Effects of sodium dodecyl sulfate surfactant on up-conversion luminescence of Er3+/Yb3+-codoped NaLa(MoO4)(2) nanocolloidal phosphor prepared by pulsed laser ablation in water

Abstract

Er3+/Yb3+-codoped NaLa(MoO4)(2) colloidal nanocrystals were synthesized by pulsed laser ablations in de-ionized water and sodium dodecyl sulfate (NaC12H25SO4, SDS) aqueous solution for up-conversion (UC) luminescence bio-labeling applications. The influences of the SDS molecules on the crystallinities, crystal morphologies, crystallite sizes, and UC luminescence properties of the prepared Er3+/Yb3+-codoped NaLa(MoO4)(2) colloidal nanocrystals were investigated in detail. Under a 980-nm excitation, the Er3+/Yb3+-codoped nanocolloidal NaLa(MoO4)(2) suspension exhibited a weak red emission near 670 nm and strong green UC emissions at 530 and 550 nm, corresponding to the intra 4f transitions of Er3+ (F-4(9/2), H-2(11/2), S-4(3/2)) -> Er3+ ((4)I(15/)2). When the SDS solution was used, a smaller average crystallite size, narrower size distribution, and enhanced UC luminescence were observed. These characteristics were attributed to the amphoteric SDS molecules attached to the positively charged Er3+/Yb3+-codoped NaLa(MoO4)(2) colloidal nanocrystals, effectively occupying the oxygen defect on their surfaces. The Er3+/Yb3+-codoped nanocrystalline NaLa(MoO4)(2) suspension prepared in the SDS solution exhibited a remarkably strong green emission visible to the naked eyes.