Zinc Oxide Nanophosphor Research Articles

Photoluminescence and thermoluminescence dosimetry properties of Ag/Y co-doped ZnO nanophosphor for radiation measurements.

This work explores the thermoluminescence (TL) and photoluminescence (PL) properties of Ag/Y co-doped zinc oxide (ZnO) nanophosphor. The proposed dosimeter was prepared by the coprecipitation method and sintered at temperatures from 400°C to 1000°C in an air atmosphere. Raman spectroscopy was studied to investigate the structural features of this composition. The new proposed dosimeter revealed two peaks at 150°C and 175°C with a small shoulder at high temperature (225°C). The PL spectrum showed strong green emissions between 500 to 550 nm. The Raman spectrum showed many bands related to the interaction between ZnO, silver (Ag), and yttrium oxide (Y2 O3 ). The rising sintering temperature enhanced the TL glow curve intensity. The Ag/Y co-doped ZnO nanophosphor showed an excellent linearity index within a dose from 1 to 4Gy. The minimum detectable dose (MDD) of the Ag/Y co-doped ZnO nanopowder (pellets) equaled 0.518 mGy. The main TL properties were achieved in this work as follows: thermal fading (37% after 45 days at 1 and 4Gy), optical fading (53% after 1h and 68% after 6h by exposure to sunlight), effective atomic number (27.6), and energy response (flat behavior from 0.1 to 1.3MeV). Finally, the proposed material shows promising results nominated to be used for radiation measurements.

Gamma-ray induced thermoluminescence emission of green synthesized zinc oxide nanophosphors

The thermoluminescence (Thermally stimulated luminescence) technique has been applied in the field of radiation dosimetry and was found to be highly successful in dating ancient pottery samples. It is also used in the study of biological and biochemical systems. The present study reports the gamma-ray exposed thermoluminescence (TL) emission of ZnO nanophosphors. ZnO nanoparticles were prepared via phyto-mediated green routes according to our previous works. Different analytical techniques such as XRD, FESEM, HRTEM, XPS, EDS, FTIR, and UV-DRS were employed to characterize the samples. The ZnO nanoparticles possess hexagonal wurtzite crystal structure of with 29–71 ​nm particle dimension. TL emission of the samples was recorded with different gamma dosages10-50 Gy at a constant heating rate of 2oCs-1. A broad single glow curve above 300 ​°C was exhibited by the samples and good linearity was reserved in integrated TL profiles. The TL emission follows first-order kinetics and the activation energies of the traps located in the samples were determined.

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.

Reddish emission of europium doped zinc oxide nanophosphor prepared through precipitation route using sodium borohydride

The main objective of this research work is to develop a desired reddish emission of europium (Eu)-doped zinc oxide (ZnO) nanophosphor, prepared through precipitation route using sodium borohydride (NaBH4), as a precipitating agent and also study its structure, powder morphology as well as photoluminescence characteristics, especially asymmetric ratio or colour purity. X-ray diffraction of the calcined (600 °C) Eu (3 mol%)-doped ZnO powders confirmed the presence of pure phase ZnO and also suggested that the europium ions are incorporated in the lattice sites of Zn ions due to the increase in lattice volume as well as peak (101) shifting towards the lower angle. FESEM and TEM analysis confirmed that the particles of Eu-doped ZnO are elongated or elliptical rod-like, having length in the range of 200 nm – 400 nm as well as polyhedral in shape. Photoluminescence behaviour indicate an intense broad transition of 5D0→7F2 (compared to transition of 5D0→7F1) corresponds to red emission, when the sample was excited at 464 nm. The ratio of integrated maximum emission intensities between 5D0 → 7F2 and 5D0 → 7F1 transitions was found to be ∼5.9. The value of asymmetric ratio or colour purity and the position of CIE coordinates suggested that the Eu-doped ZnO nanopowders may be used as red emitting phosphor material.

Broad spectral inhibitory effects of pale green zinc oxide nanophosphor on bacterial and fungal pathogens

Nd3+ doped zinc oxide nanophosphor were prepared by a modified sonochemical route. Adsorption of Aloe vera (A.V.) gel by the precursors made the final product with controlled morphology, that is A.V. gel acted as surfactant. Characterization studies confirmed the pure hexagonal phase with nanostructure, wide-bandgap was reported. Major electronic transitions in the prepared samples were due to 4f shell electrons of Nd3+ions. Emission peaks attributed to 2P3/2 → 4I13/2, 2P3/2 → 4I15/2, 1I6 → 3H4, 2P1/2 → 4I9/2 and 4G7/2 → 4I9/2 transitions under the excitation wavelength of 421 nm. The emitted wavelengths showed the redshift from blue to pale green region. Further, the prepared samples showed very good control over the growth of microbial pathogens such as Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Alternaria alternata and Fusarium oxysporum. The proposed mechanism is that the ZnO:Nd3+ interwinds the bacteria and fungal pores with a heterogeneous range of superstructues, resulting in the local perturbation at cell membrane of fungal cells. This induces to decrease the potential energy at bacterial membrane and the leakage of electrolytes of fungal spores. There is a mechanical wrapping interaction between pathogens and the nanoparticles which locally damages of the cell membrane and causes cell lysis. Biocompatible, ZnO:Nd3+ nanostructures possesses antibacterial activity against more multi-resistant bacterial and fungal phytopathogens. This additional information provides useful scientific information to prevent the various crop diseases.

Ho^3+-doped ZnO nano phosphor for low-threshold sharp red light emission at elevated temperatures

As an approach to design efficient visible luminescent material at nano scale, Ho3+ ion-doped single-phase zinc oxide (ZnO) nano phosphor to obtain red emission suitable for LED/laser applications is reported. Ho3+-doped ZnO nanoparticles with various concentrations of Ho3+ have been prepared by a simple solgel synthesis technique. Under the excitation of 488 nm, the photoluminescence emission spectra of the nano phosphor exhibit an intense emission with multiple and well-resolved narrow splitting peaking in the range from 640 to 667 nm, which is identified as the emission from the Ho3+ ion, corresponding to F55→I58 transition with multiple splitting due to the ZnO crystal field. The required excitation threshold for these emissions is, surprisingly, as low as 33.8 kW/cm2, and the narrow line width (FWHM<2 nm) is found to be persistent even at higher temperatures. Such sharp emission from Ho3+:ZnO nanoparticles could be used for lasing applications.

Rare Earth Doped Zinc Oxide Nanophosphor Powder: A Future Material for Solid State Lighting and Solar Cells

A comprehensive review of up-conversion (UP) and down-conversion (DC) or down shifting of rare earth (RE) doped zinc oxide (ZnO) nanophosphors is presented. Research interest in the development of RE3+ doped ZnO for UP and DC nanophosphors has been encouraged by the potential application of these materials in light emitting diodes and different types of photovoltaic cells. A range of remarkable characteristics, which are organized into different sections describing the structure, optical, and luminescence properties of these materials, are discussed in detail. Undoped ZnO has two characteristic emissions in the ultraviolet and visible regions related, respectively, to excitonic recombination and intrinsic defects. X-ray photoelectron spectroscopy (XPS) data demonstrated a correlation between the visible emission and intrinsic defects. In the case of the DC or shifting process, there was simultaneous emissions related to f → f transitions of RE ions and defects in ZnO host. These emissions were dependent o...

Luminescence and spectroscopic investigations on Gd3+ doped ZnO nanophosphor

The present paper describes the synthesis of 0.1 mol% Gadolinium (Gd) doped Zinc oxide (ZnO) nanophosphor by solution combustion method using Oxalyl dihydrazide (ODH) fuel. Powder X-ray diffraction (PXRD) peaks are well matched with the standard hexagonal wurtzite structure of ZnO (JCPDS card no. 36-1451). SEM and TEM analysis reveals porous morphology of as -formed sample with particles having narrow size distribution in the range ∼60–70 nm, in good agreement with XRD data. The PL spectrum of Gd doped ZnO sample exhibits an extra blue emission at 441 nm (∼2.81 eV) in addition to the emission bands from undoped ZnO. From the TL data of ZnO:Gd nanophosphor with UV irradiation, it is observed that considerable amount of re-trapping is taking place in all the TL second order peaks. The EPR spectrum exhibits a number of resonance signals suggesting that Gd3+ ions are experiencing different crystal field strength and Zeeman interactions.

Effect of Annealing on the Thermoluminescence Properties of ZnO Nanophosphor

We report the effect of annealing on the thermoluminescence (TL) properties of zinc oxide (ZnO) nanophosphor. The sample was synthesised by a wet chemical process. The characterisation report shows that the size of the grains is within 123.0 nm–160.5 nm. TL measured at 2 K/s from a fresh un-annealed sample irradiated to 60 mGy shows a composite glow curve containing three peaks at 353.2 K, 429.1 K, and 455.3 K. On the other hand, samples annealed at 473 K and 573 K followed by irradiation to 60 mGy do not give TL. However, annealing at 673 K and 773 K followed by irradiation to the same dose produces a glow curve comprising two overlapping peaks at 352.3 K and 370.6 K. In the TL emission spectrum of un-annealed sample, two emission peaks were found in green (~523 nm) and orange (~620 nm) regions whereas in annealed samples, only a peak was found in the orange region (~618 nm). Kinetic analysis shows that the activation energy corresponding to TL peaks at 353.2 K, 429.1 K, and 455.3 K of the un-annealed sample are 0.64 eV, 0.80 eV, and 1.20 eV whereas that of the peaks at 352.3 K and 370.6 K of 673 K and 773 K annealed samples are 0.64 eV and 0.70 eV, respectively. All peaks of un-annealed and annealed samples, except the one at 429.1 K of the un-annealed sample, follow first-order kinetics whereas the peak at 429.1 K follows second-order kinetics. Considering the kinetic and spectral features, an energy band model for ZnO nanophosphor has been proposed.

Thermoluminescence of Novel Zinc Oxide Nanophosphors Obtained by Glycine‐Based Solution Combustion Synthesis

High‐dose thermoluminescence dosimetry properties of novel zinc oxide nanophosphors synthesized by a solution combustion method in a glycine‐nitrate process are presented for the very first time in this work. Sintered particles with sizes ranging between ~500 nm and ~2 μm were obtained by annealing the synthesized ZnO at 900°C during 2 h in air. X‐ray diffraction patterns indicate the presence of the ZnO hexagonal phase, without any remaining nitrate peaks observed. Thermoluminescence glow curves of ZnO obtained after being exposed to beta radiation consists of two maxima: one located at ~149°C and another at ~308°C, the latter being the dosimetric component of the curve. The integrated TL fading displays an asymptotic behavior for times longer than 16 h between irradiation and the corresponding TL readout, as well as a linear behaviour of the dose response without saturation in the studied dose interval (from 12.5 up to 400 Gy). Such features place synthesized ZnO as a promising material for high‐dose radiation dosimetry applications.

Influence of ultrasonication times on the tunable colour emission of ZnO nanophosphors for lighting applications

This paper reports on the sonochemical synthesis of zinc oxide (ZnO) nanophosphors (NPr) at different ultrasonication times (5min, 30min, 1h, 5h, 10h and 15h) for near white light emission applications. X-ray photoelectron spectroscopy indicated that the O1s peak consists of two components. These were O1 (ZnO) and O2 (deficient oxygen; OH groups) centred at 529.7±0.3eV and 531.1±0.3eV, respectively. All samples showed UV and defect level emission (DLE). The DLE enhancement was due to the increase in oxygen related defects such as oxygen vacancies/interstitials. Due to the combination of near UV and DLE near white light emission in ZnO NPr was obtained. The emission could be tuned with different ultrasonic times. It was found that the ultrasonication time influenced the growth mechanism and luminescence properties of the ZnO NPr.

Origin of the red emission in zinc oxide nanophosphors

UV and orange-red light emitting zinc oxide nano-phosphors (ZnO NPr) were synthesised by a combustion method using zinc nitrate and zinc acetate as precursors and urea as a fuel. Hexagonal wurtzite structures of ZnO were synthesised. X-ray photoelectron spectroscopy (XPS) indicated that the O1s peak consist of three components: O1 (ZnO), O2 (deficient oxygen; OH groups) and O3 (adsorbed species) centred at 530.3, 531.2 and 532.6eV, respectively. A broad orange-red emission from 500 to 850nm was obtained from the ZnO NPr prepared with the nitrate precursor which may be attributed to different kinds of defects, and a sharp UV band, due to the possible passivation of defects, at 392nm from ZnO NPr prepared with acetate precursor.

Photoluminescent properties of Sm 3+-doped zinc oxide nanostructures

Sm 3+-doped zinc oxide nanophosphors were synthesized by solution combustion method. The size of the ZnO:Sm 3+ nanostructures ranges from 40–60 nm. The photoluminescence spectra of ZnO:Sm 3+ nanostructures is different from that of pure ZnO. The emission spectra of ZnO:Sm 3+ nanostructures show a strong narrow emission peak at 425 nm and weak peaks at 457, 472 and 482 nm when excited with 255 nm.