Synthesis,effect of capping agents and optical properties of manganese‐doped zinc sulphide nanoparticles

Mn²⁺‐doped ZnS nanoparticles have been successfully synthesized by a chemical precipitation method, using non‐ionic surfactants such as PMMA and PEG. The particles were prepared in an air atmosphere at 80°C. X‐ray diffraction (XRD), transmission electron microscopy (TEM), UV‐visible and photoluminescence (PL) studies were used to investigate the effect of the capping agent on the size, morphology and optical properties of the ZnS–Mn²⁺ nanoparticles. Enhanced PL was observed from the surfactant‐capped ZnS–Mn²⁺ nanoparticles. The PL spectra showed a broad blue emission band in the range 460–445 nm and a Mn²⁺‐related yellow‐orange emission band in the range 581–583 nm. Copyright © 2012 John Wiley & Sons, Ltd.     

Optical and structural characterization of CdS/ZnS and CdS:Cu2+/ZnS core–shell nanoparticles

Core‐shell CdS/ZnS (Zn 0.025?0.125 M) and CdS:Cu²⁺(1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu²⁺/ZnS core–shell nanoparticles. All absorption peaks of the synthesized samples were highly blue‐shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core–shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice. Copyright © 2013 John Wiley & Sons, Ltd.     

Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped Gd2O3 phosphors for up and down conversion luminescence

Frequency up‐conversion (UC) emission from the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped gadolinium oxide (Gd₂O₃) phosphors prepared by the solution combustion technique in the visible range have been studied by using 980 nm near infrared (NIR) laser diode excitation. The crystalline structure and formation of the cubic phase has been confirmed with the help of X‐ray diffraction (XRD) studies. XRD peak shifts have been found towards the lower diffraction angle side in the case of the Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. Surface morphology and particle size information have been observed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Down‐conversion emission study under 351 nm excitation in the visible region for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors has been performed. The UC emission bands lying in the green and red region arising from the Nd³⁺ ions have been enhanced by ~260 times, ~113 times due to incorporation of Li⁺ ions in the Nd³⁺‐Yb³⁺ co‐doped phosphors. Photometric characterization has been done for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. The present study suggests the capability of the synthesized phosphors in near‐infrared (NIR) to visible upconverter and luminescent device applications.     

Structural characterization of Er3+,Yb3+‐doped Gd2O3 phosphor,synthesized using the solid‐state reaction method,and its luminescence behavior

We report the synthesis and structural characterization of Er³⁺,Yb³⁺‐doped Gd₂O₃ phosphor. The sample was prepared using the conventional solid‐state reaction method, which is the most suitable method for large‐scale production. The prepared phosphor sample was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermoluminescence (TL), photoluminescence (PL) and CIE techniques. For PL studies, the excitation and emission spectra of Gd₂O₃ phosphor doped with Er³⁺ and Yb³⁺ were recorded. The excitation spectrum was recorded at a wavelength of 551 nm and showed an intense peak at 276 nm. The emission spectrum was recorded at 276 nm excitation and showed peaks in all blue, green and red regions, which indicate that the prepared phosphor may act as a single host for white light‐emitting diode (WLED) applications, as verified by International de I'Eclairage (CIE) techniques. From the XRD data, the calculated average crystallite size of Er³⁺ and Yb³⁺‐doped Gd₂O₃ phosphor is ~ 38 nm. A TL study was carried out for the phosphor using UV irradiation. The TL glow curve was recorded for UV, beta and gamma irradiations, and the kinetic parameters were also calculated. In addition, the trap parameters of the prepared phosphor were also studied using computerized glow curve deconvolution (CGCD). Copyright © 2015 John Wiley & Sons, Ltd.     

Dy3+‐activated NaM4 (VO4)3 (M = Ca,Ba, Sr) phosphor for near‐UV solid‐state lighting

We report the photoluminescence characterization of Dy³⁺‐activated NaM₄(VO₄)₃ (M = Ca, Ba, Sr) phosphors prepared by a solid‐state method. The synthesis was confirmed by X‐ray diffraction (XRD) characterization and photoluminescence (PL) emission results showed sharp blue and yellow bands for NaM₄(VO₄)₃ (M = Ca, Ba, Sr):Dy³⁺ phosphors at the excitation wavelength of 323 nm, which is near‐UV excitation. Thus, these phosphors could be applicable for near‐UV excited solid‐state lighting devices. Copyright © 2011 John Wiley & Sons, Ltd.     

Luminescent properties of MAl(SO4)2Br:Eu3+ (M = Sr or Mg) red phosphors for near‐UV light‐emitting diodes

Eu³⁺‐activated MAl(SO₄)₂Br phosphors (where M = Mg or Sr) are successfully prepared using a wet chemical reaction technique. The samples are characterized by X‐ray diffraction (XRD) and photoluminescence (PL) spectroscopies. The XRD pattern revealed that both the samples are microcrystalline in nature. PL of Eu³⁺‐doped SrAl(SO₄)₂Br and MgAl(SO₄)₂Br phosphors exhibited characteristic red emission coming from the ⁵D₀ → ⁷F₂ (616 nm) electron transition, when excited by 396 nm wavelength of light. The maximum intensity of luminescence was observed at a concentration of 1 mol% Eu³⁺. The intensity of the electric dipole transition at 616 nm is greater than that of the magnetic dipole transition at 594 nm. The results showed that MAl(SO₄)₂Br:Eu³⁺, (M = Mg, Sr) phosphors have potential application in near‐UV light‐emitting diodes as efficient red‐emitting phosphor. Copyright © 2014 John Wiley & Sons, Ltd.     

The structure and luminescence properties of Mn2+/Eu2+/Er3+‐doped MgO‐Ga2O3‐SiO2 glasses and glass‐ceramics

The MgO–Ga₂O₃–SiO₂ glasses and glass‐ceramics samples doped with Eu²⁺/Mn²⁺/Er³⁺ and heated in reductive atmosphere were prepared by the sol–gel method. The structure, morphology and the luminescence properties were studied using X‐ray diffraction, high‐resolution transmission electron microscope, fluorescence spectra, and up‐conversion emission. The luminescence characteristics of doped ions could be influenced by temperature and matrix component. The characteristic emission of Mn²⁺, Eu²⁺ and Er³⁺ were seen and the energy transfer efficiency from Eu²⁺ to Mn²⁺ was enhanced as Mn²⁺ concentration was increased. In addition, the two‐photon process was determined for the Er³⁺‐doped samples.     

Investigation of UV‐emitting Gd3+‐doped LiCaBO3 phosphor

Incorporating the Gd³⁺ rare earth ion in the LiCaBO₃ host lattice resulted in narrow‐band UV‐B emission peaking at 315 nm, with excitation at 274 nm. The LiCaBO₃:Gd³⁺ phosphor was synthesized via the solid‐state diffusion method. The structural, morphological and luminescence properties of this phosphor were characterized by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Electron paramagnetic resonance (EPR) characterization of the as‐prepared phosphors is also reported here. XRD studies confirmed the crystal formation and phase purity of the prepared phosphors. A series of different dopant concentrations was synthesized and the concentration‐quenching effect was studied. Critical energy transfer distance between activator ions was determined and the mechanism governing the concentration quenching is also reported in this paper. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural and optical properties of europium‐ and titanium‐doped Y2O3 nanoparticles

Luminescent nanoparticles of Y₂O₃ doped with europium (Eu) and/or titanium (Ti) were synthesized using modified sol–gel routes. The crystalline cubic phase was confirmed using X‐ray powder diffraction (XRD). Particle morphology and size were evaluated using scanning and transmission electron microscopy. High‐resolution transmission electron microscopy showed that the synthesis method affected the average particle size and the Fourier transform of the images showed the lattice plane distances, indicating that the samples presented high crystallinity degree in accordance with the XRD pattern. The Ti valence was investigated using X‐ray absorption near edge spectroscopy and the tetravalent form was the dominant oxidizing state in the samples, mainly in Eu and Ti co‐doped Y₂O₃. Optical behaviour was investigated through X‐ray excited optical luminescence and photoluminescence under ultraviolet–visible (UV–vis) and vacuum ultraviolet (VUV) excitation. Results indicated that Eu³⁺ is the emitting centre in samples doped with only Eu and with both Eu and Ti with the ⁵D₀→⁷F₂ transition as the most intense, indicating Eu³⁺ in a noncentrosymmetric site. Finally, in the Eu,Ti‐doped Y₂O₃ system, Ti³⁺ (or Ti^IV) excitation was observed but no Ti emission was present, indicating a very efficient energy transfer process from Ti to Eu³⁺. These results can aid the development of efficient nanomaterials, activated using UV, VUV, or X‐rays.     

Luminescence study of Dy or Ce activated LiCaBO3 phosphor for γ‐ray and C5+ ion beam irradiation

The photoluminescence and thermoluminescence characteristics of rare earths (Dy or Ce) activated LiCaBO₃ phosphors have been studied. Phosphors were synthesized by modified solid state synthesis. The phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and thermoluminescence (TL) for structural, morphological and luminescence studies. Dy³⁺ activated LiCaBO₃ shows emission at 486 and 577 nm due to ⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2 transition, respectively, whereas the PL emission spectra of Ce³⁺ activated LiCaBO₃ phosphor shows a broad band peaking at 432 nm, which is due to the transition from 5d level to the ground state of the Ce³⁺ ion. The thermoluminescence study was also carried out for both these phosphors for γ‐ray irradiation and carbon beam irradiation. Linearity was studied for a 0.4–3.1 Rad dose γ‐rays. Linear behaviour over this dose range was observed. Gamma ray‐irradiated phosphors were shown to be negligible fading upon storage. All the samples were also studied for 75 MeV C⁵⁺ ion beam exposure in the range of 3.75 × 10¹² – 7.5 × 10¹³ ion cm^–2 fluence. In addition to this, trapping parameters of all the samples were also calculated using Chen's peak shape method. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence properties of Sm3+‐doped YAl3(BO3)4 phosphor

A near ultraviolet excitable phosphor based on Sm³⁺‐doped YAl₃(BO₃)₄ has been synthesized by modified solid‐state reaction at 1000°C. The phase purity and photoluminescence (PL) behavior of the phosphor are studied in detail using the powder X‐ray diffraction technique and PL measurements. X‐ray diffraction reveals that the phase purity of YAl₃(BO₃)₄ critically depends upon the boric acid concentration. The phosphor has strong excitation at 406 nm in the near ultraviolet region (350–420 nm) and its emission peaks were monitored at 564, 599 and 643 nm. Further, detailed PL analysis demonstrates that the substitution of Sm³⁺ ions at sites of Y³⁺ and Al³⁺ ions enhances the PL efficiency of the phosphor appreciably. First, the PL efficiency of YAl₃(BO₃)₄:Sm³⁺ was compared with commercial (Y,Gd)BO₃:Eu³⁺ red phosphor. The Fourier transform infrared study provides essential information regarding the change in metal–oxygen bond vibrations of the phosphor. The morphology of the phosphor was investigated through scanning electron microscopy, which reveals that the phosphor possessed distorted spherical and rectangular shapes with average grain sizes in the range 0.5–1 µm. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhanced photoluminescence properties of electrospun Dy3+‐doped ZnO nanofibres for white lighting devices

Dy³⁺‐doped ZnO nanofibres with diameters from 200 to 500 nm were made using an electrospinning technique. The as‐fabricated amorphous nanofibres resulted in good crystalline continuous nanofibres through calcination. Dy³⁺‐doped ZnO nanofibres were characterized using scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) light spectroscopy, Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL). XRD showed the well defined peaks of ZnO. UV–vis spectra showed a good absorption band at 360 nm. FTIR spectra showed a Zn–O stretching vibration confirming the presence of ZnO. Photoluminescence spectra of Dy³⁺‐doped ZnO nanofibres showed an emission peak in the visible region that was free from any ZnO defect emission. Emissions at 480 nm and 575 nm in the Dy³⁺‐doped ZnO nanofibres were the characteristic peaks of dopant Dy³⁺ and implied efficient energy transfer from host to dopant. Luminescence intensity was found to be increased with increasing doping concentration and reduction in nanofibre diameter. Colour coordinates were calculated from photometric characterizations, which resembled the properties for warm white lighting devices.     

Photoluminescence,cathodoluminescence and thermal stability of Sm3+‐activated Sr3La(VO4)3 red‐emitting phosphors

A series of Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors were synthesized by a facile sol‐gel method. X‐ray diffraction patterns and photoluminescence (PL)/cathodoluminescence (CL) spectra as well as PL decay curves were employed to characterize the obtained samples. Upon 402 nm light excitation, the characteristic emissions of Sm³⁺ ions corresponding to ⁴G_5/2→⁶H_J transitions were observed in all the as‐prepared products. The PL emission intensity was increased with increase in Sm³⁺ ion concentration, while concentration quenching occurred when the doping concentration was over 4 mol%. The non‐radiative energy transfer mechanism for concentration quenching of Sm³⁺ ions was dominated by dipole–dipole interaction and the critical distance was around 21.59 Å. Furthermore, temperature‐dependent PL emission spectra revealed that the obtained phosphors possessed good thermal stability with an activation energy of 0.19 eV. In addition, the CL spectra of the samples were almost the same as the PL spectra, and the CL emission intensity showed a tendency to increase with increase in accelerating voltage and filament current. These results suggest that the Sm³⁺‐activated Sr₃La(VO₄)₃ phosphors with good color coordinates, high color purity and superior thermal stability may be a potential candidate for applications in white light‐emitting diodes and field‐emission displays as red‐emitting phosphors.     

Hydrothermal growth of Zn2SnO4:Eu,Ca for red emission

Zinc stannate (Zn₂SnO₄) and Zn₂SnO₄ codoped with Eu³⁺ and Ca²⁺ (ZTO:Eu,Ca) were synthesized by hydrothermal method and characterized with X‐ray diffraction (XRD), energy‐dispersive X‐ray analysis (EDAX), Raman spectrometer, field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV‐vis) and photoluminescence (PL) spectrophotometers. PL analysis of Zn₂SnO₄ gives broad defect induced emission in the region 500–750 nm. The crystal structure of Zn₂SnO₄ was retained even with a nominal doping of Eu, Ca and its combination in the Zn₂SnO₄. The Eu³⁺ ions were found to occupy the non‐centrosymmetric sites of the Zn₂SnO₄ and gave emissions at 592, 615 and 702 nm. Zn₂SnO₄:Eu,Ca showed red emission at 615 nm attributed to the electronic transition from the excited state ⁵D₀ → ⁷F₂ of the 4f⁶ configuration of Eu³⁺. Nominal codoping of Eu³⁺ and Ca²⁺ ions promoted the quenching of orange emission from Eu³⁺ in Zn₂SnO₄:Eu,Ca.     

Size‐tailored synthesis and luminescent properties of three‐dimensional BaMoO4, BaMoO4:Eu3+ micron‐octahedrons and micron‐flowers via sonochemical route

Almost monodisperse three‐dimensional (3D) BaMoO_4, BaMoO₄:Eu³⁺ micron‐octahedrons and micron‐flowers were successfully prepared via a large‐scale and facile sonochemical route without using any catalysts or templates. X‐Ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy dispersion X‐ray (EDS), Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy were employed to characterize the as‐obtained products. It was found that size modulation could be easily realized by changing the concentrations of reactants and the pH value of precursors. The formation mechanism for micron‐octahedrons and micron‐flowers was proposed on the basis of time‐dependent experiments. Using excitation wavelengths of 396 or 466 nm for BaMoO₄:Eu³⁺ phosphors, an intense emission line at 614 nm was observed. These phosphors might be promising components with possible application in the fields of near UV‐ and blue‐excited white light‐emitting diodes. Simultaneously, this novel and efficient pathway could open new opportunities for further investigating the properties of molybdate materials. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE = Eu/Tb) powder phosphors

Rare earth ions (Eu³⁺ or Tb³⁺)‐activated Ca₃ Ga₂ Si₃O₁₂ (CaGaSi) phosphors were synthesized by using a sol–gel method. Photoluminescence spectra of Eu³⁺:CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701 nm, which were assigned to the transitions (⁵D₀ → ⁷F₀, ⁷F_1, ⁷F₂, ⁷F₃ and ⁷F₄), respectively, with an excitation wavelength of λ_exci = 392 nm. Among these, the transition ⁵D₀ → ⁷F₂ (612 nm) displayed bright red emission. In the case of Tb³⁺:CaGaSi phosphors, four emission bands were observed at 488 (⁵D₄ → ⁷F₆), 543 (⁵D₄ → ⁷F₅), 584 (⁵D₄ → ⁷F₄) and 614 nm (⁵D₄ → ⁷F₃) from the measurement of PL spectra with λ_exci = 376 nm. Among these, the transition ⁵D₄ → ⁷F₅ at 543 nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDAX) results. Copyright © 2011 John Wiley & Sons, Ltd.     

Structural characterization and optical properties of Ca2MgSi2O7:Eu2+,Dy3+ phosphor by solid‐state reaction method

Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor was prepared by the solid‐state reaction method under a weak reducing atmosphere. The obtained phosphor was characterized using X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX) and Fourier transform infrared (FT‐IR) techniques. The phase structure of the Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor was akermanite type, which is a member of the melilite group. The surface morphology of the sintered phosphor was not uniform and phosphors aggregated tightly. EDX and FT‐IR spectra confirm the elements present in the Ca₂MgSi₂O₇:Eu²⁺,Dy³⁺ phosphor. Under UV excitation, a broadband emission spectrum was found. The emission spectra observed in the green region centered at 535 nm, which is due to the 4f–5d transition. The mechanoluminescence (ML) intensity of the prepared phosphor increased linearly with increases in the mechanical load. The ML spectra were similar to the photoluminescence (PL), which indicates that ML is emitted from the same emitting center of Eu²⁺ ions as PL. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis,phase evolution and optical properties of Tb3+‐doped KF–YbF3 system materials

KF–YbF₃ system materials have been synthesized by a hydrothermal method without any surfactant or template. By controlling the reactant ratios of KF:Yb³⁺, the hydrothermal temperature and the pH of the prepared solutions, the final products can evolve among the orthorhombic phase of YbF₃, the cubic phase of KYb₃F₁₀ and the cubic phase of KYbF₄. The X‐ray diffraction (XRD) patterns of the samples prove the phase evolution of the final products. The morphologies of the samples were characterized using field emission scanning electron microscopy (FE‐SEM) images and the evolution of the morphology is consistent with that of the crystalline phases. The optical properties of Tb³⁺ in the samples were characterized by PL excitation and emission spectra, as well as luminescent decay curves. Copyright © 2014 John Wiley & Sons, Ltd.     

Combustion synthesis of Na2Sr(PO4)F:Dy3+ white light emitting phosphor

The synthesis, X‐ray diffraction, photoluminescence, TGA/DTA and FTIR techniques in Dy³⁺ activated Na₂Sr(PO₄)F phosphor are reported in this paper. The prepared phosphor gave blue, yellow and red emission in the visible region of the spectrum at 348 nm excitation. CIE color co‐ordinates of Na₂Sr(PO₄)F:Dy³⁺ are suitable as white light‐emitting phosphors. Copyright © 2009 John Wiley & Sons, Ltd.     

Luminescence study of LiMgBO3:Dy for γ‐ray and carbon ion beam exposure

LiMgBO₃:Dy³⁺, a low Z_eff material was prepared using the solution combustion method and its luminescence properties were studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), photoluminescence (PL), Fourier transform infrared spectroscopy, and electron paramagnetic resonance (EPR) techniques. Reitvield refinement was also performed for the structural studies. The PL emission spectra for LiMgBO₃:Dy³⁺ consisted of two peaks at 478 due to the ⁴F_9/2→⁶H_15/2 magnetic dipole transition and at 572 nm due to the hypersensitive ⁴F_9/2→⁶H_13/2 electric dipole transition of Dy³⁺, respectively. A TL study was carried out for both the γ‐ray‐irradiated sample and the C⁵⁺ irradiated samples and was found to show high sensitivity for both. Moreover the γ‐ray‐irradiated LiMgBO₃:Dy³⁺ sample showed linearity in the dose range 10 Gy to 1 kGy and C⁵⁺‐irradiated samples show linearity in the fluence range 2 × 10¹⁰ to 1 × 10¹¹ ions/cm². In the present study, the initial rise method, various heating rate method, the whole glow curve method, glow curve convolution deconvolution function, and Chen's peak shape method were used to calculate kinetic parameters to understand the TL glow curve mechanism in detail. Finally, an EPR study was performed to examine the radicals responsible for the TL process.