Eu Nanocrystals Research Articles

Europium-Containing Nanospheres for Treating Ovariectomy-Induced Osteoporosis: Targeted Bone Remodeling and Macrophage Polarization Modulation.

Osteoporosis, characterized by reduced bone mass and structural deterioration, poses a significant healthcare challenge. Traditional treatments, while effective in reducing fracture risks, are often limited by side effects. This study introduces a novel nanocomplex, europium (Eu) ions-doped superparamagnetic iron oxide (SPIO) nanocrystals encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanospheres, abbreviated as SPIO:Eu@PLGA nanospheres, as a potential therapeutic agent for osteoporosis by modulating macrophage polarization, enhancing osteoblast differentiation and inhibiting osteoclastogenesis. SPIO and SPIO:Eu nanocrystals were synthesized through pyrolysis and encapsulated in PLGA using an emulsification method. To evaluate the impact of SPIO:Eu@PLGA nanospheres on macrophage reprogramming and reactive oxygen species (ROS) production, flow cytometry analysis was conducted. Furthermore, an ovariectomized (OVX) rat model was employed to assess the therapeutic efficacy of SPIO:Eu@PLGA nanospheres in preventing the deterioration of osteoporosis. In vitro, SPIO:Eu@PLGA nanospheres significantly attenuated M1 macrophage activation induced by lipopolysaccharides, promoting a shift towards the M2 phenotype. This action is linked to the modulation of ROS and the NF-κB pathway. Unlike free Eu ions, which do not achieve similar results when not incorporated into the SPIO nanocrystals. SPIO:Eu@PLGA nanospheres enhanced osteoblast differentiation and matrix mineralization while inhibiting RANKL-induced osteoclastogenesis. In vivo studies demonstrated that SPIO:Eu@PLGA nanospheres effectively targeted trabecular bone surfaces in OVX rats under magnetic guidance, preserving their structure and repairing trabecular bone loss by modulating macrophage polarization, thus restoring bone remodeling homeostasis. The study underscores the critical role of Eu doping in boosting the anti-osteoporotic effects of SPIO:Eu@PLGA nanospheres, evident at both cellular and tissue levels in vitro and in vivo. The inclusion of Eu into SPIO matrix suggests a novel approach for developing more effective osteoporosis treatments, particularly for conditions induced by OVX. This research provides essential insights into SPIO:Eu@PLGA nanospheres as an innovative osteoporosis treatment, addressing the limitations of conventional therapies through targeted delivery and macrophage polarization modulation.

Heterogenous Core-Shell Persistent Luminescent Nanoparticles with Enhanced Afterglow Luminescence.

Persistent luminescent nanoparticles (PLNPs) are promising for many bioapplications due to their unique afterglow luminescence following the stoppage of light excitation. However, PLNPs are prone to surface quenching that results in weak afterglow luminescence. Although some efforts have been made to reduce surface quenching through designing homogeneous core-shell PLNPs, the enhancement in afterglow luminescence was insignificant. We hypothesize that the independent absorption and emission of the shell caused less energy to reach the activator ions in the core. Hence, a heterogeneous core-shell PLNP where the shell has a higher band gap than the core would reduce the absorption and emission of the shell. In this work, ZnGa2O4 and Zn2GeO4 were coated on Zn1.2Ga1.6Ge0.2O4:Cr and Zn3Ga2Ge2O10:Eu nanocrystals, respectively, to form heterogeneous core-shell PLNPs and significant luminescence enhancement was achieved compared to their traditional homogeneous core-shell nanostructures.

Preparation of Eu ions doped Sr5(PO4)3F transparent glass ceramics and their luminescence properties

The lack of red light components in solid-state lighting technology urgently requires the development of new efficient red-emitting bulk phosphors. Herein, we successfully prepared a kind of red-emitting glass ceramics (GCs) (λex = 392 nm, λem = 613 nm) containing Eu-doped strontium fluorophosphates (Sr5(PO4)3F:Eu) nanocrystals via a melt-quenching method in SrF2–K2CO3–P2O5–H3BO3 glass. The heat treatment temperature was found to significantly affect the grain size of the Sr5(PO4)3F:Eu nanocrystals as well as the transmittance of the prepared GCs. After heat treatment at 600 °C for 2 h, the Sr5(PO4)3F:Eu nanocrystals with grain size of about 18 nm were precipitated inside the GCs (GC600), which exhibited a high transmittance of 58–70 % in the range of 500–800 nm, with a stronger luminescence intensity than that of PG. Under excitation of 392 and 464 nm wavelengths, the CIE 1931 color coordinates of GC600 were around (0.626, 0.373) and (0.638, 0.362), respectively, both falling in red region. The present Sr5(PO4)3F:Eu GCs are promising as red phosphors for UV-pumped white-light LEDs.

Hydrothermal synthesis and tunable luminescence of YPO4:Eu2+/Eu3+, Tb3+ nanocrystals

The homogeneous and well crystallized rare earth ions RE3+ (RE = Eu, Tb) doped YPO4 and YPO4·0.8H2O nanocrystals (NCs) are synthesized by a simple hydrothermal route. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The results indicate that the pH value of precursor affects the phase composition and surface morphology of the final product. The results of XPS indicate that both Eu2+ and Eu3+ co-exist in YPO4 NCs, implying that the self-reduction from Eu3+ to Eu2+ takes place with the absence of reducing agents, charge compensation reagents and charge carrier trapping processes. In addition, YPO4:Eu and YPO4·0.8H2O:Eu samples exhibit strong and bright blue and red emission. According to PL spectroscopy, the blue emission is originated from host lattice and Eu2+ ion luminescence and red emission from Eu3+. YPO4:Tb, Eu samples can be effectively excited at 355 nm. An energy transfer phenomenon appears between Tb3+ and Eu3+. It is interesting that by changing the concentration of Tb3+, white phosphor from Y0.90PO4:0.04 Tb, 0.06Eu NCs are successfully obtained. Moreover, the Y0.90PO4:0.04 Tb, 0.06Eu has excellent thermal stability. These results indicate that the combination of defect and rare earth luminescence in YPO4:Tb, Eu NCs can produce tunable luminescence color, which may have potential applications in fields such as solid-state lighting and field emission displays.

Influence of surface modification by organic molecules on optical properties of Eu3+-doped ZnO nanocrystals

We have fabricated Eu3+-doped ZnO (ZnO:Eu) nanocrystals (NCs) surface-modified with organic molecules such as dodecylamine (DDA) and tri-n-octylphosphine oxide (TOPO) and have studied their optical properties. In the ZnO:Eu NCs without surface modification, strong broad photoluminescence (PL) band due to surface defects is observed, so the Eu3+ PL peaks are not observed because they are covered by the strong surface-defect PL band. In the DDA-capped ZnO:Eu NCs, the Eu3+ PL and the exciton PL are observed because of suppression of the surface-defect PL caused by the inactivation of the surface defects. Contrary to expectations, the surface modification with TOPO suppressed not only the surface-defect PL but also the exciton PL. As a result, the ZnO:Eu NCs with red PL due to the Eu3+ ions have been successfully prepared. We discuss the influence of surface modification by DDA and TOPO on optical properties.

Eu3+-doped CdSe nanocrystals with blueshift emission and high quantum yield

In this work, we used an oil phase method to synthesize Eu3+-doped CdSe nanocrystals (NCs), which were characterized extensively with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV–visible (UV–vis) absorption and emission. The CdSe:Eu NCs were monodispersed and uniform spherical nanocrystals with a cubic structure resembling CdSe NCs. The particle diameter depended on the content of the Eu3+ dopant and ranged from 5.57to 4.27 nm, respectively. The CdSe:Eu NCs containing 20 mol% Eu3+ (denoted as a-20) has a 31nm blueshift in absorption and a 25 nm blueshift in emission with comparison to the pure CdSe NCs. The efficiency of energy transfer from CdSe to Eu3+ can be calculated from the variation of fluorescence lifetime to be 22%. The quantum yield (QY) of the CdSe:Eu NCs is the highest when the concentration of the Eu3+ dopant is 20 mol%. High reaction temperature and charge compensation can effectively improve the QY of the CdSe:Eu NCs.

Crystallization within Intermediate Amorphous Phases Determines the Polycrystallinity of Nanoparticles from Coprecipitation.

Intense research on nanocrystals synthesized in solution is motivated by their original physical properties, which are determined by their sizes and shapes on various scales. However, morphology control on the nanoscale is limited by our understanding of crystallization, which is challenged by the now well-established prevalence of noncrystalline intermediates. In particular, the impact of such intermediates on the final sizes and crystal quality remains unclear because the characterization of their evolution on the nanometer and millisecond scales with nonperturbative analyses has remained a challenge. Here we use in situ X-ray scattering to show that the nucleation and growth of YVO4:Eu nanocrystals is spatially restrained within amorphous, nanometer-scaled intermediates. The reactivity and size of these amorphous intermediates determine (i) the mono versus polycrystalline character of final crystals and (ii) the size of final crystals. This implies that designing amorphous intermediates themselves that form in <6 ms is one of the keys to controlled bottom-up syntheses of optimized nanoparticles.

Organic-free direct crystallization of t-LaVO4:Eu nanocrystals with favorable luminescence for LED lighting and optical thermometry

Tetragonal structured LaVO4 (t-LaVO4) is superior to its thermodynamically stable monoclinic polymorph for luminescence, but is difficult to synthesize without using chelating molecules/ions. With Ln2(OH)4SO4·2H2O layered hydroxide as an original template for phase conversion, well-crystallized t-(La0.95Eu0.05)VO4 nanocrystals (∼40–80nm) of favorable dispersion and size uniformity were directly produced via hydrothermal reaction at 200°C for 24h without using any organic additive. Luminescence analysis showed that the as-made nanocrystals have an absolute quantum yield of ∼38.2%, fluorescence lifetime of ∼1.52ms and color coordinates of around (0.33, 0.65) under 304nm UV excitation at room temperature (RT), and the 620nm main emission can retain as high as ∼66% of its RT intensity at 150°C. The activation energies for thermal quenching were analyzed to be ∼0.321, 0.286 and 0.291eV for the 537nm (5D1→7F1 transition), 593nm (5D0→7F1) and 620nm (5D0→7F2) emissions of Eu3+, respectively. Application of the nanocrystals in LED lighting found electric-field enhanced 5D0→7F4 emission of Eu3+ (∼697nm) and increasing brightness but relatively stable color correlated temperature (∼3270–3400K) at a higher driving current (30–100mA) for the lamp. The nanocrystals were also demonstrated to be well capable of temperature sensing with the I537/I593 fluorescence intensity ratio, whose maximum absolute sensitivity, maximum relative sensitivity and minimum temperature resolution are ∼0.27%K−1, 2.01%K−1, and 0.015K at 298K, respectively.

Y0.4Gd1.6O2S: Eu nanocrystals for ratiometric Pb2+ ions sensing via selectively non-radiative relaxation

Toxic divalent lead ions are broadly chosen for famous perovskite systems with great optoelectronic performances, which motivates us to explore a novel strategy for its determination with high sensitivity. In this work, lanthanide doped inorganic oxysulfide nanocrystals (NCs) are verified to be excellent candidates for ratiometric Pb2+ ions sensing. Specifically, the photoluminescence (PL) intensity of Eu3+ ions in Y0.4Gd1.6O2S NCs decreases gradually with the increase of Pb2+ ions concentration under the excitation of 254 nm, while its intensity keep unchanged under 311 nm excitation. In this occasion, a ratiometric PL sensing route for Pb2+ ions is obtained through using I311 as intrinsic reference. The detection limit for Pb2+ ions is 7.1 nM. This work provides a new ratiometric PL sensing route for Pb2+ ions via selectively non-radiative relaxation.

Luminescence behavior of Eu3+ in silica glass containing GdVO4: Eu nanocrystals

Transparent nanocrystalline glass (NCG) with GdVO4:Eu nanocrystals embedded in sintered nanoporous silica glass (NPSG) is synthesized, and intense photoluminescence and energy transfer are observed. X-ray diffraction (XRD), micro-Raman spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) analyses confirm that GdVO4:Eu nanocrystals are dispersed in silica glass. The photoluminescence intensity of Eu3+ is significantly enhanced by the microcrystallization process. After microcrystallization, the photoluminescence intensity increases by 41 and 14 times for glass that has Eu3+ singly doped and glass codoped with Gd3+, VO43−, and Eu3+, respectively. When Gd3+ and Eu3+, Gd3+ and V5+, and V5+ and Eu3+ are respectively double-doped, the efficiencies of Gd3+ → Eu3+, VO43- → Eu3+, and Gd3+ → VO43− energy transfers are assayed to be 22.3%, 24.7%, and 70.1%, respectively. In Eu3+, Gd3+, and V5+ triple-doped samples, in addition to the above energy transfer processes, there is a Gd3+ → VO43- → Eu3+ energy transfer. Nevertheless, VO43- → Eu3+ is still the main process. Especially after microcrystallization, the transfer efficiency of VO43- → Eu3+ is significantly increased to 90.9% because the lattice site of Gd3+ is replaced by Eu3+ in GdVO4 crystallites.

Calcination effects on europium doped zinc oxide as a luminescent material synthesized via sol-gel and precipitation methods

This work is aimed at the determination of the preferential calcination conditions for maximum thermoluminescence (TL) and optically stimulated luminescence (OSL) emissions of europium doped zinc oxide (ZnO:Eu) pellets after exposure to β-particles when they are synthesized using the precipitation and sol-gel methods, in micro/nanoscales. The verification of the photoluminescence (PL) signals were investigated. The calcination temperature range of 800–1200 °C and the calcination times between 2 h and 24 h were applied in the production of ZnO:Eu pellets. The phase composition and morphology of the samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The transmittance measurements were carried out by Fourier transformed infrared (FTIR) spectroscopy to understand the vibrational properties of ZnO:Eu nanocrystals. In the XRD and SEM patterns, the formation of hexagonal wurtzite phase of ZnO was observed. It was observed that the samples exhibited a weak green emission when the excitation wavelength is 350 nm. In addition, the ZnO:Eu pellets exhibited two sharp peaks at 579 and 615 nm which related to the Eu transitions. The PL intensities dropped with the increasing calcination temperatures. The TL peaks settled at 130 and 300 °C with 5 oCs−1 heating rate, were found similar to each other when the pellets calcined using different temperatures and times. β-dose linearity extended from 1 Gy to 0.2 kGy for all of the studied samples.

Luminescence and scintillation properties of Eu2+ doped CaF2 glass ceramics for radiation spectroscopy

A new scintillation material including CaF2: Eu nanocrystals contained in SiO2–Al2O3–CaO–CaF2–LiF system was successfully prepared via melting method with additional heat treatment. Structural and luminescence properties were investigated by characterization techniques including XRD, SEM, photoluminescence (PL) excitation and emission spectra and absorption profile. The emission intensity of the glass ceramics containing CaF2: Eu nanocrystals under illumination at 356 nm were significantly more than the as-made glass and enhanced with increasing the temperature and duration of the heat treatment. Spectral analysis of gamma rays showed a full-energy peak in comparison with the similar chemical compositions that do not show such a response. Also an energy continuum with specific reaction-product peak was detected for thermal neutrons. The scintillation efficiency was enhanced with increasing crystallization. The fabricated Eu-doped transparent CaF2 glass ceramics has the potential to be a desired composite scintillator for detection of low energy gamma rays and thermal neutrons.

Dual-mode luminescent core-shell nanoarchitectures for highly sensitive optical nanothermometry

Currently, FIR-based luminescent nanothermometry has aroused wide concern for its promising applications in fast-moving objects, harsh environments and microscopic temperature. Synchronously promoting the absolute and relative sensitivities of optical thermometers is one of the significant issues at present. In this work, a new nanothermometry strategy to possess both high absolute and relative sensitivities have been proposed by coupling of thermally-coupled-levels-based technique with non-thermally-coupled-levels method in the core-shell designed nanomaterials. Following this strategy, the core-shell-structured NaGdF4:Yb,Er@ NaYF4:Ce,Tb,Eu nanocrystals have been successfully prepared. Remarkably, the adverse cross-relaxation among different activators is extremely suppressed owing to the spatial separation of Er3+ and Eu3+,Tb3+ activators, being conducive to the realization of both intense green upconverting emissions and yellow downshifting luminescence. Moreover, the temperature-sensitive dual-mode luminescent behaviors of core-shell nanomaterials are systematically studied to probe the possible application in FIR-related luminescent thermometry. Specially, the thermally-coupled-levels-based FIR of Er3+:2H11/2 → 4I15/2 transition to Er3+: 4S3/2 → 4I15/2 one and non-thermally-coupled-levels-based FIR of Eu3+:5D0→7F2 transition to Tb3+:5D4→7F6 one are proved to be applicable as temperature probes, leading to the achievement of dual-mode temperature sensing. Using the pre-designed core@shell nanoarchitectures, the absolute sensitivity can reach up to 1.02% K−1 based on Eu3+,Tb3+ Stokes emissions and the relative sensitivity could reach as high as 1.12% K−1 based on Er3+ anti-Stokes luminescence. We believe that this study provides a valid approach for developing high-performance optical nanothermometers.

The doping site analysis and control of Eu3+ in ZnO:Eu crystal lattice

A new effective and convenient method is put forward to accurately analyze and control the doping sites of Eu3+ in ZnO:Eu nanocrystal. By analyzing the drift of XRD peaks, the splits of laser-stimulated fluorescence peak, intensity variation of E2 Raman scattering peaks and lattice distortion from HRTEM, the position that Eu3+ ions occupy in host lattice is accurately analyzed. There generally exists the symmetry broken regularity for disordered doped system such as ZnO:Eu — it is that Eu3+ is inclined to occupy the position with low symmetry for equilibrium growth crystal. At high annealing temperature, the crystallographic symmetry of Eu3+ is reduced from C3v to C2, which fully evidences that Eu3+ ions are separated out of host lattice. In the same time, the doping position of the Eu can be completely controlled by controlling annealing temperature. In the low symmetrical crystal field, 612 nm fluorescence peak splits to 4 splits, and the peak width of the strongest one is only about 4 nm. This nanomaterial with extremely narrow luminescence will have intensively potential applications in the fields of high quality light source with high contrast control and high signal to noise ratio such as fluorescence probe in high resolution bioimaging.

Highly stabile ZnGa2O4:Eu nanocrystals as a fluorescence probe for bio-imaging

Acetylacetonate (acac) passivated and europium incorporated ZnGa2O4 nanocrystals (ZGO:Eu NCs) were successfully prepared via a facile one-step non-injection process in oleylamine at a relatively low reaction temperature of 300 °C under N2 ambient. The resultant ZGO:Eu NCs exhibited a well-dispersed morphology with an average particle size of 4 nm. The enhanced and broad absorption band from 250 to 450 nm is attributed to the synergistic effect between the acac as an antenna and the coexistence of Eu3+ and Eu2+. Under 405 nm excitation, a full spectrum emission covering from 400 to 720 nm was observed. The sharp red emission coming from Eu(III) 5D0 → 7FJ (J = 1–4) transitions can be enhanced by adjusting Eu concentrations and reaches the optimum at 20 at% Eu. Subsequently, the as-prepared NCs were transferred into an aqueous media via a ligand exchange by polyethyleneimine (PEI) to obtain the hydrophilic ZGO:Eu@PEI NCs. The initial fluorescent properties are preserved well. Finally, the strong red fluorescence emission, suitable excitation window, high photo-stability, excellent water solubility, and prominent bio-compatibility make ZGO:Eu@PEI NCs as high quality bio-imaging probes successfully identify living KB cells. The method mentioned in this paper overcomes the bottle-neck of the inorganic bulk phosphors as probes in bio-imaging, and as a result, expands their applications in optical detection and medical diagnosis fields.

Investigation of europium(III)-doped ZnS for immunoassay**Project supported by the National Natural Science Foundation of China (Grant No. 61205193), the Project of Science and Technology of Jilin Province, China (Grant No. 20140520107JH), the Technology Foundation of Jilin Provincial Department of Human Resources and Social Security, China (Grant No. RL201306), and the Science Foundation for Young Scientists of Changchun University of Science

Biofunctional europium (III)-doped ZnS (ZnS:Eu) nanocrystals are prepared by a sol–gel method. The characteristic luminescence of ZnS:Eu is used as a probe signal to realize sensitive immunoassay. The luminescence intensity of the Eu3+ in the ZnS matrix shows strong concentration dependence, and the optimal doping concentration is 4%. However, the emission wavelengths of the ZnS:Eu nanocrystals are not dependent on doping concentration nor the temperature (from 100 K to 300 K). Our results show that these features allow for reliable immunoassay. Human immunoglobulin, used as a target analyte, is captured by antibody modified ZnS:Eu probe and is finally enriched on gold substrate for detection. High specificity of the assay is demonstrated by control experiments. The linear detection range is 10 nM–800 nM, and the detection limit is about 9.6 nM.

Luminescence properties of YVO4:Eu nanocrystals in nanoporous high-silica glass

A feasible method was used to synthesize YVO4:Eu nanocrystals in nanoporous high-silica glass (YVOE-HSG). High-resolution transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy were used to investigate its morphology, structure, and optical properties, respectively. The Eu ions were introduced as luminescence centers into the sample YVOE-HSG. Under 291 nm excitation, the samples exhibit the characteristic transitions of Eu3+ and Eu2+. With the increase of Eu3+ doping concentration, the positions of main excitation peaks shift to long waves. The reduction of Eu3+ to Eu2+ is observed, and the chromaticity coordinates (x, y) can move from the red light to cool white and then to blue light. The efficient energy transfer from VO43− to Eu3+ and Eu2+ is confirmed. Results indicated that the sample has potential application in white light-emitting diodes under UV excitation.

Sensitive detection of Brilliant Blue using fluorescence resonance energy transfer with YVO4:Eu nanocrystals as donors

A FRET system was established using YVO4:Eu nanocrystals (NCs) as the energy donors and Brilliant Blue (BB) as the energy acceptor. Based on FRET, fluorimetry was successfully applied to determine BB in juice and candy samples.

Surfactant-free aqueous synthesis of novel Ba3Gd2F12:Ln3+ nanocrystals with luminescence properties

Novel Ba3Gd2F12:Ln3+ (Ln = Eu, Dy, Tb, Ce, Er, Tm, and Yb) nanocrystals with multicolor emissions have been prepared via a surfactant-free aqueous hydrothermal route for the first time.

Influence of fluorination on structure and luminescence of ZrO2:Eu nanocrystals

The set of solid solutions ZrO2:0.005Eu3+/xF− (x=0, 0.02, 0.04, 0.08, 0.10) was prepared via solid-state route. Synthesized powders were studied by means of XRD powder analysis, scanning electron microscopy and luminescence spectroscopy. The XRD patterns for all co-substituted samples are a composition of the monoclinic and cubic phases of zirconia. The products are crystallized in a compact form with an average size of particles about 50–150nm. All studied samples at room temperature show in their PL spectra both wide band of the host-related emission (λmax≈480nm) and sharp peaks of the 5D0-7FJ (J=0–4) radiation transitions in Eu3+ ions under excitation with λex=393nm. The total intensity of the Eu3+ luminescence increases more than 6 times with fluorine content, x, increasing up to 0.08. Possible mechanisms of the luminescence behavior are discussed.