Near-infrared Upconversion Luminescence Research Articles

The single near-infrared upconversion luminescence of a novel KYb (MoO4)2: Er3+ phosphor for the temperature sensing

The rare earth doping upconversion luminescence (UCL) materials exhibit multimodal emission, which has huge potential applications. However, it is still a difficult problem to obtain a single emission by modulating UCL, especially the modulation of single red light and single near-infrared light. In this work, we report a novel UCL KYb (MoO4)2: Er3+ phosphor, which can achieve a single near-infrared emission (804 nm) under rare earth Er3+ doping. Its pure phase was successfully prepared by high-temperature solid-state method, and its optimal Er3+ doping concentration was found to be 0.1 %. Excited at 980 nm laser, KYb (MoO4)2: Er3+ exhibit a single near-infrared UCL attributed to the 4I9/2 → 4I15/2 transition of Er3+ ions. To further explain its UCL mechanism, the power dependence, ultraviolet-visible-near-infrared absorption spectrum, excitation spectrum and emission spectrum of KYb (MoO4)2: Er3+ was measured. Due to the excellent near-infrared emission, the temperature-dependent UCL properties of the KYb (MoO4)2: Er3+ material is investigated in the temperature range from 298 K to 673 K. The linear relationship between the UCL and the temperature, And the sensitivity of KYb (MoO4)2: Er3+ phosphor reaches the maximum value at 673 K, which is 0.0078 K−1. The single near-infrared luminescence with good penetrability and large sensitivity makes KYb (MoO4)2: Er3+ have a promising application prospect in the fields of non-contact temperature sensing and bioimaging.

Luminescence Thermometry Based on the Upconversion Luminescence from the Stark Sublevels of BaY2F8:Yb3+, Tm3+ Phosphor.

Visible and near-infrared (NIR) upconversion luminescence (UCL) emissions originating from the BaY2F8: Yb3+, Tm3+ systems were investigated under a laser excitation at 980nm. The BaY2F8:20mol% Yb3+, x mol% Tm3+ and BaY2F8: y mol% Yb3+, 0.5mol% Tm3+ phosphors showed prominent UCL at 800 and 810nm. The optimized doping concentrations of Yb3+ and Tm3+ in the BaY2F8 host matrix were evaluated, their spectroscopic properties were determined, and studies on their temperature-dependent behaviour were carried out. The temperature-sensing properties were studied by generating the fluorescence intensity ratio (FIR) of the UCL peaks originating from the thermally-coupled energy levels of the Tm3+ ions. The Stark sublevels of 1G4 level of Tm3+ ions were utilized to estimate the temperature-sensing abilities of the phosphor.

Optical transition and near-infrared upconversion luminescence properties of YNbO4: Er3+, Yb3+ phosphors

Optical transition and near-infrared upconversion luminescence properties of Er3+ single-doped and Er3+, Yb3+ co-doped YNbO4 phosphors are reported. Based on the framework of Judd-Ofelt theory and modified Judd-Ofelt calculation method, the optical transition properties of Er3+ and Yb3+ ions in YNbO4: Er3+, Yb3+ sample were studied, respectively. The calculated results showed that the absorption cross-section of Er3+ ion at ∼1550 nm is larger than that at ∼980 nm in YNbO4: Er3+ phosphor. And, the absorption cross-section of 2F7/2 → 2F5/2 transition of Yb3+ in YNbO4: 15.0 mol% Er3+, 15.0 mol% Yb3+ sample was calculated to be 138.70 × 10−20 cm2. According to the emission cross section of Er3+ (4I11/2 → 4I15/2) and the absorption cross section of Yb3+ (2F7/2 → 2F5/2), the energy transfer rates from Er3+ to Yb3+ were quantitatively analyzed via the Föster-Dexter model. Furthermore, 1550 nm was selected as the excitation wavelength, the near-infrared upconversion emission spectra of YNbO4: Er3+, Yb3+ samples were measured. It was found that the sample has strong emission at ∼980 nm and the emission intensity was still enhanced with the incorporation of Yb3+.

Infrared to visible up-conversion luminescence of SrF2:Ho particles upon excitation of the 5I7 level of Ho3+ ions

The visible and near-infrared (NIR) up-conversion luminescence (UCL) of a concentration series of fluoride phosphors SrF2:Ho (CHo = 1.3, 3.5, 4.8, 7.4, 8.9, 10.8, 13.0, 13.6 mol.%) upon excitation of the 5I7 level of Ho3+ ions are presented. The dependences of the UCL intensity corresponding to the 5F3→5I8, 5S2(5F4)→5I8, 5F5→5I8, 5I4→5I8, 5F3→5I6, 5I5→5I8, 5F5→5I7, 5I6→5I8 transitions on the concentration of Ho3+ ions were revealed. The UCL energy yield, color coordinates, and correlated color temperature (CCT) values were estimated. The maximum values of UCL energy yields of 0.03% (380–780 nm) and 0.09% (380–1100 nm) were registered for SrF2:Ho (3.5 mol.%) sample. All studied fluoride phosphors are characterized by a red glow of UCL. This glow corresponds to CCT of 6711–7474 K upon incident power density of 28 W/cm2. The UCL mechanisms of SrF2:Ho phosphors were proposed. The SrF2:Ho phosphors can be used as laser beam viewers of the two-micron radiation of thulium and holmium commercial lasers.

Temperature sensing properties of NaYTiO4: Yb/Tm phosphors based on near-infrared up-conversion luminescence

In this study, NaYTiO4: Yb/Tm phosphors with different concentrations of Yb3+ and Tm3+ ions were synthesized by conventional solid-state reaction. Upon a 980 nm laser excitation, the up-conversion luminescence properties in a wide temperature range (303–823 K) were investigated. By employing the fluorescence intensity ratio (FIR) techniques based on the robust near-infrared emissions of thermally coupled 3F2,3/3H4 energy levels and 3H4(1)/3H4(2) Stark energy levels, the calculated absolute sensitivity (Sa), relative sensitivity (Sr), and temperature uncertainty (δT) values demonstrated good temperature sensing properties. For the 3F2,3/3H4 energy levels, the maximum Sr and minimum δT values are 1.04% K−1 and 0.010 K at 463 K, respectively. Moreover, the maximum Sa is 0.32 × 10−3 K−1 at 823 K. In addition, the thermally coupled 3H4 Stark energy levels present the maximum Sa, Sr and the minimum δT are 0.88 × 10−3 K−1, 0.60% K−1 and 3.17 K at 303 K, respectively. Besides, due to the ratio of blue to red emission varying with elevated temperature, the NaYTiO4: Yb/Tm phosphors are expected to be applied as an intuitive high-temperature indicator.

Second near-infrared upconversion and downconversion luminescence in a core–multishell nanophotoswitch

Ho3+ is selected as both the energy trapping center and NIR-II emitter in the core.

Thermal-enhanced near-infrared upconversion luminescence of Er3+ for high-sensitive optical temperature sensing

In this paper, we report the thermal-enhanced near-infrared upconversion luminescence (UCL) from thermal-coupled (TC) energy levels of Er3+ and a new optical temperature sensing strategy in Er3+-doped phosphors. The near-infrared UCL of Er3+ in the wavelength range of 750–900 nm due to the transitions from the 2H11/2 and 4S3/2 TC energy levels to the 4I13/2 metastable energy level showed a thermally enhanced luminescence behavior at elevated temperatures that is related to the enhanced temperature-dependent non-radiative relaxation. The luminescence intensity ratio (LIR) between the near-infrared (2H11/2/4S3/2 → 4I13/2) and the green (2H11/2/4S3/2 → 4I15/2) UCL of Er3+ was studied as a function of temperature and demonstrated good optical thermometry behavior based on the classic Boltzmann distribution. The absolute sensitivity based on the LIR between near-infrared and green UCL of Er3+ was as high as 0.061 K−1, showing a nearly two orders of magnitude improvement compared to that based on the traditional LIR between two green UCL of Er3+. It is anticipated that the near-infrared UCL from TC energy levels of Er3+ can be used to construct new luminescent thermometry devices with high sensitivity, low temperature uncertainty, and good repeatability.

Nano-Crystallization of Ln-Fluoride Crystals in Glass-Ceramics via Inducing of Yb3+ for Efficient Near-Infrared Upconversion Luminescence of Tm3.

Transparent glass-ceramic composites embedded with Ln-fluoride nanocrystals are prepared in this work to enhance the upconversion luminescence of Tm3+. The crystalline phases, microstructures, and photoluminescence properties of samples are carefully investigated. KYb3F10 nanocrystals are proved to controllably precipitate in the glass-ceramics via the inducing of Yb3+ when the doping concentration varies from 0.5 to 1.5 mol%. Pure near-infrared upconversion emissions are observed and the emission intensities are enhanced in the glass-ceramics as compared to in the precursor glass due to the incorporation of Tm3+ into the KYb3F10 crystal structures via substitutions for Yb3+. Furthermore, KYb2F7 crystals are also nano-crystallized in the glass-ceramics when the Yb3+ concentration exceeds 2.0 mol%. The upconversion emission intensity of Tm3+ is further enhanced by seven times as Tm3+ enters the lattice sites of pure KYb2F7 nanocrystals. The designed glass ceramics provide efficient gain materials for optical applications in the biological transmission window. Moreover, the controllable nano-crystallization strategy induced by Yb3+ opens a new way for engineering a wide range of functional nanomaterials with effective incorporation of Ln3+ ions into fluoride crystal structures.

Sensitive quantitative image analysis of bisulfite based on near-infrared upconversion luminescence total internal reflection platform

Bisulfite (HSO3−), serves as an important additive in food industry, is one of the most widely distributed environmental pollutants. Herein, a fast and efficient quantitative image analysis method for the determination of HSO3− has been developed. The method builds a luminescence energy transfer (LET) system utilized upconversion nanoparticles (UCNPs) as an energy donor and cyanine dye molecules as an energy acceptor. The upconversion luminescence is quenched a lot on the addition of dye molecules and gets recovered well with the addition of HSO3−. All the phenomena can be recorded via traditional luminescence spectrometer and near-infrared upconversion luminescence total internal reflection platform. The quantitative image analysis performed on the near-infrared upconversion luminescence total internal reflection platform can significantly reduce sample consumption (10 μL) as well as make a quick and efficient analysis (0.1 s) with a large amout of data become easy. Meanwhile, it shows a wider linear range (1–120 μM), lower detection limit (0.070 μM) and higher detection speed than that of the classical luminescence spectrometer.

Enhanced red and near-infrared upconversion luminescence properties in CaSc2O4 microcrystals

CaSc2O4 co-doped with Yb/Er, Yb/Tm was successfully prepared through a high-temperature solid-state method. The enhanced red and near-infrared upconversion luminescence intensities in CaSc2O4 co-doped with Yb/Er, Yb/Tm were observed. As the increase of Ca2+ ion doping concentration, the crystal phase evolved from cubic Sc2O3 to orthorhombic CaSc2O4, then to cubic CaO. When Ca2+ ion doping concentration is about 40 mol%, CaSc2O4 co-doped with Yb/Er has the maximum red emission intensity (666 nm) which is increased by 39.5 times than that of Sc2O3 microcrystals (MCs). Similarly, the maximum near-infrared emission intensity (807 nm) in CaSc2O4 co-doped with Yb/Tm is enhanced by 9 times than that of Sc2O3 MCs when Ca2+ ion doping concentration is about 40 mol%. They are in accordance with that Er3+ ion and Tm3+ ion exhibit the longest luminescence lifetime in CaSc2O4 MCs than that in Sc2O3 and CaO MCs.

A near-infrared upconversion luminescence total internal reflection platform for quantitative image analysis.

A quantitative image analysis method by counting photons from different samples was developed based on a near-infrared upconversion luminescence total internal reflection platform. The proposed method can not only greatly reduce the consumption of samples (10 μL) but also ensure high-throughput and fast (0.1 s) data analysis.

Silica-Coated Ga(III)-Doped ZnO: Yb3+, Tm3+ Upconversion Nanoparticles for High-Resolution in Vivo Bioimaging using Near-Infrared to Near-Infrared Upconversion Emission.

Photon avalanche has attracted much attention due to the unique nonlinear luminescence dynamics and high-efficiency upconversion luminescence properties. In this paper, we present a simple but effective method to prepare Yb/Tm/GZO@SiO2 (GZO = gallium-doped zinc oxide). Low-threshold photon-avalanche luminescence was obtained below the milliwatts (2.5 mW) in Yb/Tm/GZO@SiO2 core/shell nanoparticles. Compared with Yb/Tm/GZO nanoparitlces, near-infrared (NIR) upconversion luminescence intensity of Yb/Tm/GZO@SiO2 was enhanced ∼12 times. Furthermore, Yb/Tm/GZO@SiO2 acted as luminescence probe, which realized the red fluorescence imaging of myocardial tissue. With injection of 6 mg/kg Yb/Tm/GZO@SiO2, the red NIR fluorescence imaging of heart tissue became brighter. The experimental results of histological assessments of representative organs indicated that there was low toxicity of Yb/Tm/GZO@SiO2 in vivo. This study proved that Yb/Tm/GZO@SiO2 posed a promising potential for bioimaging applications.

Enhancement of near-infrared up-conversion and blue down-conversion luminescence in LuNbO4 :Yb3+ ,Tm3+ with Ga3+ and Ta5+ substitutions.

Under a 980-nm excitation, the up-conversion (UC) spectra of LuNbO4 :Yb3+ ,Tm3+ powders exhibited predominantly near-infrared bands (~805nm) of Tm3+ through an energy transfer process from Yb3+ to Tm3+ . Regarding the down-conversion (DC) luminescence of the powders, the photoluminescence excitation spectra consisted of a broad charge transfer band (270nm) due to [NbO4 ]3- and sharp band (360nm) of Tm3+ , while the corresponding emission spectra exhibited a blue emission at 458nm. Upon substitution of Ga3+ and Ta5+ for Lu3+ and Nb5+ , respectively, both UC and DC luminescence properties were significantly enhanced. For the Ga3+ substitution, the increased emission intensity could be explained by the crystal field asymmetry surrounding the Tm3+ ions induced by the large difference in ionic radius between Ga3+ and Lu3+ . For the Ta5+ substitution, we believe that an M'-LuTaO4 substructure was formed in the host, which led to the formation of a TaO6 octahedral coordination instead of a NbO4 tetrahedral coordination. Consequently, the crystal symmetry of the local structure was modified, and thus the UC and DC luminescence properties were enhanced. The dual-mode (UC and DC) luminescence demonstrates that LuNbO4 :Yb3+ ,Tm3+ has a great potential in the fields of temperature sensing probes, anti-counterfeiting, and bioapplications.

Near-Infrared Upconversion Luminescence and Bioimaging In Vivo Based on Quantum Dots.

Recently, upconversion luminescence (UCL) has been widely applied in bioimaging due to its low autofluorescence and high contrast. However, a relatively high power density is still needed in conventional UCL bioimaging. In the present study, an ultralow power density light, as low as 0.06 mW cm−2, is applied as an excitation source for UCL bioimaging with PbS/CdS/ZnS quantum dots (UCL‐QDs) as probes. The speculated UCL mechanism is a phonon‐assisted single‐photon process, and the relative quantum yield is up to 4.6%. As determined by continuous irradiation with a 980 nm laser, the UCL‐QDs show excellent photostability. Furthermore, UCL‐QDs‐based probe is applied in tumor, blood vessel, and lymph node bioimaging excited with an eye‐safe low‐power light‐emitting diode light in a nude mouse with few heat effects.

Intense one-band near-infrared upconversion luminescence induced by using spontaneous polarization BiOCl sheet crystals as hosts for Yb3+ and Tm3+ ions

A new scheme that utilizes the anisotropic polarization of layered hosts to easily produce an efficient single-band NIR UC emission of Tm3+ ions.

Green, blue, red, near-infrared up-conversion luminescence of Yb3+/Er3+/Tm3+ co-doped YVO4 nanoparticles

YVO4:Yb3+,Er3+; YVO4:Yb3+,Tm3+; and YVO4:Yb3+,Er3+,Tm3+ were all synthesized via sol-gel method with a subsequent thermal treatment. Specifically, YVO4:Yb3+,Er3+,Tm3+ phosphors were prepared with different annealing temperatures to study the influence of temperature. The transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffractometer (XRD), and photoluminescent (PL) spectrofluorometer were used to investigate the morphology, crystal structure, and up-conversion luminescent properties of all samples. In summary, all samples were granular-like nanoparticles and well crystallized with the same tetragonal phase as YVO4. Under the irradiation at 980 nm, YVO4:Yb3+,Er3+ phosphors can generate green emission at 525 and 553 nm and red emission at 657 nm, while YVO4:Yb3+,Tm3+ phosphors can generate blue emission at 476 nm, red emission at 648 nm, and near-infrared emission at 800 nm. Notably, YVO4:Yb3+,Er3+,Tm3+ samples can exhibit green emission, blue emission, red emission, and near-infrared emission at the same time, which might endow the as-prepared samples with potential applications in many fields, such as luminous paint, infrared detection, and biological label.

La2O2S:Tm/Yb as a novel phosphor for highly pure near-infrared upconversion luminescence

Simple dehydration of the hydrothermally crystallized RE2(OH)4SO4·2H2O layered compound (RE=La0.97Tm0.01Yb0.02) in flowing H2 at 1200°C directly produced a La2O2S:Tm/Yb phosphor that exhibits highly pure near-infrared luminescence (~802nm, the 3H4→3H6 transition of Tm3+) under 978nm laser excitation, which is desired for near-infrared biological applications. Rietveld refinement confirmed the direct crystallization of solid solutions. The codoped Yb3+ ion significantly sensitizes Tm3+ luminescence, and improved the emission intensity by ~2000 times. Analysis of the excitation-power dependence of Tm3+ emission revealed a three-photon mechanism for the observed upconversion, and the possible photon reactions were discussed.

Visible and near infrared upconversion photoluminescence from Y2O3:Er3+, Yb3+, Li+ phosphors under 1532 nm excitation light

Visible and near-infrared upconversion luminescence from Y2O3 co-doped with Er3+, Yb3+ and Li+ phosphors under continuous excitation with 1532 nm light are reported. The upconversion emissions at 530–570 nm (green light emission region), and 640–700 nm (red light emission region) correspond to transitions from the 4S3/2to4I15/2and (4F9/2 + 4I9/2) to 4I15/2 electronic energy levels of the Er3+ ions respectively. The near infrared emissions at 900–1100 nm region correspond to inter-electronic energy levels transitions from 4I11/2 to 4I15/2 of Er3+ ions and 2F5/2 to 2F7/2 of Yb3+ ions. The role of Li+ and Yb3+ ions were to enhance the luminescence emission of these phosphors around 9, 7 and 11 times, respectively in comparison with only-erbium doped samples. The luminescence spectra of these phosphors remain unchanged when dispersed in deionized water, cholesterol and in bovine serum.

Photon upconversion in Ho3+-Yb3+ embedded tungsten tellurite glass

This article reports on the frequency upconversion property of yellow light emitting Ho3+-Yb3+ embedded tungsten tellurite (TeO2-WO3) glass prepared by the famous melt-quench technique. Holmium activated TeO2-WO3 glass gives efficient visible and near-infrared upconversion luminescence upon 980nm excitation, which improved via the incorporation of Yb3+ ions. The upconversion process was examined by a pump power dependence study that revealed the involvement of a single photon for upconversion emission around 886nm whereas two pump photons needed for the other emissions. The observed single and/or two photon upconversion feature is discussed with the help of a luminescence decay study and energy level diagram of the embedded ions.

NIR-to-NIR UCL/T1-weighted MR/CT multimodal imaging by NaYbF4:Tm@NaGdF4:Yb-PVP upconversion nanoparticles

Multimodal imaging nanoprobes are urgently sought because they can integrate different imaging function into individual nanoplatform and provide more comprehensive and accurate information for the diagnosis of early-stage tumor. Lanthanide-based upconversion nanoparticles (UCNPs) are regarded as promising nanoplatforms to fabricate these probes. Herein, we firstly developed the active core-active shell structured NaYbF4:Tm@NaGdF4:Yb-PVP UCNPs with the average diameter of 13.23±0.96nm as multimodal imaging probes. These water-dispersible nanoprobes presented excellent near-infrared to near-infrared (NIR-to-NIR) upconversion luminescence (UCL) performance, which is favorable for optical bioimaging due to deeper tissue penetration and autofluorescence reduction. After coated with the NaGdF4:Yb active shell, the UCL emission intensity at 800nm increased by 7.2times. These nanoprobes exhibited a desirable longitudinal relaxivity (r1=3.58L/(mmols)) and strong X-ray attenuation property (58.84HUL/g). The cytotoxicity assessment, histology analysis and biodistribution study revealed that NaYbF4:Tm@NaGdF4:Yb-PVP UCNPs had relatively low cytotoxicity and negligible organ toxicity. These UCNPs were applied for NIR-to-NIR UCL imaging in vivo. More importantly, the detection of small tumor was successfully achieved under T1-weighted MRI and CT imaging modalities after intravenous injection of these UCNPs. These results revealed that NaYbF4:Tm@NaGdF4:Yb-PVP UCNPs could serve as promising NIR-to-NIR UCL/MRI/CT trimodal imaging probes.