Green synthesis of Y2O3:Dy(3+) nanophosphor with enhanced photocatalytic activity

Efficient route for preparation of Nd3+ doped Y2O3 nanoparticles at intermediate temperature

Yttrium oxide nanoparticles are one of the proper host materials for rare-earth elements. The rare-earth ions doped in yttrium oxide nanoparticles have medical applications such as biological imaging and photonic applications such as waveguides in the infrared region, laser mediums, sensitizers, LEDs, etc. The preparation of rare-earth ion-doped Y2O3 nanoparticles is usually done through the solid-state process and at a very high temperature, such as 1200 °C. In this research, using the solid-state process and during multi-step heat treatment at temperatures of 210 °C, 380 °C, and 500 °C, white nanopowders of Nd:Y2O3were prepared in 6 h. The produced nanopowders were studied using various characterization methods. The results showed that the produced nanopowders have a cubic structure and an average particle size between 22 and 65 nm.

Tunable Luminescence from Bi3+ Sensitized La2 Zr2 O7 : Eu3+ Red Nanophosphors for Display Applications

Bi³⁺ sensitized, Eu³⁺ activated La₂ Zr₂ O₇ nanophosphors are prepared successfully by simple wet chemical method. Strong blue emission of singly doped La₂ Zr₂ O₇ with Bi³⁺ ions was observed at 310 nm excitation, its wide emission spectrum has a peak maximum at 465 nm ascribed to electronic transition ³ P₁ →¹ S₀ of Bi³⁺ ions. The recorded photoluminescence spectra of x at % Eu³⁺ co-doped La₂ Zr₂ O₇ , when excited at 285 nm, the emission spectrum exhibits maximum peaks at wavelength values 615 nm, 646 nm and 665 nm which are ascribed to ⁵ D₀ →⁷ F₂ , ⁵ D₀ →⁷ F₃ and ⁵ D₀ →⁷ F₄ transitions of Eu³⁺ ions respectively. The chromaticity coordinates for optimized sample was found to be (0.519, 0.329). Sensitizing with Bi³⁺ ions can affect the luminescence properties of La₂ Zr₂ O₇ :Eu³⁺ phosphors. With reference to the change in Eu³⁺ concentration from x = 1 to 5 at %, color tunable luminescence from blue to orange, red of La₂ Zr₂ O₇ : Bi³⁺ /Eu³⁺ phosphors are observed. The life time decay values, energy level description and CIE chromatic color coordinates for Bi³⁺ , Eu³⁺ in La₂ Zr₂ O₇ : Bi³⁺ /Eu³⁺ co-doped sample was discussed. The spectral overlap between sensitizer, activator ions confirms the efficient energy transfer from Bi³⁺ ions to Eu³⁺ in La₂ Zr₂ O₇ : Bi³⁺ /Eu³⁺ co-doped sample and is via dipole-quadruple mechanism.

Blue light emitting Y2O3:Tm3+ nanophosphors with tunable morphology obtained by bio-surfactant assisted sonochemical route

Modified sonochemical route was used to prepare Y₂O₃:Tm³⁺ (1-11mol%) nanophosphor using Mimosa pudica (M.P.) leaves extract as bio-surfactant. The prepared samples were exhibited high crystalline nature with various morphologies. This was due to sonochemical experimental reaction took place between cavitation bubbles and nearby solution. The average crystallite sizes of the prepared samples were about 15nm to 21nm as obtained from PXRD and TEM analysis. The ultraviolet visible absorption spectra showed prominent bands with an energy gap varied from 5.73eV to 5.84eV. Photoluminescence (PL) emission spectra shows the prominent blue light emission peak at ~456nm attributed to ¹D₂→³F₄ transitions of Tm³⁺ ions. Judd-Ofelt intensity parameters were estimated by using PL emission spectra. The photometric characteristics of the prepared compounds were very close to the blue color of NTSC standards. So the results were fruitful in making use of Y₂O₃:Tm³⁺ nanophosphor as an alternative material for effective blue component in WLED's.

Vibrational and spectroscopic analysis of white light emitting Bi2SiO5 nanophosphor

A series of Dy³⁺ ion activated Bi₂SiO₅ nanophosphors were synthesized by the hydrothermal and coprecipitation methods. Various structural and optical characterizations were made using X-ray diffraction, Scanning and Transmission electron microscopy, UV-Visible-Infrared absorption, Raman Spectroscopy, Photoluminescence, Time resolved luminescence techniques etc. Dy³⁺ ion doped samples yields characteristic bright yellow and blue emissions, on resonant excitation with 349nm and 386nm. The intensity ratio of the yellow/blue peaks was found to be function of Dy ion concentration and synthesis method. We have achieved white colour emission at 1.5mol% Dy concentration, CIE coordinate (0.36, 0.4) of which fall well within gamut of white light. The time-resolved fluorescence reveals decrease in radiative lifetime values with increasing Dy³⁺ ions concentration. A comparison between the samples synthesized by different methods, and Dy ion concentrations has been made and detail photo-physics involved is presented in the article.

Tunable luminescence and enhanced photocatalytic activity for Eu(III) doped Bi2WO6 nanoparticles

A series of Eu(III) doped Bi₂WO₆ nanoparticles were synthesized by a hydrothermal process. The obtained Bi₂WO₆:Eu(III) nanoparticles were characterized by XRD, SEM, luminescence spectrophotometer and DRS. The XRD and TEM results indicate that the Eu(III) doping concentration has no influence on the phase and morphology. However, the Eu(III) doping can tune the luminescence and enhance the photocatalytic activity of Bi₂WO₆. With the increases of Eu³⁺ doping concentrations, the emission intensity of WO₆^6- group decreases nut the photocatalytic activity increases. The tunable luminescence of Bi₂WO₆:Eu(III) nanoparticles results from the energy transfer from WO₆^6- group to Eu(III) ion. The enhanced performance can be ascribed to efficient separation of electron and hole pairs after doping Eu(III) into the Bi₂WO₆ lattice.

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

Cr³⁺ -doped Y₂ O₃ (0.5-9 mol%) 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 3 h, 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 6-19 nm. The UV-vis spectra showed absorption bands at 198, 272 and 372 nm having band gap energy in the range 4.00-4.26 eV. 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 (361 nm). The emission spectra consisted of emission peaks in the blue (⁴ F_9/2  → ⁶ H_15/2 ), orange (⁴ F_9/2  → ⁶ H_13/2 ) and red (⁴ F_9/2  → ⁶ H_11/2 ) 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.

Solution Combustion Synthesis of Nanoscale Materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol-gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual properties are outlined. To demonstrate the versatility of the approach, several application categories of SCS produced materials, such as for energy conversion and storage, optical devices, catalysts, and various important nanoceramics (e.g., bio-, electro-, magnetic), are discussed.

Facile green fabrication of nanostructure ZnO plates, bullets, flower, prismatic tip, closed pine cone: Their antibacterial, antioxidant, photoluminescent and photocatalytic properties

Green synthesis of multifunctional Zinc oxide nanoparticles (NPs) with a variety of morphologies were achieved by low temperature solution combustion route employing neem (Azadirachta indica) extract as fuel. The nanoparticles were characterized by PXRD, FTIR, XPS, Raman and UV-Visible spectroscopic studies. The Morphologies were studied by SEM and TEM analysis. The NPs were subjected for photoluminescence, photocatalytic, antibacterial and antioxidant activity studies. PXRD pattern confirmed the hexagonal wurtzite structure of the product. SEM images indicated the transformation of mushroom like hexagonal disks to bullets, buds, cones, bundles and closed pine cone structured NPs with increase in the concentration of neem extract in reaction mixture. The NPs exhibited prominent green emission due to the presence of intrinsic defect centers. The as-formed bullet shaped ZnO with 4ml of neem extract was found to decolorize Methylene blue (MB) under Sunlight and UV light irradiation. The antibacterial studies indicated that ZnO NPs of concentration 500, 750 and 1000μg resulted in significant antibacterial activity on Klebsiella aerogenes and Staphylococcus aureus but not against Escherichia coli and Pseudomonas aeruginosa in agar well diffusion method. Further, ZnO NPs exhibited significant antioxidant activity against scavenging DPPH free radicals. The current investigation demonstrated green engineering method for the synthesis of multifunctional ZnO NPs with interesting morphologies using neem extract.

Bio-mediated route for the synthesis of shape tunable Y₂O₃: Tb³⁺ nanoparticles: Photoluminescence and antibacterial properties

The study reports green mediated combustion route for the synthesis of Tb(3+) ion activated Y2O3 nanophosphors using Aloe Vera gel as fuel. The concentration of Tb(3+) plays a key role in controlling the morphology of Y2O3 nanostructures. The formation of different morphologies of Y2O3: Tb(3+) nanophosphors were characterized by PXRD, SEM, TEM and HRTEM. PXRD data and Rietveld analysis evident the formation of single phase Y2O3 with cubic crystal structure. The influence of Tb(3+) ion concentration on structural morphology, UV-visible absorption and PL emission were investigated systematically. The PL emission of Y2O3: Tb(3+) (1-11 mol%) nanophosphors were studied in detail under 271 and 304nm excitation wavelengths. The CIE coordinates lies well within green region and correlated color temperature values were found to be 6221 and 5562K under different excitations. Thus, the present phosphor can serve as an excellent candidate for LEDs. Further, prismatic Y2O3: Tb(3+) (3 mol%) nanophosphor showed significant antibacterial activity against Pseudomonas desmolyticum and Staphylococcus aureus. The present study successfully demonstrates Y2O3: Tb(3+) nanophosphors can be used for display applications as well as in medical applications for controlling pathogenic bacteria.