Upconversion Luminescence In Yb3 Research Articles

Innovative approach to tailoring upconversion luminescence in Yb3+/Eu3+ doped CaZrO3 perovskite host matrix

This study presents the synthesis and characterization of upconverter nanostructures consisting of a perovskite host matrix, CaZrO3, co-doped with trivalent ytterbium (Yb3+) and europium (Eu3+), denoted as CaZrO3:Yb3+/Eu3+. Single-doped CaZrO3:Eu3+ samples were excited using a 394 nm UV source, while CaZrO3:Yb3+/Eu3+ samples were excited with a 980 nm diode laser source. Yb3+ ions efficiently absorb the 980 nm light and transfer the absorbed energy to the nearby ion Eu3+ ions, leading to the emission of visible light around 590, 614, and 655 nm, respectively. The emission spectra of Eu3+ ions exhibit an initial increase with increasing Yb3+ concentration, peaking at 7 mol%, followed by a decrease due to luminescence quenching. The decay lifetime of Eu3+ ions under 300 nm excitation decreases simultaneously with increasing Yb3+ concentration, indicating energy migration between Yb3+ and Eu3+. Detailed explanations of the energy transfer mechanism between Yb3+ and Eu3+ ions are provided, supported by equations and diagrams. This study provides valuable insights into the optimization of dopant concentrations for enhancing upconversion luminescence in CaZrO3:Yb3+/Eu3+ nanostructures, with 3 mol% Eu3+ concentration identified as optimal based on preliminary experiments. The findings presented in this paper contribute to the understanding of energy transfer processes in luminescence upconversion materials and highlight the potential of CaZrO3:Yb3+/Eu3+ nanostructures for applications in lighting, displays, and bio-imaging. This work represents a significant advancement in the field of upconversion luminescence emission, particularly in the utilization of CaZrO3 codoped with Yb3+ and Eu3+, and lays the foundation for further research in this area.

The enhanced degradation of Bi4O5I2 photocatalyst to the various organic pollutants through the upconversion luminescence of Yb3+/Er3+

The types of pollutants in water environment are very complex, so it is very important to develop a photocatalyst that can have universal applicability to a variety of pollutants. In this study, Bi4O5I2 was modified by Yb3+ and Er3+ doping, and an efficient photocatalyst with upconversion luminescence was found. After heat treatment, the sample was transformed from BiOI to Bi4O5I2 (BI), and the crystallite size of BI was significantly reduced and the porosity increased, which provided more active sites for the photocatalytic reaction, and the photocatalytic performance of BI samples was greatly improved. Compared with Er3+ single doped samples (BIE), Yb3+ and Er3+ co-doping (BIYE) effectively promotes the photogenerated carrier migration. Under simulated sunlight, BiOI, BI, BIE and BIYE degraded 30.1%, 62.2%, 72.6% and 92.1% of RhB solution within 30 min of illumination, respectively. In addition, the degradation of MB, MO, carmine, phenol and TC by BIYE were also tested. The results show that BIYE has a good ability to degrade a variety of organic pollutants that are difficult to degrade. The results of photocurrent response test show that BIYE has a stable photocurrent response signal to near-infrared light, which means that BIYE can respond to near-infrared light. The upconversion luminescence of the sample was further investigated. The energy transfer between Yb3+ and Er3+ enhances the upconversion luminescence of Er3+, that is, the conversion of near-infrared light into visible light, which can be absorbed and utilized by Bi4O5I2 matrix. The degradation of RhB solution was tested under near-infrared conditions, and the results show that BIYE also has excellent photocatalytic ability under near-infrared light.

Enhancement of upconversion luminescence in Yb3+/Er3+-doped BiVO4 through calcination

Dopant concentration is generally increased in order to enhance the emission efficiency of the upconversion phosphor materials. However, a higher doping concentration generally results in concentration quenching of the upconversion emission resulting in low upconversion efficiency. In such instances, the calcination technique can offer an alternate way of enhancing the emission efficiency of the upconversion phosphors. Here, Yb3+/Er3+-doped BiVO4 has been synthesized by microwave hydrothermal process and the as-synthesized phosphor was calcined at 900 °C in air. Yb3+/Er3+-doped BiVO4 phosphor has been systematically characterized. The elemental distribution is homogeneous. Phase change has occurred from the tetragonal BiVO4 of the as-synthesized sample to the mixture of tetragonal and monoclinic BiVO4 in the calcined sample. The bandgap of the calcined sample has been reduced by 0.52 eV as compared to the as-synthesized one. Under 980 nm excitation, the calcined sample shows ∼ 7 and 15-fold enhancement in the upconversion and downshifting emission intensity, respectively, as compared to the as-synthesized sample. The calcination is found to have increased the lifetime of all the emitting excited states resulting in enhanced emission efficiency which has been confirmed by the time-resolved photoluminescence measurements.

Upconversion luminescence of Yb3+-Ho3+ co-doped Y18(WO4)4O23 phosphors for optical thermometers

The Yb3+-Ho3+ co-doped Y18W4O39 (YW) phosphors were prepared by using solid-state reaction method, and the upconversion (UC) luminescence was investigated for applications in optical thermometer. The single-phase samples were determined by the XRD patterns. The absorption peaks of the doping ions were attributed in the diffuse reflection spectra. Under 980 nm light excitation, the green and red emissions of Ho3+ were observed, and the optimal Ho3+ concentration was determined to be 0.5 mol%. The corresponding concentration quenching mechanism was well explained. The temperature-quenching spectra revealed that the intensities of both the green and red emissions were immensely sensitive to temperature but showed different decline rates with rising temperature, which indicated the possible applications in optical temperature sensing with fluorescence intensity ratio (FIR) strategy. The maximum absolute and relative sensitivities were obtained to be 0.0179 and 0.68% K−1 at 298 K, respectively. Furthermore, the population way on 5F5 level of Ho3+ was clarified to better understand the UC mechanism. The above investigations suggest that the YW:Yb3+,Ho3+ phosphor shows potential applications in optical thermometer.

Ambient- and calcination- temperature induced color-tunable upconversion luminescence in Yb3+/Er3+ co-doped Y2(MoO4)3 phosphors for optical thermometer

Trivalent lanthanides (Ln 3+ )-doped upconversion luminescent (UCL) materials with negative thermal expansion (NTE) property are endowed an exciting thermal enhancement performance. Hitherto, selectively thermal enhancement for the multi-narrow-band emissions of phosphor with NTE property is not implemented. Herein, Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ phosphor synthesized by the modified sol-gel method is explored in selectively enhanced green emission (Er 3+ : 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ) due to the formation of Yb-MoO 4 dimer at high ambient-temperature. The 54-fold selectively enhancement of green emission is obtained from 298 K to 523 K. In addition, the influences of dopant-concentration and calcination-temperature on UCL properties are analyzed. Accordingly, based on the fluorescence intensity ratio (FIR) of non-thermally coupled levels (NTCLs) for 2 H 11/2 / 2 F 9/2 and 4 S 3/2 / 2 F 9/2 as well as ( 2 H 11/2 + 4 S 3/2 )/ 2 F 9/2 , the optimal relative sensitivity of temperature sensing in the Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ sample could reach 0.14 K −1 at 298 K. All these indicate that this Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ material is a promising candidate for high-sensitivity optical temperature sensing.

Effect of polarization of surrounding organic molecules on upconversion emission of β-NaYF4 Co-Doped with Er3+ and Yb3+

Rare-earth-doped ceramic nanoparticles (RED-CNPs) have been studied for biological applications because they can convert biopermeable near-infrared light into visible and ultraviolet light. Both the host ceramic and the microenvironment around RED-CNPs may influence their luminescence characteristics; however, the effects of surrounding molecules have not been systematically clarified. In the present study, the effects of dispersion solvents and adsorbed polymers on the upconversion luminescence of Yb3+- and Er3+-doped NaYF4 nanoparticles (NaYF4:Yb3+,Er3+ NPs) were investigated. The effect of polymers was analyzed by encapsulating the luminescent NPs into various hydrophobic particle cores composed of poly(ethylene glycol) block copolymers. NaYF4:Yb3+,Er3+ NPs showed different upconversion spectra under different conditions when excited by 980 nm light. As the polarities of the surrounding organic molecules (solvents and hydrophobic core polymers) on the particle surface decreased, the thermal relaxation (4I11/2 → 4I13/2) was suppressed, whereas the excitation from 4I11/2 to 4F7/2 was enhanced in the upconversion excitation process, and thus, green upconversion luminescence (520–540 nm) increased. The solubility parameter was effective as an index of polarity affecting thermal relaxation. Our results showed the importance of material design considering the molecular polarity of the surrounding microenvironment for obtaining the desired upconversion emission of RED-CNPs.

Upconversion luminescence of Yb3+/Er3+ co-doped NaSrPO4 glass ceramic for optical thermometry

In order to expand the types of up-conversion (UC) luminescent materials used for optical thermometry, a novel Yb3+/Er3+ double doped glass ceramic (GC) containing NaSrPO4 nanocrystals was synthetised via melt quenching and heat treatment. The crystal structure morphology and UC optical properties were systematically studied, and the luminescence mechanism and energy transfer process were described. In addition, the relationship between the UC luminescence and temperature change of the GC specimen from 298 K to 573 K was measured under a 980 nm laser. The optical thermo-sensitive performance of GC was studied by the luminescence intensity ratio based on the thermally coupled emission states of Er3+, 2H11/2 and 4S3/2. For the GC sample annealed at 630 °C for 3 h, the maximum relative sensitivity Sr-max at 298 K was 1.78% K−1, the maximum absolute sensitivity Sa-max at 573 K was 5.28 × 10−3 K−1, which indicated that the GC materials might be potential candidates for optical temperature sensors.

Influence of thermal effect on upconversion luminescence of Y2(MoO4)3:Yb3+, Ln3+ (Ln = Er, Tm)

Upconversion luminescence of Yb3+/Er3+ and Yb3+/Tm3+ co-doped Y2(MoO4)3 phosphors under 980 nm excitation is investigated. It is demonstrated that Yb3+ co-doping causes a significant thermal effect. For Yb3+ and Er3+ co-doped case, the thermal effect, the long-distance energy migration and the energy transfer from Er3+ to Yb3+ are responsible for the abnormal luminescence quenching. In the case of Yb3+ and Tm3+ co-doped, the thermal effect improves the excited efficiency of Tm3+, and thus the luminescence of Tm3+ continues to strengthen at the Yb3+ concentration that causes Er3+ luminescence quenching. These results contribute to the design of the efficient upconversion materials.

Investigating the Luminescence Behaviors and Temperature Sensing Properties of Rare-Earth-Doped Ba2In2O5 Phosphors.

We present a strategy for selecting an optimal material in a particular temperature range by investigating the relationship between the absolute sensitivity ( Sa) and energy gap (Δ E), as well as the relationship between Sa and temperature on the basis of Yb3+/Ln3+ (Ln = Er3+, Ho3+)-codoped Ba2In2O5 phosphors. Through an investigation of optical performance, the phosphors exhibit near-infrared (NIR) downshifting and visible upconversion (UC) emissions under 980 nm excitation. The NIR spectral range from 700 to 1800 nm is referred to as the "biological window". The NIR emission peaks of Er3+ and Ho3+ are located at 1550 nm of the third biological window and 1192 nm of the second biological window, respectively. The temperature sensing behaviors based on the UC luminescence in Yb3+/Ln3+-codoped Ba2In2O5 phosphors are recorded by the fluorescence intensity ratio (FIR) technique in the temperature range from 303 to 573 K. The Ba2In2O5:Er3+/Yb3+ sample is usable at temperatures above 350 K, and the Ho3+/Yb3+-codoped Ba2In2O5 phosphor is suitable at temperatures below 350 K in our experimental region. The above results show that the Ba2In2O5:Ln3+/Yb3+ phosphors could be promising candidates for optical temperature sensors and applications in the biological imaging field.

Up-conversion luminescence in Yb3+/Er3+ co-doped ZnGa2O4 and ZnAl2O4 powder phosphors

ZnGa2O4:Yb3+,Er3+ and ZnAl2O4:Yb3+,Er3+ up-conversion powder phosphors with different Yb/Er ratio are synthesized by solid-state method and subsequent thermal treatment at 1300 ℃, which can generate strong up-conversion emissions in visible spectral range under 980 nm excitation. For the as-prepared ZnGa2O4:Yb3+,Er3+ phosphors, the green and red emissions around 524 nm (corresponding to 2H11/2 → 4I15/2 transition of Er3+), 549 nm (corresponding to 4S3/2 → 4I15/2 transition of Er3+) and 659 nm (corresponding to 4F9/2 → 4I15/2 transition of Er3+) indicate the optimal Yb/Er ratio for the sample is 7/1, while the ZnAl2O4:Yb3+,Er3+ phosphors with the same green and red emissions is Yb/Er = 3/1. Besides the up-conversion luminescence, the morphology and crystal structure are also investigated. All ZnGa2O4:Yb3+,Er3+ powders contain regular long rods with diameter of about 600–900 nm, while agglomerates composed of nonregular particles with size about 200–400 nm are shown in all ZnAl2O4:Yb3+,Er3+ powders. Additionally, all samples are spinel structure with a high degree of crystallinity. Consequently, the particles of moderate size, stable crystal structure and enough high intensity of green and red emissions in all ZnGa2O4:Yb3+,Er3+ and ZnAl2O4:Yb3+,Er3+ powder phosphors endow them potential applications in infrared detection, display devices and so on.

IR-to-visible frequency upconversion in Yb3+/Tm3+ co-doped phosphate glass

Frequency upconversion luminescence in Yb3+/Tm3+ co-doped 60P2O5·15ZnO·5Al2O3·10BaO·10PbO glass (PZABP) excited at 980 nm is reported. Pump power dependence, lifetime measurements, and the absorption spectra of the Tm3+ ions in the visible to IR region are investigated as a function of sensitizer (Yb3+) concentration. Blue light at 475 nm and red light at 660 nm generation was observed. Intensity saturation behavior is observed for the 475 nm (1G4 – 3H6), 650–664 nm (1G4 – 3F4 and/or 3F2,3 – 3H6) and 793 nm (3H4 – 3H6) upconversion emissions, when laser power was above ∼ 75 mW (∼1.9 kW/cm2). The radiative lifetimes measured for the observed emissions were 270 μs (475 nm), 195 μs (650 nm), 177 μs (664 nm), 184 μs (793 nm) and 335 μs (1211 nm). The application of the Davis-Mott model detected a slight change of 6.6% in the value of the energy bandgap for the highest doping concentration in comparison with the undoped sample. Results indicate that the PZABP glass matrix herein reported is a promising contender as host for rare-earth doped based photonic devices.

A fruitful demonstration in sensors based on upconversion luminescence of Yb3+/Er3+codoped Sb2O3-WO3-Li2O (SWL) glass-ceramic

In this article, erbium and ytterbium doped lithium tungsten antimonate (Yb3+/Er3+:Sb2O3-WO3-Li2O) glass-ceramics (GC) is synthesized and its novel applications in temperature sensing and detection of latent fingerprints is studied. It is also estimated that this material could be useful as a solar cell concentrator. The upconversion emission studies on Yb3+/Er3+:SWL glass-ceramics have shown intense green emission at 525 nm (2H11/2 → 4I15/2) & 545 nm (4s3/2 → 4I15/2). The variation of UC intensities with external temperature have shown a well-fashioned pattern, which suggests that the 2H11/2 and 4S3/2 levels of Er3+ ion are thermally coupled and can act as a temperature sensor in the 300–500 K temperature range. Dry powder of Yb3+/Er3+:SWL glass-ceramic is used to develop latent fingerprint with high contrast in green color on glass slide.

Investigation of upconversion luminescence in Yb3+/Tm3+/Ho3+ triply doped antimony-germanate glass and double-clad optical fiber

The optical properties of novel antimony-germanate glass and optical fiber co-doped with Yb3+/Tm3+/Ho3+ ions were presented. White light luminescence in glass was observed as a result of energy transfer with upconversion between donor (Yb3+) and acceptors (Tm3+, Ho3+) ions under 976 nm excitation. The double-clad optical fiber with off-set core co-doped with Yb2O3/Tm2O3/Ho2O3 system was fabricated using a modified rod-in-tube technique. In glass co-doped with 0.5 mol%Yb2O3/0.1 mol%Tm2O3/0.2 mol%Ho2O3 the spectral distribution of three luminescence bands (478, 545 and 660 nm) corresponds to x = 0.35 and y = 0.32 CIE coordinates. In comparison to glass the optical fiber emission are located in the green region (CIE, x = 0.37, y = 0.49).

Up-conversion luminescence of Yb3+ and Er3+ doped YPO4, LaPO4 and GdPO4 nanocrystals

In this article we report a comparison of structural and up-conversion (UC) luminescence properties of three compounds used as hosts for Yb3+ and Er3+ ions: YPO4, LaPO4 and GdPO4 phosphates. A co-precipitation method connected with annealing at 900°C was used in order to synthesize nanocrystalline REPO4:Yb3+,Er3+ materials (RE=Y, La, Gd). The X-ray diffraction patterns collected for the prepared materials indicated their high crystallinity and phase purity for the wide range of used dopants concentrations (0.25–7.5% of Er3+ and 5–30% of Yb3+ ions). Transmission electron microscopy images showed small nanocrystal sizes: around 20nm for YPO4-based products, 30–50nm for LaPO4 or 40–150nm for GdPO4-based materials. The nanomaterials prepared showed yellow UC under 980nm laser irradiation, which was assigned to Er3+ electronic transitions. The optimal dopants concentration were determined, giving the highest UC intensity: 25% of Yb3+ ions (or 20% in the case of LaPO4) and 1% of Er3+ ions. Also the mechanism of observed UC was analyzed. Two- and three-photon excitation and energy transfer between Yb3+ and Er3+ were confirmed. The effect of crystal cell volume on the green to red ratio of Er3+ UC and the presence of Er3+–Er3+ energy transfer were found.

Fabrication, microstructure and upconversion luminescence of Yb3+/Ln3+ (Ln = Ho, Er, Tm) co-doped Y2Ti2O7 ceramics

Y2Ti2O7:Yb3+/Ln3+ (Ln=Ho, Er, Tm) translucent ceramics were successfully fabricated by sintering method using synthetic nano-sized Y2Ti2O7:5% Yb3+, 1% Ln3+ powders for the first time. The effect of pressure and grinding on the microstructure, light transmission of the three ceramics samples was investigated. It was demonstrated that less microscopic flaws (micro-cracks and internal pores) and higher light transmission in the Y2Ti2O7:Yb3+/Ln3+ ceramics could be obtained by increasing the compacting pressure and powder grinding time. The upconversion luminescence was studied on the Y2Ti2O7:Yb3+/Ho3+, Y2Ti2O7:Yb3+/Er3+ and Y2Ti2O7:Yb3+/Tm3+ ceramics pumped by a 980nm diode laser, intense green, yellow and blue upconversion emissions were observed, respectively. The dependence of upconversion emission intensity on the excitation power was examined, and the possible upconversion mechanisms had been proposed accordingly.

Enhanced green upconversion luminescence in Yb3+/Tb3+-codoped silica fiber based on glass phase-separated method

We reported on an Yb3+/Tb3+-codoped silica fiber with a large fiber core prepared from nanoporous silica glass based on glass phase-separated method. The measured refractive index profile indicated an excellent homogeneity of the doped active fiber core. Intense green upconversion emission from Tb3+ centered at 543 nm was obtained in the Yb3+/Tb3+-codoped silica fiber under 976-nm excitation. It is suggested that the green upconversion emission is dominated by a two-photon absorption process. It is found that the Al3+ ions as a modifier can facilitate the energy transfer from Yb3+ to Tb3+ in the porous glass fiber. The energy transfer efficiency from Yb3+ to Tb3+ was calculated.

Valence state change and defect centers induced by infrared femtosecond laser in Yb:YAG crystals

The broad band upconversion luminescence in Yb3+:YAG crystal has been observed in experiments under the irradiation of focused infrared femtosecond laser. The dependence of the fluorescence intensity on the pump power shows that the upconversion luminescence is due to simultaneous two-photon absorption process, which indicates that the broad emission bands at 365 and 463 nm could be assigned to the 5d → 4f transitions of Yb2+ ions and the one at 692 nm could be attributed to the electron-hole recombination process on (Yb2+-F+) centers. The absorption spectra of the Yb:YAG crystal samples before and after femtosecond laser irradiation, and after further annealing reveal that permanent valence state change of Yb ions from Yb3+ to Yb2+ and (Yb2+-F+) centers have been induced by infrared femtosecond laser irradiation in Yb3+:YAG crystal.

Five-photon UV upconversion emissions of Er³⁺ for temperature sensing.

Under 980 nm excitation, the temperature dependence of five-photon UV (256 and 276 nm) upconversion luminescence in Yb³⁺-Er³⁺ codoped β-NaLuF₄ nanocrystals was studied from 303 K to 523 K. The ⁴D(7/2) and ⁴G(9/2) levels of Er³⁺ are confirmed to be thermally coupled levels. They are the highest energy states for optical thermometry known so far. By using fluorescence intensity ratio technique, optical temperature sensing characteristics based on the ⁴D(7/2)/⁴G(9/2) → ⁴I(15/2) transitions of Er³⁺ were reported here for the first time. The obtained sensitivity of this UV-based sensor is higher than that of green-based optical thermometer in low temperature range.

Li doping effects on the upconversion luminescence of Yb3+/Er3+-doped ABO4 (A = Ca, Sr; B = W, Mo) phosphors

ABO4 (A=Ca, Sr; B=W, Mo):Er3+/Yb3+/Li+ phosphors tri-doped with different concentrations of Li+ ion ranging from 0 to 22.5mol% were prepared by using a solid-state reaction method. And their upconversion (UC) luminescence properties were in estimated under a 975nm laser-diode excitation. The four kinds of phosphors (CaWO4, CaMoO4, SrWO4, and SrMoO4) tri-doped with Er3+, Yb3+ and Li+ ions showed strong green UC emission peaks at 530nm and 550nm and weak red UC emission. The intensity of green UC emission of Li+ doped samples was several higher than that of Li+ un-doped samples due to the reduction of lattice constant and the local crystal field distortion around rare-earth ions. The optimum doping concentration of Li+ ions was investigated and the effects of Li+ concentration for UC emission intensity were studied in detail.

Laser oscillation of Yb³⁺:Er³⁺ co-doped phosphosilicate microsphere [invited

A fiber-taper-microsphere-coupled system was used to research the characteristics of laser oscillation and upconversion luminescence of Yb3+:Er3+ co-doped phosphosilicate (YECP) microspheres. The YECP microspheres were fabricated by melting the end of phosphosilicate filaments. Single- and multimode laser oscillation at 1535-1565 nm within the C-band were obtained. In addition, the output power of the single-mode laser at 1545.5 nm can be as high as 48.98 μW, which was achieved under pump power of 9.63 mW, and the side-mode suppression ratio was 51.49 dB. Upconversion fluorescence of Er3+ at 521, 532, and 544 nm also were measured, and the pump power dependence was studied. The fluorescence intensity was lower than that of Yb3+:Er3+ co-doped silica and oxyfluoride glass ceramic microspheres. Moreover, the physical mechanism of upconversion suppression and laser oscillation enhancement observed in our experiment was presented, which is beneficial to the preparation of rare-earth-doped microcavity lasers.