Co-doped Nanophosphors Research Articles

An efficient down conversion luminescencent probe based on a NaGdF4:Eu3+/Ce3+ nanophosphor for chemical sensing of heavy metal ions (Cd2+, Pb2+ and Cr3+) in waste water

Eu3+ doped and Eu3+/Ce3+ co-doped NaGdF4 nanophosphors are fabricated via a facile hydrothermal route. The codoped counterpart is demonstrated for efficient photoluminescence sensing of heavy metal ions (Cd2+, Pb2+ and Cr3+) present in industrial effluents.

Optical analysis of interaction between Sm and Eu ions in MgAl2O4 spinel nanophosphor

This article describes structural and spectral properties of Eu:MgAl2O4, Sm:MgAl2O4 and Eu:Sm:MgAl2O4 codoped nanophosphors synthesized by hydrothermal method. The estimated crystalline size of synthesized nanophosphors was ∼07 nm (at 500 °C annealing temperature) which varies with annealing temperatures. In UV–vis absorption analysis reveals various transitions corresponding to trivalent Eu and Sm ions. FTIR gives various molecular vibrations of spinel group associated to MgAl2O4. Detail investigations about the photoluminescence properties of the Eu and Sm ions were carried out on different excitations and ion concentrations was optimized with emission intensity. Energy transfer study was performed by doping both the species at various concentrations. It was concluded that the efficient energy transfer takes place from Sm3+ to Eu3+on 405 nm laser excitation while vice-versa was not established. As revealed by CIE coordinate calculation, in consequence of energy transfer colour purity and its saturation varies. The observed photophysics was explored with experimental evidence.

Dual mode luminescence from lanthanum orthovanadate nanoparticles

The structural and optical properties of Yb3+/Er3+/Eu3+ co-doped LaVO4 nanoparticles have been investigated by XRD, FT-IR, HRSEM, DRS and fluorescence analysis. The crystal structure of all the synthesized samples showed the existence of tetragonal LaVO4. Influence of Eu3+ ions co-doping in Yb3+- Er3+: LaVO4 nanoparticles are systemically studied for both upconversion luminescence and emission studies. The energy transfer mechanism involved in LaVO4 phosphors is presented in detail based on their absorption, upconversion emission and pump power dependence study. The green to red fluorescence intensity ratio and asymmetry ratio are calculated with the variation of Eu3+ ion concentration. The upconversion fluorescence intensity ratio increases with the increase of pump power density which attributes the application of present phosphors as temperature sensors. Color purity of Yb3+/Er3+/Eu3+ co-doped LaVO4 nanophosphors hardly shows any change with variations in pump power. Dual mode luminescence of these nanophosphors finds its applications in anti-counterfeiting inks.

Effect of lanthanide ion co-doping on the luminescence in the cerium-doped zinc oxide-phosphor system

Novel cerium, praseodymium doped, and co-doped zinc oxide nanophosphors were prepared by a solid-state reaction method. The nanopowders were characterized using X-ray diffraction, energy dispersive spectroscopy, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, UV-visible, and photoluminescence. X-ray diffraction results showed high crystalinity in the nanoscale. Emission spectra of both doped and co-doped samples lay in the bluish green region. Color chromaticity co-ordinates were estimated for the Praseodymium co-doped nanophosphor. It was shown that optical emission could be modified by adding praseodymium into the cerium doped zinc oxide lattice. This work demonstrates that luminescence enhancement in zinc oxide is possible by introducing rare earth ions, and the resulting materials may have promise for lighting applications.

Effect of Mn2+ on Upconversion Emission, Thermal Sensing and Optical Heater Behavior of Yb3+ - Er3+ Codoped NaGdF4 Nanophosphors.

In thiswork, we investigate the influence of Mn2+ on the emission color, thermal sensing and optical heater behavior of NaGdF4: Yb/Er nanophosphors, which the nanoparticles were synthesized by a hydrothermal method using oleic acid as both a stabilizing and a chelating agent. The morphology and crystal size of upconversion nano particles (UCNPs) can be effectively controlled through the addition of Mn2+ dopant contents in NaGdF4: Yb/Er system. Moreover, an enhancement in overall UCL spectra of Mn2+ doped UCNPs for NaGdF4 host compared to the UCNPs is observed, which results from a closed back-energy transfer between Er3+ and Mn2+ ions (4S3/2 (Er3+) → 4T1 (Mn2+) → 4F9/2 (Er3+)). The temperature sensitivity of NaGdF4:Yb3+/Er3+ doping with Mn2+ based on thermally coupled levels (2H11/2 and 4S3/2) of Er3+ is similar to that particles without Mn2+ in the 303–548 K range. And the maximum sensitivity is 0.0043 K−1 at 523 K for NaGdF4:Yb3+/Er3+/Mn2+. Interestingly, the NaGdF4:Yb3+/Er3+/Mn2+ shows preferable optical heating behavior, which is reaching a large value of 50 K. These results indicate that inducing of Mn2+ ions in NaGdF4:Yb3+/Er3+ nanophosphors has potential in colorful display, temperature sensor.

Low-temperature synthesis of thermally stable BaWO4:Yb3+:Ho3+ nanophosphors: Tuning visible emission by controlling activator ion concentration

Abstract Upconverting nanophosphors are a special class of luminescent nanomaterials where lanthanide dopant assisted anti-stokes emission is exploited to achieve a wide range of applications. Herein we report Yb3+/Ho3+ co-doped BaWO4 nanophosphor with a significant thermal and chemical stability synthesized by a low-temperature hydrothermal process with red (655 nm) and green (538 nm) double color upconversion (UC) under 980 nm near-infrared (NIR) excitation, resulting in yellow emission. The synthesized samples were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Vis–NIR Spectroscopy and Transmission Electron Microscopy (TEM) techniques. The dependence of emission behavior on various concentrations of activator ion (Ho3+) in BaWO4: Yb3+:Ho3+ phosphors were studied in detail. Temperature dependent emission spectra revealed that the phosphor possesses stable emission up to 200 °C and luminescence intensity drop of only 11.5% of the initial luminescence intensity was observed at 150 °C. Therefore, the luminescence behavior and the thermal stability of the phosphor suggest an effective pathway in the optoelectronic applications.

Investigation of Upconversion Photoluminescence of Yb3+/Er3+:NaLaMgWO6 Noncytotoxic Double-Perovskite Nanophosphors.

Bright fluorescent rare-earth-ion-doped upconversion nanomaterials are attractive choices for photonic devices. A remarkable green upconversion emission has been obtained by the sensitizing effect of Yb3+ in a Yb3+/Er3+:NaLaMgWO6 (NLMWO) nanophosphor under near-infrared (NIR) excitation. A citrate sol-gel method was employed to synthesize the nanophosphor samples. The lack of a secondary phase in the X-ray diffraction pattern confirms that the Er3+ and Yb3+ ions are incorporated in the ordered double-perovskite structure. Surface analysis and particle evaluation are performed by field-emission scanning electron microscopy and transmission electron microscopy analysis. Upconversion and downconversion emission performances were systematically studied by varying the dopant concentrations. A strong upconversion green emission can be observed with the naked eye, and it resembles the upconversion spectra of Er3+-doped phosphors. Remarkably, because of an energy-transfer process, the green upconversion emission can be converted into a strong red emission by codoping with Yb3+ ions. We observed the color tuning effect from green to red, which can be controlled by varying the Yb3+ concentration in the codoped phosphors during NIR excitation. A systematic investigation of the upconversion mechanism from Yb3+ to Er3+ doubly doped NLMWO nanocrystals is demonstrated. The upconversion mechanism was evaluated only by varying the excitation power of the laser as well. A strong NIR emission at 1.57 μm corresponding to Er3+ can be significantly enhanced by increasing the codoping concentration of Yb3+ ions. The energy migration pathway is accurately presented. The Commission internationale de l'éclairage color coordinates were analyzed for singly and doubly doped nanophosphors. The cytotoxicity of the codoped nanophosphor system was evaluated using WI-38 cell lines. This optimized codoped nanophosphor material is noncytotoxic; thus, it can be useful for in vitro studies in biological studies. On the basis of the obtained results, the NLMWO:Yb3+/Er3+ nanophosphors can be a promising choice for novel upconversion photonic applications.

Polyol derived Bi3+ and Er3+ co-doped lanthanum oxide nanophosphors for display & LED applications

Abstract Color tunable luminescence was observed from Bi3+ and Er3+ co-doped La2O3 nanophosphor. The nanophosphors were prepared using cost effective and low temperature polyol route. The crystal structure, morphology, photoluminescence (PL) and were investigated in detail. Hue of Color changed which is observed by PL emissions on heating, La2O3:Bi3+, Er3+ phosphor powders from 700 to 900 °C. The observed emission peaks in PL from phosphor powder materials were assigned to either the broad emission originating from the transition in Bi3+ or the visible emission peaks originating transition from the Er3+ ions. All emission peaks of PL are plotted using CIE coordinates.

Size dependent optical temperature sensing properties of Y2O3: Tb3+, Eu3+ nanophosphors

Using urea as a precipitation agent, Tb3+, Eu3+ co-doped Y2O3 nanophosphors were synthesized by a homogeneous precipitation method. The sizes of the sample particles were controlled by changing the molar ratio of the urea and rare earth ions. The microstructure and crystallographic structure of the sample were determined through powder X-ray diffraction (PXRD) and field emission scanning electron microscopy (FE-SEM). The test results show that the sample is body centered cubic. As the molar ratio of urea to rare earth ions increases, the size of the sample particles decreases. The temperature-dependent emission spectra of Tb3+, Eu3+ co-doped Y2O3 phosphors with different particle sizes were measured. The results showed that because the fluorescence intensity ratio (FIR) of Tb3+ and Eu3+ varies with temperature, it can be used to visually reflect changes in temperature. In addition, the temperature sensing sensitivity of Tb3+ and Eu3+ co-doped Y2O3 phosphors increased upon a decrease in the particle size, but the relative sensitivity decreased with a decrease in the particle size. The physical mechanism of the sensitivity and relative sensitivity changes with the size of the sample particles was also explained.

Controllable white light generation from novel BaWO4: Yb3+/Ho3+/Tm3+ nanophosphor by modulating sensitizer ion concentration

Generation of white light requires a proficient strategy for appropriate mixing of red, green and blue emissions in appropriate proportion through optimization of material composition. However, it is quite challenging to develop a single host material showing emission in full visible region, which can be excited by a single excitation source. Herein, a series of Yb3+-sensitized Ho3+/Tm3+ co-doped BaWO4 nanophosphors synthesized by hydrothermal method is reported. The effect of different concentration of sensitizer ion (Yb3+) on the luminescence properties of BaWO4:Yb3+/Ho3+/Tm3+ crystal is investigated in detail to obtain white light. The phosphors exhibited red, green and blue luminescence centered at 651 nm, 539 nm and 482 nm respectively under a 980 nm excitation. The obtained novel nanophosphor could be a major potential candidate for nanobiotechnology and optoelectronics device applications.

Yb3+/Er3+ co-doped Lu2TeO6 nanophosphors: Hydrothermal synthesis, upconversion luminescence and highly sensitive temperature sensing performance

Upconversion (UC) nanophosphors of Lu2TeO6:Yb3+/Er3+ as temperature sensing material have been successfully synthesized via hydrothermal method followed by a subsequent heat treatment process. The phase and micrographs of the as-prepared phosphors were characterized by XRD, SEM, and TEM. Results indicate that the phosphors of hexagonal Lu2TeO6:Yb3+/Er3+, formed after heat-treatment at 800 °C for 5 h, consist of rice-like nanoparticles with size mostly distributed less than 200 nm in length. Under the 980-nm NIR excitation, the tellurite nanophosphors exhibit strong green and red UC emissions. The optimum Yb3+ and Er3+ concentrations for UC luminescence are determined to be 10% and 1%, respectively. The possible energy transfer mechanism implicated in the nanophosphors is discussed based on the pump power dependence of UC emissions. Furthermore, temperature sensing ability of Lu2TeO6:Yb3+/Er3+ (10/1) is investigated by employing the temperature dependent fluorescence intensity ratio (FIR) of two emission bands (2H11/2/4S3/2 → 4I15/2) of Er3+ ion. The maximum sensitivity achieved in this developed material is as high as 0.0103 K−1 at 623 K. This work provides a new qualified UC nanomaterial for application in optical remote temperature sensing.

Color tunable emission through energy transfer from Yb3+ co-doped SrSnO3: Ho3+ perovskite nano-phosphor

First time color tunable lighting observed from Ho3+ and Yb3+ co-doped SrSnO3 perovskite. Down-conversion and up-conversion (UC) photoluminescence emission spectra were recorded to understand the whole mechanism of energy migration between Ho3+ and Yb3+ ions. The intensity of green and red emission varies with Yb3+ doping which causes multicolour emissions from nano-phosphor. The intensity of UC red emission (654 nm) obtained from 1 at.% Ho3+ and 3 at.% Yb3+ co-doped nano-phosphor is nine times higher than from 1 at.% Ho3+ doped SrSnO3 nano-phosphor. Enhanced brightness of 654 nm in UC process belongs in biological transparency window so that it might be a promising phosphor in the bio-medical field. Moreover, for the other Yb3+ co-doped nano-phosphor, Commission Internationale de l’Eclairage chromaticity co-ordinates were found near the white region and their CCT values lie in the range 4900–5100 K indicating cool white. Decay time was measured for 545 nm emission of Ho3+ ion found in 7.652 and 8.734 µs at 355 nm excitation. The variation in lifetime was observed in ascending order with increasing Yb3+ concentration which supports PL emission spectra observation that with increasing Yb3+ concentration, rate of transition has changed. These studies reveal that Ho3+ and Yb3+ co-doped phosphor is useful for fabrication of white LEDs.

Zirconia based Ho3+–Yb3+ codoped upconverting nanophosphors for green light emitting devices applications

Photoluminescence study of the Ho3+–Yb3+ codoped ZrO, AlZrO and YZrO nanophosphors, synthesized by chemical co-precipitation method, upon excitation at 450 and 980 nm radiations have been performed. An improvement of about ∼4.5 times in the downconversion emission intensity of green band corresponding to the 5F4, 5S2 → 5I8 transition for codoped YZrO nanophosphors compared to ZrO codoped nanophosphors has been observed. On varying the pump power density upon 980 nm excitation the colour tunability in the codoped YZrO nanophosphors has been observed. UC emission intensity of the green band arising from the Ho3+ ion in the codoped YZrO nanophosphors is enhanced about ∼22 times compared to that of the codoped ZrO nanophosphors. The absorption and UC emission study for the codoped YZrO nanophosphors dispersed in different biologically compatible solvents viz. water, methanol, ethanol and dimethyl sulfoxide (DMSO) has been performed. The green UC emission intensity of about ∼1.3 and ∼1.7 times for the efficient codoped YZrO nanophosphors dispersed in methanol compared to that dispersed in water and DMSO respectively has been observed. The absorption spectra of an efficient upconverting YZrO nanophosphors dispersed in methanol exhibit no change with the passage of time.

Neutralizing the Charge Imbalance Problem in Eu3+-Activated BaAl2O4 Nanophosphors: Theoretical Insights and Experimental Validation Considering K+ Codoping.

In recent years, rare-earth-doped nanophosphors have attracted great attention in the field of luminescent materials for advanced solid-state lighting and high-resolution display applications. However, the low efficiency of concurrent red phosphors creates a major bottleneck for easy commercialization of these devices. In this work, intense red-light-emitting K+-codoped BaAl2O4:Eu3+ nanophosphors having an average crystallite size of 54 nm were synthesized via a modified sol–gel method. The derived nanophosphors exhibit strong red emission produced by the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ upon UV and low-voltage electron beam excitation. Comparative photoluminescence (PL) analysis is executed for Eu3+-activated and K+-coactivated BaAl2O4:Eu3+ nanophosphors, demonstrating remarkable enhancement in PL intensity as well as thermal stability due to K+ codoping. The origin of this PL enhancement is also analyzed from first-principles calculations using density functional theory. Achievement of charge compensation with the addition of a K+ coactivator plays an important role in increasing the radiative lifetime and color purity of the codoped nanophosphors. Obtained results substantially approve the promising prospects of this nanophosphor in the promptly growing field of solid-state lighting and field emission display devices.

Green Upconversion Emission of Yb3+/Er3+ co-doped Gd2Sn2O7 Nanophosphors as Wide-Range Temperature Sensor

Gd2Sn2O7:Yb3+/Er3+ (abbreviation for GSO: Yb3+/Er3+) nanophosphors codoped with Er3+ (0.1-2 at%) and Yb3+ (0.5-5 at%) were synthesized by a microwave hydrothermal process and annealed at 800 ℃ for 5 h. Powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and upconversion emission spectra were used to characterize the as-synthesized sample. Under the irradiation of 980 nm laser diode, the GSO: Yb3+/Er3+ nanophosphors emitted green emissions centered at 525 and 546 nm (Er3+ :2H11/2→4I15/2 and 4S3/2→4I15/2 transition), red emissions centered at 659 and 677 nm (Er3+:4F9/2→4I15/2 transition). The temperature dependent emission intensity ratio of the thermally coupled levels (2H11/2/4S3/2) of Er3+ in the wide-range of 110-573 K was recorded to study the optical thermometric properties of GSO: Yb3+/Er3+ nanophosphors. The maximum sensitivity of GSO: Yb3+/Er3+ nanophosphors was approximately 36.34x10-4 K-1 at 466 K. This result indicates that GSO: Yb3+/Er3+ nanophosphors are potential candidates for wide-range optical temperature sensors with high sensitivity.

Pure and Intense Green Upconversion Emission and Temperature Sensing Properties of Ba5Gd8Zn4O21:Ho3+/Yb3+ Nanophosphors

Ho3+/Yb3+ co-doped zincate Ba5Gd8Zn4O21 nanophosphors were successfully synthesized by solid-state reaction. The crystal structure and phase purity were measured by X-ray diffraction (XRD) and the luminescence spectra and CIE chromaticity were investigated. The results show that the upconversion (UC) luminescence intensities are heavily dependent on the rare-earth dopant concentration but the emission colors are almost the same. Both the green and red UC emissions under 980 nm excitation are shown to be two-photon processes independent of doping concentrations. Furthermore, the optical temperature sensing performance shows that Ho3+/Yb3+ co-doped Ba5Gd8Zn4O21 nanophosphors are promising candidates for room-temperature applications. The temperature quenching process of green UC emission was modeled using a simplified 4-level diagram and well explained by crossover process and thermal excitation.

Bright emission via energy transfer from Dy to Tb in Bi2SiO5 nanophosphor

The present article discusses the optical and structural properties of Tb and Dy co-doped Bi2SiO5 nanophosphors which were synthesized by Co-precipitation method. The synthesized sample contains plate-like morphology of uniform thickness ∼200 nm. Prepared samples were found of average crystallite size ∼20 nm, which yield bright yellow dominating white emission and green emission, in Dy: Bi2SiO5 and Tb: Bi2SiO5 nanophosphor, respectively under UV-light excitation. We have reported one-way efficient energy transfer from Dy to Tb ion, which facilitates precise colour tuning ability. The energy transfer phenomenon was well explored using, photoexcitation, photoluminescence and time-resolved luminescence techniques.

Enhanced light harvesting with novel photon upconverted Y2CaZnO5:Er3+/Yb3+ nanophosphors for dye sensitized solar cells

Trivalent erbium (Er3+) and erbium-yttribium (Er3+/Yb3+) co-doped Y2CaZnO5 (YCZ) nanophosphors were synthesized via Sol-Gel combustion method and applied as photon up-converter in dye sensitized solar cell (DSSC) and studied for their photovoltaic properties. A bright green and green–red up-conversion emission is observed upon an excitation of 980nm in Er3+:YCZ and Er3+/Yb3+:YCZ nanophosphors, respectively which indicates the possibility of using these phosphors for light harvesting applications. The prepared Er3+ and Er3+/Yb3+ co-doped YCZ nanophosphors were incorporated in TiO2 based DSSC to form the composite photoelectrode and studied the power conversion efficiency (PEC). With the incorporation of Er3+ and Er3+/Yb3+ co-doped YCZ nanophosphors in the DSSC resulted in the enhanced PCE of 6.01% and 7.21% using durable methoxypropionitrile (MPN) and volatile acetonitrile (AcN) based electrolytes, respectively. The PCE values obtained for the studied compounds are found to be either comparable or better than the other reported compounds used for the light harvesting. An enhanced photocurrent (JSC) of 12.44 and 13.28mA/cm2, for Er3+:YCZ and Er3+/Yb3+:YCZ nanophosphors based DSSC, respectively was observed under AM1.5G light due to the better photon conversion efficiency of the nanophosphor. The detailed up-conversion (UC) mechanism responsible for the enhanced PCE properties were discussed in detail and the results were compared with similar phosphor systems.

Effect of Li+ codoping on structural and luminescent properties of Mg2SiO4:RE3+ (RE = Eu, Tb) nanophosphors for displays and eccrine latent fingerprint detection

Luminescent nanophosphors find wide range of applications for the fabrication of WLEDs as well as in fingerprint detection techniques. Lithium co-doped Mg2SiO4:Tb3+ and Mg2SiO4:Eu3+ nanophosphors were prepared by low temperature solution combustion method. The effect of Li+ co-doping in Mg2SiO4 was systematically studied by Powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), UV–Vis- Diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. Further, the optimized powders were used to analyze the eccrine latent fingerprint. The DRS analysis show red shift of the absorption edges in Li+ co-doped nanophosphors. PL studies revealed that a small quantity of Li+ (1 mol %) ions was effective for charge compensation as well as creation of lattice defects to enhance the luminescence emission. The high quantum efficiency and color purity projects it to be a new material for commercial application in white light emitting diodes.

High purity green photoluminescence emission from Tb3+, Bi3+ co-doped LaGaO3 nanophosphors

A series of Tb3+ and Bi3+ co-doped LaGaO3 nanophosphors were synthesized by using polyol route and also characterised for their uncovering energy transfer mechanism of photoluminescence. An excellent characteristic emission of Bi3+ and Tb3+ ions was observed with an appreciable increase in photoluminescence at certain doping concentration. Energy transfer (ET) mechanism from the host lattice to Bi3+ and Tb3+ ions in the co-doped nanophosphor has been explained. The ET efficiency has been calculated and found to be 69.53%. The CIE chromaticity of the synthesized LaGaO3: Bi3+, Tb3+ nanophosphors indicates that they could be a suitable material for field emission display and LED applications.