Eu3+/Tb3+-Doped Silica Nanoparticles with Controllable Structure, Composition and Fluorescent Properties

Lanthanides-doped fluorescent silica nanoparticles (FSNPs) were synthesized via a two-step protocol: lanthanide ion was chelated with a conjugation of a chromophore, a ligand and a (3-aminopropyl)triethoxysilane (APTES) molecule. Then the complex was condensed in a water-in-oil microemulsion system together with tetraethyl orthosilicate (TEOS). The existence of coupling silane ensured the bonding in the formation of silica. The influence of water-to-surfactant molar ratio and the amount of prepared conjugation on controlling the particle size and the loading capacity of lanthanides were investigated. Meanwhile, an energy transfer process in lanthanides-doped FSNPs was illustrated by using different chromophores and lanthanides, so that made the excitation wavelength, emission wavelength and fluorescent intensity controllable. Thus, a framework was shaped for the design of silica nanoparticles with diverse fluorescent properties based on engineering the energy levels. In addition, the energy transfer process in rare earth doped FSNPs is further elaborated, and a new method for adjusting the fluorescence of FSNPs by energy level is proposed.