Ammonium fluoride nh4f

All analytical-grade chemicals,
including chloroplatinic acid (H₂PtCl₆·H₂O), poly(vinylpyrrolidone) (PVP; MW = 40000), cobalt nitrate
hexahydrate [Co(NO₃)₂·6H₂O],
oleylamine (C₁₈H₃₇N), tetraethylorthosilicate
(TEOS; SiC₈H₂₀O₄), ethylene glycol
(C₂H₆O₂), ethanol (C₂H₆O), mesitylene (C₉H₁₂), hydrochloric
acid (HCl), hexane (C₆H₁₂), ammonium fluoride
(NH₄F), and acetone (C₃H₆O) were
purchased from Merck Hungary Ltd. and were used without further purification.
For inductively coupled plasma mass spectrometry (ICP-MS) measurements,
concentrated HNO₃ and HCl were used (Aristar for trace
metal analysis, VWR Chemicals). Ultrahigh-purity (5.0 quality) gas
cylinders of argon, oxygen, nitrogen, hydrogen, and the gas mixture
CO₂:H₂ = 1:4 were purchased from Messer Hungarogáz
Ltd.

The CaF₂:Tb³⁺ nanoparticles were synthesized by using the hydrothermal method. The starting materials included calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O), ammonium fluoride (NH₄F) and terbium nitrate pentahydrate (Tb(NO₃)₃·5H₂O), which were purchased from Sigma Aldrich and used without further purification. For synthesis 10 mmol of calcium nitrate and 20 mmol of ammonium fluoride were separately dissolved in 70 ml and 50 ml of deionized water, respectively, and kept under magnetic stirring for 30 min. The ammonium fluoride solution was added dropwise to the calcium nitrate solution, and the resulting solution was further stirred for another 20 min until it became cloudy. This solution was transferred into a Teflon container which was put into a Yanzheng instrument microreactor and thoroughly sealed. The reaction was performed at 160 °C for 5 h under continuous magnetic stirring, after which it was cooled to room temperature. The CaF₂ nanoparticles were isolated using a centrifuge at 6000 rpm for 10 min, and washed with ethanol and water four times. The final product was dried in an oven at 70 °C for 24 h. For the synthesis of Tb doped CaF₂, different amounts of terbium nitrate were added relative to the calcium nitrate, and the synthesis procedures were maintained the same as the standard sample.

The rare earth chlorides RECl₃ • 6 H₂O (RE: Y³⁺; Yb³⁺; purities > 99.9%) and oleic acid (OA, 90% purity) were purchased from Alfa Aesar (Havelhill, MA, USA), Tm³⁺ chloride (TmCl₃ • 6 H₂O, >99.9%), ammonium fluoride (NH₄F, 99%), cyclohexane (99.5%) and 3-(N-Morpholino)propanesulfonic acid (MOPS) were purchased from Sigma Aldrich (San Luis, AZ, USA). Ethanol (≥99.8%) and sodium hydroxide (NaOH, ≥99%) were purchased from Carl Roth (Karlsruhe, Germany), and Therminol^®66 was purchased from FRAGOL GmbH+Co. KG (Mülheim, Germany). Sodium oleate was synthesized by the authors using NaOH, Ethanol and OA. All chemical reagents were used as received without further purification.
For the synthesis of DBD-6, n-BuLi (1.6 M in hexane), decanal (95%), trimethylsilyldiazomethane (2 M in hexane), NaOH (98%), mEthanol (>99%) and tetrahydrofuran (>99.5%) were purchased from Acros organics (Morris, AL, USA), acetonitrile (>99.5%) and hydrochloric acid (HCl, 37%) from VWR (Randor, PA, USA), and glutaric acid anhydride was purchased from ABCR (Karlsruhe, Germany).

Sodium alginate (alginic acid sodium salt; Sigma-Aldrich, USA) in salt form, calcium carbonate (CaCO₃, Sigma-Aldrich, USA), ammonium fluoride (NH₄F, Sigma-Aldrich, USA), D-( +)-gluconic acid δ-lactone (GDL; Sigma-Aldrich, USA), and PDRN (PDRN; Genoss, South Korea) were prepared to fabricate the Alg-PDRN hydrogel according to literature^{51 (link)}. Briefly, mixture of 2–5 w/v% Alg with a calculated amount of CaCO₃ was prepared in distilled water (DW) under continuous stirring with a fixed Alg to calcium carbonate ratio of 1 w/v%:12.5 mM, as shown in Table 1. The amount of GDL was set to achieve a CaCO₃ to GDL molar ratio of 0.5 to attain a neutral pH^{51 (link)}. The samples were named according to the Alg concentration as 2%Alg-PDRN, 3%Alg-PDRN, 4%Alg-PDRN, and 5%Alg-PDRN; PDRN was loaded in each sample at a concentration of 100 μg/ml. CaCO₃ particles were homogeneously dispersed in the composite solution, and as soon as GDL was added, CaCO₃ started to dissolve and release Ca²⁺ ions to induce the crosslinking of the hydrogel. The gelling solution was continuously stirred for different times depending on the composition of the composite solution; then, each composite solution was pipetted into a 12-mm-diameter cylindrical mold. The gels were left at room temperature for 72 h to allow for complete gelation.