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A succession of erbium single-doped and erbium/ytterbium co-doped SrF2 nanoparticles (NPs) were fabricated via a hydrothermal synthesis technique followed by high-temperature calcination. Structural, morphology, and element information of SrF2 NPs were explored using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) instruments. Under near-infrared (NIR) excitation, the SrF2:Er3+ NPs exhibit a prominent red emission peak (at 670 nm) as well as two oppositely faint green emission peaks (at 525 nm and 548 nm). The probable mechanism of the dominant red up-conversion luminescence (UCL) emission was systematically studied by UC emission spectroscopy, Raman spectroscopy, Fourier transform-infrared spectroscopy (FT-IR) and diffuse reflectance spectrum analyses. We used the energy gap law to estimate the probability of electronic transition, which determines the UCL emission route. The behavior of the R/G value (emission intensity of red to green ratio) and the slope n (the number of photons absorbed during the excitation process) reflected the existence of a highly efficient cross-relaxation (CR) effect during the UC process in the SrF2 system, so we can infer that the prominent red UCL emission is due to the CR effect among adjacent erbium atoms. After co-doping with ytterbium ions, the red UCL emission intensity is further enhanced. By comparing 2 mol% Er3+,5 mol% Yb3+ co-doped SrF2 samples with a similar composition without ytterbium doping, a red UCL emission intensity enhancement of about 200 times was observed. This increase is ascribed to the existence of effective energy transfer up-conversion (ETUC) from ytterbium to erbium, and the presence of a large absorption peak of ytterbium in the range of 830–1060 nm was observed in the diffuse reflectance spectrum, indicating that ytterbium's ability to absorb 980 nm photon energy is significantly stronger than erbium's. The strong red radiation obtained for erbium/ytterbium co-doped SrF2 NPs is expected to have potential application prospects in in vivo bio-imaging and photodynamic therapy. [ABSTRACT FROM AUTHOR]

Novel 2-formyl-8-oxy -N- phenylacetamide quinoline derivatives shows good coordination with Eu (III) ion. The target complexes performed good thermal stability, and excellent fluorescence property. • The six novel Eu (III) complexes based on 2-formyl-8-oxy-N-phenylacetamide quinoline derivatives were prepared, and their physical and chemistry properties were proved. • Based on the photoluminescence analysis and thermogravimetric analysis, the Eu(III) complexes perform red fluorescence with a good thermal stability. • The Eu(III) complexes with -Cl group performed the best fluorescence properties because of the heavy atom effect of halogen. A series of 2-formyl-8-oxy -N- phenylacetamide quinoline derivatives ligands L1-6 were synthesized and proved by 1H NMR and MS, their corresponding Eu(III) complexes were also synthesized. Their physical and chemistry properties were proved by elemental analysis, molar conductance, UV absorption spectra, FT-IR spectra and Thermogravimetric analysis. The Eu L1-6 (NO 3) 3 ·2H 2 O preform characteristic red luminescence of Eu3+. The Eu L6 (NO 3) 3 ·2H 2 O containing Cl present the strongest luminescence intensity, as well as the fluorescence quantum yield. Based on the good thermal stability and red luminescence properties of the target Eu(III) complex, it can be designed as fluorescence probe with chemistry modification and can expand quinoline derivatives development in the field of biomedicine. [ABSTRACT FROM AUTHOR]