZnO, CdO, and PbO nanoclusters were performed. The carrier lifetimes near the band-tail are in the sub- and nanosecond time ranges with different characteristics from that of bulk amorphous semiconductors and nanocrystals. The observed properties can be explained in terms of quantum confinement, structural disorder, and surface polarization.