Fabrication of Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites with enhanced fluorescence

• Fabrication of Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites with core-spacer-shell structure.
• The controllable fluorescence is achieved by adjusting the spacer thickness of silica.
• The fluorescence enhancement is 6.23-fold at an optimal spacer thickness about 30 nm.
• The metal-enhanced fluorescence mechanism is proposed.

Herein, Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites are synthesized through layer-by-layer assembly technology. Aunanoparticle@mSiO2 core–shell nanospheres were prepared at first in the presence of CTAB in aqueous solution system by the modified one-pot method. A chemical precipitation method and a succeeding calcination process were adopted to the growth of Y2O3:Eu shells on the surfaces of Aunanoparticle@mSiO2 core–shell nanospheres. The structure, morphology and composition of the nanocomposites were confirmed by XRD, TEM and UV–vis absorption spectrum. The prepared Aunanoparticle@mSiO2@Y2O3:Eu nanocomposites have showed the emission intensity enhances to 6.23 times at 30 nm thickness of the silica spacer between the core of Au nanoparticle and the shell of Y2O3:Eu. According to the observations of fluorescent lifetime and the modeling of local electric field, the metal-enhanced and quenched fluorescence is closely related with the enhancement of excitation and radiative decay rate and the quenching by NRET comes as a result of competition between the distance-dependent mechanisms. This kind of multifunctional inorganic material will be widely used in electronics, biology and medical drug loading, etc.

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