Optical and structural studies of CaMoO4:Sm, CaMoO4:Sm@CaMoO4 and CaMoO4:Sm@CaMoO4@SiO2 core-shell nanoparticles

A simple polyol and Stober surface coating process was introduced to synthesize CaMoO4:Sm and their silica-coated CaMoO4:Sm nanoparticles. Powder X-ray diffraction (XRD) and different spectroscopic techniques were employed to investigate the structural and optical properties of as-prepared nanoparticles. The surface of CaMoO4:Sm nanoparticles was modified to alter the solubility of the nanoparticles and to study the influence of surface coating on emission spectra of samarium ions. Optical properties of these nanoparticles showed a strong dependence on the surface modification of nanoparticles, indicating the influence of coating in the enhancement of luminescent intensity. These results were attributed to the formation of chemical bonds between CaMoO4:Sm@ CaMoO4 core and non-crystalline SiO2 shell via Mo-O-Si bridges, which activate the 'dormant' Sm3+ ion on the surfaces of nanoparticles. It is, therefore, concluded that good hydrophilicity resulting from active functional groups in solutions and more intense luminescence enable doped core-shell nanoparticles to have great potential to be used as fluorescence biolabels in the future.