Yolk–shell structured Bi2SiO5:Yb3+,Ln3+ (Ln = Er, Ho, Tm) upconversion nanophosphors for optical thermometry and solid-state lighting

Yolk–shell structured Bi2SiO5:Yb3+,Er3+ upconversion nanophosphors have been successfully synthesized via a simple template-assisted route, in which the reaction of Yb3+/Er3+ co-doped bismuth precursor nanospheres with the silica capping layer in situ is ingeniously designed and controlled. The phase transition and morphology evolution are investigated in detail by X-ray powder diffraction and high-resolution electron microscopy to propose the formation mechanism of the yolk–shell nanostructure. The yielded Bi2SiO5:Yb3+,Er3+ nanophosphors can emit bright green upconversion luminescence under the excitation of a 980 nm laser diode, which enables them to be promising emitters for optoelectronic devices. The potential of the Bi2SiO5:Yb3+,Er3+ nanophosphors as an optical nanothermometer is also demonstrated. The proposed facile synthetic route, unique yolk–shell nanostructure and good upconversion luminescence performance lead the way to access these lanthanide-doped Bi2SiO5 nanophosphors for applications in biotechnology and optoelectronic devices.