A Novel Multifunctional Upconversion Phosphor: Yb3+/Er3+ Codoped La2S3

Yb3+/Er3+ codoped La2S3 upconversion (UC) phosphors have been synthesized using high-temperature solid-state method. Under 971-nm excitation, the maximum luminescence power can reach 0.64mW at the excitation power density of 16W/cm2 and an absolute power yield of 0.36% was determined by an absolute method at the excitation power density of 3W/cm(2), and the quantum yield of La2S3:Yb3+, Er3+ (green similar to 0.18%, red similar to 0.03%, integration similar to 0.21) was comparable to that of NaYF4:Yb3+, Er3+ nanocrystals (integration similar to 0.005-0.30). Frequency upconverted emissions from two thermally coupled excited states of Er3+ were recorded in the temperature range 100-900K. The maximum sensitivity of temperature sensing is 0.0075K(-1). As the excitation power density increases, the temperature of host materials rapidly rises and the top temperature can reach to 600K. Given the intense UC emission, high sensitivity, as well as good photothermal stability, La2S3:Yb3+/Er3+ phosphor can become a promising composite material for photothermal ablation of cancer cells possessing the functions of temperature sensing and in vivo imaging.