Synthesis and characterization of Fe ₃O ₄/SiO ₂/CMCH/CdTe fluorescent/magnetic microspheres

Fluorescent/magnetic Fe ₃O ₄/SiO ₂/carboxymethylated chitosan(CMCH)/CdTe microspheres were prepared with Stöber method and crosslinking method, and their properties and applications were analyzed and discussed. First, silica-coated Fe ₃O ₄ composite microspheres with tetraethoxysilane(TEOS) as precursor, and mol ratio of Fe ²⁺ to Fe ³⁺ as 1:2 were prepared with supercritical dry method. Observation with transmission electron microscopy(TEM) shared that the average diameter of the Fe ₃O ₄ particals was 10 nm and the thickness of SiO ₂ layer was 5 nm. Then, the CMCH was connected onto the surface of Fe ₃O ₄/SiO ₂. CdTe fluorescent particles were prepared with hydrothermal approach, and adsorbed on the chains of CMCH by the electrostatic interaction between CMCH and CdTe. Finally, Fe ₃O ₄/SiO ₂/CMCH/CdTe particles with the diameter less than 200 nm, saturation magnetism moments of 22.16 A·m ²/kg and excellent fluorescent properties were obtained via selective crosslinking of glutaraldehyde with CMCH. The fluorescence spectrum data indicate that the maximum emission wavelength red shifts from 519 nm to 528 nm, which validates the adsorption of CdTe on the surface of Fe ₃O ₄/SiO ₂/CMCH. Animal experiment also verifies the excellent fluorescence, magnetism and stability of the composite microspheres.