Abstract
Well-crystallized and regular-shaped BaYF 5:Yb 3+/Er 3+ upconversion (UC) fluorescent nanocrystals (NCs) were synthesized in a modified water–ethanol–oleic acid system. The size and shape of the NCs were controlled by adjusting the amount of NaOH, reaction temperature and time. Well oil-dispersible NCs exhibited bright UC fluorescence under the 980 nm excitation. Furthermore, a systematic study on the photoluminescence of Yb 3+/Er 3+-doped BaYF 5 samples with different size and shapes indicated that the optical properties of products were strongly dependent on their size, and the configuration of nanocrystals were found to sensibly affect the optical properties of the products. Great enhancement of the green emission intensity was observed with increasing crystalline size. It was found that the crystalline and surface effects could be responsible for the observation and this behavior was attributed to a change of conditions and the quenching effect of the organic ligands.
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