DT-Eu

3+

and DT-Eu

3+

·OTSnanoparticles (NPs) are prepared by reprecipitation under sonication. The two kinds of fluorescent NPs are both of small size

~10 nm in diameter. But aggregation and greatly weakened luminescence of the pure chelate NPs disable them as fluorescent probes. With the introduction of appropriate hydrophobic silane

for example with 1:5 ratio of DT-Eu

3+

chelate to OTS

the hybrid chelate NPs have intensive luminescence

uniform size and are well dispersed. Such improvements originate from the outside silica layer

which is developed from the rapid hydrolysis of alkoxysilane under basic environment (pH=9). The hydrated silica layer eliminates the hydrophobic interaction then aggregation

and isolates DT-Eu

3+

chelate from water molecules.Formation details of Eu

3+

chelate NPs via reprecipitation are revealed by the time-dependent absorption and luminescence behaviors of fresh-prepared suspensions. Evenly distributed microjets are assumed as precursors of NPs

which evolve from a loose structure to a compact one with the diffusion of THF. With the exhaustion of THF

NPs are resulted.