Upconversion Luminescence Properties Of Er3 Research Articles

Synthesis and characterizations of upconverting luminescent Er3+/ Yb3+: Gd2O3 uniform nanospheres for biomedical applications

We present the synthesis of Er3+/ Yb3+ co-doped Gd2O3 nanospheres using the wet-chemical method followed by a synergistic step-by-step calcination process, a novel approach in the field. The nanospheres exhibited red color upconversion luminescence (UCL) after multi-step annealing at temperatures ranging from 650 °C to 1150 °C, achieving a fully spherical morphology. The diameter and surface morphology of the nanospheres were significantly altered by the annealing process, decreasing from 382.77 ± 1.72 nm with a smooth surface to 245.7 ± 1.31 nm with a rougher surface. The UCL intensity increased with the annealing temperature. The influence of Er3+/ Yb3+ co-doped Gd2O3 nanospheres, excited by a 975 nm laser, was investigated, and the decay time for UCL samples was analyzed. The luminescence peak at 1026 nm was attributed to the 4I11/2 (Er3+) + 2F7/2 (Yb3+) → 4I15/2 (Er3+) + 2F5/2 (Yb3+) transition/ or 2F5/2 → 2F7/2 of the Yb3+ ions within the Gd2O3 matrix. Furthermore, the UCL properties of Er3+/ Yb3+ co-doped Gd2O3 nanophosphors were explored to detect the NTERA-2 cancer cells. These findings suggest that the rare earth co-doped Gd2O3 nanospheres might hold significant potential for biomedicine and imaging diagnostics applications, sparking new interest and possibilities in these fields.

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+.

Effect of glass-ceramics network intermediate Al2O3 content on up-conversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxy-fluoride glass-ceramics

Effect of alumina as a glass network intermediate on the up-conversion luminescence (UCL) in NaYF4:Er3+/Yb3+ co-doped oxy-fluoride glass-ceramics (GCs) was investigated. Combinations of smaller NaYF4 nanocrystals (10 and 13 nm) and lower Al2O3 contents (5% and 10%), as well as larger NaYF4 nanocrystals (26 and 40 nm) and higher lower Al2O3 contents (15% and 20%) were prepared after heat-treatment, respectively. The glass network of intermediate partial replacement of SiO2 with Al2O3 was investigated, and the consequence on the response to the up-conversion of the lanthanide ions was also studied. The UCL properties of Er3+ ions were changed in accordance with the addition of Al2O3, the red UCL intensity decreased with an increased Al2O3 concentration, while the green emission intensity showed opposite tendency. Our results showed that adding Al2O3 to 20 mol% is an effective strategy to simultaneous control of the magnitude and luminescence properties of lanthanide ion doped GCs.

Preparation and up-conversion luminescence properties of Er3+-Yb3+ doped glass ceramics

The molybdate precursor glass was prepared by the melting-annealing method. After heat treatment of the precursor glass, the glass ceramics containing NaBi(MoO4)2 crystal phase were successfully synthesized. The transmittance of the precursor glass and glass ceramics and up-conversion emission spectra at 980 nm were measured and analyzed. The effect of Er3+-Yb3+ doped concentration on the up-conversion luminescence intensity of glass ceramic samples was studied, and finally the best doped concentrations of Er3+ and Yb3+ were 0.6% and 1.0%, and the doped concentration ratio is 3:5. The Er3+-Yb3+ co-doped transparent glass ceramics containing NaBi(MoO4)2 have potential applications in green up-conversion luminescence.

Morphology modulation and near infrared to visible upconversion luminescence properties of Er3+/Yb3+-doped α-NiMoO4 nanoparticles

In this work, for the first time, the near infrared (NIR) to visible upconversion luminescence (UCL) properties of α-NiMoO4 were explored by doping with Er3+/Yb3+ ions. A microwave hydrothermal method was used to fabricate Er3+ (2 mol%)/Yb3+ (12–20 mol%)-doped α-NiMoO4 phosphors. X-ray diffraction patterns suggest the formation of the Yb2(MoO4)3 phase, which is beneficial for UCL enhancement. Nanorods (α-NiMoO4), bundles of rods (α-NiMoO4: Er3+), and cactus (α-NiMoO4: Er3+/Yb3+)-like morphologies were obtained, and a morphology modulation mechanism has been proposed. TEM elemental mapping, XPS, and UV–Vis DRS measurements confirm the existence of Ni, Mo, O, Er, and Yb elements in the samples. The synthesized samples demonstrate intense green (522 nm: 2H11/2 → 4I15/2 and 546: 4S3/2 → 4I15/2), weak red (660 nm: 4F9/2 → 4I15/2), and NIR (803 nm: 4S3/2 → 4I13/2) emissions under 980 nm excitation. Downshifting emission was also obtained at 1538 nm (Er3+: 4I13/2 → 4I15/2). The highest emission intensity was achieved in the Er3+ (2 mol%)/Yb3+ (15 mol%)-doped α-NiMoO4 sample. An intense green color and strong UCL were observed in the MN/Er2/Yb15 sample based on CIE chromaticity and fluorescence decay curves. A graph of pump power versus intensity for the phosphor samples indicates that the upconversion process occurs by two photonic processes. The proposed energy transfer process is explained based on ground state absorption and excited state absorption. The particles were found to be safe at doses up to 0.125 mg/mL, as assessed by cytotoxicity investigation in bovine skeletal muscle cells. The obtained results open the possibilities of potential applications of Er3+/Yb3+-doped α-NiMoO4 as an efficient luminescent material for bioimaging applications.

Up-conversion Luminescence Properties of Er3+/Yb3+ Co-Doped Oxyfluoride Glass Ceramic

Er3+/Yb3+ co-doped glass ceramic samples were prepared by melt-quenching method utilizing nominal composition 52SiO2–8Na2CO3–16Al2O3–33NaF-3LuF3-0.15Yb2O3 − 0.03Er2O3 (in mol%). The spectral characteristic was studied based on Judd-Ofelt theory. Spectrum intensity parameters Ωλ(λ = 2,4,6) were calculated on the basis of the absorption spectrum. The theoretical and experimental oscillator strengths were calculated according to the spectrum intensitty parameters, and the root mean square deviation (δrms) of glass ceramic sample was 4.28 × 10−6. The parameters such as transition probability, decay branching ratios and level lifetime of Er3+ were obtained. Lifetimes of metastable level 4I13/2 and 4I11/2 in as-prepared samples are respectively 11.64 and 13.61 ms which are suitable for up-conversion intermediate levels. Decay branching ratio of 4I13/2→4I15/2 is nearly 100% in Er3+/Yb3+ co-doped oxyfluoride glass ceramic samples which can be used to produce 1543 nm laser. Under the excitation of 980 nm diode laser, up-conversion luminescence is observed at the wavelength of 549 nm and (653, 664) nm, corresponding to the radiative transitions of Er3+:4S3/2→4I15/2and 4F9/2→4I15/2, respectively. The numbers of absorbed photons in the transition process of Er3+/Yb3+ co-doped oxyfluoride glass ceramic samples are estimated at 1.99 and 2.06 respectively according to the relationship between the up-conversion transmitting power and the 980 nm LD laser power. It is determined that the transition process of Er3+/Yb3+ co-doped oxyfluoride glass ceramic samples is two-photon absorption process.

Effect of heat treatment mechanism on upconversion luminescence in Er3+/Yb3+ co-doped NaYF4 oxyfluoride glass-ceramics

Effect of glass heat treatment technology on upconversion (UC) luminescence in Er3+/Yb3+ co-doped NaYF4 oxyfluorode glass-ceramics (GC) was investigated. First, NaYF4 nanocrystals were precipitated from single process glasses after heat-treatment of different temperature, and the nanocrystals size of NaYF4 in the heat-treat temperature of 540 °C and 590 °C samples, the crystal size is 5 nm and 27 nm, respectively. Moreover, the two-step heating process obtain the different size nanocrystals (5 nm and 28 nm) in the same piece of glass. It is found that the UC luminescence properties of Er3+ ions were changed in accordance with the heat treatment mechanism, and the Er3+ concentration of nanocrystals. Compare with single process, the UC luminescence properties of two-step heat treatment of enhancement of green emission intensity and fluorescence strength.

Optical characterization, absorption and upconversion luminescence in Er3+and Er3+/Yb3+doped In2O3 phosphor

Combustion derived In2O3:Er3+, co-doped with Yb3+phosphor powders have been prepared. Powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy methods are used to characterize the prepared phosphor powders. The intensity parameters (Ωλ, λ=2, 4 and 6), radiative transition probabilities (AR), radiative lifetime (τR) and branching ratios (β) of certain emission transition of Er3+ions for In2O3:Er3+and In2O3:Er3+/Yb3+phosphors have been estimated in the framework of the model given by Judd–Ofelt. Upon excitation at 978nm, upconversion luminescence properties of Er3+and Er3+/Yb3+doped In2O3 phosphors are investigated. The results obtained from optical study confirm the existence of an effective Yb3+to Er3+energy transfer process and it also predict possible mechanisms to populate the 4S3/2 and 4F9/2 levels. The possible upconversion mechanisms are discussed for Er3+and Yb3+ions with energy level diagram.

Quadratic general rotary unitized design for doping concentrations and up-conversion luminescence properties of Er3+/Yb3+ co-doped NaLa(MoO4)2 phosphors

It is still a great challenge that designing proper codoping concentrations of rare earth ions for achieving intensest expected emission from the studied phosphor. In this work, the quadratic general rotary unitized design (QGRUD) was introduced into the codoping concentration option of NaLa(MoO4)2: Er3+/Yb3+ phosphor for upconversion (UC) applications, and the optimum doping concentrations of Er3+ and Yb3+ for achieving maximum UC luminescence intensity, which is close to commercial NaYF4:Er3+/Yb3+ phosphor, were obtained. The two-photon process was assigned to the green UC emissions in the optimized NaLa(MoO4)2: Er3+/Yb3+ phosphor. It was also demonstrated that the optimized phosphor presented more stable upconversion emissions than the commercial NaYF4:Er3+/Yb3+ phosphor.

Synthesis and up-conversion luminescence properties of Er3+/Yb3+ co-doped Sr2CeO4 phosphors

Er3+/Yb3+ co-doped Sr2CeO4 phosphors were synthesized using a high-energy ball milling method at 1100°C. The X-ray diffraction patterns confirmed their orthorhombic structure. The up-conversion emissions corresponding to 2H11/2→4I15/2, S3/2→4I15/2 and 4F9/2→4I15/2 transitions peaking at 526nm, 552nm and 669nm have been observed under 975nm excitation. With the help of a schematic energy level diagram the up-conversion mechanisms were discussed in detail. The excited state absorption and energy transfer process were discussed as possible up-conversion mechanisms. The energy back transfer (4S3/2+2F7/2→4I13/2+2F5/2) contribute the increased intensity ratio of red to green emission in Sr2CeO4:Er3+/Yb3+ samples. A decay curve analysis for the UC emission corresponding to the 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions in the Er3+/Yb3+ co-doped Sr2CeO4 phosphors was performed. The CIE chromaticity coordinates of the Er3+/Yb3+ co-doped Sr2CeO4 phosphors were located in the green region. The results indicate that the material may be suitable for applications in the fields of color displays and light emitting devices.

Upconversion luminescence properties and mechanism of Er3+ doped Ba0.65Sr0.35TiO3 ferroelectric oxide nanocrystals

Ba0.65Sr0.35TiO3 (BST) nanocrystals doped with different concentrations of Er3+ ion were fabricated using sol-gel method. The structure and morphology of these BST nanocrystals were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The X-ray diffraction patterns of all the nanocrystals prepared in the study correspond to polycrystalline perovskite BST structure. The blue and green upconversion luminescence properties of Er3+ doped BST nanocrystals were investigated under excitation by a 785-nm laser. The upconversion emission bands centered at 407, 523, and 547 nm can be attributed to 2H9/2, 4I15/2, 2H11/2, 4I15/2, and 4S3/2, 4I15/2 transitions of Er3+ ion, respectively. The upconversion mechanism was studied in detail, based on the laser power dependence of the upconverted emissions. In addition, we examined the dependence of the intensity of green upconverted luminescence on the doping concentration of Er3+ ions, and discussed the mechanism underlying the process.

Crystallization and up-conversion luminescence properties of Er3+/Yb3+-doped NaYF4-based nano-glass-ceramics

A crystallization study of Er3+/Yb3+-doped NaYF4-based nano-glass-ceramics and their optical characterisation is presented. NaYF4 nano-crystals were precipitated from heat treatments close to the glass transition temperature. The crystallization process occurs from a constant number of nuclei. The increase of dopant ions has a nucleating effect. Crystal growth is limited with the length of the heat treatment, keeping the crystal size to the nanometric scale. Er3+-single doped samples show a predominant green up-conversion emission under near infrared excitation at 980nm, while a predominant red emission is observed in the Er3+/Yb3+ co-doped samples. The efficiency of the up-conversion emission is higher in the glass-ceramics than in the parent glasses.

Upconversion luminescence properties of Er3+-doped TeO2–PbF2 glass with and without Ag nanoparticles

Er3+-doped TeO2–PbF2 glasses with and without Ag nanoparticles (NPs) were prepared using a melt-quenching method. Ag precipitation was subsequently induced by heat treatment. The influence of Ag nanoparticles on the optical properties of Er3+-doped glasses was determined using optical absorption and photoluminescence spectroscopy. Upconversion (UC) emission properties were mainly dominated by the structural properties of the glass matrix. Ag+ doping and NP formation contributed to the enhancement of the total UC emission intensities. However, the green emission property of the glasses closely depended on the Ag NP size, and transition from quenching to enhancement occurred when the NP size of the Er3+–Ag co-doped glasses was increased. This size-dependent effect originated from the trade-off between the absorption and local field enhancement of Ag NPs with respect to the green emission of Er3+ ions.

Understanding the infrared to visible upconversion luminescence properties of Er3+/Yb3+ co-doped BaMoO4 nanocrystals

In this paper we report the infrared to visible upconversion luminescence properties of Er3+/Yb3+ co-doped BaMoO4 nanocrystals synthesized via microwave assisted sol–gel processing route. Structural, morphological and upconversion luminescence properties were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and Upconversion Photoluminescence spectra analysis. Results revealed that the oval shaped BaMoO4 nanocrystals ranging in size from 40 to 60nm having tetragonal scheelite crystal structure were obtained by sol–gel route. The infrared to visible upconversion luminescence has been investigated in Er3+/Yb3+ co-doped in BaMoO4with different Yb3+ concentrations. Intense green upconversion emissions around 528, 550nm, and red emission at 657nm corresponding to the 2H11/2, 4S3/2, and 4F9/2 transitions, respectively to the 4I15/2 ground state were observed when excited by CW laser radiation at 980nm. The green emissions were greatly enhanced after the addition of sensitizer (Yb3+ ions). The effect of Yb3+ on the upconversion luminescence intensity was analyzed and explained in terms of the energy transfer process based. The reported work establishes the understanding of molybdates as an alternative host material for upconversion luminescence.

Visible-light photocatalytic activity of Pt supported TiO2 combined with up-conversion luminescence agent (Er3+:Y3Al5O12) for hydrogen production from aqueous methanol solution

In this paper, a high effective up-conversion luminescence agent (Er3+:Y3Al5O12) is synthesized by sol–gel method, and then its corresponding visible-light photocatalyst (Er3+:Y3Al5O12/Pt–TiO2) is successfully prepared by direct mixing and calcination methods. For comparison, Er3+:Y3Al5O12, Pt–TiO2 and Er3+:Y3Al5O12/Pt–TiO2 are all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). At first, the up-conversion luminescence properties of Er3+:Y3Al5O12 are reviewed by excitation spectrum in visible-light region and emission spectrum in ultraviolet-light region. And then, under visible-light irradiation the visible-light photocatalytic activity of Er3+:Y3Al5O12/Pt–TiO2 is examined through photocatalytic hydrogen production from aqueous methanol solution. Lastly, the influence factors such as Er3+:Y3Al5O12 and Pt–TiO2 mole ratio, heat-treated temperature and heat-treated time on the visible-light photocatalytic hydrogen production activity of Er3+:Y3Al5O12/Pt–TiO2 are studied. Particularly, Er3+:Y3Al5O12/Pt–TiO2 with 6:100 M ratio heat-treated at 550 °C for 90 min shows the highest photocatalytic activity in hydrogen production from aqueous methanol solution.

Structure and upconversion luminescence properties of Er3 +–Mo6 + codoped Yb2Ti2O7 films

Er3+–Mo6+ codoped Yb2Ti2O7 thin films have been prepared on Si(100) substrates by a sol–gel method and spin-coating technique. A well-defined face-centered cubic phase of Yb2Ti2O7 was observed without the existence of either an Er or a Mo compound in Er3+–Mo6+ codoped Yb2Ti2O7 films. Mo6+ codoping improved the morphology quality and increased the grain size of Er3+ doped Yb2Ti2O7 films. Compared with Er3+–Mo6+ codoped Yb2Ti2O7 powder, Er3+–Mo6+ codoped Yb2Ti2O7 films show different green and red upconversion emissions properties under 976nm laser diode excitation. The Er3+–Mo6+ codoped Yb2Ti2O7 films showed higher luminescence intensity than the Er3+ doped Yb2Ti2O7 films, which was attributed to the transfer of high excited state energy from Yb3+–MoO42− dimers to Er3+.

980 nm upconversion luminescence from oxy-fluoride glasses and glass-ceramics doped with Yb3 +and Er3 + ions

Infrared upconversion luminescence properties of Er3+/Yb3+ co-doped oxy-fluoride glasses and glass-ceramics were investigated. Under 1550nm laser excitation, infrared emission centered at ~980nm that originated from the Yb3+: 2F5/2→2F7/2 and Er3+: 4I11/2→4F15/2 transitions was observed. The upconversion luminescence was enhanced both by Yb3+ content increase and by precipitation of β-PbF2 nano-crystals in the glass matrix. The energy transfer process between Yb3+ and Er3+ ions dominated IR upconversion emission, and Yb3+ can be used as energy acceptor. The strong upconverted luminescence can be used to increase the efficiency of silicon solar cells.

Highly Efficient IR to NIR Upconversion in Gd2O2S: Er3+ for Photovoltaic Applications

Upconversion (UC) is a promising option to enhance the efficiency of solar cells by conversion of sub-bandgap infrared photons to higher energy photons that can be utilized by the solar cell. The UC quantum yield is a key parameter for a successful application. Here the UC luminescence properties of Er3+-doped Gd2O2S are investigated by means of luminescence spectroscopy, quantum yield measurements, and excited state dynamics experiments. Excitation into the maximum of the 4I15/2 → 4I13/2 Er3+ absorption band around 1500 nm induces very efficient UC emission from different Er3+ excited states with energies above the silicon bandgap, in particular, the emission originating from the 4I11/2 state around 1000 nm. Concentration dependent studies reveal that the highest UC quantum yield is realized for a 10% Er3+-doping concentration. The UC luminescence is compared to the well-known Er3+-doped β-NaYF4 UC material for which the highest UC quantum yield has been reported for 25% Er3+. The UC internal quantum yields were measured in this work for Gd2O2S: 10%Er3+ and β-NaYF4: 25%Er3+ to be 12 ± 1% and 8.9 ± 0.7%, respectively, under monochromatic excitation around 1500 nm at a power of 700 W/m2. The UC quantum yield reported here for Gd2O2S: 10%Er3+ is the highest value achieved so far under monochromatic excitation into the 4I13/2 Er3+ level. Power dependence and lifetime measurements were performed to understand the mechanisms responsible for the efficient UC luminescence. We show that the main process yielding 4I11/2 UC emission is energy transfer UC.