Ba2LaF7 Nanocrystals Research Articles

The effect of Al3+ ions on the self-reduction process of Yb3+ to Yb2+ ions and optical properties of Nd3+/Ybn+ (n = 3, 2) co-doped transparent silicate glass-ceramics containing Ba2LaF7 nanocrystals and Ag nanoparticles

The effect of Al3+ ions in the AlF3 compound on the reduction process of Yb3+ to Yb2+ ions in SiO2–AlF3–BaF2–TiO2–LaF3 (SABTL) transparent silicate glass-ceramics was investigated. The valence states of the elements in the raw materials mixture existing in the transparent silicate glass-ceramics were determined using X-ray photoelectron spectroscopy (XPS) spectrum analysis. The transparent silicate glass-ceramics SABTL containing Ba2LaF7 nanocrystals and Silver (Ag) nanoparticles (AgNPs) were identified through X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) image. With the increase of Al3+ ions molar concentration, the self-reduction process of Yb3+ to Yb2+ ions was enhanced and thus significantly affected the optical bandgaps and upconversion (UC)-, near-infrared (NIR)- emissions of Nd3+/Yb3+ co-doped in SABTL containing Ba2LaF7 nanocrystals and AgNPs under excitation of 980 nm laser diode (LD). The optimal molar concentration ratio between SiO2 and AlF3 compound was determined such that the NIR bandwidth flatness of Nd3+/Yb3+ co-doped in SABTL containing Ba2LaF7 nanocrystals in the wavelength range of 1000–1200 nm was the flattest. In addition, the CIE 1931 (x, y) color coordinates for UC- and visible (VIS)- emissions of Nd3+/Yb3+ co-doped SABTL-0.5Nd2Yb-xAg (x = 0, 2, 3, 4, and 5) glass-ceramics samples are also calculated and determined the color region for light-emitting diode (LED) application.

Multifunctional rare earth ions-doped Ba2LaF7 nanocrystals for simultaneous temperature sensing and photothermal therapy

As an urgent problem, cancer has boosted the development and application of many treatment technologies in biomedicine. Photothermal therapy with precise control for tumors has gained more and more attention as a promising technology in biomedical fields. In this work, rare earth ions-doped Ba2LaF7 nanocrystals have been successfully developed by the high-temperature solid-phase method as the core material in a multi-functional system. Optical temperature measurement based on fluorescence intensity ratio improves sensitivity by widely separating Er3+ and Nd3+ emission bands. Meanwhile, the relative sensitivity increases with increasing temperature. From the comparison between the fitting curve and the actual temperature, it can be concluded that the nanocrystals have a good photothermal response to the laser pumping power and can even be used for photothermal imaging. On this basis, to study its optical measurement and photothermal conversion performance, we made a multifunctional system acting on biological tissues. The results suggest that the developed material has a potential application in bio-targeted photothermal therapy.

High‐Resolution X‐Ray Time‐Lapse Imaging from Fluoride Nanocrystals Embedded in Glass Matrix

AbstractA latent image of the target after the X‐ray irradiation induced via a 980 nm laser or thermal excitation provides great potentials for healthcare diagnostics and nondestructive inspection. Taking the advantage of X‐ray time‐lapse imaging, simplified facilities and visualized information can be achieved. However, information acquisition with higher resolution, combined with long‐term storage for the corresponding X‐ray images remains a challenge. Herein, Tb3+‐doped Ba2LaF7 nanocrystals (NCs) grown in situ and dispersed uniformly in an amorphous glass matrix is explored, which performs a fascinating X‐ray response for imaging with an impressive spatial resolution reaching 20.0 lp mm−1. Moreover, the as‐developed corresponding scintillators exhibit excellent optical storage capability upon X‐ray irradiation for the constructed deep traps, and a controllable release of the captured carriers induced by thermal disturbance, and 980 nm laser stimulation can be achieved. Notably, the imaging resolution is well preserved to be 20.0 lp mm−1 even recorded after 10 days. The as‐explored Ba2LaF7:Tb3+ NCs embedded within an amorphous matrix realize a feasible approach for a simplified X‐ray imaging system with high‐resolution information production.

Enhanced red upconversion emission and energy transfer of Tm3+/Cr3+/Yb3+ tri-doped transparent fluorosilicate glass-ceramics

In this paper, the upconversion (UC) emission of Tm3+/Cr3+/Yb3+ tri-doped in SiO2–AlF3–BaF2–La2O3 transparent fluorosilicate glass-ceramics (SGC) containing Ba2LaF7 nanocrystals were investigated. The enhancement of red UC emission of Tm3+/Cr3+/Yb3+ tri-doped in SiO2–AlF3–BaF2–La2O3 transparent SGC were also investigated. Through the energy transfer processes between Cr3+ and Tm3+, and the combination of Cr3+-Tm3+ led to the red UC emission intensity of Tm3+/Cr3+/Yb3+ tri-doped transparent SGC bands centered at ~806 and ~858 nm has been significantly enhanced. The CIE chromaticity coordinates for UC emission of Tm3+/Cr3+/Yb3+ tri-doped in SGC-0.2Tm1Cr2Yb transparent SGC sample is calculated (x = 0.704; y = 0.296) and the UC emission of Tm3+/Cr3+/Yb3+ tri-doped in SiO2–AlF3–BaF2–La2O3 transparent SGC has been identified in red color region of CIE chromaticity coordinates. In addition, the ET processes between Cr3+ and Tm3+ are also proposed and discussed.

Morphology evolution, energy transfer and multicolor luminescence of lanthanide-doped Ba2LaF7 nanocrystals via a one-step hydrothermal synthesis

Lanthanide-doped Ba2LaF7 nanocrystals were successfully synthesized via a one-step hydrothermal method.

Study of Crystallization and Coalescence of Nanocrystals in Amorphous Glass at High Temperature.

Amorphous fluoride glass is used as the reaction chamber (i.e., solid cell) to grow Ba2LaF7 (BLF) nanocrystals at elevation temperatures (i.e., 300-500 °C) so that in situ real-time crystallization and coalescence of BLF nanocrystals can be observed. Due to the inherent advantages of the liquid-like solid medium, high temporal and spatial resolution transmission electron microscopy images can be obtained. Hence, we reveal that the twinned and quadruplet BLF nanocrystals are formed at low temperature (≤430 °C) and the unification of two nanocrystals via the two pathways (i.e., migration with and without rotation) to a single defect-free BLF nanocrystal is favored at high temperature (≥470 °C).

Optical thermometry based on up-conversion emission behavior of Ba2LaF7 nano-crystals embedded in glass matrix

Ba2LaF7:Yb3+, Er3+ nano-crystals embedded in a transparent aluminium silicate glass matrix was successfully fabricated by a traditional high temperature melt-quenching technique and the subsequently heat treatment process. The formation of Ba2LaF7 nano-crystals was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The enhancement of the up-conversion (UC) emission intensity of Er3+ in the glass ceramic (GC) was attributed to the crystallization of Ba2LaF7 nano-crystals with a low phonon energy compared to the precursor glass counterpart. The temperature-depended fluorescence intensity ratio (FIR) of thermally coupled emitting states (4S3/2, 2H11/2) behavior of Er3+ was studied under the excitation of 980nm. The maximum thermal sensitivity was approximately 0.43% K−1 at 298K. Besides, the temperature of Ba2LaF7 GC rose from 336 to 407K, when the laser pump power density increased from 1.01 to 9.59W/cm2. Moreover, the excellent thermal stability of the sample for temperature detection in the range of 398-573K was proved. The results indicate that the Yb3+/Er3+ co-doped Ba2LaF7 GCs could be potential candidates for integrating heaters and thermometers.

Adjustable multicolor up-energy conversion in light-luminesce in Tb3+/Tm3+/Yb3+ co-doped oxyfluorifFde glass-ceramics containing Ba2LaF7 nanocrystals

Transparent oxyfluoride glasses with highly efficient up-energy conversion (UEC) luminescence were developed in the 45SiO2-15Al2O3-12Na2CO3-21BaF2-7LaF3-xTbF3-yTmF3-zYbF3 composition (in mol%), and structural investigation by X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of face-centered cubic Ba2LaF7 nanocrystals. The colors of UEC luminescences could be tuned easily by adjusting the concentration of doped rare earth ions and the excitation power of laser simultaneously. The relationship between the emission intensity of Tb3+/Tm3+/Yb3+ co-doped oxyfluoride glass-ceramics and the excitation pump power revealed that three-photon and two-photon absorptions predominated in the conversion process from the infrared into blue and red luminescences, respectively. A novel UEC mechanism of red emission from Tm3+ was proposed, energy transfers from Yb3+ to Tm3+ and Tb3+ and from Tm3+ to Tb3+ were evidenced. The possible mechanism responsible for the color variation of UEC in Tb3+/Tm3+/Yb3+ co-doped was discussed.

Surface Plasmon Resonance Enhanced Spontaneous Upconversion and Stimulated Emissions in Glass Ceramics Containing Ba2LaF7 Nanocrystals

Glass ceramics containing Yb3+, Er3+ codoped Ba2LaF7 nanocrystals were fabricated via melt quenching method and the subsequent heating treatment. The formation of Ba2LaF7 nanocrystals in the glass ceramics was confirmed by X-ray diffraction (XRD) and transmission electron microscope (TEM). The spontaneous upconversion (UC) emission and the stimulated counterpart as a random lasing action of Er3+, which were related to the characteristic transitions of Er3+ ions, were achieved in the Yb3+, Er3+-doped Ba2LaF7 nanocrystals embedded glass ceramic hybrid. Furthermore, the absorption spectra verified the surface plasmon resonance (SPR) band of Ag, which precipitated from the matrix glasses as Ag nanoparticles (NPs). By incorporating Ag NPs in the glass ceramic hybrid, spontaneous UC emission intensity of Er3+ in visible region was significantly enhanced, while the threshold of the random lasing was decreased from 480 to 350 nJ/cm2.

Effects of Li+ ions on the enhancement of up-conversion emission in Ho3+-Yb3+ co-doped transparent glass–ceramics containing Ba2LaF7 nanocrystals

The up-conversion (UC) emission of Ho3+-Yb3+ and Li+ co-doped transparent glass ceramics 45SiO2-15Al2O3-12Na2CO3-21BaF2-7LaF3-0.2HoF3-1YbF3-xLi2CO3 (x = 0, 0.5, 1, 2, 4 and 6 mol%) containing Ba2LaF7 nanocrystals were investigated. These glass ceramics samples were prepared using the conventional quenching techniques. The Ba2LaF7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction (XRD). Compared with the glass ceramics sample without Li+, the UC emission intensity of glass ceramics samples with Li+ were enhanced. It can be proved that the Li+ can affect the enhancement up-conversion (UC) emission. Particularly, the green UC emission intensity band centered at 546 nm was strongly increased twice with the concentration of Li+ increasing up to 4 mol%. Through the comparison and analysis of the energy graph, it was shown that the 5F4/5S2→5I8 transition of Ho3+ ion obtained the green (546 nm) light. There are two weak fluorescences in the red (657 nm) region and near infrared (753 nm) region of spectrum, which is the 5F4/5S2→5I7 and 5F5→5I8 transition of Ho3+. Therefore, the emission results showed that the incorporation of Li+ ions into the Ba2LaF7:Eu3+ lattice could induce a remarkable change of the emission intensity in red region (R = IED/IMD) with 393 nm excitation wavelength. It was indicated that the symmetry of the lattice was destroyed by Li+ in glass ceramics. The possible mechanism responsible for the enhancement of UC emission in Ho-Yb co-doped was discussed.

Near-Green-Emitting Tb3+-Doped Transparent Glass Ceramics Containing Ba2LaF7 Nanocrystals for Application in White Light-Emitting Diodes

Tb3+-activated transparent glass ceramics containing Ba2LaF7 were successfully synthesized by a conventional melt–quenching technique, and the glass ceramics displayed a near-green emission under near-ultraviolet excitation. Differential scanning calorimetry and X-ray diffraction were used to monitor the evolution and microstructural changes in the prepared glass specimens. The transparency levels of the glass ceramics remained high with increasing treatment temperatures from 640 to 690°C. Investigations on the luminescence properties of the glass ceramics revealed that Tb3+ ions were gradually incorporated into the precipitated fluoride crystalline phase. After heat treatment at 640°C for 2 h, major emission was observed at 543 nm owing to 5D4 → 7F5 transition of Tb3+ under 373-nm excitation. Current findings indicate that the prepared materials have potential as replacements to commonly employed green phosphors in white light-emitting diodes. Additionally, the decay lifetimes of Tb3+ ions at 543 nm under 373-nm excitation were studied.

Near-white light-emitting Dy3+-doped transparent glass ceramics containing Ba2LaF7 nanocrystals

Glass ceramics Ba2LaF7:xDy3+ are obtained through the conventional melt-quenching technique, and their luminescent properties are investigated. Under 350 nm excitation, the emission spectra consists of a strong blueyellow band as well as a weak red emission centered at 660 nm, which are attributed to the 4F9/2 \rightarrow 6H15/2, 4F9/2 \rightarrow 6H13/2 and 4F9/2 \rightarrow 6H11/2 transitions of the Dy3+ ion, respectively. The corresponding Commission Internationale de L’Eclairage (CIE) chromaticity coordinate for a sample of 2 mol.% Dy2O3 after being heat-treated at 690 oC is (0.313, 0.328). It is concluded that the formed materials may have the possibility of applications for white light-emitting diodes (LEDs).

Effect of Mn2+ ions on the enhancement red upconversion emission of Mn2+/Er3+/Yb3+ tri-doped in transparent glass-ceramics

Abstract The glass and glass-ceramics samples with composition of 50SiO2–10AlF3–(30−x)BaF2–5TiO2–3.95LaF3– xMnCO3–0.05ErF3–1YbF3 (in mol%, x=0, 0.5, 0.8, 1.0, and 1.2) were prepared using the conventional quenching techniques. The effects of Mn2+ ions on the enhancement red upconversion emission of Mn2+/Er3+/Yb3+ tri-doped transparent glass-ceramics under the changing of heat treatment temperatures and concentrations of Mn2+ ions were investigated. The structural investigation carried out by X-ray diffraction (XRD), and transmission electron microscopy evidenced the formation of cubic Ba2LaF7 nanocrystals. The efficiency upconversion emission of Mn2+/Er3+/Yb3+ tri-doped was observed in the glass-ceramics. The upconversion mechanism and energy transfer between Mn2+–Yb3+ dimer and Er3+ ions were investigated.

Energy transfer and upconversion emission of Er3+/Tb3+/Yb3+ co-doped transparent glass-ceramics containing Ba2LaF7 nanocrystals under heat treatment

Transparent glass-ceramics SiO2–AlF3–BaF2–TiO2–LaF3 (SABTL) containing Ba2LaF7 nanocrystals were successfully prepared by heat treatment process through conventional melting method. The crystal size in the glass-ceramics increased gradually under the changing of heat treatment temperatures and times, which was confirmed by the results of XRD, TEM measurements. The intensity of the blue, green and red upconversion luminescence around 490nm, 525nm, 546nm, 657nm which originate from the transitions 5D4→7FJ (J=6 and 5) of Tb3+ ions and (2H11/2, 4S3/2, 4F9/2)→4I15/2 transitions of Er3+ ions, respectively, were strongly observed after heat treatment under 980nm laser diode excitation. The intensity of upconversion luminescence was increased gradually with the increase of Yb3+ concentrations and reaches its maximum at 2.5mol%. The upconversion luminescence and energy transfer process between Tb3+, Yb3+ and Er3+ ions in the glass-ceramics were discussed.

Up-conversion of Er3+/Yb3+ co-doped transparent glass-ceramics containing Ba2LaF7 nanocrystals

The up-conversion of Er3+/Yb3+ co-doped transparent glass-ceramics 50SiO2-10AlF3-5TiO2-30BaF2-4LaF3-0.5ErF3-0.5YbF3 containing Ba2LaF7 nanocrystals under the changing of heat treatment temperature and time were investigated. The Ba2LaF7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction (XRD). The structural investigation carried out by XRD and transmission electron microscopy (TEM) evidenced the formation of cubic Ba2LaF7 nanocrystals with crystal size of about 14 nm. Comparing with the samples before heat treatment, the high efficiency up-conversion emission of Er3+/Yb3+ co-doped samples was observed in the glass-ceramics under 980 nm laser diode excitation. The increase in red emission intensity bands was stronger than the green bands when the crystal size increased. The mechanism for the up-conversion process in the glass-ceramics and the reasons for the increase of Er3+/Yb3+ co-doped up-conversion intensity after heat treatment were discussed.

Energy transfer and upconversion emission of Tm3 +/Tb3 +/Yb3 + co-doped transparent glass-ceramics containing Ba2LaF7 nanocrystals

The energy transfer and upconversion emission of Tm3+/Tb3+/Yb3+ co-doped transparent glass-ceramics 50SiO2–10AlF3–30BaF2–5TiO2–4LaF3 (SABTL) containing Ba2LaF7 nanocrystals under the changing of heat treatment temperatures and concentrations of Tm3+/Tb3+/Yb3+ ions were investigated. The structural investigation carried out by X-ray diffraction (XRD) and transmission electron microscopy evidenced the formation of cubic Ba2LaF7 nanocrystals. The efficiency upconversion emission of Tm3+/Tb3+/Yb3+ ions was observed in the glass-ceramics. The upconversion emission and energy transfer between Tm3+ and Tb3+ ions were investigated with the Yb3+ ions cooperatively upconversion emission, energy transfer between Tm3+ and Tb3+ ions.

Multicolor upconversion luminescence in monodispersed Ba2LaF7:Ln3+ (Ln=Yb/Er and Yb/Tm) nanocrystals

Lanthanide-doped Ba2LaF7 nanocrystals have been successfully synthesized via a modified liquid–solid-solution process. The yielded nanocrystals are determined to be pure cubic Ba2LaF7 phase and consist of nearly square-shaped nanoparticles with an average 14nm in size. The Yb3+/Er3+ (Tm3+) co-doped Ba2LaF7 nanocrystals emit bright multicolor upconversion luminescence following the excitation of 980nm laser diode. Proposed mechanisms for the emission were analyzed based on the emission spectra and their dependence on pumping power, as well as corresponding energy level diagram.

White light generation of glass ceramics containing Ba2LaF7:Eu2+, Tb3+ and Sm3+ nanocrystals

The Eu2+/Tb3+/Sm3+ co-doped oxyfluoride glass ceramics containing Ba2LaF7 nanocrystals are prepared in the reducing atmosphere. The X-ray diffraction results show that Eu2+, Tb3+ and Sm3+ ions are enriched into the precipitated Ba2LaF7 nanophase after the annealing process. It deduces efficient energy transfers from Eu2+ to Tb3+ and Sm3+ and intenses warm white luminescence of the glass ceramics. Comparing with the glass, the luminescence quantum yield of the glass ceramics is also enlarged by about 3 times. This demonstrates the potential white light-emitting diode application of the glass ceramics produced in this letter.

Lanthanide doping-facilitated growth of ultrasmall monodisperse Ba2LaF7 nanocrystals with excellent photoluminescence

Lanthanide doping not only works as sensitizer and activator, but also plays an important role to facilitate the growth of nanocrystal and to control the size, shape, and property of nanocrystals. Here, reported was the synthesis of monodisperse Ba2LaF7 nanocrystals with the size of sub-10nm through a solvothermal method. We found the dopants of Ho3+, Er3+, or Yb3+ facilitated the growth of Ba2LaF7 nanocrystals obviously to a certain size within a shorter reaction time. Similar phenomenon can also be observed in the synthesis of LaF3 nanocrystals. We find that Ln3+ (e.g., Ho3+, Er3+, or Yb3+) with smaller radius can reduce the nucleation energy and lead to heterogeneous nucleation, which favors the growth of Ba2LaF7 nanocrystals obviously. In addition, intense upconversion emission can be observed from Ln3+-doped Ba2LaF7 nanocrystals under the 980nm laser excitation, providing great potential application in biological imaging. Especially, Ba2LaF7:Yb/Er (20/1mol%) nanocrystals present more intense upconversion emission than α-NaYF4:Yb/Er (20/1mol%) nanocrystals under the same conditions.

Preparation Process and Upconversion Luminescence of Er3+-Doped Glass Ceramics Containing Ba2LaF7 Nanocrystals

The preparation process and upconversion luminescence of the Er(3+)-doped glass ceramics containing Ba(2)LaF(7) nanocrystals were investigated. The formation of Ba(2)LaF(7) nanocrystals in the glass ceramics was confirmed by X-ray diffraction. Er(3+)-doped glass ceramics containing Ba(2)LaF(7) nanocrystals exhibited highly efficient upconversion luminescence in comparison with glasses. With the increase of heat treatment temperature the upconversion luminescence intensity increased gradually. The composition of glasses was also found to have significant influence on the crystallization process of glass ceramics. The mixture of Ba(2)LaF(7) and La(2)O(3) nanocrystals and the mixture of La(2)F(3) and La(2)O(3) nanocrystals in the glass ceramics could be obtained by controlling different compositions of glasses. The upconversion luminescence intensity also varied significantly with different nanocrystals in the glass ceramics.