Six new 4-acyl pyrazolone derivatives and their complexes with the terbium nitrates were synthesized and characterized by mass spectra, elemental analysis, EDTA titrimetric analysis, UV spectra, infrared spectra, molar conductivity and thermal analysis. The results showed that pyrazolone derivatives formed good coordination with the terbium ions. The introduction of electron-donating group in the ligands not only increased the luminescence intensity and fluorescence quantum yield, but also enlarged the HOMO and LUMO energy levels of corresponding terbium complexes. All the complexes possessed high luminescence intensity and showed relatively high fluorescence quantum yields. These target complexes may have vast potential to be developed as luminescence materials in the future.Download high-res image (97KB)Download full-size image

A novel Eu2+–Dy3+co-doped strontium aluminate green long-lasting phosphors were synthesized via conventional sol–gel method with citric acid and polyethylene glycol used as chelating agent, respectively. Orthogonal experiments were employed to optimize the main synthesis conditions and obtain the optimum technological parameters. Subsequently, the crystal structure, morphology, decay curve and luminescence property of the composites were characterized. X-ray diffraction (XRD) showed that the samples were composed of single-phase SrAl2O4. Scanning electron microscopy (SEM) revealed that the resultant nanoparticles performed graininess with a size of 100 nm around. The excitation and emission spectra indicated that, excitation broadband chiefly lay in the ultraviolet range, and nanocrystalline particles emitted strong light at 510 nm, which corresponding to the typical characteristic 5d–4f transition of Eu2+ ion excited at around 360 nm. The long afterglow photoluminescence of nanoparticles SrAl2O4: Eu2+, Dy3+ (denoted as SAO: ED) was observed in the dark with the naked eye even after the removal of the excitation light. The luminescence properties suggested that SAO: ED phosphor may be regarded as a potential green phosphor candidate for near-UV and blue light-emitting diodes (LEDs).

Gd3+-ion-doped upconversion nanoparticles (UCNPs), integrating the advantages of upconversion luminescence and magnetic resonance imaging (MRI) modalities, are capturing increasing attention because they are promising to improve the accuracy of diagnosis. The embedded Gd3+ ions in UCNPs, however, have an indistinct MRI enhancement owing to the inefficient exchange of magnetic fields with the surrounding water protons. In this study, a novel approach is developed to improve the MR imaging sensitivity of Gd3+-ion-doped UCNPs. Bovine serum albumin (BSA) bundled with DTPA-Gd3+ (DTPAGd) is synthesized both as the MR imaging sensitivity synergist and phase-transfer ligand for the surface engineering of UCNPs. The external Gd3+ ion attachment strategy is found to significant improve the MR imaging sensitivity of Gd3+-ion-doped UCNPs. The relaxivity analysis shows that UCNPs@BSA·DTPAGd exhibit higher relaxivity values than do UCNPs@BSA without DTPAGd moieties. Another relaxivity study discloses a striking message that the relaxivity value does not always reflect the realistic MRI enhancement capability. The high concentration of Gd3+-ion-containing UCNPs with further surface-engineered BSA·DTPAGd (denoted as UCNPs–H@BSA·DTPAGd) exhibits a more pronounced MRI enhancement capability compared to the other two counterparts [UCNPs–N@BSA·DTPAGd and UCNPs–L@BSA·DTPAGd (−N and –L are denoted as zero and low concentrations of Gd3+ ion doping, respectively)], even though it holds the lowest r1 of 1.56 s–1 per mmol L–1 of Gd3+. The physicochemical properties of UCNPs are essentially maintained after BSA·DTPAGd surface decoration with good colloidal stability, in addition to improving the MR imaging sensitivity. In vivo T1-weighted MRI shows potent tumor-enhanced MRI with UCNPs–H@BSA·DTPAGd. An in vivo biodistribution study indicates that it is gradually excreted from the body via hepatobiliary and renal processing with no obvious toxicity. It could therefore be concluded, with improved MR imaging sensitivity by an internal and external incorporation of Gd3+ strategy, that UCNPs–H@BSA·DTPAGd presents great potential as an alternative in tumor-targeted MR imaging.

A series of coumarin derivatives obtained from salicylaldehyde and phenol were synthesized. Their corresponding terbium complexes were prepared and characterized by elemental analysis, EDTA titrations, molar conductivity, UV–vis spectra, IR spectra, and thermal analysis. The luminescent properties and electrochemical properties of the terbium complexes were also investigated. The results showed that all the terbium complexes exhibited characteristic emissions of terbium ions. The introduction of electron-donating groups can improve the luminescent properties, decrease the HOMO and LUMO energy levels of the terbium complex, while electron-withdrawing groups can weaken the luminescent properties, and increase the HOMO and LUMO energy levels of terbium complex.

Novel Schiff base ligands derived from N′-benzylidene-benzohydrazide (substituted by –H, −CH3, −OCH3, −Cl) and 2-chloro-N-phenylacetamide were synthesized. The solid complexes of rare earth (Eu, Tb) nitrate with these Schiff base ligands were synthesized and characterized by elemental analysis, EDTA titrimetric analysis, thermal analysis, infrared spectra and UV–Vis spectra analysis. The fluorescence properties of rare earth (Eu, Tb) complexes in solid were studied. Under the excitation of ultraviolet light, these complexes exhibited characteristic emission of europium and terbium ions. The results showed that the ligand favored energy transfer to the emitting energy of Eu and Tb ions. Effects of different ligands on the fluorescence intensity of rare earth (Eu, Tb) complexes had been discussed. The electrochemical properties of rare earth (Eu, Tb) complexes were also investigated.

Amide-type podands derived from N,N′-(ethane-1,2-diyl)bis(2-hydroxybenzamide) and 2-chloro-N-phenylacetamide (substituted with methyl, methoxy, chlorine, nitrogen) were synthesized. Solid complexes of europium nitrate with podands were also synthesized and characterized by elemental analysis, ethylenediaminetetraacetic acid (EDTA) titrimetric analysis, thermal analysis, molar conductivity analysis, and infrared (IR) and ultraviolet–visible (UV–Vis) spectra analysis. The fluorescent properties of the europium(III) [Eu(III)] complexes in a solid state were also investigated. Under excitation of UV light, target Eu(III) complexes exhibited characteristic europium ion emissions. The influence of the substituent on the fluorescence intensity was discussed. Electrochemical properties were also investigated and discussed.

•NaYF4:Yb3+,Tm3+ up-conversion luminescence phosphors have been fabricated.•The preparation conditions were optimized by single factor and orthogonal experiment design.•The influence of the complexing agent types on NaYF4:Yb3+,Tm3+ products was discussed.•The crystal form of the target products was hexagonal prisms.•The target products exhibited the bright blue up-conversion luminescence emission.An up-conversion luminescent material, NaYF4 doped with rare-earth (RE), possessed a high luminescence efficiency and excellent stability. As described herein, a series of hexagonal nano-prismatic NaYF4:Yb3+,Tm3+ up-conversion phosphors had successfully been synthesized through mild hydrothermal method. The influence of hydrothermal time, the content of sodium tartrate, activator, sensitizer and ammonium fluoride on the luminescence properties of the target product were systematically investigated by means of single factor experiments. Based on the single factor experiments, the orthogonal method was used to obtain the optimal preparation conditions of the sodium tartrate/RE mole ratio, the sensitizer Yb3+ ions content, the NH4F/RE mole ratio, and the hydrothermal time which were 0.5, 23%, 11, 13 h, respectively. The fluorescent emission spectra analysis results showed that the strongest blue up-conversion luminescence emission peaks (1G4→3H6 transition of Tm3+ ion) of the NaYF4:Yb3+,Tm3+ phosphors using sodium tartrate as complexing agent was located at 477 nm under 980 nm near infrared (NIR) laser diode excitation. Finally the target products using different complexing agent were prepared at optimum preparation condition, and characterized by X-ray diffraction, scanning electron microscope. The crystal structure of products using tartaric acid and citric acid as complexing agent was hexagonal, consisting of spheres with 100 nm diameter.