Strong Green Upconversion Luminescence Research Articles

Strong green up-conversion luminescence and optical thermometry of Ho3+/Yb3+ Co-doped AlN submicron towers

Rare-earth (RE) doped aluminum nitride (AlN) holds great promise for integrated optoelectronic devices. Here, the Ho and Yb co-doped AlN (AlN:Ho3+/Yb3+) submicron towers were prepared by a direct nitridation route. XRD, Raman, XPS and EDS studies showed successful doping of Ho and Yb ions into AlN. SEM images show that the submicron towers have an interesting layered structure by layer-by-layer stacking of hexagonal AlN nanosheets. Under excitation at 980 nm, AlN:Ho3+/Yb3+ submicron towers exhibit up-conversion (UC) luminescence at 540, 550, 659, and 762 nm, which are due to Ho3+/Yb3+ system from 5F4, 5S2→5I8, 5F5→5I8, and 5F4, 5S2→5I7 respectively. Based on the intensity ratio and decay lifetime of UC luminescence, the optical temperature sensing characteristics are investigated from 298 K to 548 K. The maximum relative sensitivities associated with the intensity ratio of I540, 550 and I659 and decay lifetime of 659 nm are as high as 2.73% K−1 and 0.43% K−1, respectively. This work broadens the optoelectronic properties of RE doped AlN.

Preparation and strong green upconversion luminescence of Ca9Y(VO4)7: Yb3+/Er3+ phosphor

Exploring novel oxysalt compounds remains significant due to their affordability and versatile applications, such as serving as laser crystals, piezoelectric crystals, frequency-doubling crystals, and luminescent materials. Specifically, this study introduces a new near-single green upconversion luminescent Ca9(VO4)7: Yb3+/Er3+ material, synthesized through high-temperature solid-phase methods. When subjected to 980 nm near-infrared laser irradiation, the Ca9(VO4)7: 0.3 Yb3+, 0.02 Er3+ phosphor demonstrates robust green luminescence at 531 nm (2H11/2 → 4I15/2) and 558 nm (4S3/2 → 4I15/2), accompanied by faint red luminescence at 665 nm (4F9/2 → 4I15/2). The optimal doping concentrations for Yb3+ and Er3+ ions, yielding the highest upconversion luminescence intensity, are determined to be 0.3 and 0.02, respectively. The investigation elucidates the upconversion luminescence mechanism through the downward shift spectrum in photoluminescence and the pumping power dependence of upconversion green-red luminescence. The primary excitation pathway identified for the upconversion process in Ca9Y(VO4)7: 0.3 Yb3+, 0.02 Er3+ involves Yb3+ (2F5/2) + Er3+ (4I11/2) → Yb3+ (2F7/2) + Er3+ (4F7/2). This research contributes to the exploration of new materials, injecting vitality into modern industries and production processes.

Upconversion luminescence properties of NaBi(MoO4)2:Ln3+, Yb3+ (Ln = Er, Ho) nanomaterials synthesized at room temperature

Studies on lanthanide ions doped upconversion nanomaterials are increasing exponentially due to their widespread applications in various fields such as diagnosis, therapy, bio-imaging, anti-counterfeiting, photocatalysis, solar cells and sensors, etc. Here, we are reporting upconversion luminescence properties of NaBi(MoO4)2:Ln3+, Yb3+ (Ln = Er, Ho) nanomaterials synthesized at room temperature by simple co-precipitation method. Diffraction and spectroscopic studies revealed that these nanomaterials are effectively doped with Ln3+ ions in the scheelite lattice. DR UV–vis spectra of these materials exhibit two broad bands in the range of 200–350 nm correspond to MoO42− charge transfer, s-p transition of Bi3+ ions and sharp peaks due to f-f transition of Ln3+ ions. Upconversion luminescence properties of these nanomaterials are investigated under 980 nm excitation. Doping concentration of Er3+ and Yb3+ ions is optimized to obtain best upconversion photoluminescence in NaBi(MoO4)2 nanomaterials and is found to be 5, 10 mol % for Er3+, Yb3+, respectively. NaBi(MoO4)2 nanomaterials co-doped with Er3+, Yb3+ exhibit strong green upconversion luminescence, whereas Ho3+, Yb3+ co-doped materials show strong red emission. Power dependent photoluminescence studies demonstrate that emission intensity increases with increasing pump power. Fluorescence intensity ratio (FIR) and population redistribution ability (PRA) of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 transitions of Er3+ increases with increasing the Yb3+ concentration. Also, these values increase linearly with increasing the pump power up to 2 W. It reveal that these thermally coupled energy levels are effectively redistributed in co-doped samples due to local heating caused by Yb3+.

Selective enhancement of green upconversion luminescence from NaYF4:Yb, Er microparticles through Ga3+ doping for sensitive temperature sensing

Temperature sensors based on upconversion luminescence (UCL) intensity ratio have attracted great attention due to the high sensitivity. The enhancement of UCL is helpful to improve the sensitivity of temperature sensor. Doping is an effective way to achieve the UCL enhancement. Ga3+ ions doped NaYF4:18%Yb,2%Er have been prepared through a facile one-pot solvothermal method. Upconversion (UC) emission intensity was significantly enhanced by introducing Ga3+ ions into the lattice of NaYF4:Yb,Er, especially the green UC emission. With Ga3+concentration increasing, the size of the resulting NaYF4:Yb,Er,x%Ga particles decreases gradually. By doping 25% Ga3+, the green UC emission is increased by 30 times, while the red emission is enhanced by only 8 times. The morphology of particles and local symmetry around Er3+ ions have been changed, resulting in the selective enhancement of green UC emission. In addition, the temperature-dependent UCL properties of NaYF4:Yb,Er,25%Ga and NaYF4:Yb,Er were investigated. The maximum thermal sensitivity of NaYF4:Yb,Er,25%Ga could reach 0.0046 K−1 at 498 K. Therefore, NaYF4:Yb,Er,25%Ga with strong green UCL could be served as a potential candidate for sensitive temperature sensing.

Enhanced bipolar fatigue-resistance and optical temperature sensing in Er-modified 0.94(Bi0.5Na0.5)TiO3-0.06(K0.5Na0.5)NbO3 lead-free ceramics

0.94Bi0.5Na0.5TiO3-0.06K0.5Na0.5NbO3-xEr ceramics were prepared by the conventional solid-state reaction, and their bipolar fatigue and optical temperature sensing properties were investigated. Results showed that the addition of Er3+ led to the reduced NaBiO3 phase, which could effectively improve their fatigue behavior. Strong green upconversion luminescence from the two thermally coupled 2H11/2 and 4S3/2 levels of Er3+ was recorded in the temperature range from 20°C to 200°C under 980nm laser excitation. The maximum sensing sensitivity was found to be 0.0022K−1.

Temperature and impurity concentration effects on upconversion luminescence in LaInO3 doped with Er3+

In this paper a novel method for synthesis of LaInO3:Er3+ is reported and upconversion luminescence properties of the synthesized material at different temperatures (9–300 K) are studied. The samples were prepared by co-precipitation and subsequent heat treatment of lanthanum, indium and erbium hydroxides. It is shown that the excitation at 980 nm leads to a strong green upconversion luminescence in the material. At the concentrations above 0.1 mol. % of Er3+ the energy transfer upconversion mechanism of the luminescence becomes evident. Further increase of Er3+ content in the material leads to higher red-to-green upconversion luminescence intensity ratio. The mechanisms responsible for the observed variation are discussed.

Er3+-doped Na0.5Bi0.5TiO3 ferroelectric thin films with enhanced electrical properties and strong green up-conversion luminescence

Ferroelectric materials with up-conversion luminescence (UCL) properties have potential optoelectrical applications for display and sensing, etc. Here, we demonstrate strong green UCL and enhanced electrical properties in Er3+-doped Na0.5Bi0.5TiO3 thin films. The thin films are prepared via using a modified chemical solution deposition method. These thin films are phase-pure and crystallized in perovskite structure. The largest remnant polarization (P r) and highest dielectric constant (ε) are obtained from Na0.5Bi0.49Er0.01TiO3 thin films, and their values are 22 μC/cm2 and 1166, respectively. Meanwhile, strong green UCL at 525 and 548 nm is observed in Er3+-doped thin films. They are attributed to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ ions. These thin films have potentials in optoelectrical device applications.

Preparation of Gd2O2S:Yb,Ho Phosphor via Thermolysis of Sulfur-Contained (Gd,Yb,Ho)[S2CN(C4H8)]3 Phen Complexes

A novel handy single-source precursor method is adopted to prepare Gd2O2S:Yb,Ho up-conversion phosphors. Pure Gd2O2S:Yb0.06Ho0.02 phosphors are prepared via thermolysis of the air-stable ternary solid complexes RE[S2CN(C4H8)]3phen (RE=Gd, Yb, Ho) in a nitrogen atmosphere with certain amount of oxygen at 600–1100°C. The as-prepared Gd2O2S:Yb0.06Ho0.02 exhibits a strong green up-conversion luminescence under 980 nm IR excitation. The intensity of the green emission component is 37.4 and 53.4 times more than that of the red and NIR emissions, respectively. It is indicated that the material is of excellent color purity. Under an IR excitation density of 34.75 mW/mm2 with a laser beam diameter of 1 mm, the material exhibits an up-conversion luminescence brightness of 43.68 Cd/m2.

Optical gain and upconversion luminescence in LaF3: Er, Yb nanoparticles-doped organic–inorganic hybrid materials waveguide amplifier

A LaF3: Er, Yb nanoparticle-doped organic–inorganic hybrid materials waveguide amplifier is demonstrated using reactive ion etching. A maximum gain of approximately 6.8 dB is observed in a 20-mm-long waveguide. Under excitation at 976 nm, the waveguides emit a strong green upconversion luminescence. The possible upconversion mechanisms are discussed. The dependence of upconversion emission intensity on excitation power confirms a three-photon process contributes to the upconversion of the emission band 405 nm and two-photon processes for the green and red emission bands. The temperature behavior by the measurement of the fluorescence intensity ratio of the signals at 520 nm and 544 nm as a function of the pump power demonstrates a fast thermalization between the 2H11/2 and 4S3/2 levels. The influence of upconversion emission on the gain performance of the waveguide amplifier is analyzed.

Infrared-to-green upconversion luminescence and mechanism of Ho 3+ , Nd 3+ and Yb 3+ ions in oxyfluoride glass ceramics

New oxyfluoride glasses and glass ceramics co-doped with Nd3+, Yb3+ and Ho3+ were prepared. The upconversion of infrared radiation into green fluorescence has been studied for Nd3+, Yb3+ and Ho3+ in the transparent oxyfluoride glass ceramics. At room temperature very strong green upconversion luminescence due to the Ho3+: (5F4, 5S2)→5I8 transition under 800 nm excitation was observed in the glass ceramics. The intensity of the green upconversion luminescence in a 1mol% YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ upconversion luminescence in the oxyfluoride glass ceramics is discussed. The upconversion mechanism is also investigated.

Nd3+, Yb3+ and Ho3+ Codoped OxyfluorideGlass Ceramics with High Efficient Green Upconversion Luminescence

New oxyfluoride glasses and glass ceramic codoped with Nd3+,Yb3+ and Ho3+ were prepared. The x-ray diffractionanalysis revealed that the heat treatments of the oxyfluorideglasses could cause the precipitation of (Nd3+, Yb3+,Ho3+)-doped fluorite-type crystals. Very strong greenup-conversion luminescence due to the Ho3+: (5F4,5S2)→5I8 transition under 800-nm excitation wasobserved in these transparent glass ceramics. The intensity of the greenup-conversion luminescence in a 1-mol% YbF3-containing glassceramic was found to be about 120 times stronger than that in theprecursor oxyfluoride glass. The reason for the highly efficientHo3+ up-conversion luminescence in the oxyfluoride glass ceramicsis discussed.

Frequency up-conversion luminescence in Yb3+–Ho3+ co-doped PbxCd1−xF2 nano-crystals precipitated transparent oxyfluoride glass-ceramics

Oxyfluoride glasses were developed with composition 30SiO2·15AlO1.5·28PbF2·22CdF2·(4.9 – x)GdF3·0.1HoF3·x YbF3 (x ¼ 0; 0.1, 0.2, 0.5, 1, 2, 3, and 4) in mol%. Powder X-ray diffraction analysis revealed that the heat-treatments of the oxyfluoride glasses at the first crystallization temperature cause the precipitation of Yb3+–Ho3+ co-doped fluorite-type nano-crystals of about 17.8 nm in diameter in the glass matrix. These transparent glass-ceramics exhibited very strong green up-conversion luminescence due to the Ho3+: (5F4, 5S2) → 5I8 transition under 980 nm excitation. The intensity of the green up-conversion luminescence in the glass-ceramics was much stronger than that in the precursor oxyfluoride glass. The reasons for the highly efficient Ho3+ up-conversion luminescence in the oxyfluoride glass-ceramics are discussed.

Highly efficient green up-conversion luminescence of Nd3+–Yb3+–Ho3+ codoped fluorite-type nanocrystals in transparent glass ceramics

Oxyfluoride glasses were developed with composition 30SiO2⋅15AlO1.5⋅28PbF2⋅22CdF2⋅(4.8−x)GdF3⋅0.1NdF3⋅0.1HoF3⋅xYbF3 (x=0, 0.1, 0.2, 0.5, 1, 2, 3, 4, and 4.8) in mole percent. Powder x-ray diffraction analysis revealed that the heat treatments of the oxyfluoride glasses at 450 °C for 0.5 h cause the precipitation of Nd3+–Yb3+–Ho3+ codoped fluorite-type nanocrystals of about 16.3 nm in diameter in the glass matrix. These transparent glass ceramics exhibited very strong green up-conversion luminescence due to the Ho3+: (5F4, S25)→5I8 transition under 800 nm excitation. The intensity of the green up-conversion luminescence in a 1 mol % YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ up-conversion luminescence in the oxyfluoride glass ceramics is discussed. An up-conversion mechanism is also proposed.

Selectively strong green up-conversion luminescence in co-doped -based fluoride glasses under 800 nm excitation

Blue, green and red up-conversion luminescences at around 490, 545 and 650 nm, which result from the , and transitions, respectively, were observed in co-doped -based fluoride glasses under 800 nm excitation. Among these up-conversion luminescences, the green emission was extremely strong and the blue and red emission intensities were very weak. Selectively strong green up-conversion luminescences of these glasses indicate a high possibility for realizing a green up-conversion laser. Up-conversion processes for the blue, green and red emissions are two-photon processes assisted by energy transfer. It is proposed that the up-conversion mechanism for the blue and green emissions is different from that for the red emission. The respective mechanisms are discussed.