Intense Green Upconversion Luminescence Research Articles

Structural, luminescent and upconversion characteristics of Er3+ doped titanium zinc tellurite glass

The TeO 2 –TiO 2 –ZnO glass was single doped with Er 3+ and its structural, luminescent, and upconversion properties were analyzed. The amorphous nature of the fabricated glass was confirmed by X-ray diffraction, and the characteristic vibrational modes of the tellurite-titanium-zinc glass network were identified by Raman spectroscopy. The photoluminescent and upconversion properties of Er 3+ doped glass was analyzed by time decay measurements at different excitation wavelengths. The spectra recorded upon excitations at 808 nm and 975 nm show an intense green upconversion luminescence corresponding to the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 transitions and a very weak red emission associated to the 4 F 9/2 → 4 I 15/2 transition. The experimental results suggest that in Er 3+ doped glass the excited state absorption and/or energy transfer mechanisms are responsible for upconversion luminescence observed upon 808 nm and 975 nm excitations. • TeO–TiO 2 –ZnO glasses optically activated with Er 3+ single doping. • Up-conversion luminescence takes place as a double photon absorption process. • Up-conversion produced by excited-state absorption and/or energy transfer mechanism. • Intense green up-conversion emission upon 808 and 975 nm excitation.

Detection of hydrogen concentration based on an all-fiber fluorescence intensity ratio optical thermometer with Er3+/Yb3+ codoped NaBi(WO4)2 phosphors

The detection of hydrogen concentration was realized by measurement the change of local environmental temperature using an all-fiber fluorescence intensity ratio (FIR) optical thermometer. The temperature sensing optical material Er3+/Yb3+ codoped NaBi(WO4)2 phosphors were synthesized and used for the development of temperature sensing probe. Intense green upconversion luminescence was observed at an excitation power of 1.5 mW at room temperature and the dependence of FIR on the environmental temperature was obtained at the temperature range of 298.15–373.15 K. The maximum absolute temperature sensitivity reached the maximum value of 0.0127 K−1 at 373.15 K and the absolute error was 0.4 K to 0.3 K at 303.15 K, which laid the foundation for further research on real-time and remote H2 concentration detection. The local temperature change ∆T was measured due to the heat release from the reaction of H2 embedded with Pt-loaded WO3/SiO2 film. The relationship between ∆T and H2 concentration was established, which may be used to detect the leakiness of H2 gas during the traffic and storage process.

Reliable temperature sensing based on intense green upconversion emissions of Y2Mo4O15:Yb3+,Er3+ under 980 nm excitation

In this paper, Y2Mo4O15:Yb3+/Er3+ upconversion phosphors are prepared by a co-precipitation method. In the case of 20% Yb3+ doping, the intense green upconversion luminescence is obtained, which can be attributed to the energy transfer from Yb3+-MoO42- dimer to Er3+ that suppresses the multi-phonon relaxation of 4I11/2 to 4I13/2. Similar the Yb3+ sensitization, the dimer sensitization is also dependent on the Yb3+ concentration. When the Yb3+ concentration exceeds 20%, the luminescence is quenched by the cross relaxation and energy migration between dimers. A method for evaluating the reliability of temperature measurement standards is reported. Moreover, in term of the reliable temperature scale, the maximum absolute sensitivity of sample doped with 20% Yb3+ is determined to be 0.0117 K-1. Favorable sensing ability and strong upconversion luminescence indicate that the optimum sample is potentially applicable as the optical thermometric materials.

Calibration of optical temperature sensing of Ca1-xNaxMoO4:Yb3+,Er3+ with intense green up-conversion luminescence

High luminescence intensity is crucial for realizing luminescent temperature sensing with a large signal-to-noise ratio. In this work, the temperature sensing behavior of Ca1-xNaxMoO4:Yb3+,Er3+ with intense green up-conversion luminescence was studied. It has been demonstrated that the single-band green emission was dependent on the Yb3+-MoO42- dimer sensitization as well as the low multi-phonon relaxation rate of 4S3/2 → 4F9/2. In addition, it was found that the uncorrected thermometer could not accurately measure temperature due to thermal effects. A simple method for calibration of up-conversion temperature sensing was reported. Due to high luminescence intensity and temperature sensitivity, Ca1-xNaxMoO4:Yb3+,Er3+ is a promising candidate for up-conversion temperature sensing.

Selective enhancement of green upconversion luminescence of Er–Yb: NaYF4 by surface plasmon resonance of W18O49 nanoflowers and applications in temperature sensing**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474046 and 61775024), the Program for Liaoning Innovation Team in University, China (Grant No. LT2016011), the Science and Technique Foundation of Dalian, China (Grant Nos. 2017RD12 and 2015J12JH201),

The W18O49 nanoflowers with a diameter of 500 nm are prepared by a facile hydrothermal method. The Er–Yb: NaYF4 nanoparticles are adsorbed on the petals (the position of the strongest local electric field on W18O49 nanoflowers). With a 976 nm laser diode (LD) as an excitation source, the selectively green upconversion luminescence (UCL) is observed to be enhanced by two orders of magnitude in Er–Yb: NaYF4/W18O49 nanoflowers heterostructures. It suggests that the near infrared (NIR)-excited localized surface plasmon resonance (LSPR) of W18O49 is primarily responsible for the enhanced UCL, which could be partly reabsorbed by the W18O49, thus leading to the selective enhancement of green UCL for the Er–Yb: NaYF4. The fluorescence intensity ratio is investigated as a function of temperature based on the intense green UCL, which indicates that Er–Yb: NaYF4/W18O49 nanoflower heterostructures have good potential for developing into temperature sensors.

High quality colloidal GdVO4:Yb,Er upconversion nanoparticles synthesized via a protected calcination process for versatile applications

GdVO4:Yb,Er upconversion nanoparticles with high crystallinity and water dispersibility have been synthesized by a facile hydrothermal approach followed by a protected calcination treatment. The crude GdVO4:Yb,Er nanoparticles obtained by hydrothermal approach show cubic morphology with a diameter of about 45nm. A layer of SiO2 was coated on the surface of nanoparticles to avoid particles growth and aggregation during thermal treatment. After the dissolution of SiO2 layer by chemical etching in aqueous NaOH solution, the as-prepared highly crystalline GdVO4:Yb,Er nanoparticles not only maintain their nanostructure properties but show high chemical stability and good water dispersibility. Intense green upconversion luminescence is achieved under the 980nm laser diode excitation. The approach reported here can be “borrowed” to guide the synthesis of other oxide-based luminescent nanoparticles and will access their suitability for many technologically important applications.

Up-conversion luminescence of Er3+ ions in lead-free germanate glasses under 800 nm and 980 nm cw diode laser excitation

Up-conversion luminescence spectra of Er3+ ions in multicomponent oxyfluoride glasses GeO2 – BaO – BaF2 – Ga2O3 – Er2O3 were examined. It was found that the up-conversion luminescence spectra of Er3+ are dependent on pumping wavelengths. The spectra recorded upon the excitation at 800 nm contained an intense green up-conversion luminescence corresponding to the 2H11/2,4S3/2 → 4I15/2 transitions and a very weak red luminescence related to the 4F9/2 - 4I15/2 transition. In spectra recorded upon 980 nm excitation the contribution of the red luminescence was markedly higher. The interaction mechanisms involved in up-conversion processes are proposed and observed dependence of intensity of up-converted luminescence on excitation power is discussed. The experimental results suggest that Er3+ singly doped lead-free oxyfluoride germanate glass is useful for up-conversion luminescence applications.

Ca2+掺杂对NaYF4∶Yb,Er微米晶上转换发光性能的影响

Hexagonal NaYF4∶ Yb/Er microcrystals were prepared by a facile trisodium citrate-assisted hydrothermal method. The microparticles were characterized by TEM,X-ray diffraction(XRD),and luminescent spectra. Intense green upconversion luminescence was observed under 980 nm excitation. By introducing Ca2+ dopants into the grain lattices,the upconversion luminescence intensity of NaYF4∶ Yb/Er microcrystal was improved significantly. The enhancement is proposed to originate from a modification of the crystal structure and an improvement in the crystallinity of NaYF4∶ Yb/Er microcrystals.

Upconversion luminescence properties of Er3+/Yb3+ in transparent α-Sialon ceramics

Er3+ stabilized transparent α-Sialon ceramics with upconversion (UC) luminescence properties were fabricated for the first time by hot press sintering method. The fabricated samples show better transparency as well as UC luminescence properties. Moreover, the effect of Yb2O3 as a sensitizer on UC properties was analyzed in Er-α-Sialon system. The change in Sialon phases and crystal structure were analyzed by X-ray diffraction. The chemical compositions and morphology of grains and intergranular phase were analyzed by EDS and Transmission Electron Microscopy, respectively. The UC emissions were observed around 527, 547 and 670nm corresponding to the 2H11/2, 4S3/2 and 4F9/2 transitions, respectively when excited by 980nm continuous wave (CW) laser diode. UC process in Er3+ is found to be two photon processes. Intense green UC luminescence was observed with Er3+ and low amount of Yb3+ addition but higher amount of Yb3+ addition shows higher UC luminescence in red region. The transparency was higher in higher Er2O3 and low Yb2O3 content Sialon that was around 60% in visible light region. The chromaticity was also calculated for different samples and high color purity above 90% was obtained for green and yellow emissions. The mechanical properties were also investigated in this study.

Synthesis of Yb/Er Doped NaYF<sub>4</sub> Nanoparticles with Intense Green up-Conversion Emission

The luminescent rare-earth nanomaterials have great potential in the biological and biomedical applications due to their unique optical characteristics. An infrared-to-visible up-conversion NaYF4: Yb3+, Er3+nanoparticle was synthesized by hydrothermal method. More intense green up-conversion luminescence was obtained due to using citrate as a chelator. Different sizes of up-conversion particles (UCNPs) in the range of 40 to 1000 nm were available by adjusting the molar ratio of fluoride to Ln3+. The UCNPs were coated by silica and functionalized with amino groups for a conjugation with biomolecules. The UCNPs prepared might be promising for bioassay, bioimaging and diagnostics, especially in vivo environment and living cells.

Rare-earth ions doped heavy metal germanium tellurite glasses for fiber lighting in minimally invasive surgery

In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers.

Half opened microtubes of NaYF 4:Yb,Er synthesized in reverse microemulsion under solvothermal condition

NaYF 4:Yb,Er micro/nanocrystals with different sizes and morphologies such as nanospheres, short flexural nanorods, and half opened microtubes, were synthesized in reverse microemulsion under solvothermal condition using the quaternary reverse microemulsion system, CTAB/1-butanol/cyclohexane/aqueous solution. The X-ray diffraction analysis confirmed that cubic phase NaYF 4:Yb,Er can completely transform to hexagonal phase with increasing reaction time. The scanning electron microscope and transmission electron microscope images revealed that the morphology of the product can be tailored by varying the reaction time. A possible crystalline growth process of the NaYF 4:Yb,Er micro/nanocrystals was discussed. The obtained half opened microtubes exhibited an intense green upconversion luminescence, which may be attractive in novel optoelectronic devices.

Cooperative energy transfer in Tb 3+/Yb 3+- and Nd 3+/Yb 3+/Tb 3+-codoped oxyfluoride glasses

This paper reports on cooperative energy transfer and upconversion luminescence properties of Tb 3+/Yb 3+- and Nd 3+/Yb 3+/Tb 3+-codoped oxyfluoride glasses. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence along with weak ultraviolet (UV)–visible emissions has been observed in Yb 3+/Tb 3+-codoped oxyfluoride glasses. Power dependence of UV–visible upconversion luminescence intensity has been examined, revealing that a cooperative energy transfer mechanism from Yb 3+ ions is responsible for the excitation of Tb 3+ ions. Meanwhile, it is noticed that Tb 3+ upconversion emission bands have also been clearly detected at 487, 542, 587 and 620 nm in Nd 3+/Yb 3+/Tb 3+-codoped oxyfluoride glasses upon excitation with a 808 nm laser diode. The quadratic dependence of the upconversion luminescence on the pump-laser power indicates two-photon process for the population of Tb 3+: 5D 4 state via Nd 3+→Yb 3+→Tb 3+ energy transfer. However, no emission has been observed in the oxyfluoride glasses codoped with Yb 3+/Tb 3+ or Nd 3+/Tb 3+, respectively, upon excited at a 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd 3+ to Yb 3+, and then a cooperative energy transfer process from two excited Yb 3+ to Tb 3+ has been presented.

Synthesis and upconversion luminescence properties of Yb 3+/Er 3+ codoped BaGd 2(MoO 4) 4 powder

Synthesis and upconversion luminescence properties of the new BaGd 2(MoO 4) 4:Yb 3+,Er 3+ phosphor were reported in this paper. The phosphor powder was obtained by the traditional high temperature solid-state method, and its phase structure was characterized by the XRD pattern. Based on the upconversion luminescence properties studies, it is found that, under 980 nm semiconductor laser excitation, BaGd 2(MoO 4) 4:Yb 3+,Er 3+ phosphor exhibits intense green upconversion luminescence, which is ascribed to 2H 11/2 → 4I 15/2 and 4S 3/2 → 4I 15/2 transition of Er 3+. While the observed much weaker red emission is due to the non-radiative relaxation process of 4S 3/2 → 4F 9/2 and 4F 9/2 → 4I 15/2 transition originating from the same Er 3+. The concentration quenching effects for both Yb 3+ and Er 3+ were found, and the optimum doping concentrations of 0.5 mol% Yb 3+ and 0.08 mol% Er 3+ in the new BaGd 2(MoO 4) 4 Gd 3+ host were established.

Cooperative Energy Transfer and Frequency Upconversion in Yb3+–Tb3+ and Nd3+–Yb3+–Tb3+ Codoped GdAl3(BO3)4 Phosphors

Polycrystalline GdAl(3)(BO(3))(4) phosphors co-doped with Yb(3+)/Tb(3+) and/or Nd(3+)/Yb(3+)/Tb(3+) have been synthesized by combustion method. Upon excitation with a 980 nm laser diode, an intense green upconversion luminescence has been observed in GdAl(3)(BO(3))(4):Yb,Tb phosphor. The quadratic dependence of the luminescence on the pump-laser power indicating a cooperative energy transfer process. Meanwhile, it is noticed that upon excitation with 808 nm laser diode, intense luminescence has clearly been detected in GdAl(3)(BO(3))(4):Nd,Yb,Tb phosphor. The luminescence intensity exhibits also a quadratic dependence on incident pump-laser power. However, no green-emission has been observed in GdAl(3)(BO(3))(4) phosphors co-doped with Yb(3+)/Tb(3+) or Nd(3+)/Tb(3+) respectively upon excited at 808 nm laser diode. A proposed upconversion mechanism involving energy transfer from Nd(3+) to Yb(3+), and then a cooperative energy transfer process from two excited Yb(3+) to Tb(3+) has been presented.

Upconversion properties of Er3+/Yb3+co-doped TeO2–Nb2O5–Li2O glasses

The Er3+/Yb3+ co-doped TeO2–Nb2O5–Li2O glass is prepared by conventional melting method and its upconversion spectra are measured. The intense green upconversion luminescence upon excitation with a 976 nm laser diode is observed with the naked eyes. The dependence of luminescence intensity on the ratio of Yb3+/Er3+ is discussed in detail and the relationship between the ratio of green luminescence intensity to red luminescence intensity and the ratio of Yb3+/Er3+ is also studied. The luminescence intensity increases with the ratio of Yb3+/Er3+increasing. The ratio of Yb3+/Er3+ plays a more important role than the concentration of Er3+ in determining the upconversion luminescence intensity. The ratio of green luminescence intensity to red luminescence intensity reaches a maximum when ratio of Yb3+/Er3+ is 3. Thus the glass could be one of the potential candidates for LD pumping solid-state lasers.