Synthesis and Characteristics of Infrared-to-Visible Upconversion Nanoparticles Through a Microemulsion System

Infrared-to-visible upconversion phosphors Y_2O_3∶Yb, Er and Gd_2O_3∶Yb, Er with narrow size distribution were synthezed by using a stable microemulsion system, which included triton x-100,n-hexanol, cyclohexane and water. Appearance-controllable nanocrystals were achieved by adjusting the ratios of assistant surfactant and surfactant. These upconversion phosphors may be used as fluorescent labels for the sensitive detection of biomolecule, immunoassay or DNA assys. The x-ray diffraction (XRD) patterns of the samples showed that the powders were cubic phases of Y_2O_3 and Gd_2O_3, respectively. After calcination with different temperature settings in air atmosphere, the particles were spherical through the observation by scanning electronic microscopy (SEM). Red and green upconversion luminescence was obtained under 980 nm infrared excitation. Several contributions to the intensity of upconversion emission were also investigated.