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.     

Tuneable luminescence properties of EDTA‐assisted ZnS:Mn nanocrystals from a yellow‐orange to a red emission band

Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn²⁺ ions by a wet chemical route stabilized by ethylenediamine tetra‐acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X‐ray diffraction (XRD), High‐resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)–visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow‐orange bands were red shifted towards the red region under the same excitation wavelength. The orange‐red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn²⁺ ions [⁴T₁(⁴G)‐⁶A₁(⁶S)]; the ZnS matrix varied with Mn²⁺ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn²⁺‐doped ZnS nanocrystal emission bands can be tuned from the yellow‐orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications.     

Synthesis and characterization of pure and Li+ activated Alq3 complexes for green and blue organic light emitting diodes and display devices

Pure and Li⁺‐doped Alq₃ complexes were synthesized by simple precipitation method at room temperature, maintaining the stoichiometric ratio. These complexes were characterized by X‐ray diffraction, ultraviolet‐visible absorption and Fourier transform infrared and photoluminescence (PL) spectra. X‐ray diffraction analysis reveals the crystalline nature of the synthesized complexes, while Fourier transform infrared spectroscopy confirm the molecular structure, the completion of quinoline ring formation and presence of quinoline structure in the metal complex. Ultraviolet‐visible and PL spectra revealed that Li⁺ activated Alq₃ complexes exhibit the highest intensity in comparison to pure Alq₃ phosphor. Thus, Li⁺ enhances PL emission intensity when doped into Alq₃ phosphor. The excitation spectra lie in the range of 383–456 nm. All the synthesized complexes other than Liq give green emission, while Liq gives blue emission with enhanced intensity. Thus, he synthesized phosphors are the best suitable candidates for green‐ and blue‐emitting organic light emitting diode, PL liquid‐crystal display and solid‐state lighting applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and characterization of high quantum yield and oscillator strength 6‐chloro‐2‐(4‐cynophenyl)‐4‐phenyl quinoline (cl‐CN‐DPQ) organic phosphor for solid‐state lighting

A novel blue luminescent 6‐chloro‐2‐(4‐cynophenyl) substituted diphenyl quinoline (Cl‐CN DPQ) organic phosphor has been synthesized by the acid‐catalyzed Friedlander reaction and then characterized to confirm structural, optical and thermal properties. Structural properties of Cl‐CN‐DPQ were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X‐ray diffraction technique (XRD) and scanning electron microscopy (SEM) and energy dispersive analysis of X‐ray (EDAX) spectroscopy. FTIR spectra confirmed the presence of different functional groups and bond stretching. ¹H–NMR and ¹³C–NMR confirmed the formation of an organic Cl‐CN‐DPQ compound. X‐ray diffraction study provided its crystalline nature. The surface morphology of Cl‐CN‐DPQ was analyzed by SEM, while EDAX spectroscopy revealed the elemental analysis. Differential thermal analysis (TGA/DTA) disclosed its thermal stability up to 250°C. The optical properties of Cl‐CN‐DPQ were investigated by UV–vis absorption and photoluminescence (PL) measurements. Cl‐CN‐DPQ exhibits intense blue emission at 434 nm in a solid‐state crystalline powder with CIE co‐ordinates (0.157, 0.027), when excited at 373 nm. Cl‐CN‐DPQ shows remarkable Stokes shift in the range 14800–5100 cm^?1, which is the characteristic feature of intense light emission. A narrow full width at half‐maximum (FWHM) value of PL spectra in the range 42–48 nm was observed. Oscillator strength, energy band gap, quantum yield, and fluorescence energy yield were also examined using UV–vis absorption and photoluminescence spectra. These results prove its applications towards developing organic luminescence devices and displays, organic phosphor‐based solar cells and displays, organic lasers, chemical sensors and many more.     

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.     

Luminescence investigation of a cerium‐doped yttrium vanadate phosphor

Cerium (Ce³⁺)‐doped (1, 3, and 7 mol%) yttrium vanadate phosphors were prepared using a co‐precipitation technique. The structural and optical properties of the synthesized samples were studied using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HR‐TEM), optical absorption, and photoluminescence (PL) spectroscopy techniques. The tetragonal structure and the formation of the nanosized crystallites in the YVO₄:Ce phosphor were confirmed using XRD analysis. HR‐TEM morphology showed rod‐like nanoparticles of different sizes. Optical absorption spectra demonstrated strong absorption bands at 268 and 276 nm. PL spectra showed strong peaks at 546, 574, and 691 nm following excitation at 300 nm. The calculated CIE chromaticity coordinates demonstrated that YVO₄:Ce could be used as a novel phosphor for the development of light‐emitting diode lamps.     

Synthesis,characterization and optical studies of highly luminescent ZnS nanoparticles associated with hypromellose matrix as a green and novel stabilizer

ZnS nanoparticles stabilized by a carbohydrate‐based matrix, hypromellose (hydroxypropyl methylcellulose) were prepared via a wet chemical method. The nanocomposite was characterized by X‐ray diffraction, transmission electon microscopy and Fourier transform infrared spectroscopy. X‐Ray diffraction patterns revealed a zinc blende structure. Thermogravimetric analysis suggested that polymer attached to the surface decomposes at 700 °C. Absorption measurements were carried out and calculation of the diameter polydispersity index (DPI) suggests the formation of monodisperse nanoparticles. The optical properties of the as‐prepared samples were studied by UV/vis spectroscopy and steady‐state photoluminescence (PL) spectroscopy. The PL studies indicate the applicability of these nanoparticles as biocompatible sensors or luminescence markers in future. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural and photoluminescence study of Mn2+‐activated CaYAl3O7 blue phosphors

The structural and photoluminescence properties of CaYAl₃O₇ phosphor material doped with varying concentration of Mn²⁺ have been studied. The phosphor material was synthesized by the combustion method at 500 °C and was characterized using X‐ray diffraction, Fourier transform infrared spectroscopy and photoluminescence spectroscopy (PL). X‐ray diffraction showed that the crystallites have average sizes in the range of ~58–70 nm. Corresponding Fourier transform infrared spectroscopy investigations confirm the phase formation and the presence of aluminate group (Al‐O bands) in CaYAl₃O₇:Mn²⁺ phosphor. Under the excitation at 356 nm wavelength, the PL spectra show the occurrence of two emission peaks obtained in the blue region at 389 nm and 412 nm, which is attributed to the 4 T1(G) → 6A1 transition of Mn²⁺ ion. Upon increasing Mn²⁺ concentration, the relative PL intensity shows an initial decrement followed by an increase displaying the effect of concentration quenching. Overall the results suggest the possibility of using this material in white lighting devices and plasma display panels. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,characterization and optical properties of polymer‐based ZnS nanocomposites

Nanostructured polymer–semiconductor hybrid materials such as ZnS–poly(vinyl alcohol) (ZnS–PVA), ZnS–starch and ZnS–hydroxypropylmethyl cellulose (Zns–HPMC) are synthesized by a facile aqueous route. The obtained nanocomposites are characterized using various techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy and photoluminescence (PL). XRD studies confirm the zinc blende phase of the nanocomposites and indicate the high purity of the samples. SEM studies indicate small nanoparticles clinging to the surface of a bigger particle. The Energy Dispersive Analysis by X‐rays (EDAX) spectrum reveals that the elemental composition of the nanocomposites consists primarily of Zn:S. FTIR studies indicate that the polymer matrix is closely associated with ZnS nanoparticles. The large number of hydroxyl groups in the polymer matrix facilitates the complexation of metal ions. The absorption spectra of the specimens show a blue shift in the absorption edge. The spectrum reveals an absorption edge at 320, 310 and 325 nm, respectively. PL of nanocomposites shows broad peaks in the violet–blue region (420–450 nm). The emission intensity changes with the nature of capping agent. The PL intensity of ZnS–HPMC nanocomposites is found to be highest among the studied nanocomposites. The results clearly indicate that hydroxyl‐functionalized HPMC is much more effective at nucleating and stabilizing colloidal ZnS nanoparticles in aqueous suspensions compared with PVA and starch. Copyright © 2015 John Wiley & Sons, Ltd.     

Intense green‐, red‐emitting Tb3+, Tb3+/Bi3+‐doped and Sm3+, Sm3+/La3+‐doped Ca2Al2SiO7 phosphors

This paper focuses on an optical study of a Tb³⁺/Bi³⁺‐doped and Sm³⁺/La³⁺‐ doped Ca₂Al₂SiO₇ phosphor synthesized using combustion methods. Here, Ca₂Al₂SiO₇:Sm³⁺ showed a red emission band under visible light excitation but, when it co‐doped with La³⁺ ions, the emission intensity was further enhanced. Ca₂Al₂SiO₇:Tb³⁺ shows the characteristic green emission band under near‐ultraviolet light excitation wavelengths, co‐doping with Bi³⁺ ions produced enhanced photoluminescence intensity with better colour tunable properties. The phosphor exhibited better phase purity and crystallinity, confirmed by X‐ray diffraction. Binding energies of Ca(2p), Al(2p), Si(2p), O(1s) were studied using X‐ray photoelectron spectroscopy. The reported phosphor may be a promising visible light excited red phosphor for light‐emitting diodes and energy conversion devices.     

Luminescence study of monodispersed ZnS nanoparticles

Monodispersed ZnS nanoparticles have been successfully synthesized by a chemical precipitation method in an air atmosphere using polyvinylpyrrolidone (PVP) and sodium hexametaphosphate (SHMP) as surfactants. The synthesized nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT‐IR), UV–Vis optical absorption and photoluminescence (PL) spectra. Prepared surfactants capped ZnS nanoparticles are highly homogeneous and well dispersed. Optical absorption spectra showed a strong blue shift from the uncapped particles due to the quantum confinement effect. The capped ZnS emission intensity is enhanced than more the uncapped particles. The size of the synthesized particles is around 4–6.5 nm range. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of capping agent concentration on thermoluminescence and photoluminescence of copper‐doped zinc sulfide nanoparticles

Copper‐doped zinc sulfide (ZnS:Cu) nanoparticles with varying concentrations of capping agent were prepared using a chemical route technique. These particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy and X‐ray diffraction (XRD). Optical absorption studies showed that the absorption edge shifted towards the blue region as the concentration of the capping agent increased. Using effective mass approximation, calculation of the nanoparticle size indicated that effective band gap energy increases with decreasing particle size. The thermoluminescence (TL) properties of sodium hexameta phosphate (SHMP)‐passivated ZnS:Cu nanoparticles were investigated after UV irradiation at room temperature. The TL glow curve of capped ZnS:Cu showed variations in TL peak position and intensity with the change in capping agent concentration. The photoluminescence (PL) spectra of ZnS:Cu nanoparticles excited at 254 nm exhibited a broad green emission band peaking around 510 nm, which confirmed the characteristic feature of Zn²⁺ as well as Cu²⁺ ions as the luminescent centres in the lattice. The PL spectra of ZnS:Cu nanoparticles with increasing capping agent concentrations revealed that the emission becomes more intense and shifted towards shorter wavelengths as the sizes of the samples were reduced. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and spectral investigations of Cu(II) ion‐doped NaCaAlPO4F3 phosphor

Cu(II) ion‐doped NaCaAlPO₄F₃ phosphor has been synthesized using a solid state reaction method. The prepared sample is characterized by powder X‐ray diffraction, scanning electron microscope, optical absorption, electron paramagnetic resonance photoluminescence and Fourier transform infrared spectroscopy techniques. The crystallite size evaluated from x‐ray diffraction data is in nanometers. Scanning electron microscopy micrographs showed the presence of several irregular shaped particles. From optical absorption and electron paramagnetic resonance spectral data the doped Cu(II) ions are ascribed to distorted octahedral site symmetry. The synthesized phosphor exhibits emission bands in ultraviolet, blue and green regions under the excitation wavelength of 335 nm. The CIE chromaticity coordinates (x = 0.159, y = 0.204) also calculated for the prepared sample from the emission spectrum. The Fourier transform infrared spectroscopy spectrum revealed the characteristic vibrational bands of the prepared phosphor material. Copyright © 2014 John Wiley & Sons, Ltd.     

Novel Na+ doped Alq3 hybrid materials for organic light‐emitting diode (OLED) devices and flat panel displays

Pure and Na⁺‐doped Alq₃ complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X‐ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X‐ray diffractogram exhibits well‐resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium‐doped Alq₃ complexes exhibit high emission intensity in comparison with Alq₃ phosphor, proving that when doped in Alq₃, Na⁺ enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242–457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na⁺ is doped into Alq₃. Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light‐emitting phosphors for organic light‐emitting diodes, flat panel displays, solid‐state lighting technology – a step towards the desire to reduce energy consumption and generate pollution free light. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization and luminescence properties of CaMgSi2O6:Eu2+ blue phosphor

A blue CaMgSi₂O₆:Eu²⁺ phosphor was prepared by the solid‐state reaction method and the phosphor characterized in terms of crystal structure, particle size, photoluminescence (PL), thermoluminescence (TL) and mechanoluminescence (ML) properties using X‐ray diffraction (XRD), transmission electron microscopy (TEM), PL spectroscopy, TLD reader and ML impact technique. The XRD result shows that phosphor is formed in a single phase and has a monoclinic structure with the space group C2/c. Furthermore, the PL excitation spectra of Eu²⁺‐doped CaMgSi₂O₆ phosphor showed a strong band peak at 356 nm and the PL emission spectrum has a peak at 450 nm. The depths and frequency factors of trap centers were calculated using the TL glow curve by deconvolution method in which the trap depths were found to be 0.48 and 0.61 eV. The formation of CaMgSi₂O₆:Eu²⁺ phosphor was confirmed by Fourier transform infrared spectroscopy. The ML intensity increased linearly with the impact velocity of the piston used to deform the phosphor. It was shown that the local piezoelectricity‐induced electron bombardment model is responsible for the ML emission. Finally, the optical properties of CaMgSi₂O₆:Eu²⁺ phosphors are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications

Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo‐hydrothermal (S‐H) method using water–acetonitrile–ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), Fourier transform (FT)‐Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380–580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm^–1. Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Dy3+ or Eu2+ co‐activator on a BaCa(SO4)2:Ce3+ mixed alkaline earth sulfate phosphor

The individual emission and energy transfer between Ce³⁺ and Eu²⁺ or Dy³⁺ in BaCa(SO₄)₂ mixed alkaline earth sulfate phosphor prepared using a co‐precipitation method is described. The phosphor was characterized by X‐ray diffraction (XRD) and photoluminescence (PL) studies and doped by Ce;Eu and Dy rare earths. All phosphors showed excellent blue–orange emission on excitation with UV light. PL measurements reveal that the emission intensity of Eu²⁺ or Dy³⁺ dopants is greater than when they are co‐doped with Ce³⁺. An efficient Ce³⁺ → Eu²⁺ [²T_2g(4f⁶5d) → ⁸S_7/2(4f₇)] and Ce³⁺ → Dy³⁺ (⁴ F_9/2 → ⁶H_15/2 and ⁴ F_9/2 → ⁶H_13/2) energy transfer takes place in the BaCa(SO₄)₂ host. A strong blue emission peak was observed at 462 nm for Eu²⁺ ions and an orange emission peak at 574 nm for Dy³⁺ ions. Hence, this phosphor may be used as a lamp phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of synthesis parameters on the optical and photocatalytic properties of solvo/hydrothermal CuS and ZnS nanoparticles

Copper sulfide and zinc sulfide nanostructures were synthesized using a solvo/hydrothermal method and a thio Schiff base ligand, N‐benzylidene ethanethioamide, as a source of sulfide ions. The effects of different synthesis parameters including the type of solvent, temperature, and duration of reactions on the morphology of the CuS and ZnS products were investigated using field emission scanning microscopy and transmission electron microscopy, respectively. The structural aspects of the samples were characterized using powder X‐ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X‐ray analysis. The optical properties of the samples were studied through their optical absorption and photoluminescence spectra. The photocatalytic ability of the as‐synthesized sulfides was explored by studying the colour removal of methylene blue under ultraviolet light irradiation.     

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.