Cationic Effects on Photo- and X-ray Radioluminescence of K3RE(PO4)2:Ce3+/Pr3+ (RE = La, Gd, and Y) Phosphors toward X-ray Detection.

Cationic tuning for lanthanide (Ce3+/Pr3+)-activated inorganic phosphors with stable, efficient, and fast-decay 5d-4f emissions has emerged as an important strategy toward the continuing pursuit of superior scintillators. The in-depth understanding of the cationic effects on photo- and radioluminescence of lanthanides Ce3+ and Pr3+ centers is requisite for the rational cationic tuning. Here, we perform a systematic study on the structure and photo- and X-ray radioluminescence properties of K3RE(PO4)2:Ce3+/Pr3+ (RE = La, Gd, and Y) phosphors to elucidate the underlying cationic effects on their 4f-5d luminescence. By using the Rietveld refinements, low-temperature synchrotron-radiation vacuum ultraviolet-ultraviolet spectra, vibronic coupling analyses, and vacuum-referred binding energy schemes, the origins of lattice parameter evolutions, 5d excitation energies, 5d emission energies, and Stokes shifts as well as good emission thermal stabilities of K3RE(PO4)2:Ce3+ systems are revealed. In addition, the correlations of Pr3+ luminescence to Ce3+ in the same sites are also discussed. Finally, the X-ray excited luminescence manifests that the K3Gd(PO4)2:1%Ce3+ sample possesses a light yield of ∼10,217 photons/MeV, indicating its potentiality toward X-ray detection application. These results deepen the understanding of cationic effects on Ce3+ and Pr3+ 4f-5d luminescence and inspire the inorganic scintillator development.

VUV-UV-vis photoluminescence, X-ray radioluminescence and energy transfer dynamics of Ce3+ and Eu2+ in Sr2MgSi2O7.

Ce3+ and Eu2+ doped and Ce3+-Eu2+ co-doped Sr2MgSi2O7 phosphors are prepared via a high-temperature solid-state reaction technique. The synchrotron radiation vacuum ultraviolet-ultraviolet (VUV-UV) excitation and ultraviolet-visible (UV-vis) emission spectra of diluted Ce3+ and Eu2+ doped Sr2MgSi2O7 samples are measured at cryogenic temperatures. The electron-vibrational interaction (EVI) between Ce3+ and its surroundings is analyzed. The dependencies of the 4f-5d transitions of Ce3+ on the structure of the host compounds Sr2MgSi2O7, Ba2MgSi2O7 and BaMg2Si2O7 are discussed in detail. Then the thermal quenching channel is proposed based on the measurements of temperature dependent luminescence intensities and decay times of Ce3+ and Eu2+ in Sr2MgSi2O7, and the Ce3+ → Eu2+ energy transfer mechanism is understood by three luminescence dynamic models. In addition, Sr2MgSi2O7:Ce3+/Eu2+ samples are evaluated for the possibilities of X-ray detection applications using X-ray excited luminescence (XEL) spectroscopy, and it was found that they are not suitable.

Shining Transparent Displays with Stable Narrow-Band Blue-Emitting Phosphor in Layered Film.

Transparent displays (TDs) rendering "levitating" images on screen have appeared as an emerging technology toward augmented/mixed reality applications. However, the traditional phosphor design and screen construction have severely limited the TD performance owing to the lack of efficient narrow-band blue emitters and stable screen structure. Herein, the novel narrow-band (full width at half maximum: 32 nm) NaLi3 SiO4 :Eu2+ phosphor with a peak at 467 nm as a key blue emitter is explored, and it is sandwiched in layered film as a unique screen design. The devised screen features decent transparency, high emission color purity, and good reliability, and the TD prototype renders "floating" static images and vivid animation with broad viewing angle (15°-165°) and large color gamut (97% of National Television Standards Committee). Spectroscopic and microstructural characterizations reveal the TD superior performance originates from synergistic contributions of moderate crystal field effect (εc  ≈ 1.13 eV; εcfs  ≈ 1.60 eV), weak vibronic coupling (S ≈ 3; hω ≈ 285 cm-1 ), and limited thermal ionization of 5d electrons (Ea  ≈ 0.43 eV) for NaLi3 SiO4 :Eu2+ emission and layered architecture for screen film. These findings establish fundamental guidelines for narrow-band emitting materials design and shine light on superior TD innovative development.

Tunable Luminescence and Energy Transfer of Sr3B2O6:Ce3+, Sm3+ Phosphors with Potential Anti-Counterfeiting Applications.

Sm3+ and Ce3+ singly doped and Sm3+ and Ce3+ co-doped Sr3B2O6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm3+-doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm3+ ions. Upon 340 nm excitation, the Ce3+-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6H5/2 → 6P3/2 excitation line of Sm3+ and implies the possible energy transfer from Ce3+ to Sm3+. The spectral and decay measurements of the Ce3+ and Sm3+ co-doped samples are conducted and the Inokuti-Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce3+. Owing to the evident sensitization of the Sm3+ by the Ce3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.

Experimental and Theoretical Studies of the Site Occupancy and Luminescence of Ce3+ in LiSr4(BO3)3 for Potential X-ray Detecting Applications.

Ce3+-doped LiSr4(BO3)3 phosphors have been prepared by a high-temperature solid-state reaction method, and structural refinement of the host compound has been performed. The excitation and emission spectra in the vacuum ultraviolet-ultraviolet-visible range at cryogenic temperatures reveal that Ce3+ ions preferentially occupy eight-coordinated Sr2+ sites in LiSr4(BO3)3. Such experimental attribution is well corroborated by the calculated 4f-5d transition energies and defect formation energies of Ce3+ ions at two distinct Sr2+ sites in the first-principles framework. In addition, the doping concentration-dependent luminescence and the temperature-dependent luminescence are systematically investigated by luminescence intensity and lifetime measurements, respectively. This shows that concentration quenching does not occur in the investigated doping range, but inhomogeneous broadening exists in the concentrated samples. With the estimated thermal quenching activation energy, the discussions on the thermal quenching mechanisms suggest that the thermal-ionization process of the 5d electron is a dominant channel for thermal quenching of Ce3+ luminescence, despite the fact that thermally activated concentration quenching cannot be excluded for the highly doped samples. Finally, the X-ray excited luminescence measurement demonstrates the promising applications of the phosphors in X-ray detection.

Site Occupancies, Electron-Vibration Interaction and Energy Transfer of CaMgSi2 O6 : Eu2+ , Mn2+ Phosphors for Potential Temperature-Sensing and Anti-counterfeiting Applications.

Eu2+ -, Mn2+ - and Eu2+ -Mn2+ -doped CaMgSi2 O6 phosphors have been prepared by a high-temperature solid-state reaction. Systematic investigation of the concentration- and temperature-dependent luminescence of Mn2+ showed that Mn2+ ions occupy two distinct sites in CaMgSi2 O6 . Electron-vibration interaction (EVI) analyses of Mn2+ ions revealed Huang-Rhys factors of 4.73 and 2.82 as well as effective phonon energies of 313 and 383 cm-1 for the two sites. Eu2+ -Mn2+ energy transfer is also discussed, and its efficiency is estimated by lifetime and luminescence spectra. The different thermal quenching behaviours of Eu2+ and Mn2+ , the distinct emission colours of Eu2+ (blue, band peak at ∼451 nm) and Mn2+ (yellow-red range, band peaks at ∼583 and 693 nm) endow the co-doped samples with potential applications in luminescence thermometry and temperature-/excitation wavelength-responsive dual anti-counterfeiting.

Structure, luminescence of Eu2+ and Eu3+ in CaMgSi2O6 and their co-existence for the excitation-wavelength/temperature driven colour evolution.

Luminescent materials with controllable colour evolution features are demanded for the development of multi-level anti-counterfeiting technologies. Here we report the structural and luminescence properties of CaMgSi2O6:Ln (Ln = Eu2+, Eu3+, Eu2+/3+) samples in detail and reveal their excitation-wavelength/temperature driven colour evolution characteristics. By tuning either the excitation-wavelength (276, 304, 343, 394 nm) or temperature (in the 330-505 K range), the designed samples with co-existing Eu2+/Eu3+ ions can achieve diverse and controllable colour evolution from red, to pink, purple and blue. This shows their potential application in anti-counterfeiting with the help of sophisticated pattern design. In addition, the underlying mechanism of the Stokes shift of the Eu2+ emission and valence stability of both Eu2+/Eu3+ ions in CaMgSi2O6 are also studied in depth. These results are valuable for designing colour-controllable luminescent materials based on the co-existence of the Eu2+/Eu3+ ions for anti-counterfeiting applications.

Site Occupancies, VUV-UV-vis Photoluminescence, and X-ray Radioluminescence of Eu2+-Doped RbBaPO4.

RbBaPO4:Eu2+ phosphors have been prepared by a high-temperature solid-state reaction method, and the structure was determined by Rietveld refinement based on powder X-ray diffraction (P-XRD) data. Their VUV-UV-vis photoluminescence properties are systematically investigated with three objectives: (1) based on low-temperature spectra, we clarify the site occupancies of Eu2+, and demonstrate that the doublet emission bands at ∼406 and ∼431 nm originate from Eu2+ in Ba2+ [Eu2+(I)] and Rb+ [Eu2+(II)] sites, respectively; (2) an electron-vibrational interaction (EVI) analysis is conducted to estimate the Huang-Rhys factors, the zero-phonon lines (ZPLs) and the Stokes shifts of Eu2+ in Rb+ and Ba2+ sites; (3) the studies on luminescence decay of Eu2+(I) reveal that dipole-dipole interaction is mainly responsible for the energy transfer from Eu2+(I) to Eu2+(II), and the energy migration between Eu2+(I) is weak. Finally, the X-ray excited luminescence (XEL) spectrum indicates that the light yield of the sample RbBa0.995Eu0.005PO4 is ∼17 700 ph/MeV, showing its potential application in X-ray detecting.

Host Differential Sensitization toward Color/Lifetime-Tuned Lanthanide Coordination Polymers for Optical Multiplexing.

Optical multiplexing based on luminescent materials with tunable color/lifetime has potential applications in information storage and security. However, the available tunable luminescent materials reported so far still suffer from several drawbacks of low efficiency or poor stability, thus restraining their further applications. Herein, we demonstrate a strategy to develop efficient and stable lanthanide coordination polymers (LCPs) with tunable luminescence as a new option for optical multiplexing. Their multicolor emission from green to red and naked-eye-sensitive green emission with tunable lifetime (from ca. 300 to ca. 600 µs) can be controlled by host differential sensitization and energy transfer between lanthanide ions. The quantum efficiencies of developed samples range from around 20 % to 46 % and the luminescence intensity/lifetime appear quite stable in polar solvents up to ten weeks. Furthermore, with the aid of inkjet printing and concepts of luminescence lifetime imaging and time-gated imaging, we illustrate their promising applications of information storage and security in spatial and temporal domains.

The stability of coordination polyhedrons and distribution of europium ions in Ca6BaP4O17.

In this work, the coordination polyhedron stabilities and distributions of europium ions in Ca6BaP4O17 (CBPO) luminescent materials are investigated. The density functional theory (DFT)-based first principles calculation results show that the PO4 tetrahedrons can tilt in the structure, which leads to the atomic distortion of O13 and O12 in CBPO and the Eu2+/Eu3+-doped systems. The energy scale of about ∼0.1 eV suggests that stabilities of coordination polyhedrons are easily influenced by dynamic factors. The atomic distortion and vacancy of work as charge compensations in CBPO:Eu3+, and three lattice sites of europium are extracted and summarized. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) confirm that Eu3+ can occupy the Ca1, Ca2 and Ba sites of CBPO. The combination of first principles calculation and X-ray absorption fine structure (XAFS) provides more information about microstructures of luminescent materials.

Impacts of 5d electron binding energy and electron-phonon coupling on luminescence of Ce3+ in Li6Y(BO3)3.

In this work, the crystal structure and electronic structure as well as the synchrotron radiation vacuum ultraviolet-ultraviolet-visible (VUV-UV-vis) luminescence properties of Li6Y(BO3)3 (LYBO):Ce3+ phosphors were investigated in detail. The Rietveld refinement and DFT calculation reveal the P21/c monoclinic crystal phase and the direct band gap of the LYBO compound, respectively. Only one kind of Ce3+ 4f-5d transition is resolved in terms of the low temperature VUV-UV excitation, UV-vis emission spectra and luminescence decay curves. Furthermore, by constructing the vacuum referred binding energy (VRBE) scheme and applying the frequency-degenerate vibrational model, the impacts of 5d electron binding energy and electron-phonon coupling on luminescence of Ce3+ in LYBO are analysed. The results show that the Ce3+ emission in LYBO possesses a moderate intrinsic thermal stability. With the increase in concentration, the thermal stability of the emission gets worse due to the possible thermally-activated concentration quenching. In addition, the simulation of Ce3+ emission profile at low temperature reveals that the 4f-5d electronic transitions of Ce3+ ions can be treated to couple with one frequency-degenerate vibrational mode having the effective phonon energy of ∼257 cm-1 with the corresponding Huang-Rhys parameter of ∼6, which indicates a strong electron-phonon interaction of Ce3+ luminescence in the Li6Y(BO3)3 host. Finally, the X-ray excited luminescence spectrum of the LYBO:5%Ce3+ phosphor is measured to check the potential scintillator applications.

Luminescence and Cationic-Size-Driven Site Selection of Eu3+ and Ce3+ Ions in Ca8Mg(SiO4)4Cl2.

In this work, the morphology, composition, crystal, and electronic structure of Ca8Mg(SiO4)4Cl2 (CMSOC) prepared by a high-temperature solid-state reaction technique are characterized first. To investigate the site occupancies of Eu3+ and Ce3+ in CMSOC, the emission spectra under well-chosen wavelength excitations and the corresponding excitation spectra by monitoring of the specific wavelength emissions are measured in detail for singly doped samples with different concentrations. Two kinds of Eu3+ or Ce3+ luminescence spectra are found. On the basis of the chemical environments of two Ca2+ sites and dielectric chemical bond theory, the sites of these two kinds of Eu3+ and Ce3+ luminescence spectra are respectively assigned. Because energy transfer between the two types of luminescent centers, concentration-dependent emission-wavelength shifting, and luminescence concentration quenching are negligible, the emission spectra of Eu3+ and Ce3+ give us a hint of their occupation preferences on two Ca2+ sites. The results indicate that, with an increase of the doping concentration, the Eu3+ ions with smaller cationic size show an occupation preference on the smaller Ca2+(1) sites, but the Ce3+ ions with larger cationic size are inclined to enter the larger Ca2+(2) sites. These opposite occupation preferences of Eu3+ and Ce3+ in CMSOC are thought to be the cationic-size-driven site selection.

Concentration-Driven Selectivity of Energy Transfer Channels and Color Tunability in Ba3La(PO4)3:Tb3+, Sm3+ for Warm White LEDs.

Here, we report the large-scale emission color tunability in Ba3La(PO4)3:Tb3+, Sm3+ (BLPO:TS) system based on the detailed discussion on the concentration-driven selectivity of energy transfer (ET) channels from Tb3+ to Sm3+. It is induced by the concentration-dependent 5D3 and 5D4 emissions of Tb3+ and the different interaction mechanisms of ET from Tb3+ to Sm3+ via 5D3 and 5D4 channels. In the diluted Tb3+ scenario, the red emission of Sm3+ is efficiently sensitized via the 5D3 channel, while in the concentrated Tb3+ case, the contribution of 5D4 channel is dominant. Therefore, by simply adjusting the doping concentrations of Tb3+ and Sm3+, the emission color of the phosphors can be tuned from green to red. In view of the phosphors with red emissions are critical to the warm white light-emitting diodes (WLEDs), an orange-red Tb3+, Sm3+ coactivated phosphor Ba3La0.90Tb0.05Sm0.05(PO4)3 (BLPO:5T5S) with good thermal and chromaticity stability and internal quantum efficiency ∼67% is developed in the system. Then, a near-UV WLED (CCT ≈ 4500 K, Ra ≈ 81) is fabricated using this phosphor. These findings not only indicate that the orange-red phosphor BLPO:5T5S is available for near-UV warm white LEDs but also deliver new insights into the ET processes in Tb3+ and Sm3+ activated phosphors.

Reversible immobilization of laccase onto metal-ion-chelated magnetic microspheres for bisphenol A removal.

Increasing attention has been given to nanobiocatalysis for commercial applications. In this study, laccase was reversibly immobilized onto Cu(ΙΙ)- and Mn(ΙΙ)-chelated magnetic microspheres and successfully applied to remove bisphenol A (BPA) from water. The results indicated that the loading of laccase onto the metal-ion-chelated magnetic microspheres was approximately 100mg/g. After five successive adsorption-desorption cycles, the laccase adsorption capacities did not change. In comparison with free laccase, the thermal and storage stabilities of immobilized laccase were significantly improved. Immobilized laccase exhibited a high removal efficiency for BPA under the combined actions of biodegradation and adsorption. Greater than 85% of BPA was removed under optimum conditions. The effects of various factors on the BPA removal efficiency of immobilized laccase were analysed. The results showed that metal-ion-chelated magnetic microspheres have great potential for industrial applications.

Association of variants on ADIPOQ and AdipoR1 and the prognosis of gastric cancer patients after gastrectomy treatment.

Adiponectin is a protein hormone secreted exclusively by adipocytes and it is responsible for insulin sensitization in the human body. Deregulation of adiponectin and its downstream signaling pathway genes have been found to be involved in the gastric cancer carcinogenesis; however, whether the variants on adiponectin (ADIPOQ) and adiponectin receptor 1 (ADIPOR1) affect the prognosis of gastric cancer patients are still unknown. Here we have recruited 455 gastric cancer patients, who have received the gastrectomy treatment to evaluate the prognostic effects of variants on ADIPOQ (rs266729 and rs822395) and AdipoR1 (rs12733285 and rs1342387) for the gastric cancer patients. No significant association between the four variants and the overall survival of the gastric cancer patients was found. However, for those patients without a previous history of alcohol drinking, the rs266729 GG/CG genotype carriers showed a significantly decreased gastric cancer mortality compared to homogeneity CC patients (HR 0.74, 95 % CI 0.56-0.97; p = 0.032) after adjustment for variants age, sex, smoking status, tumor stage, tumor location and post-surgery chemotherapy. No significant association between the variant rs266729 genotypes and overall survival for the gastric cancer patients with an alcohol drinking habit. These data suggested that the variant rs266729 was an independent prognostic factor for the never drinking gastric cancer patients who received surgical treatment.

Associations between variants on ADIPOQ and ADIPOR1 with colorectal cancer risk: a Chinese case-control study and updated meta-analysis.

BACKGROUND: Epidemiological studies have suggested that variants on adiponectin (ADIPOQ) and its receptor ADIPOR1 (adiponectin receptor 1) are associated with colorectal cancer (CRC) risk; however, the results were inconclusive. The aim of the study was to evaluate the associations between the variants on ADIPOQ and ADIPOR1 and the CRC risk with a hospital-based case-control study in the Chinese population along with meta-analysis of available epidemiological studies. METHODS: With a hospital-based case-control study of 341 cases and 727 controls, the associations between the common variants on ADIPOQ (rs266729, rs822395, rs2241766 and rs1501299) and ADIPOR1 (rs1342387 and rs12733285) and CRC susceptibility were evaluated. Meta-analysis of the published epidemiological studies was performed to investigate the associations between the variants and CRC risk. RESULTS: For the population study, we found that variant rs1342387 of ADIPOR1 was associated with a reduced risk for CRC [adjusted odds ratio (OR) = 0.74, 95% confidential intervals (95% CI) = 0.57-0.97; CT/TT vs. CC]. The meta-analysis also suggested a significant association for rs1342387 and CRC risk; the pooled OR was 0.79 (95% CI = 0.66-0.95) for the CT/TT carriers compared to CC homozygotes under the random-effects model (Q = 8.06, df = 4, P = 0.089; I(2) = 50.4%). The case-control study found no significant association for variants rs266729, rs822395, rs2241766, and rs1501299 on ADIPOQ or variant rs12733285 on ADIPOR1 and CRC susceptibility, which were consistent with results from the meta-analysis studies. CONCLUSIONS: These data suggested that variant rs1342387 on ADIPOR1 may be a novel CRC susceptibility factor.

Selenium and colorectal adenomas risk: a meta-analysis.

Selenium, as an important component of some antioxidants, has been suggested to have protective effects against colorectal adenomas. This meta-analysis examined the association between selenium level in blood and risk of colorectal adenomas. Data from 7 studies (3 cross-sectional studies, 3 case-control studies, 1 nested case-control study) published before December 2011 was included in this meta-analysis. Fixed and random-effects model was explored to calculate odds ratio (OR) and 95% confidence intervals (CI). Heterogeneity among studies was measured using Cochrane Q-test together with the I (2) statistic. There was a significant inverse correlation between selenium level and colorectal adenomas risk according to fixed-effects model. The overall OR of highest selenium level to lowest for colorectal adenomas is 0.67 (95% CI: 0.55-0.81). Heterogeneity was moderate among the pooled studies (P = 0.05 for the Q test, I (2) = 48%). These results suggested a protective effect of selenium for colorectal adenomas. Some factors, such as age, gender, smoking, and characteristics of the adenomas need to be further considered within the association between selenium levels and risk of colorectal adenomas.