Upconversion Emission Of Er3 Research Articles

Infrared-to-visible upconversion emission in Er3+ doped TeO2-WO3-Bi2O3 glasses with silver nanoparticles

The influence of silver nanoparticles (NPs) on the frequency upconversion luminescence in Er3+ doped TeO2-WO3-Bi2O3 glasses is reported. The effect of the NPs on the Er3+ luminescence was controlled by appropriate heat-treatment of the samples. Enhancement up to 700% was obtained for the upconverted emissions at 527, 550, and 660 nm, when a laser at 980 nm is used for excitation. Since the laser frequency is far from the NPs surface plasmon resonance frequency, the luminescence enhancement is attributed to the local field increase in the proximity of the NPs and not to energy transfer from the NPs to the emitters as is usually reported. This is the first time that the effect is investigated for tellurite-tungstate-bismutate glasses and the enhancement observed is the largest reported for a tellurium oxide based glass.

Effects of Mo on phase structure and up-conversion emissions of Er:Al2O3 nanocrystals

A simple and efficient approach was presented to enhance up-conversion emissions significantly for the Er:Al2O3 nanocrystals by Mo support (Er-Mo:Al2O3) with a 976 nm laser diode excitation. Mo support had evident effects on the phase structure and up-conversion emissions for the Er:Al2O3 nanocrystals, which promoted the θ-(Al,Er)2O3 transformed to α-(Al,Er,Mo)2O3 phase. Compared with the Er:Al2O3, the maximal green and red up-conversion emissions intensities increased about 3×103 and 1.4×102 times for the Er-Mo:Al2O3 nanocrystals, respectively. It suggests that the enhancement of up-conversion emissions is caused by the high excited state energy transfer process from |4I15/2, 3T2> state of the Er3+-MoO42− dimer to the 4F7/2 level of Er3+.

Enhanced infrared to visible upconversion emission in Er3+ doped phosphate glass: Role of silver nanoparticles

Phosphate glasses with compositions (59.5–x)P2O5–MgO–xAgCl–0.5Er2O3 (0.0≤x≤1.5mol%) containing fixed concentration of Er3+ ion with and without silver nanoparticles (NPs) are prepared using melt quenching technique. The amorphous nature of the glass is confirmed using the X-ray diffraction method. The homogeneous distribution of spherical Ag NPs (average size ∼37nm) in the glassy matrix is evidenced from the transmission electron microscopy (TEM) analyses. The UV–vis–NIR absorption spectra shows 10 bands corresponding to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 4S3/2, 2H11/2, 4F7/2, 4F5/2, 2G9/2, 4G11/2 transitions in which the most intense bands are 2H11/2 and 4G11/2. The absorption spectrum of Er3+ ions free glass sample containing Ag NPs displays a prominent surface Plasmon resonance (SPR) band located at 528nm. The infrared to visible frequency upconversion (UC) emission under 797nm excitation shows two emission bands green (4S3/2–4I15/2) and red (4F9/2–4I15/2) centered at 540nm and 634nm, respectively, corresponding to Er3+ transitions. An enhancement in UC emission intensity of green band (4S3/2–4I15/2) is observed in the presence of silver NPs and the maximum enhancement occurred for 1.5mol% AgCl. However, the enhancement of emission intensity of the red band (4F9/2–4I15/2) is smaller. The enhancement of UC emission is understood in terms of the intensified local field effect due to silver NPs.

Synthesis, Structural Properties and Upconversion Emission of Er3+ and Er3+/Yb3+ Doped Nanocrystalline NaNbO3

Synthesis, Structural Properties and Upconversion Emission of Er³⁺ and Er³⁺/Yb³⁺ Doped Nanocrystalline NaNbO₃

Upconversion emission and color tunability in Al_2Y_4O_9: Yb, Er inverse opal

We present firstly the preparation of color tunable Al2Y4O9: Yb, Er inverse opal photonic crystal and influence of photonic bandgap on upconversion emissions of Er3+. The results show that Al2Y4O9: Yb, Er upconversion inverse opals were successfully prepared by a self-assembly technique in combination with a sol-gel method. The intensity of upconversion emission can be tuned by controlling the structure of the inverse opal. Significant suppression of the green or red upconversion emission in the Al2Y4O9: Yb, Er inverse opals was obtained if the photonic band-gap overlaps with the Er3+ ions emission band, resulting in color tunable upconversion Al2Y4O9 phosphors. This research not only realizes the colour modification of upconversion emission, but also opens the opportunity to control the propagation of photons.

Color tuning by co-doping of Er doped TiO2 phosphors within a fixed Er concentration

In this paper, we report the color tuning of Er doped TiO2 upconversion phosphors within a fixed Er concentration using 976 nm semiconductor laser diode excitation. By codoping with Mo, Yb or Li ions in the Er doped TiO2, the green and red upconversion emissions from the 2H11/2/4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er ions were enhanced selectively and the color output of Er doped TiO2 could be tuned by different intensity ratios of green to red emissions. The two-photon absorption processes were responsible for the green and red upconversion emissions of Er–Mo, Er–Yb and Er–Li codoped TiO2 phosphors, and the corresponding enhanced mechanisms were discussed. It is expected that these color tuned phosphors within a fixed Er concentration have great potential for applications in biology, displays and other optical technology.

1.5 μm and visible up-conversion emissions in Er3+/Yb3+ co-doped tellurite glasses and optical fibers for photonic applications

Glasses with base composition (in mol%) 70TeO2–15GeO2–5K2O–10Bi2O3 were prepared by the melt-quenching method. Er3+/Yb3+-doped and non-doped glass compositions were used as core and cladding, respectively, in the preparation of optical fibers through the sucking method. Infrared emission at 1550 nm and up-conversion emission in the visible range under 980 nm pumping are reported for glasses and optical fibers. A relatively large (Δλ = 91 nm) bandwidth was observed for the Er3+ 1550 nm emission. Up-conversion luminescence was observed and evaluated as a function of pump power at 980 nm. The efficient emission in the visible and infrared ranges makes this optical fiber potentially useful for amplifier and laser applications in photonics.

Enhancement of 1.54 μm emission in Er:LiNbO3 crystal by codoping with Zn2+ ions

The enhanced intensity and lengthened lifetime of 1.54 μm emission were observed for Er:LiNbO3 crystal codoped with Zn2+ ions. The ZnO codoping led to the reduction of the green upconversion emission in Er:LiNbO3 crystals. The decay trace of the 4S3/2→4I15/2 was obviously nonexponential for Er:LiNbO3 codoped with 0 and 3 mol.% ZnO, but became exponential for one codoped with 6 mol.% ZnO. The OH− absorption spectra showed after codoping with Zn2+ ions, the OH− absorption peaking position shifted from ∼3495 to 3484 cm−1, and the absorption cross section decreased. These spectroscopic characteristics suggested that the improvement of 1.54 μm emission was attributed to the reduction of Er3+ cluster sites.

Optical Temperature Sensor Using Infrared-to-Visible-Frequency Upconversion in Er3+/Yb3+-Codoped Bi3TiNbO9 Ceramics

An optical temperature sensor based on infrared-to-visible upconversion emission in Er3+/Yb3+ co-doped Bi3TiNbO9 (BTN) ceramics is reported. The fluorescence intensity ratio of the green upconversion photoluminescence (UC-PL) around 524 nm and 545 nm depends on temperature. The operating temperature range and the maximum sensitivity of Er3+/Yb3+ co-doped Bi3TiNbO9 ceramics are 123–693 K and 0.0032 K−1, respectively. BTN:Er3+/Yb3+ ceramic has good thermal, physical and chemical stability, great UC-PL intensity and low cost fabrication. The results imply that Er3+/Yb3+ co-doped Bi3TiNbO9 ceramic is promising for applications in wide-temperature-range sensors.

Upconversion Emission in Er and Cr Co-Doped KNbO3Phosphors

Upconversion Emission in Er and Cr Co-Doped KNbO₃Phosphors

Upconversion Emission in Er and Cr Co-Doped KNbO3 Phosphors

Near-infrared to visible upconversion emission was observed with 980 nm excitation and analyzed in Er-doped and Er/Cr-codoped KNbO3 phosphors. In both systems, exciton emission appeared at 555 nm under 405 nm excitation. In the codoped phosphors, upconversion emissions in the green, red, and infrared region were observed from the 4S3/2 and 4F9/2 states of Er3+ ions and the 4T2 state of Cr3+ ions respectively. We explain the emissions by two-step absorption of Er ions and the energy transfer processes between Er ions, from Er to Cr ions, and from Cr to Er ions.

Significant reduction of upconversion emission in CaTiO3: Yb, Er inverse opals

Inverse opal photonic crystals of Yb3+, Er3+ co-doped CaTiO3 (CaTiO3: Yb, Er) were prepared using self-assembled polystyrene templates combined with the infiltration of sol–gel precursor. The influence of the photonic band gap on upconversion emission of Er3+ has been investigated in the CaTiO3: Yb, Er inverse opals. Significant reduction of the upconversion emission was detected if the photonic band-gap overlaps with the Er3+ ions emission band.

Effect of heat treatment on structure and up-conversion emission of Er3+-doped GaF3/InF3 based fluoride glasses

GaF3/InF3 based oxyfluoride glasses 20GaF3-15InF3-10SnF2-15ZnF2-17CdF2-3P2O5-(20-x) PbF2−xErF3 were obtained by melt quenching method. By appropriate heat treatment of the as-prepared glasses above, transparent glass-ceramics were obtained with the formation of tetragonal ZnF2 and cubic ErGa5O12 nanocrystals in the glass matrix confirmed by X-ray diffraction. Differential scanning calorimetry (DSC), transform infrared spectrum and up-conversion luminescence measurements excited at 980nm were performed on as-prepared glasses and glass-ceramics. The different effects of Er3+ content on ΔT1 (ΔT1 = Tx − Tg) and ΔT2 (ΔT2 = Tp2 − Tp1) suggest the best content is 0.1 ∼ 1 mol.% for controllable crystallization. The intensity of green luminescence significantly increased in transparent glass-ceramic until the content of Er3+ reaches at 2 mol.% compared to that in as-prepared, but it did not enhance linearly with the increasing time. These results are attributed to the change of environment of Er3+ ions and the decrease distance when Er3+ ions are incorporated into the precipitated nanocrystals.

Optical thermometry through green and red upconversion emissions in Er3+/Yb3+/Li+:ZrO2 nanocrystals

Variations of fluorescence intensity ratio of green (generated from Er3+ 2H11/2 and 4S3/2 levels) and red (generated from the sublevels of Er3+ 4F9/2 level) upconversion emissions in Er3+/Yb3+/Li+:ZrO2 nanocrystals have been studied as a function of temperature under 976nm laser diode excitation. In the temperature range of 323–673K, the maximum sensitivities of about 0.0134K−1 and 0.0104K−1 are obtained by using green and red emission, respectively. Er3+/Yb3+/Li+:ZrO2 nanocrystals show potential application value in nanoscale thermal sensor.

Spectroscopic properties of Er3+ in a oxyfluoride glass and upconversion and temperature sensor behaviour of Er3+/Yb3+-codoped oxyfluoride glass

Spectroscopic properties of Er 3+ -singly doped SiO 2– –BaF 2 –ZnF 2 glass have been investigated on the basis of the Judd–Ofelt theory. Upconversion emissions in Er 3+ /Yb 3+ -codoped SiO 2 –BaF 2 –ZnF 2 glass have been observed under 980 nm excitation. The temperature dependence of fluorescence intensity ratio corresponding to the two thermally coupled levels ( 2 H 11/2 , 4 S 3/2 ) has been studied and it is concluded based on the results that the method can be possibly applied for temperature sensing.

A Novel Near-Infrared Antibacterial Material Depending on the Upconverting Property of Er3+-Yb3+-Fe3+ Tridoped TiO2 Nanopowder

A novel near-infrared antibacterial material, Er3+-Yb3+-Fe3+ tridoped TiO2 nanopowder, was synthesized and applied to kill Aeromonas hydrophia with a maximal bactericidal rate of 65% in 90 min under 980 nm laser irradiation. However, Fe3+-TiO2 or Er3+-Yb3+-TiO2 nanopowders obtained under the same conditions barely could kill Aeromonas hydrophia. The initial energy applied in the photocatalysis antibacterial process is supplied by the upconversion emission of Er3+ and Yb3+ and the codoping of Fe3+, which has intensified the light absorption intensity and enlarged the absorption range. The analyses of phase structure and the optical properties including XRD, UV−vis diffuse reflectance spectra, and upconversion photoluminescence spectra of Er3+-Yb3+-Fe3+ tridoped TiO2 nanopowder have been performed in detail to reveal the complex energy transfer and change mechanism. According to our experimental results, the mechanism has been demonstrated involving the upconversion emission, multistep excitation by means o...

Enhancement of upconversion emission in Y 3Al 5O 12:Er 3+ induced by Li + doping at interstitial sites

The influence of site occupancy of Li +, including substitutional and interstitial sites, on the upconversion emissions of Er 3+ doped Y 3Al 5O 12 powders is reported. The intensity of green emission increases slightly when the Li + occupies substitutional site, but when the Li + enters into interstitial site it enhances drastically accompanied with a change of emission spectra. These phenomena originate from the increase, induced by interstitial Li +, in the lifetime of 4 I 11 / 2 level, the ratio of radiation rate in green emission and the absorptivity at 980 nm.

Color tunability of the upconversion emission in Er–Yb doped the wide band gap nanophosphors ZrO2 and Y2O3

Recently an increasing interest in the investigation of nanocrystalline wide band gap oxides for both fundamental research and potential applications in upconversion phosphors, fluorescent labels for sensitive detection of biomolecules, white light generation, and two-photon confocal-microscope imaging. Er 3+ /Yb 3+ doped Y 2 O 3 and ZrO 2 present favorable physical properties, such as a wide band gap between 5.6 and 7.0 eV, and ease of synthesis in the nanometer regime. In particular, the intensity of the visible rare earth luminescence depends on dopant concentration, crystalline phase and size of the nanocrystals. As a result, it is possible to control the emission color between red and green by adjusting the Er and Yb dopant concentrations. In this work, based on a stationary solution of the rate equations that govern the luminescence emission, we derive a simple model that allows the prediction of the overall color emission depending on the Yb and Er concentration. In addition, our model allows the facile quantification of the upconversion mechanisms responsible of the visible color emission in these nanophosphors under 970 nm excitation.

Upconversion Emission of BaTiO3:Er3+ Nanocrystals: Influence of Temperature and Surrounding Medium

Here, we report the role of crystallite size and surrounding medium on the upconversion emission of Er3+ in BaTiO3 oxide nanocrystals. The samples were prepared by sol-emulsion-gel method and heat-treated at two different temperatures yielding powders containing nanoparticles of different sizes. Green (550 nm) and red (660 nm) upconversion emission were observed at room temperature from the 4S3/2 and 4F9/2 levels of BaTiO3:Er3+ nanocrystals. The pump power dependence study confirms that all these upconversion emission lines are a two-photon absorption process. We observed that the luminescence lifetime is shorter for the sample containing smaller particles. Optical thermometry experiments were performed in air, water and glycerol in a temperature range from 27.1 up to 47.1 degrees C aiming to use this material as a biological temperature sensor.

Opposite effect of Li+ codoping on the upconversion emissions of Er3+-doped TiO2 powders

The Er3+-Li+ codoped TiO2 powders have been prepared by the non-aqueous sol–gel method. The green and red upconversion emissions centered at about 526, 550 and 663 nm were observed by the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. Li+ codoping has opposite effect on the upconversion emissions intensities for Er3+-doped TiO2 at sintering temperatures of 1,073 and 1,273 K. At 1,073 K, the Er3+-doped TiO2 phase transition from anatase to rutile was accelerated with increasing Li+ codoping concentration, leading to the increase of crystal field symmetry of Er3+, thus the upconversion emissions intensities decreased. At 1,273 K, Li+ codoping had no effect on the phase structure of Er3+-doped TiO2 and only increased the Er–O bond length, it indicated that the upconversion emissions intensities greatly enhanced because of the decrease of crystal field symmetry of Er3+.