Doped Y2O3 Nanophosphors Research Articles

Photoluminescence Property of Erbium-Doped Yttrium Oxide: Doping Concentration and Its Effect

Er3+ doped Y2O3 nanophosphors were synthesized by combustion techniques using urea as fuel, and their photoluminescence properties were measured. Furthermore, the morphology and particle size were calculated using Transmission electron microscopy (TEM), with the histogram showing the average particle size. Photoluminescence spectra of doped Y2O3:Er3+ phosphors were efficiently excited in the range of 200–400 nm. The phosphors prepared below 356 nm excitation exhibit three major peaks located at 506 nm (green) and 522 nm (green) and 711 nm (red) corresponding to 2H11/2 → 4I15/2 and 4F9/2 → 4I15/2 transition, respectively. The chromaticity calculation by the Commission Internationale de I’Eclairage (CIE) confirms that with Er3+ doping, the luminescence coordinates of Y2O3 phosphor with Er3+ doping shift to an almost white (0.291, 0.397) region which is very much close to the ideal white emission. Therefore, the prepared phosphor is used for UV-based LEDs and display devices.

Radioluminescence results, thermoluminescence analysis and kinetic parameters of Y2O3:Ln3+ (Ln: Dy, Nd, Sm) nanophosphors obtained by sol-gel method

Dy3+, Nd3+, Sm3+ doped Y2O3 nanophosphors were produced with high homogeneity at low sintering temperature using the sol-gel method. To compare the structural and optical changes of different rare-earth ions included in the crystal lattice, the dopant ratio was chosen as constant 2 mol%. In the light of X-ray diffraction (XRD) analysis, the unit cell volume and average crystallite size of the doped nanophosphors and their pure Y2O3 sintered under the same heat treatment regime were calculated and compared. Scanning electron microscopy (SEM) techniques were used to describe their structures and morphologies; an average particle size histogram of nanostructures was generated. The Radioluminescence (RL) spectra of Y2O3:Ln3+ (Ln: Dy, Nd, Sm) nanophosphors were presented for the first time. Splittings were seen in detail in the emission spectra given the 200–1100 nm range. For Dy3+4F9/2 → 6H13/2, for Nd3+; in the visible region 4H11/2-4I9/2 in the NIR region 4F3/2-4I9/2, for Sm3+; in the visible region 4G5/2-6H7/2 in the NIR region 4G5/2-6F5/2 transitions were determined to have the most vigorous emission. It was observed that the optical band gap calculated from the absorption spectrum of Y2O3 was 4.97 eV; this value changed the most with Dy contribution and decreased to 4.77 eV. The thermoluminescence (TL) behaviors of nanophosphors were compared under both UV and X-ray excitation. The kinetic parameters were calculated by applying computerized glow curve deconvolution (CGDC), and various heating rate (VHR) methods to the glow curves obtained UV excitation. The obtained E (eV) values correlated with each other are highly compatible.

Enhancement of Luminescence Efficiency of Y2O3 Nanophosphor via Core/Shell Structure.

We successfully fabricated Y2O3:RE3+ (RE = Eu, Tb, and Dy) core and core–shell nanophosphors by the molten salt method and sol–gel processes with Y2O3 core size of the order of 100~150 nm. The structural and morphological studies of the RE3+-doped Y2O3 nanophosphors are analyzed by using XRD, SEM and TEM techniques, respectively. The concentration and annealing temperature dependent structural and luminescence characteristics were studied for Y2O3:RE3+ core and core–shell nanophosphors. It is observed that the XRD peaks became narrower as annealing temperature increased in the core–shell nanophosphor. This indicates that annealing at higher temperature improves the crystallinity which in turn enhances the average crystallite size. The emission intensity and quantum yield of the Eu3+-doped Y2O3 core and core–shell nanoparticles increased significantly when annealing temperature is varied from 450 to 550 °C. No considerable variation was noticed in the case of Y2O3:Tb3+ and Y2O3:Dy3+ core and core–shell nanophosphors.

Thermoluminescence behavior of gamma irradiated Y2O3:Sm3+ nanophosphor

Thermoluminescence (TL) properties of 60Co gamma irradiated Sm3+ doped Y2O3 nanophosphors were investigated for possible application for high dose gamma radiation dosimetry. Sm3+ doped Y2O3 nanophosphors were synthesized by the solution combustion method. The crystalline phase was analyzed with X-ray diffraction and an average crystallite size was found to be ~20–33 nm. TL glow curves of gamma irradiated Sm3+ doped Y2O3 nanophosphors were recorded. The TL glow curves showed a prominent glow peak at ~400 K, a smaller intensity peak at 510 K and a very weak intensity glow peak at ~640 K. These glow peaks were ascribed to host defects and Sm3+ characteristic emission. The effect of Sm3+ concentration on the TL was explored and the optimum Sm3+ concentration was found to be 0.1 mol%. The number of overlapping TL glow peaks were identified from the broad TL glow curve by the thermal cleaning method. The kinetic parameters were obtained by the glow curve deconvolutions method using the general order kinetics expression. The variation of the TL intensity with dose, the effect of heating rates, repeatability and the fading effects of gamma irradiated Sm3+ doped Y2O3 nanophosphors were also studied. TL emission showed a strong green (545 nm) emission at ~400 K and a characteristic Sm3+ emission was observed at a high dopant concentration. The results obtained were favorable for the application of high dose gamma radiation dosimetry.

Rapid ultrasonic-microwave assisted synthesis of Eu3+ doped Y2O3 nanophosphors with enhanced luminescence properties

A series of Eu3+ doped Y2O3 nanophosphors have been synthesized via an ultra-fast ultrasonic-microwave method followed by thermal annealing. The emission of Y2O3:Eu3+ nanophosphors depends tremendously on the concentration of Eu3+ ions and maximum emission intensity is achieved at 612 nm (red luminescence) with a doping concentration of 3 mol%. Moreover, the Y2O3:Eu3+ nanophosphors in this work have much higher photoluminescence lifetime (1.570 ms) and quantum efficiency (80.88%) than that synthesized by other methods. The results of chromaticity coordinates indicate that the Y2O3:Eu3+ as red-emitting phosphor is promising candidate for white light-emitting diodes (LEDs).

Upconversion luminescence of Er<SUP align="right">3+</SUP> doped Y<SUB align="right">2O<SUB align="right">3 and Gd<SUB align="right">2O<SUB align="right">3 nanophosphors

The luminescence process and mechanism of Er3+ doped Y2O3 and Gd2O3 nanophosphors are investigated with focus on their upconversion luminescence properties. Here the strong up-conversion (UC) emissions of both Y2O3:Er3+ nanoparticles prepared by combustion with EDTA and Gd2O3:Er3+ nanospheres synthesised by multistep chemical reaction using urea have been measured at room or low temperatures. The downward-conversion luminescence spectra in visible and near infrared region have been assigned from the transitions in the energy level system of Er3+ion. For Y2O3:Er3+nanoparticles, the upconversion luminescent intensity depends on excitation power at 980 nm have properly indicated the two photon process which are the calculated slope values of main transitions in Er3+ions: 2H11/2-4I15/2, 4S3/2-4I15/2and 4F9/2-4I15/2 are 2.07, 1.72, 1.87 (0.5% Er) and 2.32, 1.82 and 2.07 (Er 1.0%) respectively. The integral intensity of the red band is smaller than that of the green band in the upconversion emission of nanoparticles Y2O3 doped with Er3+ with 0.50, 1.00 and 1.50%. However it was the integral intensity of red emission bands that dominated in Gd2O3: 1% Er3+. The lifetimes of the band in green colour peaked at 562 nm upon excitation at 380 nm in Y2O3:Er3+ with 0.50, 1.00 and 1.50%, and have shown the two sequent time decay processes, the shorter and the longer, both in millisecond scale, 0.14 ms (0.5%); 0.28 ms (1.00%) and 0.13 ms (1.50%) and 4.49 ms (0.5%); 6.89 ms (1.00%) and 5.16 ms (1.50%), respectively. For the nanoparticles Gd2O3: 1% Er the intensity decrease of the upconversion emission peaked at 562 nm with only a single process with a decay time of 1.24 ms. Both nanophosphors Y2O3 and Gd2O3 doped with Er3+ are promising materials to develop multifunctional units for medical applications.

Aloe vera (L.) Burm. F Assisted Green Synthesis and Biological Applications of Y2O3:Mg2+ Nanocomposites

For the first time green route method was used to synthesize pure and Mg2+ (1–11 mol%) doped Y2O3 nanophosphors by using Aloe vera leaves extract as a fuel. The final product was well characterized by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The PXRD results showed formation of single phase, cubic structure of Y2O3 with crystallite sizes ~ 25 nm and TEM images showed crystallite size of the material and were found to be around ~ 25 nm. In an in vitro test, nanocomposites showed significant antibacterial activity against four different gram negative human pathogenic microorganisms viz., Salmonella typhimurium, Enterobacter aerogenes, Pseudomonas aeruginosa and Escherichia coli and maximum zone of inhibition is observed from Y2O3/Mg (1%) nanocomposites which is closely comparable with the standard commercial drug streptomycin. Whereas, the nanoparticles and nanocomposites have showed significant DPPH and H2O2 scavenging activity, higher scavenging activity were registered in Y2O3/Mg (1%) and Y2O3/Mg (5%) respectively.

Sonochemical driven ultrafast synthesis of Praseodymium doped Y2O3 nanostructures for display applications

For the first time Pr3+ (1-11 mol %) doped Y2O3nanophosphors were synthesized by ultrasound supported sonochemical method using mimosa pudica (MP) leaves extract as bio-surfactant. The obtained product was heat treated at 700°C for 3 h and used for characterization. The powder X-ray diffraction (PXRD) profiles of nanophosphors showed cubic phase structure. The sonication time and concentration of bio-surfactant play a vital role in tuning the morphologies of Y2O3. The particle size was further confirmed by transmission electron microscope (TEM) and it was found to be in the range of 20-30 nm. The band gap energy of the phosphors were estimated by making use of diffuse reflectance spectrum (DRS) and the values were found to be in the range of 5.67 – 5.80 eV. Under 447 nm excitation wavelength, the photoluminescence (PL) emission spectrum was recorded. The PL emission spectra consist of sharp peaks centred at 554, 612 and 738 nm and were attributed to 3P0→3H5, 3P0→3H6, and 3P0→3F4 transitions respectively. The 5 mol% Pr3+ doped Y2O3nanophosphors showed maximum intensity. Further CIE and CCT were estimated and found that the color coordinates lies in between (0.593, 0.412) and (0.358, 0.544) respectively. Results obtained evident that the phosphor was highly useful in display device applications.

Novel ultrasound assisted Eu3+ ions doped Y2O3 nanostructures suitable for display device applications

Eu3+ (1-11 mol %) doped Y2O3 nanophosphors were synthesized by modified sonochemical method using Epigallocatechingallate (EGCG) extract. The obtained products were calcined at 700 oC for 3 h and subjected to structural and photometric studies. The powder x-ray diffraction profile showed crystalline cubic phase structure. The particle size, micro strain, dislocation densities and stacking faults were estimated and it was observed that the particle size decreases and micro strain increases with increase of Eu3+ concentration. The scanning electron microscope images showed spherical particles fused to form a rod like structure. The particle size was found to be in the range of 30-47 nm as confirmed by transmission electron microscope. Photoluminescence spectra showed lines corresponding to 5D0→7FJ (J = 0,1,2,3 & 4) transitions. The 3 mol% Eu3+ doped Y2O3 NPs showed maximum intensity peaks. The present results indicate that the present nanophosphors can be used in the red color light emitting laser devices

Concentration and wavelength dependent frequency downshifting photoluminescence from a Tb3+ doped yttria nano-phosphor: A photochromic phosphor

In this article, the Tb3+ doped Y2O3 nano-phosphor has been synthesized through solution combustion method. The structural measurements of the nano-phosphor have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques, which reveal nano-crystalline nature. The Fourier transform infrared (FTIR) measurements reveal the presence of different molecular species in the nano-phosphor. The UV–Vis–NIR absorption spectrum of the nano-phosphor shows large number of bands due to charge transfer band (CTB) and 4f-4f electronic transitions of Tb3+ ion. The Tb3+ doped Y2O3 nano-phosphor emits intense green downshifting photoluminescence centered at 543 nm due to 5D4 → 7F5 transition on excitation with 350 nm. The emission intensity of the nano-phosphor is optimized at 1.0 mol% concentration of Tb3+ ion. When the as-synthesized nano-phosphor is annealed at higher temperature the emission intensity of the nano-phosphor enhances upto 5 times. The enhancement in the emission intensity is due to an increase in crystallinity of the nano-phosphor, reduction in surface defects and optical quenching centers. The CIE diagram reveals that the Tb3+ doped nano-phosphor samples show the photochromic nature (color tunability) with a change in the concentration of Tb3+ ion and excitation wavelength. The lifetime measurement indicates an increase in the lifetime for the annealed sample. Thus, the Tb3+ doped Y2O3 nano-phosphor may be used in photochromic displays and photonic devices.

Synthesis, thermoluminescence and defect centres in Eu3+ doped Y2O3 nanophosphor for gamma dosimetry applications

Europium doped Y2O3 nanophosphors have been prepared by the solution combustion method. The prepared nanophosphors were characterized by powder x-ray diffraction (XRD). XRD revealed that the cubic phase with crystallite size in the range 25–37 nm formed. Surface morphology of the samples was studied by field emission scanning electron microscopy and the particles were observed as spherical in nature, having an average size ~30 nm. The electron spin resonance spectrum of the irradiated nanophosphor exhibited a signal having peaks at g = 2.1646 and 2.0035 which are attributed to and defect centers, respectively. Thermoluminescence (TL) emission showed a strong red (611 nm) emission at 417 K. The prominent TL glow (417 K) peak exhibited low fading, good reproducibility and linear dose response in the range 0.01–2.0 kGy. This behavior is favorable for TL dosimetry applications. The Y2O3:Eu3+ nanophosphor has prodigious potential as a dosimeter to be use for monitoring high dose ionizing radiation fields.

Structural, morphological and photometric properties of sonochemically synthesized Eu3+ doped Y2O3 nanophosphor for optoelectronic devices

Synthesis of Eu3+ doped Y2O3 nanophosphors via modified sonochemical method was presented. Morphologies of the prepared products were analyzed with respect to the influential parameters during the preparation time. The photoluminescence (PL) emission spectra exhibits several peaks at ∼537nm, 598nm, 613nm and 662nm attributed to 5D0→7FJ (J=0, 1–3) transitions of Eu3+ ions in the host lattice. The types of energy transfer between the Eu3+ ions were responsible for concentration quenching confirms the electric dipole–quadrupole interaction among the ions. The Judd-Ofelt intensity parameters and other radiative properties were estimated by using PL emission spectra. The photometric characteristics of the prepared samples indicate that the color co-ordinates were tune towards pure red emission with color purity of ∼88%. The results signified that the prepared Y2O3:Eu3+ was a potential amber phosphor for solid state and LED’s applications.

Surface analysis and enhanced photoluminescence via Bi3+ doping in a Tb3+ doped Y2O3 nano-phosphor under UV excitation

The Tb3+, Bi3+ co-doped Y2O3 nano-phosphor has been synthesized through solution combustion method for the first time. The surface analysis of the phosphor has been done using XRD and TEM measurement techniques, which reveal strong crystallinity and spherical particles agglomerated to each other. The EDS spectra of Tb3+, Bi3+ co-doped Y2O3 phosphor show the presence of Y, O, Tb and Bi elements. The Tb3+ doped Y2O3 phosphor emits intense green emission centered at 542 nm due to 5D4 → 7F5 transition along with other weak bands on excitation with 266 nm. The emission intensity is found to be optimum at 1 mol% concentration of Tb3+ ions. The sample annealed at higher temperature gives larger emission intensity due to reduction in the optical quenching centers. The presence of Bi3+ ions in the Tb3+ doped phosphor further enhances the emission intensity of Tb3+ up to two times. The enhancement in the emission intensity is due to energy transfer from Bi3+ to Tb3+ ions, which has been confirmed by lifetime measurements. Thus, the Tb3+, Bi3+ co-doped Y2O3 nano-phosphor may be a suitable candidate for solid state lighting.

Combustion synthesis and characterisation of Eu<SUP align="right">3+</SUP>-activated Y<SUB align="right">2O<SUB align="right">3 red nanophosphors for display device applications

Europium activated yttrium oxide red phosphors have gathered more attention because of their good luminescent characteristics, acceptable atmospheric stability, reduced degradation under applied voltages, and lack of hazardous constituents. In order to achieve improved luminescent properties of Y2O3:Eu3+, the synthetic methods are playing an important role. In the present study, Eu3+ (2 mol %) doped Y2O3 nanophosphors were synthesised by the facile nitrate citrate gel combustion method at relatively low temperature and shorter duration (700°C for 2 h). Further samples were characterised by powder X-ray diffraction (XRD) technique. The morphology and particle size of the phosphors were studied by scanning electron microscope (SEM), UV reflectance spectroscopy and Raman spectroscopy. The photoluminescence measurements of the Y2O3:Eu3+ particles showed red emission peaks at 610-612 nm (5D0 → 7F2). CIE chromaticity diagram and CCT calculations confirmed that these nanophosphors can act as a red component in the fabrication of white light emitting diodes (WLEDs) for display and other optical device applications.

Tailoring the luminescence properties of Y2O3:Sm3+ nanophosphors by 6 MeV electron beam irradiation

Sm3+ (3 mol%) ions doped Y2O3 nanophosphors were synthesized by green synthesis route using Aloe Vera gel as fuel. The final product was irradiated by 6 MeV electron beam (E-beam) to different fluences in the range (2–10 × 1013 e− cm−2) and well characterized. Powder X-ray Diffractogram (PXRD) results revealed the loss of crystalline nature due to lattice disorder created during irradiation. Fourier Transform Infrared (FTIR) spectroscopic results showed absorption peaks around 688–843 cm−1 (Y-O bond), 1076 and 1398 cm−1 (C-O bond), 1505–1765 cm−1 and 3498 cm−1 (O-H bond). Scanning Electron Microscopic (SEM) images showed flake like morphological features. The Photoluminescence (PL) emission spectrum recorded at 407 nm excitation showed magnetic and electric dipole transitions at ∼569–575 (4G5/2 → 6H5/2), ∼607–623 (4G5/2 → 6H7/2) and ∼655–668 nm (4G5/2 → 6H9/2) respectively. Thermoluminescence (TL) glow curve consists of three peaks in E-beam irradiated nanophosphors at 158, 243 and 352 °C due to creation of more number of trapping and luminescent centers. The E-beam irradiated Y2O3:Sm3+ nanophosphors showed strong PL emission with color co-ordinate values lying in the orange-red region. Therefore, this material can be potentially used as a red component in WLEDs (White LEDs).

Extraction of Y2 O3 :Cr3+ nanophosphor by eco-friendly approach and its suitability for white light-emitting diode applications.

Cr3+ -doped Y2 O3 (0.5-9mol%) was synthesized by a simple solution combustion method using Aloe vera gel as a fuel/surfactant. The final obtained product was calcined at 750°C for 3h, which is the lowest temperature reported so far for the synthesis of this compound. The calcined product was confirmed for its crystallinity and purity by powder X-ray diffraction (PXRD) studies which showed a single-phase nano cubic phosphor. The particles size estimated by Scherrer formula was in the range of 6-19nm. The UV-vis spectra showed absorption bands at 198, 272 and 372nm having band gap energy in the range 4.00-4.26eV. In order to investigate the possibility of its use in white light emitting display applications, the photoluminescence properties of Cr3+ -doped Y2 O3 nanophosphors were studied at an excitation wavelength in the near ultraviolet (UV) light region (361nm). The emission spectra consisted of emission peaks in the blue (4 F9/2 →6 H15/2 ), orange (4 F9/2 →6 H13/2 ) and red (4 F9/2 →6 H11/2 ) regions. The CIE coordinates (0.33, 0.33) lie in the white light region. Hence Y2 O3 :Cr3+ can be used for white light-emitting diode (LED) applications.

Mimosa pudica (L.) assisted green synthesis and photoluminescence studies of Y2O3:Mg2+ nanophosphor for display applications

For the first time green route method was used to synthesize pure and Mg2+(1-11 mol %) doped Y2O3 nanophosphors by using Mimosa pudica leaves extract as a fuel. The final product was well characterized by powder x-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL).The PXRD result shows the formation of single phase, cubic structure of Y2O3 with crystallite sizes ∼25 nm. The SEM results showed porous and agglomerated structures, TEM images showed the crystallite size of the material and was found to be around ∼ 25 nm. PL emission spectra show the blue light emission under the excitation wavelength of 315 nm. The emission peaks of Mg2+were observed at 428 nm, 515 nm and 600 nm corresponding to the transitions of 4F9/2 → 6Hi7/2 (violet), 4F9/2 → 6Hi5/2 (blue), 4F9/2 → 6HJ3/2 (yellow) respectively. The estimated CIE chromaticity co-ordinate was very close to the national television standard committee value of blue emission. CCT was found to be ∼ 6891 K as a result the present phosphor was potential to be used for warm white light emitting display applications.

Ab-initio simulations at the atomic scale of an exceptional experimental photoluminescence signal observed in Ce3+-doped Y2O3 sesquioxide system

Intense blue emission is observed in Ce3+-doped Y2O3 nanophosphors, successfully prepared by simple sol gel method. The nano-powder is characterized by diffractometry (XRD) and room temperature steady photoluminescence. The XRD analysis shows that the crystallite size is 10nm. The excitation and emission observed bands are assigned to 4f-5d transition and investigated. VASP code is used to performed the first principle calculations study of Y2O3:Ce3+ nanomaterial system. The Ueff parameter is tuned to give best agreement with experimental results. Hybrid functional (HSE06) is used calculated the band gap of Y2O3 and 5d orbitals of Ce3+.

Facile route to produce spherical and highly luminescent Tb3+ doped Y2O3 nanophosphors

Terbium doped yttrium oxide (Y2O3:Tb3+) nanophosphor has been synthesized via a facial yet modified co-precipitation method. To get maximum luminescence output from Y2O3:Tb3+ nanophosphors, surfactants namely, Cetyl trimethylammonium bromide (CTAB) and Trioctylphosphine oxide (TOPO) were added during synthesis. Further, it has been observed that combined addition of surfactant (CTAB + TOPO) at the time of synthesis has resulted in nearly spherical morphology of the nanophosphor. Furthermore, these optimized material are observed to have enhanced integrated photoluminescence (PL) intensity of ∼23% as compared to the one synthesized without the addition of any surfactant. The results are further supported by detailed structural and optical studies. Optimum use of surfactants during synthesis shows for the first time that both nano-sized distribution and high crystallinity can be achieved simultaneously which has resulted in bright green emission in Tb3+ doped Y2O3 nanophosphors.

Tailoring red-green-blue emission from Er3+, Eu3+ and Tb3+ doped Y2O3 nanocrystals produced via PVA-assisted sol-gel route

Y2O3 luminescent nanoparticles were synthesized via PVA-assisted sol-gel method and their structural and optical properties were investigated. Effects of rare earth (Er3+, Eu3+ and Tb3+) doping on luminescence properties of the produced nanophosphors have been investigated under NIR (800nm) and UV (240–300nm) excitation. Intense infrared to red and green emissions were observed and a weak blue upconverted luminescence was also detected. Moreover, it was observed that changing the doping ions, the color emitted by the samples could be modified and different combinations of UV excitation and doping produced effective white light emissions. The obtained results demonstrate that PVA-assisted sol-gel is an effective methodology for the synthesis of rare-earth doped Y2O3 nanophosphors.