Tmcl3 6h2o

Tm³⁺, Yb³⁺ and Eu³⁺-tridoped SrF₂ upconverting nanoparticles (UCNPs) were synthesized following a hydrothermal method.^{29 (link)} Briefly, SrCl₂·6H₂O, YbCl₃·6H₂O, TmCl₃·6H₂O and EuCl₃·6H₂O (Aldrich, 99.9%) were used as metal precursors (with Sr²⁺ : Yb³⁺ : Eu³⁺ : Tm³⁺ = 0.745 : 0.220 : 0.030 : 0.005 as the nominal molar ratio). As a reference sample, Yb³⁺ and Eu³⁺-codoped SrF₂ nanoparticles (with Sr²⁺ : Yb³⁺ : Eu³⁺ = 0.750 : 0.220 : 0.030 as the nominal molar ratio) were synthesized following the same procedure and are denoted as SrF₂:Yb,Eu nanoparticles. Stoichiometric amounts of the metal chlorides (3.5 mmol of total metal ions) were dissolved in 7 mL of deionized water. This solution was then added to 25 mL of a 0.8 M sodium citrate dihydrate solution (Fluka, >99%) and 3.0 mL of a 3.5 M NH₄F solution (Aldrich, 99.9%). The obtained solution was heat treated at 190 °C for 6 hours in a stainless-steel Teflon-lined digestion pressure vessel (DAB-2, Berghof). Subsequently, the UCNPs were precipitated with acetone and directly dispersed in deionized water. The colloidal dispersion is stable for at least one month.

YCl₃·6H₂O, YbCl₃·6H₂O, TmCl₃·6H₂O, NdCl₃·6H₂O, oleic acid, 1-octadecene, and dimethyl sulfoxide (DMSO) were purchased from Sigma-Aldrich. Streptavidin, Lipofectamine 3000 reagent, and organic dye DiO for staining phospholipid bilayer membrane were purchased from Thermo Fisher Scientific Co. HCl (37%), methanol, ethanol, and cyclohexane were obtained from Sinopharm Chemical Reagent Co. Phosphate-buffered solution (PBS) (pH 7.4) was obtained from Shanghai Runcheng Biomedical Co. Ltd. All chemicals were obtained commercially and used without further purification.