New variations in the colloidal route to ErIII@ZnO nanocrystals and films
1-propanolic particulate ZnO nanocolloids were co-doped with Er-III ions and various silanes prior to coating. The resulting functionalized sols and sintered films were examined by UV/Vis-, FTIR- and time-resolved NIR-fluorescence spectroscopy. As a result, methyl- and phenyl triethoxysilanes (MTEOS, PTEOS) were found to block the slow ageing of the ZnO sols while the higher substituted silanes did not. Furthermore, film samples prepared from TEOS co-doped Er-III/ZnO sols and sintered at 400degreesC showed no fluorescence whereas PTEOS co-doping allows to detect the complex NIR-Er-III-fluorescence decay. In the last part of this contribution, the effect of thermal ZnO particle healing on the subsequent co-dopings and NIR-fluorescence dynamics will be discussed. Briefly, with increasing healing temperature the life time of the 1.54 mum fluorescence decreases. Interestingly, in ZnO sols healed at 170degreesC, the erbium acetate precursor is no more soluble which means that the ZnO nanocrystals could not be doped either.