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In this paper, we designed Eu2+-doped BaAlF5 and BaSiF6 downconversion nanophosphors with strong f–f transition emission to realize the quantitative detection of TNP. The surface of the as-prepared nanophosphors was modified by polyethylenimine (PEI) to increase the water solubility and to provide a pair of electrons to bind to the benzene ring in TNP, forming a Meisenheimer complex. The detection principle of TNP is based on luminescence resonance energy transfer (LRET) technology, where the PEI-functionalized BaAlF5:Eu2+ and BaSiF6:Eu2+ nanophosphors are used as energy donors and TNP is an energy acceptor. With increasing TNP concentrations, the luminescence intensity of the BaAlF5:Eu2+ and BaSiF6:Eu2+ nanophosphors at 359 nm [4f7(6P7/2)→4f7(8S7/2) transition of Eu2+] displays dramatic luminescent quenching. The BaAlF5:Eu2+@PEI or BaSiF6:Eu2+@PEI nanophosphor downconversion luminescent sensors show great sensitivity and selectivity and good linearity, and the detection limits of TNP are 0.57 and 2.82 ng/mL, respectively.

The probing and quantitative detection of nitroaromatics is key for public safety and the monitoring of wastewater. Currently, most techniques used for the detection of nitroaromatics require ideal conditions rather than real conditions, making practical applications challenging. As nitroaromatics have strong absorption in the range of 350-370 nm, we can design a kind of KMgF

In this paper, two novel bismaleimide resins based on 9, 9-bis[4-(4-maleimidophenoxy) phenyl] fluorene (PFBMI), 9, 9-bis[4-(4-maleimidophenoxy)-3-methylphenyl]fluorene (MFBMI), and 2, 2’-diallyl bisphenol A (DABPA) were prepared. Their curing mechanism and curing kinetic were carefully investigated by Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The thermal mechanical properties of the composites based on these BMI resins and the glass cloth were obtained by Dynamic mechanical analysis (DMA), displaying that the novel resins whose Tg were 296°C and 289°C had excellent thermal performance. In addition, Thermogravimetric analysis (TGA) results showed that both the cured PD and MD resins possessed good thermal stability, and their T5% were all higher than 410°C.

The probing and quantitative detection of nitroaromatics is key for public safety and the monitoring of wastewater. Currently, most techniques used for the detection of nitroaromatics require ideal conditions rather than real conditions, making practical applications challenging. As nitroaromatics have strong absorption in the range of 350-370 nm, we can design a kind of KMgF3:Eu2+ nanophosphor with a strong f-f transition emission located at 362 nm, and an energy resonance transfer system based on the overlap of the emission peak of nanophosphors and the absorption peak of nitroaromatics can be constructed to realize the quantitative detection of nitroaromatics in municipal wastewater. Based on this, in this paper, a fluorescence resonance energy transfer (FRET) sensor is designed by choosing polyethylenimine (PEI)-capped KMgF3:Eu2+ nanoparticles as an energy donor for the ultrasensitive detection of nitroaromatics, which can also work as an energy acceptor. The KMgF3:Eu2+ nanoparticle sensor shows great sensitivity and selectivity and good linear characteristics in both DI water and wastewater. The detection limits in municipal wastewater were 0.456, 0.598, 0.667, 0557 and 0.678 ng/mL for TNT, TNP, p-nitrotoluene, dinitrobenzene (DNB), and nitrobenzene (NB), respectively. The detection accuracy was identified by high-performance liquid chromatography (HPLC). The results showed that the sensor had superior sensitivity and great accuracy and could be used in practical applications.

The preparation of Eu3+-doped NaGd(WO4)2 (NGW) nanophosphors was conducted by using a coprecipitation method. The characterization of the final products was performed in this work. The X-ray diffraction (XRD) results presented that our prepared NGW:Eu3+ phosphors are single-phase and belong to the tetragonal system, and the field emission scanning electron microscopy (FE-SEM) study showed that our synthesized samples consist of many irregular rod-like particles. The characteristic emissions due to Eu3+ transitions of 5D0→7FJ(J = 1–4) were observed upon 395 nm excitation. Based on the Huang and Van Uitert models, the impact of Eu3+ concentration on the luminescent intensity was studied. The concentration quenching of Eu3+ ions in NGW nanophosphors was contributed to the electric dipole-dipole interaction. The red light emission of NGW:Eu3+ nanophosphors indicates the promising applications for white LED, flat panel displays and biological field.

Eu²⁺- and Eu³⁺-doped SrAIF₅ nanorods were synthesized via a hydrothermal process. The crystal structure and morphology of the final products were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The prepared nanorods' diameters range from 40 to 50 nm, and lengths range from 400 nm to 2 µm along with the doped concentration of rare earth. The f-f transitions of Eu²⁺ can be observed in the SrAlF₅:Eu²⁺ nanorods at room temperature, and the photo-luminescent (PL) properties of SrAlF₅:Eu³⁺ nanorods are also described.

Eu 2+ -doped BaSiF 6 microrods with average diameter of 200 nm, and length of 1–4 μm were synthesized via a facile hydrothermal method. The crystal structure and morphology of final products were characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). Upon the excitation of 257 nm UV light, the as-prepared samples exhibit strong and sharp line emission, which originates from the transitions within the 4f 7 electron configuration of Eu 2+ ions. The optimal doping concentration of Eu 2+ ions in BaSiF 6 matrix was confirmed to be about 15 mol%.

In this article, a new process for the synthesis of metal-organic framework (MOF) particles that uses water as the only solvent is presented. High-quality Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) crystals were obtained via a facile and environmentally benign route in water at room temperature by directly mixing aqueous solutions of Cu(NO3)2 and the methylammonium salt of H3BTC. By adjusting the concentrations of the two reactants, we could obtain polyhedral crystals (500–1000nm), micro rods (15 × 3 μm) with hierarchical structures and rods (10 × 1 μm) with smooth surfaces. X-ray diffractions and gas sorption measurements revealed highly crystalline particles with large BET surface areas and total pore volumes.

Novel bismaleimide resins based on 9,9-bis[4-(4-maleimidophenoxy)phenyl]fluorene (PFBMI), 2,2′-diallyl bisphenol A (DABPA), and 4,4′-dimaleimido diphenylmethane (BDM) were prepared in this article. The thermal properties of PFBMI/DABPA in different proportions (1:0.87, 1:1, and 1:1.2) were carefully characterized using differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The results showed that resins had good thermal stabilities especially the one at 1:0.87. Its 10% weight loss reached 433.4°C, and the residual weight percentage (RW%) was more than 50%. In addition, PFBMI was blended into BDM/DABPA in a different ratio, and the curing characteristic, thermomechanical behavior, thermal stability, mechanical properties, and moisture absorption behavior of these blends were investigated. The results revealed that the introduction of PFBMI into BDM/DABPA did not decrease the thermal stability of the modified resins but increased the RW% at 600°C. Moreover, the impact strength of the modified resins can be significantly enhanced; when the ratio is 0.08:1, it increased by 35%. The water absorption rate also decreased with the increase in the concentration of PFBMI. PFBMI monomers play an important role on the toughness reinforcement of the BDM/DABPA resin.

Graphical abstract: Rice-shaped BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via one-pot hydrothermal process. The as-prepared BaAlF{sub 5}:Eu{sup 2+} are composed of many particles with an average diameter of 40 nm. When excited at 260 nm, the sharp line emission located at 361 nm of Eu{sup 2+} was observed. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The strong ultraviolet emission of Eu{sup 2+} ions in BaAlF{sub 5}:Eu{sup 2+} nanoparticles suggests that these nanoparticles may have potential applications for sensing, solid-state lasers and spectrometer calibration. - Highlights: • BaAlF{sub 5}:Eu{sup 2+} nanophosphors were synthesized via a mild hydrothermal process. • The Van and Huang models were used to research the mechanism of concentration quenching. • The optimum doping concentration of Eu2+ was confirmed to be 5 mol%. - Abstract: Eu{sup 2+}-doped BaAlF{sub 5} nanophosphors were synthesized via a facile one-pot hydrothermal method. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. XRD results showed that the prepared samples are single-phase. The FE-SEM and TEM images indicated that the prepared BaAlF{sub 5}:Eu{sup 2+} nanophosphors are composed of many rice-shaped particles with an average diametermore » of 40 nm. When excited at 260 nm, BaAlF{sub 5}:Eu{sup 2+} nanophosphors exhibit the sharp line emissions of Eu{sup 2+} at room temperature. The optimum doping concentration of Eu{sup 2+} was confirmed to be 5 mol%. The Van and Huang models were used to study the mechanism of concentration quenching and the electric dipole–dipole interaction between Eu{sup 2+} can be deduced to be a dominant for quenching fluorescence in BaAlF{sub 5}:Eu{sup 2+} nanophosphors. The strong ultraviolet emission of Eu{sup 2+} in BaAlF{sub 5}:Eu{sup 2+} nanophosphors suggests that these nanoparticles may have potential applications for sensing, spectrometer calibration and solid-state lasers.« less

Water-soluble Ce3+ and Tb3+ co-doped LaF3 nanoparticles with surfaces functionalized by a layer of polyethylenimine (PEI) were synthesized via a facile one-step hydrothermal method. Bovine serum albumin (BSA) protein was conjugated with LaF3:Ce, Tb nanoparticles via free amino groups on the surfaces of the nanocrystals. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), ultraviolet (UV) spectrophotometry, and photoluminescence (PL) spectroscopy. XRD results showed that pure hexagonal phase LaF3:Ce, Tb nanoparticles could be obtained via a PEI assisted hydrothermal process at 180 degrees C for 24 h. The FE-SEM results showed that the morphology of pure LaF3:Ce, Tb nanoparticles was spherical with an average diameter of -20 nm. The UV spectra showed that BSA had been conjugated with LaF3:Ce, Tb nanoparticles. The photoluminescent (PL) properties of LaF3:Ce, Tb nanoparticles were also studied. The strong green emission of Tb3+ in LaF3:Ce, Tb nanoparticles suggests that these nanoparticles may have potential applications for labels in biological imaging and immunoassays.

Water-soluble BaYF5:Yb3+/Er3+ nanoparticles with the surface functionalized by a layer of poly(acrylic acid) (PAA) were synthesized via a facile one-step PAA-assisted hydrothermal method. Bovine serum albumin (BSA) protein was conjugated with BaYF5:Yb3+/Er3+ upconversion nanoparticles via free carboxylic acid groups on the surface of nanoparticles. The final products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectrophotometry, ultraviolet (UV) spectrophotometry and photoluminescence spectroscopy (PL). The XRD results showed that PAA-capped BaYF5:Yb3+/Er3+ upconversion nanoparticles could be obtained via a PAA assisted hydrothermal process with the pH value of 8 at 200 degrees C for 24 h. The TEM results showed that the morphology of BaYF5:Yb3+/Er3+ nanoparticles was spherical particles with an average diameter of about 4 nm. The IR and UV spectra showed that BSA has been conjugated with BaYF5:Yb3+/Er3+ up-conversion nanoparticles. The luminescence properties of BaYF5:Yb3+/Er3+ up-conversion nanoparticles were also studied. The luminescence properties of the products suggest that BaYF5:Yb3+/Er3+ upconversion nanoparticles have promising applications for labels in biological assays.

Two novel bismaleimide (BMI) monomers containing fluorene cardo group and aryl ether linkage, that is, 9,9-bis[4-(4-maleimidophenoxy)phenyl] fluorene (PF-BMI) and 9,9-bis[4-(4-maleimidophenoxy)-3-methylphenyl] fluorene (MPF-BMI) based on 9,9-bis(4-hydroxyphenyl)fluorene and its derivative were designed and synthesized. The chemical structures of the monomers were confirmed from 1H NMR, 13C NMR spectroscopy, and Fourier transform infrared spectroscopy. Both monomers obtained are readily soluble in common organic solvents, such as acetone, dichloromethane, and chloroform, enabling an easy solution processing. The thermal curing behavior of the monomers and their non-isothermal thermal curing processes were investigated using differential scanning calorimetry, displaying that both monomers have lower melt points and broad thermal processing windows. The corresponding kinetic data, for example, activation energy (Ea), pre-exponential factor (A), and the order of the reaction (n), were obtained by the Kissinge...

Yb 3+ and Er 3+ co-doped SrAlF 5 nanorods with average diameter of 35 nm and average length of 400 nm were synthesized via a microemulsion-hydrothermal process, and their crystal structure and morphology were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The optimum doping concentration of Yb 3+ /Er 3+ in SrAlF 5 matrix was about 4 mol%. The upconversion luminescence intensity dependence on the laser diode (LD) working current was studied and the possible upconversion mechanism was analyzed. Furthermore, the temperature effect of upconversion luminescence was investigated. It was also found that the post heat-treatment could greatly improve upconversion luminescence.

Carboxylic acid-functionalized Yb3 +/Er3 + co-doped α- and β-NaYF4 nano-/micro-spheres were prepared through a simple poly(acrylic acid) (PAA)-assisted hydrothermal process. Bovine serum albumin (BSA) protein was conjugated with Yb3 +/Er3 + co-doped α-(β-)NaYF4 upconversion phosphors via free carboxylic acid groups on the surface of phosphors. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), infrared (IR) spectrophotometer, ultraviolet (UV) spectrophotometer and photoluminescence spectroscopy (PL). XRD results showed that pure α-NaYF4:Yb3 +, Er3 + nanospheres could be obtained via PAA assisted hydrothermal process at the pH value of 4–5 and 160 °C for 1–4 h. The obtained product is a mixture of α and β phases NaYF4:Yb3 +, Er3 + when the reaction time increased from 5 to 24 h. When the solution was treated at 200 °C for 8–24 h at the pH value of 8–9, pure β-NaYF4:Yb3 +, Er3 + microspheres were obtained. The FE-SEM results showed that the morphology of pure α-NaYF4:Yb3 +, Er3 + was spherical nanoparticles with an average diameter of about 70 nm and the pure β-NaYF4:Yb3 +, Er3 + was microsphere with an average diameter of about 700 nm, which is composed of spherical nanoparticles (30 nm). The FT-IR and UV spectra showed that BSA had been conjugated with α-NaYF4:Yb3 +, Er3 + upconversion phosphors. The luminescence properties of α-(β-) NaYF4:Yb3 +, Er3 + phosphors were also studied. Under 980 nm excitation, the upconversion luminescence (UCL) intensity of β-NaYF4:Yb3 +, Er3 + microspheres was much stronger than that of α- NaYF4:Yb3 +, Er3 + nanoparticles. Moreover, both red and green upconversion were ascribed to the two-photon process.

Eu²⁺- and Eu³⁺-doped SrAIF₅ nanorods were synthesized via a hydrothermal process. The crystal structure and morphology of the final products were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The prepared nanorods' diameters range from 40 to 50 nm, and lengths range from 400 nm to 2 µm along with the doped concentration of rare earth. The f-f transitions of Eu²⁺ can be observed in the SrAlF₅:Eu²⁺ nanorods at room temperature, and the photo-luminescent (PL) properties of SrAlF₅:Eu³⁺ nanorods are also described.

Spindle-like CaWO 4 :Sm 3+ phosphors were prepared via a Polyvinylpyrrolidone (PVP)-assisted sonochemical process, and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectroscopy (PL). The XRD results suggested that the prepared samples are single-phase. The FE-SEM images indicated that the prepared CaWO 4 :Sm 3+ phosphors are composed of many spindles with maximum average diameter of 150 nm and maximum average length of 500 nm. Under 404 nm excitation, the characteristic emissions corresponding to 4 G 5/2 → 6 H J ( J = 5/2, 7/2, 9/2 and 11/2) transitions of Sm 3+ in CaWO 4 phosphors were observed. The color coordinates for 1 mol% Sm 3+ doped CaWO 4 phosphor were calculated to be (0.595, 0.404). The fluorescent concentration quenching of Sm 3+ doped spindle-like phosphors was studied based on the Van Uitert's model, and it was found that the electric dipole–dipole (D–D) interaction is the dominant energy transfer mechanism between Sm 3+ ions in the CaWO 4 :Sm 3+ phosphors. The critical energy transfer distance was estimated.

Hexagonal phase NaYF 4 microtubes co-doped with Yb 3+ and Er 3+ were synthesized through a hydrothermal process with YF 3 submicrospindles as precursor. The X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were utilized to characterize the structure and morphology of the as-prepared products. XRD results show that pure cubic NaYF 4 crystals can be obtained when reaction time is 2 h. While the product is mixture of cubic and hexagonal phase NaYF 4 when reaction time is from 7 to 20 h. Continuing to increase the reaction time to 24 h, the pure hexagonal NaYF 4 crystals were formed. The FE-SEM and TEM results show that the morphology of pure cubic NaYF 4 is spherical clusters composed of spherical nanoparticles with average diameter of about 100 nm and the pure hexagonal NaYF 4 crystals have tubular structure with out diameter of about 0.3–0.5 μm, inner diameter of about 0.5–1 μm and length ranging from 3 to 12 μm. The luminescence properties of Yb 3+ /Er 3+ co-doped cubic and hexagonal phase NaYF 4 microcrystals were also studied. Under 980-nm excitation, the upconversion luminescence (UCL) intensity of hexagonal phase NaYF 4 microtubes is much stronger than that of cubic phase clusters. Moreover, both red and green upconversion are ascribed to the two-photon process. Therefore, hexagonal phase NaYF 4 microtubes with high UCL efficiency may have a potential application in photonic device.

A three-dimensional lanthanide metal-organic coordination polymer Yb3(BDC)4.5(DMF)2(H2O)3 · (DMF)2 has been synthesized by the reaction of the lanthanide metal ion (Yb3+) with 1,4-benzenedicarboxylic acid (H2BDC) under mild condition. The compound crystallizes in the triclinic system, space group PI with unit cell parameters a = 10.7428(9) A, b = 11.2786(9) A, c = 26.172(2) A, α = 85.060(2)°, β = 88.1060(10)°, γ = 62.3670(10)°, V = 2798.9 (4) A3, Z = 2. The crystal structure exhibits one-dimensional channels along the [011] direction. The fluorescent results showed that there were two emission peaks at 375 and 420 nm when the compound was excited by a 235 nm excitation. The preparation, X-ray structure and luminescent property are presented for a new lanthanide metal-organic coordination polymer Yb3(BDC)4.5(DMF)2(H2O)3 · (DMF)2.

The preparation, X-ray structure and magnetic properties are presented for a new mixed-valence tetranuclear manganese complex that functions as a single-molecule magnet (SMM): [Mn4(CF3COO)4(hmp)6], where hmp− is the anion of 2-(hydroxymethyl) pyridine and is a N,O bidentate chelate. The compound crystallizes in a monoclinic system, space group P 21/c (No. 14) with unit cell parameters a = 13.663(3) A, b = 14.705(3) A, c = 14.734(3) A, β = 98.51(3)°, V = 2927.6 A3 and Z = 2. The structure of the complex shows a novel coordination of the trifluoroacetate (TFA) anions, with one anion acting as a monodentate ligand while the second one coordinating through both oxygens to the same Mn center. Direct current magnetic susceptibility measurement in the 2–300 K temperature range supports a high-spin ground state. The presence of a frequency-dependent alternating current susceptibility signal indicates that the individual molecule is acting as magnet.

The complex fluorides Li 2 BeF 4 and LiSrAlF 6 were synthesized solvothermally at 180–240 °C and characterized by means of X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). The different influence factors such as solvents, molar ratios of initial mixtures, reaction temperature and reaction time were investigated. The experimental results indicated that Li 2 BeF 4 and LiSrAlF 6 powders could be controllably synthesized in the solvothermal process.

Water-soluble Ce3+ and Tb3+ co-doped LaF3 nanoparticles with surfaces functionalized by a layer of polyethylenimine (PEI) were synthesized via a facile one-step hydrothermal method. Bovine serum albumin (BSA) protein was conjugated with LaF3:Ce, Tb nanoparticles via free amino groups on the surfaces of the nanocrystals. The final products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), ultraviolet (UV) spectrophotometry, and photoluminescence (PL) spectroscopy. XRD results showed that pure hexagonal phase LaF3:Ce, Tb nanoparticles could be obtained via a PEI assisted hydrothermal process at 180 degrees C for 24 h. The FE-SEM results showed that the morphology of pure LaF3:Ce, Tb nanoparticles was spherical with an average diameter of -20 nm. The UV spectra showed that BSA had been conjugated with LaF3:Ce, Tb nanoparticles. The photoluminescent (PL) properties of LaF3:Ce, Tb nanoparticles were also studied. The strong green emission of Tb3+ in LaF3:Ce, Tb nanoparticles suggests that these nanoparticles may have potential applications for labels in biological imaging and immunoassays.

Water-soluble BaYF5:Yb3+/Er3+ nanoparticles with the surface functionalized by a layer of poly(acrylic acid) (PAA) were synthesized via a facile one-step PAA-assisted hydrothermal method. Bovine serum albumin (BSA) protein was conjugated with BaYF5:Yb3+/Er3+ upconversion nanoparticles via free carboxylic acid groups on the surface of nanoparticles. The final products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectrophotometry, ultraviolet (UV) spectrophotometry and photoluminescence spectroscopy (PL). The XRD results showed that PAA-capped BaYF5:Yb3+/Er3+ upconversion nanoparticles could be obtained via a PAA assisted hydrothermal process with the pH value of 8 at 200 degrees C for 24 h. The TEM results showed that the morphology of BaYF5:Yb3+/Er3+ nanoparticles was spherical particles with an average diameter of about 4 nm. The IR and UV spectra showed that BSA has been conjugated with BaYF5:Yb3+/Er3+ up-conversion nanoparticles. The luminescence properties of BaYF5:Yb3+/Er3+ up-conversion nanoparticles were also studied. The luminescence properties of the products suggest that BaYF5:Yb3+/Er3+ upconversion nanoparticles have promising applications for labels in biological assays.

beta-Cyclodextrin (beta-CD) forms a series of supramolecular complexes with aromatic or aliphatic guest molecules such as benzaldehyde, butyl acrylate, etc. Remarkable blue shifts (lambda max) of the UV-vis absorption peaks of the guest molecules are observed after the formation of inclusion complexes. The congestion lines appearing in the guest molecules are reduced in a remarkable extent accordingly. The mechanisms of the blue shifts are investigated herein.