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The reactions of VOSO4·3H2O with Na2(cbdc) (cbdc2− – dianion of cyclobutane-1,1-dicarboxylic acid) and lanthanide(III) nitrates taken in a molar ratio of 1 : 2 : 1 were found to yield a series of isostructural heterometallic compounds [NaLn(VO)2(cbdc)4(H2O)10]n (1Ln, Ln = Tb, Dy, Ho, Er, Tm, Yb). These compounds are constructed from trinuclear anionic units [Ln(VO)2(cbdc)4(H2O)8]− ({LnV2}−) linked by Na+ ions into 1D polymeric chains. The crystal structures of 1Dy and 1Er were determined by single-crystal X-ray diffraction (XRD), and their isostructurality with 1Tb, 1Ho, 1Tm, and 1Yb was proved by powder X-ray diffraction (PXRD). According to alternating current (ac) magnetic susceptibility measurements, 1Dy, 1Er, and 1Yb exhibited field-induced slow relaxation of magnetization. Compound 1Er is the first representative of ErIII–VIV single-molecule magnets. Measuring the temperature dependences of the phase memory time (Tm) for 1Dy and 1Yb using pulsed EPR spectroscopy allowed us to observe the phenomenon of phase relaxation enhancement (PRE) at temperatures below 30 K. In future, this phenomenon may contribute to the evaluation of relaxation times of the lanthanide ions. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR)-emitting phosphors with broadband absorption from ultraviolet to visible light have been considered significant spectral converter materials for solar cells. In this work, NIR phosphor Zn3Ga2GeO8 (ZGGO):Cr3+,Yb3+ spinel solid solutions were synthesized using the classical high-temperature solid-state method. With an increase in the doping concentration of Cr3+ ions in ZGGO:Cr3+,Yb3+, a more distorted octahedron appeared around Cr3+ ions, which increased crystal field splitting. This process was accompanied with a broadening of NIR emission from Cr3+ 4T2 → 4A2 transition and enlarged the overlap area between the absorption spectrum of Yb3+ and the emission spectrum of Cr3+, resulting in an efficient energy transfer between Cr3+ and Yb3+. In the case of high-concentration Cr3+ doping, the near-infrared luminescence intensity of Yb3+ was more than 8 times that of low-concentration doped Cr3+. Therefore, it is proposed that the Cr3+,Yb3+ co-doped ZGGO phosphor is a potential spectral convert materials for silicon-based solar cells and thereby improves photovoltaic conversion efficiency. [ABSTRACT FROM AUTHOR]

Cubic and hexagonal structured SrTa4O11(STO):Er3+/Yb3+ phosphors were synthesized by a solid state reaction (SSR) and molten salt synthesis (MSS). The upconversion luminescence (UCL) intensity of these samples was investigated. Hexagonal STO:Er3+/Yb3+ with much or a little β-Ta2O5 can be synthesized by SSR in air or vacuum, respectively, and the UCL intensity of the sample synthesized by SSR in a vacuum is higher. Cubic STO:Er3+/Yb3+ can be synthesized by MSS with KCl flux, and hexagonal STO:Er3+/Yb3+ can be synthesized by MSS with B2O3 flux, which has the strongest UCL intensity among all the samples compared with samples prepared by SSR. The sample by MSS with B2O3 flux was acid pickled (AP) with HCl solution, and the green UCL intensity increased by 2.18 times, which reached 32.95% for β-NaYF4:Er3+/Yb3+. The UCL intensity of the hexagonal STO:Er3+/Yb3+ is much higher than that of the cubic structure, which is due to the layered structure and the non-central symmetry of the Er3+/Yb3+ doped sites in hexagonal STO:Er3+/Yb3+. The temperature sensitivity of samples is evaluated by luminescence intensity ratio (LIR) technology. The maximum relative sensitivity is 0.0099 K−1 at 303 K. All the results show that hexagonal STO:Er3+/Yb3+ has excellent pure green UCL intensity and high temperature sensitivity, which can be used in UCL display and temperature sensing. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR)-emitting phosphors with broadband absorption from ultraviolet to visible light have been considered significant spectral converter materials for solar cells. In this work, NIR phosphor Zn3Ga2GeO8 (ZGGO):Cr3+,Yb3+ spinel solid solutions were synthesized using the classical high-temperature solid-state method. With an increase in the doping concentration of Cr3+ ions in ZGGO:Cr3+,Yb3+, a more distorted octahedron appeared around Cr3+ ions, which increased crystal field splitting. This process was accompanied with a broadening of NIR emission from Cr3+ 4T2 → 4A2 transition and enlarged the overlap area between the absorption spectrum of Yb3+ and the emission spectrum of Cr3+, resulting in an efficient energy transfer between Cr3+ and Yb3+. In the case of high-concentration Cr3+ doping, the near-infrared luminescence intensity of Yb3+ was more than 8 times that of low-concentration doped Cr3+. Therefore, it is proposed that the Cr3+,Yb3+ co-doped ZGGO phosphor is a potential spectral convert materials for silicon-based solar cells and thereby improves photovoltaic conversion efficiency. [ABSTRACT FROM AUTHOR]

Ratiometric thermometry is among the emerging applications in phosphor materials. Particularly, the technique of ultrafine-space thermometry has garnered significant attention in bio-imaging. Near-infrared (NIR) light, with its high tissue permeability, serves not only as an excitation source for up-conversion photoluminescence (UCPL) but also induces down-shifting photoluminescence (DSPL) at longer wavelengths. These luminescence mechanisms offer promising avenues for bio-available thermometry. In this study, we focused on highly bio-adaptable yttria-stabilized zirconia (YSZ), Zr0.85Y0.15O1.925, and prepared phosphor materials with yttrium partially substituted by ytterbium (Yb), erbium (Er), and thulium (Tm) using a hydrothermal reaction method. The synthesized YSZ:Yb–Er/Tm phosphors with different Yb3+ contents showed multi-line UCPL in the visible to NIR region due to Er3+ and Tm3+ ions under the laser irradiation at 980 nm; in particular, it showed strong UCPL at 800 nm originating from Tm3+. Furthermore, under the same excitation conditions, the phosphor exhibited not only UCPL but also DSPL due to 4I13/2 → 4I15/2 transition of Er3+ in the deeper NIR region of 1400–1700 nm. Interestingly, these DSPLs exhibit significant PL enhancement (anti-thermal quenching; anti-TQ) with increasing temperature. The thermometric properties based on the luminescence intensity ratio (LIR) of UCPL, which shows normal thermal quenching, and DSPL, which shows anti-thermal quenching, demonstrated excellent temperature sensitivity (Sr > 3% K−1 @ 283 K) and temperature resolution (δT < 0.1 K @ 283 K). This study suggests that the LIR thermometry technique using UCPL/DSPL, specifically anti-TQ/normal-TQ, can contribute to further advancements in luminescence-based temperature measurement. [ABSTRACT FROM AUTHOR]

Lanthanide doped multicolor luminescent materials have attracted extensive attention due to their advanced anti-counterfeiting properties. However, designing a simple, hard-to-copy and multicolor anti-counterfeiting strategy based on upconversion nanoparticles (UCNPs) remains a huge challenge. Herein, a strategy to modulate luminescence color by altering the mediating action of Tm3+ was proposed. As a proof of concept, the mediating action of Tm3+ was explored in NaYbF4:30%Er,1%Tm@NaYF4 by changing the doping ratio of Yb3+/Er3+/Tm3+, and red, yellow and blue luminescence was successfully obtained. Then, NaYbF4:x%Er,1%Tm@NaYF4 (x = 2, 10, 30, 50, 99), NaYbF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) and NaYbF4:1%Tm@NaYF4:x%Er@NaYF4 (x = 2, 10, 30, 50, 100) were synthesized to further identify that the mediating action of Tm3+ was related to the doping ratio and distance between dopant ions. In addition, the luminescence color of NaYbF4:30%Er,1%Tm@NaYF4 changed from red to yellow with the increase of excitation power density. Based on the above, NaYbF4:Er,Tm@NaYF4 UCNPs show excellent performance in anti-counterfeiting of paintings, thus revealing their great potential in advanced anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Treatment of Yb(II) complex [L2Yb(THF)2] (L = PhC(NSiMe3)2) with elemental sulfur, selenium or tellurium resulted in the isolation of a series of dinuclear Yb(III) complexes featuring side-on bound S32− (1), Se22− (2) or Te22− (3) moieties, respectively. Magnetic study on these complexes revealed that 3 is a rare lanthanide telluride single-molecule magnet (SMM). [ABSTRACT FROM AUTHOR]

New organophosphate complexes [Ln(dippH)3(dippH2)3]·(H2O)6, (Ln = Dy, Yb and Y; dippH2 = 2,6-diisopropylphenyl phosphate), displaying octahedral coordination geometry around the metal ion, exhibit unusual slow relaxation of magnetisation, which is investigated through experimental studies and ab initio CASSCF calculations. [ABSTRACT FROM AUTHOR]

A systematic study of the impact on the chemical reactivity of the oxidising n-dodecane radical cation (RH˙+) with f-element complexed 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) has been undertaken utilizing time-resolved electron pulse radiolysis/transient absorption spectroscopy and high-level quantum mechanical calculations. Lanthanide ion complexed species, [Ln((HEH[EHP])2)3], exhibited vastly increased reactivity (over 10× faster) in comparison to the non-complexed ligand in n-dodecane solvent, whose rate coefficient was k = (4.66 ± 0.22) × 109 M−1 s−1. Similar reactivity enhancement was also observed for the corresponding americium ion complex, k = (5.58 ± 0.30) × 1010 M−1 s−1. The vastly increased reactivity of these f-element complexes was not due to simple increased diffusion-control of these reactions; rather, enhanced hole transfer mechanisms for the complexes were calculated to become energetically more favourable. Interestingly, the observed reactivity trend with lanthanide ion size was not linear; instead, the rate coefficients showed an initial increase (Lu to Yb) followed by a decrease (Tm to Ho), followed by another increase (Dy to La). This behaviour was excellently predicted by the calculated reaction volumes of these complexes. Complementary cobalt-60 gamma irradiations for select lanthanide complexes demonstrated that the measured kinetic differences translated to increased ligand degradation at steady-state timescales, affording ∼38% increase in ligand loss of a 1 : 1 [La((HEH[EHP])2)3] : HEH[EHP] ratio system. [ABSTRACT FROM AUTHOR]

Two new ytterbium coordination compounds Yb(HPTC)(H2O)2 (Yb1) and Yb(HPTC)(Phen) (Yb2) were obtained using 10-carboxyperylene-3,4,9-tricarboxylate ion (HPTC3−) as a sensitizer. Both coordination compounds exhibited intense NIR-II luminescence upon excitation in the visible range and formed stable suspensions with nanoparticles of 50–70 nm in size in an aqueous solution of sodium alginate. Both complexes demonstrated non-toxicity up to at least 25 mg L−1 in two cell cultures: cancer cells MCF7 and embryonic cells HEK293T – making them suitable for bioimaging. For both complexes, the accumulation in cells was directly measured and it was shown that the accumulation of Yb2 was the same for both cell types (0.51–0.52 πg per cell), while Yb1 demonstrated selective accumulation in cancer cells (0.04 πg per cell for HEK293T and 7.00 πg per cell for MCF7). Thus, Yb1 can also be proposed as a selective vis-excited NIR emitting bioprobe. [ABSTRACT FROM AUTHOR]

Herein, a series of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors is prepared via a solid-state reaction. The upconversion and downshift luminescence properties of the phosphors were investigated under an excitation of 980 nm. The bright blue light emission from Tm3+ ion and the green and red light emissions from Ho3+(Er3+) ions were observed. The near-infrared light intensity of NIR-I (Tm3+, ∼850 nm), NIR-II (Er3+: ∼1550 nm; Tm3+: ∼1783 nm) and NIR-III (Ho3+: ∼2050 nm) were analyzed. In particular, the dramatic thermal enhancement phenomenon in visible and NIR regions was exhibited by the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors. Among them, the green light intensity of Er3+ ions increased 26.77 times, from 303 to 573 K. The NIR-II emission band (∼1783 nm) intensity of Tm3+ ions at 533 K increased 168.7 times compared to that at 313 K. The possible thermal enhancement mechanism is illustrated by the negative thermal expansion (NTE) and Frenkel defect of the Y2W3O12 host. Finally, the optical temperature sensing performances of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) samples are investigated according to the luminescence intensity dependence relationship on temperature. The maximum value of SR reached 4.24% K−1 at 353 K for Y2W3O12:10%Yb3+/0.6%Ho3+ phosphor. The results indicate that the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors possess anti-thermal quenching properties and are suitable for developing optical temperature sensors. [ABSTRACT FROM AUTHOR]

Until now, double perovskite tellurates have not been reported to exhibit inherent NIR photoluminescence. Therefore, the current study's revelation of inherent NIR luminescence in SrLaLiTeO6 double perovskite centered at 970 nm under 340 nm excitation is particularly intriguing. This phenomenon is attributed to the photoluminescence of Te4+ ions. This study also examines the NIR luminescence of Cr3+–Yb3+ co-doped SrLaLiTeO6. The host and SrLaLiTeO6:3%Cr3+, y%Yb3+ (y = 1, 2, 4, 6, 8, 10 mol%) were synthesized using the solid-state ceramic route. The successful incorporation of Cr3+ and Yb3+ ions into the host lattice was confirmed through XRD, Raman, and diffuse reflectance spectral analyses. Under 270 nm excitation, the photoluminescence (PL) of SrLaLiTeO6:Cr3+ exhibits a blueshift of the PL band to 965 nm due to the 4T2(4F) → 4A2g(4F) emission component of Cr3+ ions. The excited-state lifetime of SrLaLiTeO6:0.5%Cr3+ was measured at 36 μs, but this decreased to 26 μs as the Cr3+ concentration reached 10 mol%, primarily due to the enhancement of non-radiative energy transfer between Cr3+ ions. Incorporating Yb3+ into the system results in additional spectral lines with an enhanced intensity in the range of 970 nm to 1125 nm when excited at 270 nm. These emission lines correspond to the 2F5/2 → 2F7/2 transitions of Yb3+ ions, indicating an efficient energy transfer from Cr3+ to Yb3+. Furthermore, the study also reveals that Yb3+ emission is observed even without Cr3+ ions in SrLaLiTeO6 under 340 nm excitation, suggesting the possibility of energy transfer from the host to Yb3+ ions. The thermal stability and crystal field parameters of the synthesized phosphors are also explained in detail. To explore the potential of these phosphors in practical applications, phosphor-converted NIR LEDs were fabricated using SrLaLiTeO6, SrLaLiTeO6:3% Cr3+, and SrLaLiTeO6:3% Cr3+, 1%Yb3+. [ABSTRACT FROM AUTHOR]

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

Upconversion luminescence (UCL) is a fluorescence process where two or more lower-energy photons convert into a higher-energy photon. Lanthanide (Ln3+)-doped UCL materials often suffer from weak luminescence, especially when directly synthesized by a hydrothermal (HT) process due to the existing hydroxyl group and undesirable arrangement of dopants within host lattices which quench luminescence and limit energy transfer. Therefore, additional heat treatment processes are required to enhance their UCL emission, even though direct hydrothermal synthesis without further heat treatment has the advantages of low energy consumption, fast synthesis, and wide applicability to generate UCL materials. In this study, via a HT process without annealing, we have produced Yb3+ and Er3+ co-doped SrMoO4 submicron spindles with a strong green UCL emission which can be seen with the naked eye, which HT produced oxide-based UCL materials often fail to demonstrate. We have investigated different HT synthesis conditions, such as temperature, time, pH and dopant composition, which control the nucleation, growth, lattice structure arrangement, and ultimately their UCL properties through XRD, SEM, EDS and UCL measurements. The bright green UCL from the SrMoO4:Yb,Er submicron spindles is further enhanced by post-synthesis annealing within a molten NaNO3/KNO3 system to prevent particle size growth. The green UCL intensity from the annealed SrMoO4:Yb,Er submicron spindles surpasses samples produced by the solid-state method and is comparable to that from the commercial NaYF4:Yb,Er sample. We have further studied the temperature-dependent luminescence of both the HT-prepared and molten-salt annealed SrMoO4:Yb,Er submicron spindle samples. The strong UCL from our SrMoO4:Yb,Er submicron spindles could warrant their candidacy for bioimaging and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

The first Yb complexes comprising a quinoline-2-carboxylate (quinaldinate, Q−) ligand, namely 1D-polymeric [Yb(acac)2(Q)]n (1, acac− is the acetylacetonate (pentane-2,4-dionate) anion) and mononuclear [Yb(acac)2(Q)(Phen)] (2, Phen is 1,10-phenanthroline), are reported. The bifunctionality of both complexes as field-induced single-molecule magnets (SMMs) and near IR luminophores has been revealed. The SMM properties of 1 and 2 have been discussed in terms of the geometry and composition of the coordination environment. Also, 1 is the first example of 1D-polymeric SMMs with the capped octahedral surrounding of Yb3+. The photoluminescence quantum yields (PLQYs) of 1 and 2 are 2 and 4%, respectively. The origins of this difference are discussed. Surprisingly, the PLQY value of 2 is high for compounds comprising a lot of C–H vibrational quenchers, being the highest one for reliably characterized Yb β-diketonate complexes, and surpassing those for complexes with a broad range of anionic ligands. In this respect, the role of the Phen ligand is to tune the coordination mode of Q− thereby decreasing the energy of coordinating C–O oscillators rather than to act as a typical antenna ligand. These results can give rise to an alternative route to elaborate efficient Yb-based luminophores via the substitution of the β-diketonate ligands controlled by the introduction of appropriate neutral ligands. [ABSTRACT FROM AUTHOR]

Power-based upconversion luminescence color regulation (PUCR) is especially suitable for developing dynamic luminescence anti-counterfeiting owing to its straightforward usage. However, it remains a challenge to achieve visually remarkable Ho3+-based PUCR. Herein, favorable PUCR behavior is achieved by codoping Yb3+ and Ho3+ into the Lu2Mo4O15 lattice. It has been demonstrated that the ultrashort lifetime of the Ho3+:5I6 level and the anomalous three-photon nature of green emission are essential. The former causes high-purity red emission at low power, while the latter enables power-responsive tuning from red to green. Compared with Er2Mo4O15:4% Tm3+ we recently reported that Lu2Mo4O15:90% Yb3+/1% Ho3+, thanks to the high solubility of Yb3+ ions, showed a ∼25-fold enhancement in emission intensity. This new material is potentially applicable in dynamic luminescence anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Pressure and temperature are fundamental physical parameters, so their monitoring is crucial for various industrial and scientific purposes. For this reason, we developed a new optical sensor material that allows monitoring of both the physical parameters. The synthesized material exhibits upconversion (UC) emission of Er3+ in the red and green spectral regions under NIR (975 nm) laser irradiation. These UC emissions are strongly temperature-dependent, allowing multimode temperature sensing, either based on the luminescence intensity ratio between thermal-coupled energy levels (TCLs) or non-thermal-coupled energy levels (NTCLs) of Er3+ ions. Meanwhile, the luminescence lifetime of the 4S3/2 state of Er3+ ions was used as the third temperature-dependent spectroscopic parameter, enabling multi-parameter thermal sensing. Moreover, the observed enhancement of laser-induced heating of the sample under vacuum conditions allows for the conversion of the luminescent thermometer into a remote vacuum sensor. The pressure variations in the system are correlated with changes in the band intensity ratio (525/550 nm) of Er3+ TCLs, which are further applied for optical, contactless vacuum sensing. This is because of the light-to-heat conversion effect, which is greatly enhanced under vacuum conditions and manifests as a change in the intensity ratio of Er3+ bands (525/550 nm). The obtained results indicate that an Y2Mo4O15:Er3+/Yb3+ (YMO) phosphor has great application potential for the development of multi-functional and non-invasive optical sensors of pressure and temperature. [ABSTRACT FROM AUTHOR]

The crystal structure of YbSbO4 was determined from powder X-ray diffraction data using the Rietveld method. YbSbO4 is found to be monoclinic and isostructural to α-PrSbO4. We have also tested the influence of pressure on the crystal structure up to 22 GPa by synchrotron powder X-ray diffraction. No phase transition was found. The P–V equation of state and axial compressibilities were determined. Experiments were combined with density-functional theory calculations, which provided information on the elastic constants and the influence of pressure in the crystal structure and Raman/infrared phonons. Results are compared with those from other orthoantimonates. Reasons for the difference in the high-pressure behaviour of YbSbO4 compared with most antimony oxides will be discussed. [ABSTRACT FROM AUTHOR]

In this study, up-conversion fluoride phosphors NaY1−x-y−m−nMxF4:Er3+y,Ho3+m,Yb3+n (M = Lu3+/Gd3+) were synthesized by a low-temperature combustion method. The optimal ionic ratios in the matrix lattice were also determined by a controlled variable method. It was confirmed that doping a small amount of Ho3+ ions and Yb3+ ions in the Er-doped sample matrix lattice can form a mutual sensitizer and a transient energy capture center to enhance the sample's up-conversion luminescence under excitation at the 1550 nm band, respectively. It was also found that the lanthanide ion introduced can modulate the red-to-green ratio of the up-conversion luminescence of the sample. The phase composition and morphology of phosphors were investigated using X-ray diffraction and scanning electron microscopy. The up-conversion luminescence mechanism of Er–Ho–Yb tri-doped samples excited at the 1550 nm band was also investigated. This work presents a novel approach for improving up-conversion luminescence with high color-purity phosphors for display lighting applications when excited at 1550 nm. [ABSTRACT FROM AUTHOR]

This study investigates multimodal light emission from an Eu3+/Yb3+ activated Y3Ga5O12 (YGG) nanophosphor synthesized using a low temperature solution combustion method. The prepared sample possesses a cubic phase and an Ia3¯d space group and this is confirmed with X-ray diffraction and Rietveld refinement analysis. The synthesized sample shows orange-red emission bands because of the f–f transitions of Eu3+ under UV (393 nm) and NIR (980 nm) excitations via downshifting (DS) and upconversion (UC) processes, respectively. Upon UV (393 nm) excitation of the sample, the Eu3+ ions absorb this energy and then transfer it to a neighboring pair of Yb3+ ions giving NIR emission (900–1100 nm) corresponding to the 2F5/2 → 2F7/2 transition of Yb3+. The energy transfer from a single Eu3+ ion to a pair of Yb3+ ions is possible because of the quantum cutting (QC) process and this energy transfer efficiency is found to increase with the increasing concentration of the Yb3+. The quantitative estimation of energy transfer and internal quantum cutting efficiency is determined by measuring the decay kinetics. An activation energy of 0.25 eV indicates the good thermal stability of the sample. Furthermore, samples are suitable for use in practical applications in lighting devices by combining them with the near-ultraviolet (NUV; InGaN) chip. The fabricated LED device shows stability with the driving current flow values. Studies indicate that the present nanophosphor could be useful for display devices, and in enhancing the spectral conversion efficiency of the solar cells. [ABSTRACT FROM AUTHOR]

Optical ceramics YSAG:Yb,Er with an average grain size of 6 ± 1 microns were fabricated by vacuum sintering of nanocrystalline powders of the compositions Y2.34Yb0.45Er0.09Sc0.20Al4.92O12, Y1.66Yb0.45Er0.09Sc1.00Al4.80O12 and Y0.96Yb0.45Er0.09Sc1.70Al4.80O12. The linear transmittance coefficients of the YSAG:Yb,Er ceramic samples exceed 80% in the visible and infrared regions. The refractive index of ceramics increased from 1.827 to 1.859 with an increase in scandium content. The effect of scandium cations at the dodecahedral site of the YSAG crystal lattice on the optical and luminescence characteristics of Yb3+ (2F7/2 and 2F5/2) and Er3+ (4I15/2, 4I13/2, 4F9/2 and 4S13/2) in wavelength ranges of 530–690 nm, 890–1080 nm, and 1430–1680 nm was revealed. [ABSTRACT FROM AUTHOR]

At present, most fluorescent materials that can be used for optical temperature measurement exhibit poor thermochromic performance, which limits their applications. In this study, the phosphor Ba3In(PO4)3:Er/Yb was synthesized with a high doping concentration of Yb3+, and it emitted composition- and temperature-induced wide color gamut up-conversion luminescence from red to green. Four modes of fluorescence thermometry can be realized in the temperature range of 303–603 K, which is based on the ratio of fluorescence intensity between thermally coupled energy levels and non-thermally coupled energy levels, color coordinate shift, and fluorescence decay lifetime, respectively. The highest Sr value obtained was 0.977% K−1. Taking advantage of the fact that temperature can significantly change the luminous color of the phosphor Ba3In(PO4)3:0.02Er3+/0.05Yb3+, we demonstrated 'temperature mapping' on a smooth metal surface with multiple optical encryptions. These results indicate that the Ba3In(PO4)3:Er/Yb phosphor is an excellent fluorescent material for thermal imaging and has great application potential in temperature visualization measurement and optical encryption. [ABSTRACT FROM AUTHOR]

Oxides are physically and chemically stable. Non-contact thermometer—Yb3+–Er3+ ions co-doped solid solution (Y0.5In0.5)2O3, is prepared by the regular solid method. The structural results obtained by XRD indicate that a pure phase solid solution (Y0.5In0.5)2O3 has been obtained. The solid solution (Y0.5In0.5)2O3 has a similar crystal structure, especially Y2O3 and In2O3 with the same space group (Ia3¯). Green emission from 500 to 600 nm is due to Er3+ 4f–4f transitions: 4S3/2 → 4I15/2 at 567 nm and 2H11/2 → 4I15/2 at 528 nm. Red emissions from 630 to 720 nm are attributed to Er3+: 4F9/2 → 4I15/2. UC luminescence changes greatly with laser diode power and Er3+ and Yb3+ content. Furthermore, the two-photon process is confirmed to be dominant between Yb3+ and Er3+ in oxide solid solution (Y0.5In0.5)2O3. Optical temperature sensitivity is also investigated systematically in order to explore the application of the oxide solid solution (Y0.5In0.5)2O3. The temperature-dependent green fluorescence at 528 and 567 nm was investigated with the range of 313–573 K. 0.316% K−1 is the maximum absolute sensitivity at 503 K, which is higher than most Yb3+/Er3+ co-doped systems. In addition, the solid solution (Y0.5In0.5)2O3:Yb3+,Er3+ has better thermal stability and stronger UC emission than a simple substance with excellent temperature sensing performance. It indicates that Yb3+–Er3+ ions co-doped (Y0.5In0.5)2O3 solid solution is a good candidate for optical temperature sensing. [ABSTRACT FROM AUTHOR]

Rare earth ion doped luminescent materials are considered potential candidates with a wide range of applications because of their unique optical characteristics. In this work, single-phase Yb3+–Er3+ and Yb3+–Tm3+ co-doped La1.55SiO4.33 (LS) phosphors of a hexagonal system for optical thermometers are reported. Three characteristic emissions of Er3+ were observed at 521, 553 and 659 nm in the LS:Yb3+,Er3+ phosphors under 980 nm excitation, which are assigned to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. In the LS:Yb3+,Tm3+ phosphors, one can find two strong emissions at 474 and 790 nm and two weak emissions at 648 and 685 nm. Their upconversion (UC) luminescence mechanisms were studied from their pump-power-dependent spectra. When the samples were measured at various temperatures, their spectral features revealed that different fluorescence intensity ratio (FIR) strategies can be used to characterize their optical temperature-sensing behaviors. The sensor sensitivities were determined from the temperature-dependent UC emission spectra using thermally coupled energy levels (TCELs) and non-TCELs, which had improved compared with those of some other reported optical temperature-sensing luminescent materials. The device fabrication indicated that the developed UC phosphors are promising for applications in optical thermometers. [ABSTRACT FROM AUTHOR]

BiTa7O19:Er3+/Yb3+/Sb phosphors were successfully synthesized by high temperature solid sintering. X-ray diffraction (XRD), fluorescence spectrometry and X-ray photoelectron spectroscopy (XPS), were used to analyze the phase structure, upconversion luminescence (UCL) features and Sb valence state, respectively. The results suggest that polyvalent Sb with Sb3+ and Sb5+ can replace the Ta5+ sites in a BiTa7O19 host to form a pure phase. Compared with BiTa7O19:0.1Er3+/0.4Yb3+, polyvalent Sb doping further improves UCL intensity by 1.2 times under 980 nm laser stimulation with a powder density of 44.59 W cm−2. This is due to the adjustment of the local lattice structure of BiTa7O19 by the polyvalent Sb. The maximum absolute sensitivity (SA) and relative sensitivity (SR) can be estimated from the UCL variable-temperature spectra as 0.0098 K−1 at 356 K and 0.0078 K−1 at 303 K using the luminescence intensity ratio (LIR) approach. The outcomes show that host local lattice adjustment using polyvalent elements is an effective way to improve luminescence intensity, and it is possible to use BiTa7O19:Er3+/Yb3+/Sb as a temperature sensor. [ABSTRACT FROM AUTHOR]

A new series of BaRE6(Ge2O7)2(Ge3O10) (RE = Tm, Yb, Lu) germanates and activated phases BaYb6(Ge2O7)2(Ge3O10):xTm3+ and BaLu6(Ge2O7)2(Ge3O10):12yYb3+,yTm3+ have been prepared using a solid-state reaction. An XRPD study has revealed that the compounds crystallize in the monoclinic system (space group P21/m, Z = 2). The crystal lattice consists of zigzag chains of edge-sharing distorted REO6 octahedra, bowed trigermanate [Ge3O10] units, [Ge2O7] groups, and eight-coordinated Ba atoms. The density functional theory calculations have confirmed a high thermodynamic stability of the synthesized solid solutions. According to the results of vibrational spectroscopy studies and diffuse reflectance measurements, the BaRE6(Ge2O7)2(Ge3O10) germanates are promising compounds for the creation of efficient lanthanide ion activated phosphors. Under 980 nm laser diode excitation, the BaYb6(Ge2O7)2(Ge3O10):xTm3+ and BaLu6(Ge2O7)2(Ge3O10):12yYb3+,yTm3+ samples exhibit upconversion luminescence corresponding to the characteristic 1G4 → 3H6 (455–500 nm), 1G4 → 3F4 (645–673 nm) and 3H4 → 3H6 (750–850 nm) transitions in Tm3+ ions. Heating of the BaLu6(Ge2O7)2(Ge3O10):12yYb3+,yTm3+ phosphor with the optimal composition up to 498 K leads to the enhancement of a broad band at 673–730 nm, caused by 3F2,3 → 3H6 transitions. It has been revealed that the fluorescence intensity ratio between this band and the band at 750–850 nm may be used for temperature sensing. The absolute and relative sensitivities in the studied temperature range reach 0.021% K−1 and 1.94% K−1, respectively. [ABSTRACT FROM AUTHOR]

Na2MgScF7 (NMSF) was experimentally obtained for the first time by combining hydrothermal and high-temperature solid-state reactions. X-ray powder diffraction (XRD) combined with Rietveld refinement confirms that NMSF is crystallized in the space group Imma with the cell parameters a = 10.40860(18), b = 7.32804(12) and c = 7.52879(11) Å, α = β = γ = 90° and V = 574.256(24) Å3. Through doping with Tb3+ or Eu3+ ions, downshifting yellow-green or red emission could be achieved in NMSF-based phosphors, respectively. Upconversion emission could also be designed by doping with Yb3+–Er3+, Yb3+–Tm3+, Yb3+–Ho3+ or Er3+. Moreover, the NMSF:Er3+ phosphor exhibited green upconversion emission upon excitation at 980 nm, and it exhibited red emission upon excitation at 1532 nm. Finally, recognizable patterns were obtained under excitation at 254, 365 and 980 nm, indicating that the as-prepared phosphors can be applied to multicolor anti-counterfeiting. Moreover, our synthesis strategy opens up new avenues for the synthesis of novel fluorides. [ABSTRACT FROM AUTHOR]

In this work, novel carbon skeleton materials were prepared by high-temperature carbonization of rare earth phthalocyanines (MPcs) (M = Yb, La) under a nitrogen atmosphere. The resulting carbon materials of YbPc-900 (carbonisation temperature of 900 °C for 2 h) and LaPc-1000 (carbonization temperature of 1000 °C for 2 h) have a graphite-layered structure in predominantly ordered states, with a smaller particle size, a larger specific surface area and a higher degree of hard carbonization compared to those of the uncarbonized sample. As a result, the batteries using the YbPc-900 and LaPc-1000 carbon skeleton materials as electrodes display excellent energy storage behaviors. The initial capacities of the YbPc-900 and LaPc-1000 electrodes at 0.05 A g−1 were 1100 and 850 mA h g−1, respectively. After 245 cycles and 223 cycles, the capacities remain at 780 and 716 mA h g−1 with retention ratios of 71% and 84%. At a high rate of 1.0 A g−1, the initial capacities of the YbPc-900 and LaPc-1000 electrodes were 400 and 520 mA h g−1, respectively, and after 300 cycles, the capacities can still remain at 526 and 587 mA h g−1 with retention ratios of 131.5% and 112.8%, respectively, which were much higher than those of the pristine rare earth phthalocyanine (MPc) (M = Yb, La) electrodes. Moreover, better rate capabilities were also observed during the YbPc-900 and LaPc-1000 electrode tests. The capacities of the YbPc-900 electrode at 0.05, 0.1, 0.2, 0.5, 1 and 2C were 520, 450, 407, 350, 300 and 260 mA h g−1 respectively, which were higher than those of the YbPc electrode (550, 450, 330, 150, 90 and 40 mA h g−1). Similarly, the rate performance of the LaPc-1000 electrode at different rates was also significantly improved compared to that of the pristine LaPc electrode. In addition, the initial Coulomb efficiencies of the YbPc-900 and LaPc-1000 electrodes were also greatly improved compared to those of pristine YbPc and LaPc electrodes. After carbonization, the YbPc-900 and LaPc-1000 carbon skeleton materials derived from rare earth phthalocyanines (MPcs) (M = Yb, La) exhibit improved energy storage behaviors, which would provide new ideas for developing novel organic carbon skeleton negative materials for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Monomeric, divalent ytterbium primary amides TptBu,MeYb(NHR)(thf)x (R = C6H3iPr2-2,6 = AriPr = Dipp, C6H3(CF3)2-3,5 = ArCF3, SiPh3) supported by the bulky hydrotris(3-tBu-5-Me-pyrazolyl)borato scorpionate ligand are synthesized acccording to salt metathesis and protonolysis protocols, respectively. Yb(II) precursors comprise YbI2(thf)2, Yb[N(SiMe3)2]2(thf)2 and TptBu,MeYb[N(SiMe3)2]. Complexes TptBu,MeYb(NHR)(thf)x readily engage in donor (thf) exchange with nitrogen donors like DMAP (4-dimethylaminopyridine) and pyridine. Treatment of TptBu,MeYb(NHArCF3)(thf)2 with the Lewis acids AlMe3 and GaMe3 results in the heterobimetallic complexes TptBu,MeYb(NHArCF3)(MMe3) (M = Al, Ga). Reactions of TptBu,MeYb(NHR)(thf)x (R = AriPr, ArCF3) with the halogenating agents C2Cl6 and TeBr4 give access to trivalent complexes [TptBu,MeYb(NHR)(X)] (X = Cl, Br). The ytterbium(II) complexes under study display 171Yb NMR chemical shifts in the range 582 ppm for TptBu,MeYb(NHArCF3)(GaMe3) to 954 ppm for TptBu,MeYb(NHSiPh3)(dmap). The salt-metathesis route is also applicable for the synthesis of complexes TptBu,MeLn(NHAriPr)(thf) (Ln = Sm, Eu) and TptBu,MeYb(NHArMe) (ArMe = C6H3Me2-2,6). [ABSTRACT FROM AUTHOR]

The chemistry of the tris-carbene anion phenyltris(3-alkyl-imidazoline-2-yliden-1-yl)borate, [C3Me]− ligand, is initiated for f-block metal cations. Neutral, molecular complexes of the form Ln(C3)2I are formed for cerium(III), while a separated ion pair [Ln(C3)2]I forms for ytterbium(III). DFT/QTAIM computational analyses of the complexes and related tridentate tris(pyrazolyl)borate (Tp) – supported analogs demonstrates the anticipated strength of the σ donation and confirms greater covalency in the metal–carbon bonds of the [C3Me]− complexes in comparison with those in the TpMe,Me complexes. The DFT calculations demonstrate the crucial role of THF solvent in accurately reproducing the contrasting molecular and ion-pair geometries observed experimentally for the Ce and Yb complexes. [ABSTRACT FROM AUTHOR]

The cubic Laves-phase aluminides REAl2 with RE = Sc, Y, La, Yb and Lu were prepared from the elements by arc-melting or using refractory metal ampoules and induction heating. They all crystallize in the cubic crystal system with space group Fd3¯m and adopt the MgCu2 type structure. The title compounds were characterized by powder X-ray diffraction and spectroscopically investigated using Raman and 27Al and in the case of ScAl2 by 45Sc solid-state MAS NMR. In both, the Raman and NMR spectra, the aluminides exhibit only one signal due to the crystal structure. DFT calculations were used to calculate Bader charges illustrating the charge transfer in these compounds along with NMR parameters and densities of states. Finally, the bonding situation was assessed by means of ELF calculations rendering these compounds aluminides with positively charged REδ+ cations embedded in an [Al2]δ− polyanion. [ABSTRACT FROM AUTHOR]

Rare earth-doped oxyfluoride glass-ceramic (GC) demonstrate the physical, chemical, and mechanical stabilities of oxide glass and excellent optical properties of fluoride crystals and is regarded as a potential material for developing advanced optical devices. In the present study, Li+-doped NaYF4:Er,Yb GC was prepared by the traditional melt-quenching method. Upon the excitation of single 980 and 1550 nm lasers, the upconversion (UC) luminescence intensities of green and red emission were enhanced due to the introduction of the crystal field symmetry reducing available Li+ ions of the use of dual-wavelength (980 and 1550 nm) co-excitation and could further enhance the UC luminescence intensity owing to its synergetic effect, which is suitable for the design of all-optical logic gates. The all-optical UC logic gates and complex logic operations ("YES + OR", "INH + YES", "XOR + YES", and "INH + AND + YES + OR") are designed by taking the two excitation sources as input signals and UC emission as output signals. The results provide a novel strategy to enhance UC luminescence and further information for the design of novel photonic logic devices for future optical computing technologies. [ABSTRACT FROM AUTHOR]

Luminescent anti-counterfeiting materials have drawn much attention in anti-counterfeiting applications due to their photochemical stability and emission patterns. However, conventional materials majorly use single-mode luminescence, leaving a growing demand for new materials to prevent counterfeiting. In this work, multi-mode anti-counterfeiting is guaranteed from a single luminescent material CaCd2Ga2Ge3O12:Tb3+,Yb3+via a high-temperature solid-state reaction. The experimental result showed that this single material features green luminescence with excellent photoluminescence, afterglow, thermoluminescence, and up-conversion luminescence, which are ascribed to Tb3+ transitions. Upon co-doping with Yb3+ as a sensitiser, the photo-stimuli responsiveness was achieved at 254 and 980 nm excitation sources, respectively, and the thermo-stimuli responsiveness was realised after exposure to UV of 254 nm for 10 s and heating at 45 °C, respectively. The band structure calculation, trap distribution, and effective trap depths were used to explain the luminescence mechanism. Based on the two-stimuli responsiveness and four-state emission performance, we prepared images of optical devices using silk screen printing technology. It was found that the images displayed green emission under different luminescence modes. The results prove that we successfully constructed an advanced luminescence anti-counterfeiting material. [ABSTRACT FROM AUTHOR]

The reaction between the 2-(1-(2,6-di(pyrazol-1-yl)-4-methylpyridyl)-4,5-(4,5-bis(propylthio)-tetrathiafulvalenyl)-1H-benzimidazol-2-yl)-pyridine ligand (L), 1 equivalent of Ln(hfac)3·2H2O/Dy(tta)3·2H2O (hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate, tta− = 2-thenoyltrifluoroacetonate) and M(hfac)2·2H2O leads to the formation of heteroleptic 3d–4f dinuclear complexes of formula [MLn(hfac)5(L)]n (M(II) = Cd, Zn, Co, Mn, Ni and Ln(III) = Dy, Yb, Nd) and [ZnDy(tta)2(hfac)3(L)]·(CH2Cl2). Their X-ray structures reveal that the two coordination sites are occupied by one Ln(III) ion and one M(II) transition metal respectively. The M(II) ions are coordinated to the benzoimidazolylpyridine (bzip) moiety in a N2O4 coordination sphere, while the Ln(III) ions are coordinated to the 2,6-di(pyrazol-1-yl)-4-pyridine (dpp) moiety in a N3O6 surrounding. When Dy(III) ion is used a field-induced Single-Molecule Magnet (SMM) behavior is detected with a magnetic relaxation time slightly dependent to the nature of the vicinal divalent transition metal. On the other hand, when the Yb(III) is used, intense, moderated or quenched 2F5/2 → 2F7/2 NIR luminescence is observed when the Yb(III) ion is respectively associated with the Zn(II), Mn(II) and Ni(II)/Co(II) ion. The emission intensity can be modulated in function of the metal-to-ligand charge transfer and d–d transition intensities. The replacement of the divalent transition metal by a trivalent lanthanide leads to the formation of heteroleptic 4f–4f′ dinuclear complexes of formula [Ln2−xLn′x(hfac)6(L)]·a(CH2Cl2)·b(C6H14) and [Dy1.11Nd0.89(tta)3(hfac)3(L)]. The coordination selectivity is based on the radius. Among the 4f–4f′ series, the Dy(III) derivatives displayed such ion in N2O6 eight-coordinated sphere allowing the observation of SMM behavior. The three compounds [Dy1.21Nd0.79(hfac)6(L)]·2(CH2Cl2)·(C6H14), [Yb1.04Nd0.96(hfac)6(L)] and [YbPr(hfac)6(L)] displayed respectively Nd(III), modarated Yb(III) and intense Yb(III) NIR emissions. [ABSTRACT FROM AUTHOR]

Red up-conversion luminescence with both emission and excitation peaks within the "tissue transparency window" makes for ideal fluorescent labels for deep tissue penetration and low-background biological imaging. In this work, an efficient strategy is proposed to realize bright red up-conversion luminescence based on interfacial energy transfer (IET), and the luminescence centers (Er3+ and Tm3+) and sensitizers (Yb3+) are doped in separate layers to avoid deleterious cross-relaxation. The IET process between Yb3+ and Er3+ can enable bright red photon up-conversion under 980 nm excitation via fine control and manipulation of the lanthanide ion concentration and shell thickness. By appropriately employing the fluorescence intensity ratio technique, an optical thermometer based on non-thermally coupled energy levels demonstrates a superior relative sensitivity of 2.02% K−1 across the whole temperature region. NaYF4:Er3+,Tm3+@NaYF4:Yb3+ with strong red UC luminescence and highly sensitive performance exhibits potential for application in the field of non-contact temperature sensing. [ABSTRACT FROM AUTHOR]

A new rare-earth borate Na3YB8O15 was fabricated by the flux method. The compound crystallizes in the P1¯ group, and shows a three-dimensional network built by [B8O17] fundamental building blocks (FBBs) with [NaO6], [NaO7], and [YO7] polyhedra. The [B8O17] FBBs are composed of five planar BO3 and three BO4 tetrahedra and connected via corner-sharing to construct a unique one-dimensional (1D) [B8O15]∞ infinity chain that is observed for the first time in the Na2O–Y2O3–B2O3 system compound, enriching the structural diversity of rare-earth borate. The title compound exhibits a short ultraviolet (UV) cutoff edge of ∼195 nm and a wide experimental band gap of 5.50 eV. DFT calculations indicate that Na3YB8O15 is a direct band gap compound with a calculated GGA band gap of 5.14 eV, and the band gap is mainly determined by B 2p and O 2p orbitals. The results update the phase diagram of Na2O–Y2O3–B2O3 and enrich the diversity of rare-earth metal borates. [ABSTRACT FROM AUTHOR]

Coordination chemistry of cyclic (alkyl)(amino)carbene (CAAC) ligands has blossomed in recent years, exemplified by their strong σ-donating and π-accepting ability. However, trivalent rare-earth metal CAAC complexes remain elusive. By using M(CH2SiMe3)3(THF)2 (M = Sc, Y and Lu) as precursors, we synthesized mono CAAC coordinated rare-earth metal trisalkyl complexes, (RCAAC)M(CH2SiMe3)3 (R = Me and Et, M = Sc, Y and Lu). In addition, when MI3(Et2O)n (M = Y and Yb) were employed as metal precursors, bis(CAAC)-stabilized rare-earth metal triiodide complexes (MeCAAC)2MI3 (M = Y and Yb) could be obtained. All new compounds were characterized by X-ray crystallography, elemental analysis and NMR spectroscopy. Density functional theory calculations were conducted for these rare-earth metal CAAC complexes to gain insight into their electronic structures and bonding interactions. The bonding analysis unveils that the CAAC ligands act as σ donors to trivalent rare-earth metal ions and may be involved in π-bonding upon reduction. [ABSTRACT FROM AUTHOR]

Unusual tridentate β-diketiminato rare-earth metal chlorides LRECl(μ-Cl)2Li(THF)2 (RE = Y (1a), Yb (1b), and Lu (1c); L = MeC(NDipp)CHC(Me)N(CH2)2NC4H8O; Dipp = 2,6-iPr2C6H3) and the corresponding dialkyl complexes LRE(CH2SiMe3)2 (RE = Y (2a), Yb (2b), and Lu (2c)) were prepared by reaction of a morpholine-functionalized β-diketiminato proligand HL with anhydrous RECl3 and rare-earth metal trialkyl complexes RE(CH2SiMe3)3(THF)2, respectively. In 1 and 2, the morpholine moiety displayed a stable chair conformation and the resulting ligand coordinated to the rare-earth metal ion in a [NNN]-tridentate chelating fashion. Further studies demonstrated that these dialkyl complexes showed high activity towards the catalytic formation of C–O and C–N bonds in the alcoholysis of isothiocyanates and aminolysis of epoxides. A series of O-thiocarbamate derivatives were achieved in good to excellent yields by reaction of various alcohols with aromatic and aliphatic-substituted isothiocyanates at room temperature. In addition, under solvent-free conditions, the ring-opening reaction of terminal and internal epoxides with arylamines yielded the corresponding β-amino alcohols with excellent regioselectivity. More importantly, a novel β-diketiminato/anilido yttrium alkyl complex LY(NHDipp)(CH2SiMe3) (5a) was isolated and characterized by the stoichiometric reaction of 2a with diisopropylaniline. [ABSTRACT FROM AUTHOR]

Two new ternary compounds, Eu10Mn6Bi12 and Yb10Zn6Sb12, were synthesized and structurally characterized. The synthesis was achieved either through reactions in sealed niobium tubes or in alumina crucibles by combining the elements in excess molten Sb. Their structures were elucidated using single-crystal X-ray diffraction, and they were determined to crystallize in the orthorhombic space group Cmmm (no. 65) with the Eu10Cd6Bi12 structure type. Akin to the archetype phase, both Mn and Zn sites contain about 25% of vacancies. The anionic substructure of the title phases can be described as [M6Pn12] (M = Zn, Mn; Pn = Sb, Bi) double layers composed of the corner and edge-sharing [MPn4] tetrahedra, linked by [Pn2]4− dumbbells. Eu2+/Yb2+ cations fill the space between the layers, with the valence electron counts adhering closely to the Zintl–Klemm rules, i.e., both Eu10Mn6Bi12 and Yb10Zn6Sb12 are expected to be valence-precise compounds. Analysis of the electronic structure and transport properties of Yb10Zn6Sb12 indicate semimetallic behavior with relatively low Seebeck coefficient and resistivity that slightly decreases as a function of temperature. [ABSTRACT FROM AUTHOR]

Two new ternary compounds, Eu10Mn6Bi12 and Yb10Zn6Sb12, were synthesized and structurally characterized. The synthesis was achieved either through reactions in sealed niobium tubes or in alumina crucibles by combining the elements in excess molten Sb. Their structures were elucidated using single-crystal X-ray diffraction, and they were determined to crystallize in the orthorhombic space group Cmmm (no. 65) with the Eu10Cd6Bi12 structure type. Akin to the archetype phase, both Mn and Zn sites contain about 25% of vacancies. The anionic substructure of the title phases can be described as [M6Pn12] (M = Zn, Mn; Pn = Sb, Bi) double layers composed of the corner and edge-sharing [MPn4] tetrahedra, linked by [Pn2]4− dumbbells. Eu2+/Yb2+ cations fill the space between the layers, with the valence electron counts adhering closely to the Zintl–Klemm rules, i.e., both Eu10Mn6Bi12 and Yb10Zn6Sb12 are expected to be valence-precise compounds. Analysis of the electronic structure and transport properties of Yb10Zn6Sb12 indicate semimetallic behavior with relatively low Seebeck coefficient and resistivity that slightly decreases as a function of temperature. [ABSTRACT FROM AUTHOR]

In this work, Yb3+/RE3+ (RE = Er/Ho) co-doped Zn3Mo2O9 phosphors were synthesized by high-temperature solid-state reactions. Under 980 nm excitation, the upconversion (UC) luminescence thermal enhancement was obtained for Zn3Mo2O9:Yb3+/RE3+ phosphors. The green emission intensity of the Zn3Mo2O9:Yb3+/Er3+ sample was increased 5 times from 373 to 573 K. The red emission intensity of the Zn3Mo2O9:Yb3+/Ho3+ sample was enhanced 7.92 times. The anomalous thermal enhancement of UC emission was induced by the negative thermal expansion (NTE) of the Zn3Mo2O9 host. The energy transfer rate from the sensitizer (Yb3+) to the activator (RE3+) was enhanced because of the lattice contraction and distortion for NTE materials. Compared with the UC emission of Er3+single doped Zn3Mo2O9 sample, the luminescence thermal enhancement was absent, which contributed to proving the physical mechanism. The temperature sensing properties of the Zn3Mo2O9:Yb3+/Er3+ and Zn3Mo2O9:Yb3+/Ho3+ samples were also investigated based on the fluorescence intensity ratio (FIR) technology. The absolute sensitivity (SA) and relative sensitivity (SR) of Zn3Mo2O9:Yb3+/Er3+ phosphor reached 0.0060 K−1 and 0.72% K−1, which is based on the thermal coupling levels (2H11/2, 4S3/2) FIR of Er3+ ions. In addition, the SA and SR of Zn3Mo2O9:Yb3+/Ho3+ phosphor reached 0.0119 K−1 and 0.86% K−1, that is based on the non-thermal coupling levels (5S2/5F4, 5F5) FIR of Ho3+ ions. The research results indicate that the Zn3Mo2O9 host shows NET. The Yb3+/RE3+ co-doped Zn3Mo2O9 phosphors are good materials for highly sensitive optical temperature measurement, which can be used to develop thermally enhanced ratiometric optical thermometers. [ABSTRACT FROM AUTHOR]

A series of Er3+/Yb3+ co-doped Cs3BiSr(P2O7)2 (CBSPO) phosphors with significant thermal enhancement were successfully prepared using the solid-state method and the thermal-enhancing effect was studied in detail. When the temperature increased from 303 to 723 K, the upconversion luminescence (UCL) emission intensities of 2H11/2 → 4I15/2 and 2H11/2 + 4S3/2 → 4I15/2 of Er3+ in CBSPO:0.1Er3+/0.2Yb3+ were enhanced 22.81 and 10.06 times under 980 nm laser excitation, respectively. Meanwhile, the UCL color of the sample obviously changed from orange to green with the increase in temperature. Furthermore, the UCL thermal enhancement mechanism was demonstrated, which originates from phonon-assisted transitions. In addition, the maximum absolute temperature sensitivity for CBSPO:0.1Er3+/0.2Yb3+ was calculated to be 0.01026 K−1 at 563 K via luminescence intensity ratio (LIR) technology. All the results show that the CBSPO:Er3+/Yb3+ phosphors can be used for safety warning and temperature measurement at high temperatures. [ABSTRACT FROM AUTHOR]

Rare earth (RE) doped perovskite oxide hosts especially titanates, are promising phosphor materials in terms of white-light emission owing to their extraordinary properties such as an exceptional hosting environment for RE-ions and a switchable crystal phase near the phase boundary. Here, we report a new strategy of crystal phase modification to enhance the blue upconversion (UC) efficiency to such an extent that the combinational mixing of blue and green/red-emitting phosphor gives intense white emission. The Lead free (Ba0.85Ca0.15)(Zr,Ti)O3 ceramics were synthesised at different sintering temperatures by incorporation of Tm3+/Yb3+ ions as dopants. The UC quantum efficiency of the Tm3+/Yb3+:BCZT sample sintered at 1300 °C was recorded at different excitation power densities. It was observed that the crystal phase transformation from tetragonal to rhombohedral symmetry in the sample near the phase boundary plays a cruicial role in improving the quantum efficiency. White-light emission applications were demonstrated by preparing biphasic samples with powder mixing of a BCZT:Tm3+/Yb3+ (blue-emitting) + BCZT:Er3+/Yb3+ (green/red-emitting) phosphor, and their composition were optimised at a mixed ratio. Thereafter, photometric characterization (CIE chromaticity, colour purity and corelated colour temperatures) was performed, and it indicated the suitability of the current biphasic samples in direct white-light (cooler) applications on an industrial scale. Crystal phase modified blue emission efficiency enhancement is a key feature of this work, which helps to generate approximately pure white-light with ideal chromacity (∼0.333, 0.343) emission when Tm3+/Yb3+:BCZT is mixed with a green emitting BCZT:Er3+/Yb3+ phosphor. [ABSTRACT FROM AUTHOR]

Phosphors with rare earth (RE) ions are widely applied to optical temperature measurements. Moreover, the near-infrared (NIR) emission of phosphors has potential applications in the biological field. Herein, Gd2O3:x%Nd3+/Yb3+(0.2 ≤ x ≤ 0.8) samples are successfully synthesized by the sol–gel method, and their phase and morphology are characterized. The XRD data are refined by Rietveld. Under 980 nm continuous wave (CW) laser excitation, the upconversion (UC) and downshift (DS) emissions are studied. The temperature sensing performances of thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) of Gd2O3: Nd3+/Yb3+ phosphors are investigated through the fluorescence intensity ratio (FIR) technology. In the temperature range of 303–523 K, the maximum relative sensitivity of I761 nm/I550 nm reaches 6.54% K−1, which is based on non-TCLs. At the same time, the maximum relative sensitivity of I761 nm/I1000 nm–1500 nm reaches 3.13%. In addition, the influence of the laser induced heating (LIH) effect is studied. Compared with square wave (SW) pumping, the relative sensitivity would decrease at CW excitation. Finally, the durability and temperature uncertainty are also discussed. The results prove that the Gd2O3:Nd3+/Yb3+ samples present higher relative sensitivity and durability and lower temperature uncertainty in the biological window. Therefore, the phosphors can be used as optical thermometers in the biological field. [ABSTRACT FROM AUTHOR]

Heterobimetallic Ln(III)–Pd(0) complexes (Ln = Y, Sm, Gd, Yb) featuring tetranuclear structures with COD as bridges were obtained via the metallation of tris(phosphinoamido) rare-earth metal complexes [Ph2PNAd]3Ln (Ad = adamantyl) with (COD)Pd(CH2SiMe3)2. Notably, the Sc(III)–Pd(0) complex possesses a C3-symmetry with a very short Sc–Pd bond length of 2.432(2) Å, while the tetranuclear complexes exhibited versatile structures both in solution and in the solid state. Reduction of the trivalent complex (Ph2PNAd)3Yb with one equivalent of KC8 in the presence of 18-c-6 afforded the divalent complex [(Ph2PNAd)3Yb][(18-c-6)K(THF)2], which was further reacted with (Ph3P)4Pd to form the first Yb(II)–Pd(0) complex. The Pd(0) → Yb dative interaction weakened significantly from Yb(III) to Yb(II) based on computational studies, which was attributed to the attenuated Lewis acidity of the Yb(II) center. Reactions of Ln(III)–Pd(0) complexes (Ln = Sc and Yb) with the disulfide PhSSPh showed that the Pd(0) center served as a two-electron donor while the reaction apparently occurred on the Ln(III) centers to form Ln(III)–Pd(0) bis-sulfide complexes. [ABSTRACT FROM AUTHOR]

In this paper, Er3+/Yb3+ co-doped CdMoO4 phosphors were prepared by a traditional high temperature solid state reaction method. Based on the 3D network structure of the CdMoO4 host and the efficient Er3+/Yb3+ upconversion luminescence combinations, excellent green emission properties were observed when the prepared sample is irradiated with a laser at about 980 nm. For optical temperature sensors based on the fluorescence intensity ratio (FIR), the prepared phosphors have excellent sensitivity to temperature in the range of 293 to 473 K. With increasing environmental temperatures, the absolute sensitivity of the CdMoO4:0.02Er3+,0.08Yb3+ sample reached a maximum at about 473 K (Sa = 1.388% K−1). The calculated relative sensitivity of the optical temperature sensor was Sr = 1.631% K−1 at 293 K. This is due to the sensitive thermally coupled energy levels (TCLs) of the Er3+ ions (2H11/2 and 4S3/2) in the CdMoO4 structure. Therefore, it is shown that the prepared CdMoO4:0.02Er3+,0.08Yb3+ phosphor has excellent applications in non-contact optical temperature measurement. [ABSTRACT FROM AUTHOR]

Five novel lanthanide-substituted polyoxomolybdates (NH4)5Na3H2[{Ln(H2O)7}2{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]·nH2O [Ln = Tb3+ (1), Ho3+ (2), Er3+ (3), Tm3+ (4), Yb3+ (5); n = 33, 32, 41, 30, 47] have been prepared in a conventional aqueous solution reaction of ammonium molybdate with Ln3+ ions and p-xylyenediphosphonic acid. Crystal structure analyses reveal that 1–5 are isomorphic. The prominent architecture characteristic is that their structural units consist of a tetrameric cyclic-shaped [{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]16− segment stabilized by two [Ln(H2O)7]3+ cations, which are connected to propagate one-dimensional chain by Ln3+ ions. As is known, compounds 1–5 stand for the first Ln-substituted aromatic-bisphosphonate-functionalized polyoxomolybdates. The solid-state photoluminescence measurement of 1 has been performed at ambient temperature, and it displayed the characteristic emissions of Tb ions based on its 4f–4f transitions. In addition, the magnetic properties of 1–5 compounds show that they all exhibit anti-ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Multimetallic neodymium–ytterbium–gadolinium compounds with 9-anthracenate and 9-acridinate anions were tested in order to create the first luminescent thermometer for elevated temperatures. High luminescence intensity and high signal resolution were reached thanks to the concentration quenching elimination due to the partial substitution of the emitting ions with Gd3+. As a result, NIR emitting materials for luminescence thermometry in the wide temperature range (83–393 K) based on lanthanide coordination compounds (CCs) were obtained. The best thermometric properties among the studied systems were demonstrated by Yb0.02Nd0.12Gd0.86(ant)3, and its temperature sensitivity reached 1.8% K−1 in the temperature range of 293–393 K. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of rare-earth metal complexes with redox-active formazanate ligands are described. Deprotonation of the neutral formazan ligand L1H (L1 = PhNNC(Ph)NNPh) with [Ln{N(SiMe3)2}3] (Ln = Y, Sm, Dy) resulted in homoleptic tris(formazanate) complexes with the general formula [(L1)3Ln] (Ln = Y (1), Sm (2), Dy (3)), in which the central metal atom is coordinated by six N atoms, revealing a propeller-type structure. To generate heteroleptic complexes, a novel formazan ligand L2H (L2 = {PhNNC(4-tBuPh)NNPh}) was employed. Salt metathesis by using the trivalent precursors [SmCp*2(μ-Cl)2K(thf)] (Cp* = η5-C5Me5) or [LnCp2Cl]2 (Cp = η5-C5H5, Ln = Dy, Yb) and [L2K(thf)] formed mono(formazanate) complexes, [L2SmCp*2] (4) and [L2LnCp2] (Ln = Dy (5), Yb (6)), respectively. Unexpectedly, a redox reaction occurred between [L2K(thf)] and the divalent ytterbium precursor, [YbI2(thf)2], generating the trivalent ytterbium complex [(L2)3Yb] (7). When the neutral formazan ligand (L2H) reacted with [SmCp*2(thf)2], the oxidised samarium complex 4 was formed. These novel compounds were fully characterised and their electrochemical properties were explored by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

In the last few years, huge progress has been made in the development of remote optical thermometry strategies, due to their non-contact, high-sensitivity and fast measurement characteristics, which are especially important for various industrial and bio-applications. For these purposes, lanthanide-doped particles seem to be the most promising luminescence thermometers. In this study, Tm3+/Yb3+:Na3GdV2O8 (NGVO) phosphors were prepared using a sol–gel method. Under 980 nm excitation, the upconversion (UC) and down-shifting (DS) emission spectra are composed of two visible emission bands arising from the Tm3+ transitions 1G4 → 3H6 (475 nm) and 1G4 → 3F4 (651 nm), a strong emission at 800 nm (3H4 → 3H6) in the first biological window and emission in the third biological window at 1625 nm (3F4 → 3H6), respectively. Accordingly, the luminescence intensity ratio (LIR) between the Tm3+ LIR1 (800/475) and LIR2 (1625/475) transitions demonstrates excellent relative sensing sensitivity values (4.2% K−1–2% K−1) and low-temperature uncertainties (0.4 K–0.5 K) over a wide temperature sensing range of 300 K to 565 K, which are remarkably better than those of many other luminescence thermometers. This phosphor exhibits strong NIR emission at low excitation density, meaning that it has potential uses in deep tissue imaging, optical signal amplification and other fields. The results indicate that Tm3+/Yb3+:NGVO is an ideal candidate for thermometers and particularly for biological applications. [ABSTRACT FROM AUTHOR]