Facile synthesis of colloidal photoluminescent BiPO4:Ln (Eu,Tb) nanoparticles well-dispersed in polar solvents

An innovative and simple approach to prepare colloidal photoluminescent BiPO4:Ln (Eu,Tb) nanoparticles has been demonstrated. XRD and TEM testing indicated that the BiPO4:Ln nanoparticles had monoclinic phase and single crystalline structure. Oleic acid (OA) was used to tailor the sizes and shapes of the samples. FT-IR spectra showed that the OA molecules were adsorbed on the surface of the BiPO4:Ln nanoparticles. Generally, nanoparticles prepared with OA as a surfactant have good dispersibility in nonpolar solvents. However, BiPO4:Ln nanoparticles obtained in our reaction system could disperse well in polar solvents such as water or ethanol to form a transparent colloidal solution. Under UV lamp, BiPO4:Eu and BiPO4:Tb colloidal solutions exhibited organic-red and green colours, respectively, which would be particularly beneficial for application in specific areas. A possible mechanism has been proposed herein. This facile method could be extended to synthesize the LnPO(4) nanoparticles well-dispersed in polar solvents.