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Orthogonal three‐color luminescence materials designed based on lanthanide doping multi‐component nano‐systems have exhibited great potential in volume display technology. Previous studies devoted to integrate the different color emitters within a single core‐shell nanoparticle, which suffers complexity in synthesis and difficulty in repeatability. In this work, an alternative is proposed. Three kinds of upconversion nanocrystals (UCNCs) with relatively simple configurations are prepared separately. Each kind of nanocrystals takes charge of emit a specific color upon one particular excitation (i.e., 808, 980, and 1540 nm pumps). Luminescent property of the mixture containing these nanocrystals are investigated. Excitation wavelength driven orthogonal three‐color luminescence property is found in this mixture. With the combination excitation, the emission color can be modulated, covering a gamut with its aera of 110% sRGB, superior to the previous reports. In addition, a quantized strategy to evaluate the orthogonality of the luminescence is also proposed, which will be useful for the further investigation and development of remote‐type controlled luminescent materials. Finally, the demonstration of colored 3D display application is conducted and presented in this work. [ABSTRACT FROM AUTHOR]

Particle velocimetry based on the temporal feature of upconversion luminescent nanocrystals is a newly-raising fluid velocimetry. Exploiting the availability to low flow rate fluid and exempting redundance external calibration (achieving once calibration for all) are highly expected and challenging. Herein, an engineered core-shell nano-probe, NaYF4:Yb/Ho/Ce@NaGdF4, was proposed, in which the Ce3+ ions were utilized to manipulate the upconversion dynamic of Ho3+. Through optimization, a superior sensitive against low-speed flow is achieved, and the external calibrations before each operation can be avoided. Application demonstrations were conducted on a fluid circulation system with controllable flow rate. The fluid velocity was monitored successfully, no matter it is permanent, or cyclically variating (imitating the in vivo arterial blood). Moreover, this velocimetric route is competent in spatial scanning for handling the spatially inhomogeneous velocity field. Such sensing nanomaterial and fluid velocimetric method exhibit promising application potential in human blood velocimetry, industrial control, or environmental monitoring. [ABSTRACT FROM AUTHOR]

Red (Ho3+:5F5→5I8), green (Ho3+:5S2,5F4→5I8), and blue (Tm3+:1D2→3F4 and 1G4→3H6) upconversion emissions were simultaneously generated in the transparent glass ceramics containing Nd3+/Yb3+/Tm3+/Ho3+:β-YF3 nanocrystals under 796 nm excitation. It was experimentally evidenced that Yb3+ ions acted as the bridging centers to prompt energy transfer from Nd3+ to Tm3+ and Ho3+. With appropriately optimizing the contents and relative ratios of the doped rare earth species, luminescence of various colors, including bright white light, was easily tuned in the glass ceramics. The related upconversion mechanisms were proposed. [ABSTRACT FROM AUTHOR]

A transparent SiO2–Al2O3–LiF–YF3 glass ceramic doped with Nd3+ was fabricated by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscope results demonstrated that orthorhombic β-YF3 nanocrystals with a mean size of 23 nm were homogeneously precipitated among the glass matrix. Confirmed by the energy dispersive x-ray spectroscopy measurements, the crystal-like absorption and emission of Nd3+ indicated the partition of Nd3+ into YF3 nanocrystals in the glass ceramic. Detailed characterizations of the Stark components of the 4I9/2, 4I11/2, and 4I13/2 manifolds were performed using the low temperature fluorescence spectra for 4F3/2→4I9/2, 4F3/2→4I11/2, and 4F3/2→4I13/2 transitions of Nd3+ in the glass ceramic. The stimulated emission cross sections of the 4F3/2→4I11/2 intermanifold transition and the 4F3/2(R1)→4I11/2(Y1) inter-Stark transition were determined to be 7.24×10-20 and 11.55×10-20 cm2, respectively, being preferable to those of Nd3+-doped laser glasses and glass ceramic embedding (Pb,Cd)F2 nanocrystals. [ABSTRACT FROM AUTHOR]

Transparent SiO2-Al2O3-NaF-YF3 glass ceramics co-doped with Er3+ and Tm3+ were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy experiments revealed that β-YF3 nanocrystals incorporated with Er3+ and Tm3+ were precipitated homogeneously among the oxide glass matrix. An integrated broad near-infrared emission band in the wavelength region of 1300-1700 nm, consisting of Tm3+ emissions around 1472 nm (3H4→3F4) and 1626 nm (3F4→3H6), and Er3+ emission around 1543 nm (4I13/2→4I15/2), was obtained under 792 nm laser excitation. The full width at half maximum of this integrated band increased with the increasing of [Tm]/[Er] ratio, and it reached as large as 175 nm for the 0.1 mol% Er3+ and 0.8 mol% Tm3+ co-doped sample. The energy transfers between Er3+ and Tm3+ were proposed to play an important role in tailoring the emission bandwidth of the sample. [ABSTRACT FROM AUTHOR]

Abstract Lanthanide-doped transparent bulk glass ceramics containing cubic KGd 3 F 10 nanocrystals were successfully fabricated via self-crystallization and subsequent heat-treatment. Elemental mapping and Eu3+ optical spectroscopy evidenced the incorporation of lanthanide dopants into low-phonon-energy KGd 3 F 10 crystalline lattice. As a consequence, bright red(green) photoluminescence was achieved for the Ce/Eu(Tb) co-doped glass ceramics via energy transfer of Ce3+→Gd3+ →Eu3+(Tb3+), and intense tunable upconversion emissions were realized for the Yb/Ln (Ln = Er, Ho, Tm) co-doped glass ceramics via a multi-photon absorption process. Furthermore, temperature-dependent optical performance of Yb/Er and Yb/Tm co-doped glass ceramics was systematically studied to explore their possible application as optical thermometric media. Impressively, fluorescence intensity ratios of Er3+2H 11/2 /4S 3/2 thermally coupled states as well as Tm3+3F 2,3 /1G 4 non-thermally coupled ones were evidenced to be applicable as temperature probes. Graphical abstract Image 1 Highlights • Self-crystallization glass ceramics containing KGd 3 F 10 nanocrystals were fabricated. • Lanthanide activators were evidenced to incorporate into KGd 3 F 10 crystals. • Energy transfers of Ce→Gd→Eu(Tb) in glass ceramics contributed to multi-color emissions. • The glass ceramics showed promising application in upconversion temperature sensors. [ABSTRACT FROM AUTHOR]

The precipitation of monoclinic Na 3 ScF 6 nanocrystals from aluminosilicate glass with specially designed compositions of SiO 2 -Al 2 O 3 -Na 2 O-NaF-ScF 3 -YbF 3 was achieved for the first time. Impressively, competitive nanocrystallization of cubic NaYbF 4 and monoclinic Na 3 ScF 6 has been evidenced to be dependent on Na + content and F/Na ratio in glass. Adopting Er 3+ and Eu 3+ dopants as structural probes, optical spectroscopic analyses verified that these emissive centers preferred to partition into NaYbF 4 nanocrystals rather than Na 3 ScF 6 ones. [ABSTRACT FROM AUTHOR]

Yb 3+ /Er 3+ /Tm 3+ doped transparent glass ceramic containing orthorhombic YF 3 nanoparticles was successfully synthesized by a melt-quenching method. After glass crystallization, tremendously enhanced (about 5000 times) upconversion luminescence, obvious Start-splitting of emission bands as well as long upconversion lifetimes of Er 3+ /Tm 3+ confirmed the incorporation of lanthanide activators into precipitated YF 3 crystalline environment with low phonon energy. Furthermore, temperature-dependent upconversion luminescence behaviors of glass ceramic were systematically investigated to explore its possible application as optical thermometric medium. Impressively, both fluorescence intensity ratio of Er 3+ : 2 H 11/2 → 4 I 15/2 transition to Er 3+ : 4 S 3/2 → 4 I 15/2 one and fluorescence intensity ratio of Tm 3+ : 3 F 2,3 → 3 H 6 transition to the combined Tm 3+ : 1 G 4 → 3 F 4 /Er 3+ : 4 F 9/2 → 4 I 15/2 ones were demonstrated to be applicable as temperature probes, enabling dual-modal temperature sensing. Finally, the thermal effect induced by the irradiation of 980 nm laser was found to be negligible in the glass ceramic sample, being beneficial to gain intense and precise probing signal and detect temperature accurately. [ABSTRACT FROM AUTHOR]

In upconversion nanocrystals where Er3+ acts as the activator, concentration quenching will easily occur when the content of Er3+ is high (generally ＞5mol%), and the Er3+ spatial distribution which is a key factor affecting the concentration quenching is an important issue that must be considered. Herein, we selected Yb:NaErF4 as a light-emitting layer and investigated its upconversion performance and temperature sensing behaviors in two kinds of core–shell nanoarchitectures. Yb3+ and Er3+ activators were distributed in a three-dimensional sphere and two-dimensional thin layer in Yb:NaErF4@Yb/Nd:NaYF4@NaGdF4 and NaGdF4@Yb:NaErF4@Yb/Nd:NaYF4@NaGdF4 core–shell nanocrystals, respectively. The difference in Er3+ spatial distribution in the core–shell structure resulted in significant modification of red-to-green ratios and decay behaviors upon excitation at 376 nm, 808 nm, 980 nm and 1532 nm, and the related mechanisms were systematically investigated. In addition, the spatial distribution of Er3+ was demonstrated to have no obvious effect on the transitions of Er3+ thermally coupled 2H11/2→4I15/2 and 4S3/2→4I15/2 and the relative sensitivity for temperature determination under 808 nm laser excitation. [ABSTRACT FROM AUTHOR]

Yb/Er: BiOX (X = Cl, Br) nanoplatelets were prepared via a template-free route simply by introducing water into ethylene glycol solution containing reactants at room temperature. Post-sintering on the product was found to have no obvious influence on the size and morphology but greatly enhance Er 3+ upconversion luminescence probably owing to the improvement in crystallinity of nanoplatelets. Impressively, benefited from the confined energy interactions between Yb 3+ and Er 3+ dopants within [X–Bi–O–Bi–X] layer in BiOX host, the investigated Yb/Er: BiOX (X = Cl, Br) nanoplatelets exhibited intense intrinsic near-single-band red upconversion emission under 980 nm or 1530 nm laser excitation. [ABSTRACT FROM AUTHOR]

Lanthanide-doped upconversion nanocrystals have been proposed to be suitable for temperature detecting on a nanometer scale. However, there are few studies concerning temperature sensing behaviors of core@shell nanoarchitectures, which are widely used as luminescent biomarkers so far. In this paper, Yb/Er: NaGdF 4 @NaYF 4 core@shell nanocrystals with various shell thicknesses were prepared. High-angle annular dark-field scanning transmission electron microscopy was adopted to evidence the formation of core@shell structures. With increase of shell thickness, Er 3+ upconversion luminescence was gradually enhanced and the optimal upconversion intensity of the core@shell sample was about 78 times as high as that of the core-only one. Temperature-dependent upconversion emission spectra revealed that the shell thickness had no obvious influence on the fluorescence intensity ratio between 2 H 11/2 → 4 I 15/2 transition and 4 S 3/2 → 4 I 15/2 one of Er 3+ as well as the related sensitivity. However, the thermal effect caused by the input 980 nm laser was severe for the core-only sample, whereas it was negligible for the core@shell product. As a consequence, the high absolute sensitivity of ∼1% per K and quantum efficiency of ∼2.2% for the core@shell upconversion nanoarchitectures may make them applicable for accurate temperature measurement in bio-field. [ABSTRACT FROM AUTHOR]

Yb/Tm: YF 3 nanoparticles embedded transparent bulk glass ceramic was successfully prepared to explore its possible application in optical temperature sensors. Specifically, owing to the competition of electron population in the thermally coupled Tm 3+ 3 F 2,3 and 3 H 4 excited states, two upconversion emission bands corresponding to Tm 3+ : 3 F 2,3 → 3 H 6 transition and 1 G 4 → 3 F 4 one exhibited opposite temperature-dependent behaviors, which resulted in monotonous enhancement of the related fluorescence intensity ratio with increase of temperature. As a consequence, Tm 3+ activators in the present YF 3 glass ceramic had advantages of a high sensitivity of 1.84% per K, an avoidable spectral overlapping and a negligible thermal effect for accurate temperature detecting. [ABSTRACT FROM AUTHOR]

Yb/Ho: NaLuF 4 self-crystallized glasses were successfully synthesized. After further heat-treatment (forming nano-glass-ceramics), Ho 3+ upconversion luminescence was enhanced by about 25 times, owing to the increased size and improved crystallinity of cubic NaLuF 4 nanocrystals. Impressively, the introducing of Ce 3+ dopants into glass ceramics resulted in an increase of red to green emission ratio of Ho 3+ from ∼0.11 to ∼32 and ultimately induced an intense near-single-band red upconversion luminescence. Such color tunable luminescence was proved to be attributed to the competition of radiation transitions from Ho 3+ 5 S 2 , 5 F 4 green-emitting and 5 F 5 red-emitting intermediate states. [ABSTRACT FROM AUTHOR]

A series of Cr 3+ -doped transparent bulk glass ceramics embedded with LiGa 5 O 8 , Ga 2 O 3 or ZnGa 2 O 4 nanocrystals were fabricated as the alternatives for Cr 3+ -doped single-crystals to explore their possible application in fluorescence lifetime based temperature sensing. X-ray diffraction, transmission electron microscopy and optical spectroscopy were adopted to investigate their microstructure and luminescent behaviors. Impressively, the decay lifetimes of these glass ceramic samples were found to be highly temperature-sensitive, attributing to the competition of radiation transitions from the thermally coupled Cr 3+2 E state with a long lifetime and 4 T 2 one with a short lifetime. Finally, such temperature-dependent luminescence of Cr 3+ was successfully interpret by a two-level kinetic model, which gives a highest temperature sensitivity of 0.76% K −1 (at 295 K), 0.46% K −1 (at 370 K) and 0.58% K −1 (at 420 K) for the Cr 3+ -doped LiGa 5 O 8 , Ga 2 O 3 and ZnGa 2 O 4 glass ceramics, respectively. [ABSTRACT FROM AUTHOR]

NaLu 1− x Yb x F 4 solid-solution nanocrystals embedded glass ceramics were successfully fabricated via the glass self-crystallization route for the first time. Importantly, the Eu 3+ or Er 3+ dopants are demonstrated to enter into the crystalline lattice by scanning transmission electron microscopy mapping and optical spectroscopy analysis. Further crystallization treatment is advantageous to improving the crystallinity and reducing surface-to-volume of NaLu 1− x Yb x F 4 nanocrystals where lanthanide activators reside, which induces great enhancement of optical performance of nanostructured glass ceramics. Under 980 nm near-infrared laser excitation, multi-color upconversion luminescence tuning from green to yellow and finally to red was easily realized by simply modifying Lu/Yb ratio in the glass ceramics containing Er 3+ : NaLu 1− x Yb x F 4 ( x = 0 ∼ 1) nanocrystals. It is expected that such glass self-crystallization strategy may offer a great opportunity to design and develop other new transparent nano-composites with a wide range of tunable optical properties. [ABSTRACT FROM AUTHOR]

Tb 3+ /Eu 3+ co-doped transparent bulk glass ceramics containing orthorhombic β-YF 3 nanocrystals were successfully synthesized by melt-quenching and subsequent heating. The partition of the active centers into the YF 3 crystalline lattice was confirmed by elemental mapping in the scanning transmission electron microscope, emission spectra and decay curves. As a consequence, Tb 3+ → Eu 3+ energy transfer was demonstrated to be more efficient in the glass ceramic than in the precursor glass, which resulted in color tunable luminescence by simply modifying Eu 3+ content and induced the linearly temperature-dependent fluorescence intensity ratio between the Tb 3+ : 5 D 4 → 7 F 5 transition and the Eu 3+ : 5 D 0 → 7 F 4 one in the Tb 3+ /Eu 3+ co-doped glass ceramic. It is expected that the investigated glass ceramic might be a promising candidate for solid-state lighting as well as optical temperature sensor. [ABSTRACT FROM AUTHOR]

A series of γ-Ga 2 O 3 and β-YF 3 nanocrystals embedded dual-phase glass ceramics co-doped with rare earth (Eu 3+ or Tm 3+ ) and transition metal (Cr 3+ ) activators were successfully prepared by high-temperature melt-quenching to explore blue/red luminescent materials for potential application in photosynthesis of green plants. It is experimentally verified that Eu 3+ (or Tm 3+ ) ions partitioned into the crystallized orthorhombic YF 3 nanophases, while Cr 3+ ones entered into the precipitated cubic Ga 2 O 3 nanocrystals after glass crystallization. Such spatial separation of the different active ions in the dual-phase glass ceramics can effectively suppress adverse energy transfers between rare earth and transition metal ions, resulting in their independent and efficient luminescence. As an example, it is experimentally demonstrated that both intense Tm 3+ blue and Cr 3+ deep-red emissions are easily achieved in the Tm 3+ /Cr 3+ co-doped dual-phase glass ceramics. [ABSTRACT FROM AUTHOR]

Lanthanide doped hexagonal β-NaGdF 4 nanocrystals embedded transparent bulk glass ceramics were successfully fabricated via a phase-separation-controlled crystallization route. Elemental mapping in the scanning transmission electron microscope and optical spectroscopy analysis demonstrated the partition of the active centers into the β-NaGdF 4 crystalline lattice. As a result, upconversion luminescence of the glass ceramic co-doped with Yb 3+ and Er 3+ is about 60 times as high as that of the precursor glass, attributing to the modification of Yb 3+ /Er 3+ surrounding from phase-separated amorphous nanoparticle to β-NaGdF 4 crystalline lattice with low phonon energy and high crystallinity after crystallization. Furthermore, the temperature-dependent green upconversion emissions assigned to 2 H 11/2 → 4 I 15/2 (520 nm) and 4 S 3/2 → 4 I 15/2 (540 nm) transitions were investigated, and the corresponding fluorescence intensity ratio of these two thermally coupled emitting-states greatly enhanced with increase of temperature. Using such fabricated glass ceramic as an optical thermometric medium, the maximum sensitivity reached as high as 0.0037 K −1 at 580 K. It is expected that the investigated Er 3+ /Yb 3+ codoped glass ceramic might be a very promising candidate for accurate optical temperature sensors. [ABSTRACT FROM AUTHOR]

Lanthanide-activated cubic NaLuF 4 nanocrystals were precipitated from a borosilicate glass with a specifically designed composition. The precursor glass is already phase-separated after melt-quenching, which is beneficial to the realization of the controllable glass crystallization for affording desirable size, morphology and activator partition. Using Eu 3+ as structural probe, the partition of lanthanide activators into the NaLuF 4 lattice was evidenced by excitation/emission and time-resolved spectra. As a result, such fabricated glass ceramic co-doped with Yb 3+ /Er 3+ (or Yb 3+ /Tm 3+ ) activators exhibited intense upconversion luminescence, which was about 10,000 (or 2000) times higher than that of the corresponding precursor glass, ascribing to the low-phonon-energy environment of the lanthanide ions enriched in nanocrystals and the efficient Yb 3+ –Er 3+ (or Yb 3+ –Tm 3+ ) inter-ionic interactions. It is anticipated that such phase-separation synthesis strategy with precise control over nanostructure of glass ceramics offer a great opportunity to design other highly transparent nanocomposites with a wide range of tunable optical properties. [ABSTRACT FROM AUTHOR]

Yb3+/Ho3+ activated glass ceramics containing β-YF3 nanocrystals were successfully fabricated. The green (5S2/5F4→5I8) upconversion emission is dominant in the glass ceramics and is about 160 times stronger than that of the precursor glass, resulting from the partition of lanthanide activators into a low-phonon-energy crystalline lattice and the subsequent low probability of multi-phonon nonradiative relaxation from the 5S2/5F4 and 5I6 states to the lower ones. Upon the introduction of Ce3+ ions into nano-glass-ceramics, two efficient cross-relaxation processes between Ho3+ and Ce3+, i.e., Ho3+:5S2/5F4 + Ce3+:2F5/2→Ho3+:5F5 + Ce3+:2F7/2 and Ho3+:5I6 + Ce3+:2F5/2→Ho3+:5I7 + Ce3+:2F7/2, are demonstrated to greatly suppress the population of the green-emitting 5S2/5F4 state and to enhance the population of the red-emitting 5F5 one, leading to the intense single-band red UC radiation of Ho3+. [ABSTRACT FROM AUTHOR]

Lanthanide-activated cubic Na 5 Gd 9 F 32 nanocrystals were precipitated from a borosilicate glass with a specifically designed composition. The precursor glass is already phase-separated after melt-quenching, which is beneficial to the realization of the controllable glass crystallization for affording desirable size, morphology and activator partition. Elemental mapping in the scanning transmission electron microscopy evidenced that the segregation of lanthanide ions into the Na 5 Gd 9 F 32 lattice was in situ formed without the requirement of long-range ionic diffusion. Impressively, such fabricated glass ceramic co-doped with Yb 3+ /Er 3+ ions exhibited intense upconversion luminescence, which was about 500 times higher than that of the precursor glass, and its luminescent color could be easily tuned from red to green by controlling glass crystallization temperature. It is anticipated that such phase-separation synthesis strategy with precise control over nanostructure of glass ceramics offer a great opportunity to design other highly transparent nanocomposites with a wide range of tunable optical properties. [ABSTRACT FROM AUTHOR]

After coating 20 Yb/2 Er:NaGdF4 core nanocrystals with a NaYbF4 shell, upconversion emission of the rare earth ions weakens. So far, the exact reason for this phenomenon is still unclear due to lack of the direct evidence. In this report, a core@shell@shell sandwich-like structure is designed and fabricated to investigate this phenomenon. We find that high Yb3+ concentration in the shell has mainly two adverse impacts: it promotes not only the deleterious back energy transfer from Er3+ in the core to Yb3+ in the shell but also the energy transfer from Yb3+ in the core to Yb3+ in the shell. To obtain nanocrystals with high upconversion efficency, appropriate Yb3+ concentration should be introduced into the shell or the transition layer. [ABSTRACT FROM AUTHOR]

Upon introducing Ca2+ dopants into the grain lattices by substituting Gd3+ ions, irregular Yb/Er:NaGdF4 nanocrystals prepared through a simple solvothermal route convert into highly uniform nanorods. Meanwhile, their upconversion luminescence intensifies by about 200 times, probably due to a modification of the crystal structure of NaGdF4 and an improvement in the crystallinity of the nanophase. [ABSTRACT FROM AUTHOR]

Abstract: Eu3+ doped nano-composites containing CeO2 nano-crystals are fabricated by a sol–gel process. The Stark splitting emissions as well as the low forced electric dipole 5D0 → 7F2 transition of Eu3+ reveals the partition of them into CeO2 nano-crystals. Increasing CeO2 content results in a growth of Eu3+ quantity incorporated in the nano-crystals and therefore the enhancement of Eu3+ photoluminescence. CeO2 nano-crystals not only afford a low phonon energy environment to Eu3+, but also sensitize their emissions and protect them from OH− quenching. [Copyright &y& Elsevier]

Abstract: Ultraviolet multiphoton upconversion emissions of Eu3+ (5 H 3–7, 5 G 2–6, 5 L 6 → 7 F 0) and Gd3+ (6 I J , 6 P J → 8 S 7/2) are studied in the Eu3+ (or Gd3+) doped SiO2–Al2O3–NaF–YF3 precursor glasses and glass ceramics containing β-YF3 nanocrystals, under continuous-wavelength 976nm laser pumping. It is experimentally demonstrated that energy transfer from Yb3+ to Tm3+, then further to Eu3+ or Gd3+ is responsible for the upconversion process. Compared to those in the precursor glasses, the upconversion emission intensities in the glass ceramics are greatly enhanced, owing to the participation of rare earth ions into the low-phonon-energy environment of β-YF3 nanocrystals. Hopefully, the studied glass ceramics may find potential applications in the field of ultraviolet solid-state lasers. [Copyright &y& Elsevier]

The GeS2–In2S3–CsI chalcohalide glass ceramics with In2.67S4nanocrystallites embedded in the glassy matrix are prepared by melt–quenching and subsequent heating, and the thermal crystallization behaviour of the In2.67S4nanophase is systematically investigated. Evidently, the In2.67S4crystallization is dependent on the In2S3/CsI component ratio in the precursor glass: it proceeds when In2S3/CsI > 1, and is prohibited when In2S3/CsI < 1. In2S3/CsI = 1 seems to be the critical point, and the situation is uncertain for the critical samples. Based on Raman spectra analyses, it is concluded that both the [S3In–InS3] ethane-like and the [InS4] tetrahedral units in the precursor glass play key roles in forming the In2.67S4nanocrystals. The present study may provide a guide for the crystallization control of other chalcohalide glasses. [ABSTRACT FROM AUTHOR]

Abstract: We report the Na2EDTA-assisted synthesis of the lanthanide (Ln3+) ion doped one-dimensional YVO4 nanobelts and nanorods by a facile hydrothermal route. XRD, TEM, EDS and FTIR techniques are used to characterize the microstructures of the synthesized nano-crystals. The morphology-dependent luminescent behaviors of Eu3+:YVO4 are systematically investigated. Under a single wavelength UV light excitation, the Ln3+:YVO4 (Ln=Nd, Sm, Eu, Dy, Ho, Er, Tm, or Yb) nanorods exhibit visible to near-infrared (NIR) multicolor tunable luminescence via efficient host sensitization, while no emissions are detected for the Ce3+, Pr3+, or Tb3+ doped samples. Based on the results, possible mechanisms depicting the YVO4 host sensitizing or quenching of lanthanide emissions are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Cooperative downconversion was realized in glass ceramics containing Eu2+/Yb3+:CaF2 nanocrystals with Eu2+ greatly absorbing ultraviolet photons. Upon excitation of Eu2+ ions to the 5d level with an ultraviolet photon at 320nm, emission of two near infrared photons at 976nm of Yb3+ were achieved. The dependence of the visible and near-infrared emissions, decay lifetime, and quantum efficiency on the Yb3+ doping content has been investigated. The maximum energy transfer efficiency and the corresponding downconversion quantum efficiency were estimated to be 51% and 151%, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Eu3+ doped transparent glass ceramics embedding SnO2 nano-crystals were prepared by melt quenching and subsequent heating. Site selective excitation experiments revealed that some Eu3+ ions were incorporated in the SnO2 lattices by substituting Sn4+ ions, whereas the rest located in the oxide glassy matrix. Interestingly, it is found that the Eu3+ ions residing in the SnO2 lattices exhibited much longer luminescent decay lifetime than those in the glassy matrix. Measurements on the photoluminescence excitation and photoluminescence spectra demonstrated the occurrence of energy transfer from the SnO2 nano-crystals to the Eu3+ ions. The influences of Eu3+ content, and furthermore, their location on the energy transfer process were discussed. [Copyright &y& Elsevier]

Monodisperse Eu3+:CeO2 nanoparticles 5–8nm in size were prepared by a facile solvothermal route. A high content of Eu3+, up to 20.0mol.%, is shown to incorporate into the CeO2 lattice. Upon heating from 600 to 800°C, the incorporation of Eu3+ in CeO2 nanocrystals is basically stable for the sample with relatively low doping content; however, Eu3+ ions are partially expelled from the lattice to the surfaces of the CeO2 nanocrystals when the doping content is high. [Copyright &y& Elsevier]

Abstract: Transparent SiO2–Al2O3–BaCO3–YF3–BaF2 glass ceramics co-doped with Yb3+/Ho3+ ions were prepared by melt quenching and subsequent heating. X-ray diffraction and transmission electron microscopy observation revealed that BaYF5 nanocrystals incorporated with Yb3+ and Ho3+ were precipitated homogeneously among the oxide glass matrix. Three upconversion emission bands centered at 483nm, 545nm and 645nm, corresponding to the 5 F 3 → 5 I 8, 5 S 2, 5 F 4 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho3+ respectively, were detected under 976nm excitation, ascribing to the efficient energy transfer from Yb3+ to Ho3+. The red emission is prevailing in the precursor glass, while the green one turns to be dominant in the glass ceramic. [Copyright &y& Elsevier]

Abstract: Er3+/Yb3+ co-doped transparent glass ceramics containing NaYF4 nanocrystals were prepared by melt-quenching and subsequent heating. Judd–Ofelt analyses of Er3+ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω 2,4,6. The Ω 2 value of glass ceramic is smaller than that of glass, which reflects the change of Er3+ local structure after crystallization, i.e., Er3+ partitions into the precipitated NaYF4 nanocrystals. Under 980nm excitation, intense red and green upconversion luminescence induced by efficient energy transfer from Yb3+ to Er3+ was achieved in the glass ceramics. Based on the fluorescence decay lifetimes, the energy transfer efficiency was evaluated, with the maximum value exceeding 68% for the 1mol% Yb3+/2mol% Er3+ co-doped sample. [Copyright &y& Elsevier]

Abstract: The olive-like YF3 micro-particles were fabricated via a two-step route. The precursor NH4Y3F10 nano-cages sized 8nm with hollow interiors were first synthesized in a solid reaction at room temperature. In the course of subsequent hydrothermal treating, the unstable NH4Y3F10 nano-cages were decomposed, resulted in the formation of Y(OH)1.63F1.37 micro-tubes. Prolonging the hydrothermal reaction induced the further decomposition of Y(OH)1.63F1.37 to produce YF3 nano-crystals, which then aggregated together forming the final olive-like YF3 micro-particles. For the Er3+/Yb3+ co-doped olive-like YF3 micro-particles, intense visible upconversion emissions were measured under 976nm excitation owing to the partition of rare earth ions in the lattice, indicating this material a promising luminescent host. [Copyright &y& Elsevier]

Abstract: Transparent glass ceramics containing YF3 nano-crystals were fabricated by heat treatment of the SiO2–Al2O3–NaF–YF3–LnF3 (Ln=Er, Yb) glasses. X-ray diffraction and transmission electron microscopy analyses evidenced the homogeneous distribution of spherical YF3 nano-crystals sized 25–30nm among the glassy matrix. Energy dispersive X-ray spectroscopy measurement, combined with the Stark splitting of the absorption and emission bands, verified the incorporation of Er3+ and Yb3+ ions into YF3 nano-crystals. The infrared to visible up-conversion emission of Er3+ intensified with the increasing of Yb3+ concentration, ascribing to the increase of the efficiency of non-radiative energy transfer from Yb3+ to Er3+ which exceeded 45% for the 0.5Er3+/1.0Yb3+ co-doped sample. The up-conversion luminescence at 545 and 660nm were affirmed coming from two-photon excitation process. [Copyright &y& Elsevier]

Abstract: In this paper, the spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics containing LaF3 nano-crystals were systematically studied. The formation and distribution of LaF3 nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd–Ofelt theory, the intensity parameters Ω t (t =2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd3+ were evaluated. Particularly, the effect of Nd3+ doping level on them was discussed. With the increase of Nd3+ concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4μs, 78.3% and 1.86×10−20 cm2 to 214.7μs, 39.9% and 1.52×10−20 cm2, respectively. The comparative study of Nd3+ spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06μm emission. [Copyright &y& Elsevier]

Abstract: The influence of Yb3+ content on structural evolution and fluorescence properties of oxyfluoride glass ceramics containing LaF3 nano-crystals were systematically investigated. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) experiments indicated that Yb3+ ions acted as nucleating agent to facilitate LaF3 crystallization. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results verified the incorporation of Yb3+ into LaF3 nano-crystal lattice. The absorption, emission spectra and fluorescence decays were measured. The infrared emission intensity of 4F5/2 → 4F7/2 transition under 980nm excitation enhanced, while the measured lifetime reduced due to the increase of non-radiative transition probability, with the increase of Yb3+ content in glass ceramic. However, when Yb3+ doping reached 4.0mol% the concentration quenching effect appeared. [Copyright &y& Elsevier]

Abstract: Transparent 45SiO2–25Al2O3–5CaO–10NaF–15CaF2 glass ceramics doped with different content of erbium ion (Er3+) were prepared. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses evidenced the spherical CaF2 nanocrystals homogeneously embedded among the glassy matrix. With increasing of Er3+ content, the size of CaF2 nanocrystals decreased while the number density increased. The crystallization kinetics studies revealed that CaF2 crystallization was a diffusion-controlled growth process from small dimensions with decreasing nucleation rate. Er3+ could act as nucleating agent to lower down crystallization temperature, while some of them may stay at the crystal surfaces to retard the growth of crystal. Intense red and weak green upconversion emissions were recorded for glass ceramics and their intensities increased with the increasing of Er3+ content under 980nm excitation. However, the concentration quenching effect appeared when Er3+ doping reached 2mol%. These results could be attributed to the change of ligand field of Er3+ ions due to the incorporation of Er3+ ions into precipitated fluoride nanocrystals. [Copyright &y& Elsevier]

Abstract: Transparent BaF2–SiO2 glass ceramics doped with different content of Er3+ were prepared by sol–gel method. The microstructural evolution of the samples was studied with X-ray diffraction (XRD), transmission electron microscope (TEM), absorption and infrared spectra (IR). BaF2 nano-crystals with 2–15nm in size, depending on the crystallization temperature, distributed homogeneously among the amorphous silica matrix. The BaF2 lattice parameters decreased with the increasing of Er3+ doping, indicating the incorporation of Er3+ into nano-crystals, which was further confirmed by energy dispersive X-ray spectroscopy (EDS) and absorption spectra analysis. The upconversion emissions of Er3+ emerged under the excitation at 980nm for glass ceramic heat-treated at 800°C. [Copyright &y& Elsevier]

Monodisperse Yb3+/Er3+:MFCl nanocrystals were fabricated viaa simple and effective seed-based chlorination route for the first time. Remarkably, their upconversion emissions are found to be greatly intensified compared with those of the well-reported Er3+/Yb3+:SrF2with the same size and shape. [ABSTRACT FROM AUTHOR]

Monodisperse pure cubic ZrO2nano-phase is selectively synthesized by employing Gd3+as a nucleation agent in solution. The heteronucleation and growth mechanism as well as the phase selective effect are proposed for the formation of cubic ZrO2nanocrystals. By changing the Gd3+content, the size of ZrO2nanocrystals can be finely controlled. [ABSTRACT FROM AUTHOR]

The infrared to ultraviolet upconversion emissions of Tm3+ 1I6→3F4 (346 nm) and 1D2→3H6 (362 nm) transitions, originating from the five- and four-photon upconversion processes, respectively, were observed in the Tm3+/Yb3+ codoped precursor glass and glass ceramic containing β-YF3 nanocrystals. The ultraviolet luminescence of the glass ceramic is 30 times stronger than that of the precursor glass, which could be attributed to the decreased probability of the 3F2→3F4 transition and the increased cross relaxation of 3F2+3H4→3H6+1D2 resulted from the partition of rare earth ions into nanocrystals. [ABSTRACT FROM AUTHOR]

Recently, Mn2+‐doped CsPb(Cl/Br)3 perovskite nanocrystals (NCs), showing the advantages of dual‐color emissions via exciton‐to‐dopant energy transfer and reduced usage of toxic Pb2+ heavy metal ions by nontoxic Mn2+ substitution, are widely explored. However, photoluminescence quantum yields (PLQYs) for Mn2+‐doped CsPb(Cl/Br)3 NCs still need to be further improved. Here, a halogen‐hot‐injection strategy is developed to prepare Mn:CsPb(Cl0.6Br0.4)3 NCs with the maximal PLQY of 65%. With this method, intense blue narrowband emission from excitonic recombination and orange broadband emission from Mn2+ 4T1 → 6A1 transition can be simultaneously achieved. The competitive luminescence between perovskite NCs and Mn2+ dopants is systematically investigated by controlling the injected halogen types and ratios. As a proof‐of‐concept experiment, the present Mn2+‐doped CsPb(Cl/Br)3 perovskite NCs with highly efficient dual‐color emissions are demonstrated to be applicable as color converter in UV‐excitable solid‐state lighting. [ABSTRACT FROM AUTHOR]

The commonly used automotive head‐up display (HUD) technology is confronted with the problems of poor stability in organic resin counterpart and the unsatisfactory display effect of projection lighting source. To solve these issues, developing state‐of‐the‐art materials and designing new HUD schemes with a wide color gamut is of necessity. Herein, a series of pure red/green/blue (R/G/B) upconverting (UC) nano‐glass‐ceramics (GCs) containing lanthanide‐doped NaLuF4 nanocrystals (NCs) are synthesized in a cost‐effective, environment‐friendly, and scalable manner, simultaneously achieving high crystallinity (≈45.44%) and high transparency (>80%). Yb3+ is chosen as the sensitizer to Tm3+ (blue UC)/Ho3+ (green UC), due to its large absorption cross section from ground state 2F7/2 to excited state 2F5/2; meanwhile Er3+, Tm3+ co‐doped into NCs can obtain pure red UC emission via promoting the population of Er3+ red‐emitting 4F9/2 state. Consequently, the as‐prepared materials exhibit high R/G/B color purity of > 80% owing to the energy transfer between different lanthanide ions (Yb3+, Tm3+, Ho3+, and Er3+) upon 980 nm near‐infrared (NIR) laser excitation, and possess superior thermal reversibility/water resistivity. Remarkably, two unprecedented HUD prototypes are constructed to demonstrate the application feasibility of developed pure R/G/B UC GCs. [ABSTRACT FROM AUTHOR]

The inherent low-efficiency for upconversion fluorescence materials constricts their further applications in many research domains. Over the last decades, considerable efforts have been paid to the fluorides, less works concering LaVO 4 are reported. Based on series of impurity content-dependent experiments, Ti4+ ions doped LaVO 4 :Yb3+/Er3+ crystals are hydrothermally fabricated. The products are characterized by XRD, ICP, TEM and luminescence spectroscopy. Through modulating the Ti4+ ions doping concentration, the UCL intensity of 533 nm and 664 nm emissions are greatly intensified. The reasons are analyzed on the basis of three major factors. Meanwhile, extra DFT calculations are performed to support the experimental result. This report paves a new way for enhancing upconversion luminescence intensity of LaVO 4 nanocrystals based on impurity doping. [ABSTRACT FROM AUTHOR]

Hexagonal Yb3+/Er3+:NaGdF 4 nanocrystals codoped with Sn2+ ions were prepared via a modulated solvothermal method. Upon introducing 25mol% Sn2+ ions into the host lattice by substituting Gd3+ ions, a portion of Yb3+/Er3+:NaGdF 4 nanocrystals was converted into nanorods. Meanwhile, the upconversion (UC) luminescence intensity of 542 nm and 652 nm were intensified by 24 and 33 times respectively, when compared with samples without Sn2+ ions doping. The effect of Sn2+ ions doping content on the morphology and UC emission performances of Yb3+/Er3+:NaGdF 4 nanocrystals were discussed in detail. The enhancement of UC luminescence intensity could be attributed to the growth of UC nanocrystals and the low crystal local symmetry around Yb3+/Er3+ ion pairs. This study may be beneficial for fabricating high-performance UC materials and realizing their practical applications. [ABSTRACT FROM AUTHOR]

In this communication, a thermolysis route is developed to synthesize novel Cu1.94S–ZnS–Cu1.94S nanoheterostructures with interesting sandwich-like architectures, taking Cu1.94S nanoplates as precursors. Evidently, the trimeric nanostructure is formed by a three-stage process, which includes the Zn-oleate induced assembling of Cu1.94S nanoplate couples, the heteronucleation and growth of a ZnS layer between two Cu1.94S plates dominated by interfacial diffusion, and the catalyst assisted axial growth of ZnS nanorod following the solution–liquid–solid mechanism. With epitaxial growth of ZnS nanocrystal between two Cu1.94S nanoplates, the localized surface plasmon resonance frequency of Cu1.94S shifts from 1875 to 1323 nm, indicating that this new material is potentially applicable as a light absorbing agent in laser photothermal therapy. The reported growth mechanism may provide new strategies for designing and fabricating various technologically important polymeric nanoheterostructures. [ABSTRACT FROM AUTHOR]

Abstract: Ni2+/Er3+ dual-doped transparent glass ceramic containing γ-Ga2O3 and β-YF3 nanocrystals is prepared by melt quenching and subsequent heating. It is experimentally demonstrated that Ni2+ and Er3+ are partitioned into γ-Ga2O3 and β-YF3 nanocrystals, respectively, which greatly reduces the adverse energy transfer between them. Accordingly, an integrated broad near-infrared emission band in the wavelength region of 1020–1650nm, consisting of Ni2+: 3T2(F)→ 3A2(F) emission around 1220nm and Er3+: 4I13/2 → 4I15/2 emission around 1540nm, is observed under 980nm excitation. Compared to that in the Ni2+/Er3+ dual-doped glass ceramic containing γ-Ga2O3 and LaF3 nanocrystals, the integrated near-infrared emission intensity in the present sample is increased by two times, ascribing to the higher Er3+ solubility in β-YF3 crystallites. [Copyright &y& Elsevier]

Abstract: Tm3+-sensitized up-conversion and down-conversion are studied in transparent glass ceramics embedded with β-YF3 nanocrystals. Upon excitation at 1220nm, where crystalline silicon (c-Si) solar cells no longer absorb, the sub-bandgap photons could be converted to the higher-energy ones via up-conversion. In addition, under excitation at 468nm (a wavelength close to the peak in the air-mass 1.5 global solar spectrum), one blue photon might be split in up to two near-infrared ones via down-conversion. In both cases, the frequency-converted photons match the spectral response of c-Si solar cell well. Hopefully, the investigated luminescent materials may act as the spectral conversion layers to reduce the sub-bandgap transmission and charge carrier thermalization losses of c-Si solar cells, and in turn, enhance the energy efficiency. [Copyright &y& Elsevier]

Abstract: The 1.53μm emission of Er3+-doped transparent glass ceramics containing NaYF4 nanocrystals is investigated systematically. The appearance of Stark splits in the absorption and emission peaks of the glass ceramics confirms the incorporation of Er3+ into NaYF4 nanocrystals. With the raising of heating temperature for NaYF4 crystallization, the 4I13/2 level lifetime increases due to the incorporation of more Er3+ into NaYF4, while the 1.53μm emission bandwidth decreases resulting from the structural ordering around Er3+. With the increase of Er3+ content, the obvious concentration quenching effect is observed in glass ceramics. The present glass ceramic possesses large 1.53μm emission cross-section and high quantum efficiency, which implies that it is potentially applicable in Er3+-doped fiber amplifiers. [Copyright &y& Elsevier]