Composite & Ceramic Materials
Vithal Muga; Vaishnavi Kammara; Venkataswamy Perala; Manasa Sunku; Ramaswamy Kadari; Hima Bindu Gaddameedi; Sudhakar Reddy Chandiri
Abstract
Doping of cations into wide bandgap semiconductors is an effective method of increasing photocatalytic activity. This work aims to find out how dopant ions like Ag+, Cu2+ and Sn2+ affect the structural, optical and photocatalytic properties of Li2GeTeO6. The parent Li2GeTeO6 (LGTO) was synthesized by ...
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Doping of cations into wide bandgap semiconductors is an effective method of increasing photocatalytic activity. This work aims to find out how dopant ions like Ag+, Cu2+ and Sn2+ affect the structural, optical and photocatalytic properties of Li2GeTeO6. The parent Li2GeTeO6 (LGTO) was synthesized by conventional solid-state method, whereas the Ag+, Cu2+ and Sn2+-doped Li2GeTeO6 were prepared by a simplistic ion-exchange method. Techniques such as XRD, FT-IR, SEM-EDS, N2 adsorption-desorption analysis, UV-Vis DRS, XPS, and PL were employed to examine the physico-chemical properties of the as-prepared materials and their photocatalytic activities on the degradation of methyl violet (MV) under visible light irradiation. The acquired photocatalytic activity results revealed that all doped samples displayed enhanced photocatalytic performance compared with parent LGTO. The Ag-LGTO had the best photocatalytic activity for MV degradation, with 68.6% degradation efficiency in 180 min of irradiation. Scavenging experiments were carried out to determine the role of various active species generated on the surface of Ag-LGTO during the photocatalytic degradation of MV. The reusability and stability of Ag-LGTO up to five cycles against MV degradation were also investigated. A photocatalytic mechanism for MV degradation over the Ag-LGTO sample was also proposed based on the findings described above.
G. Usha; R. Vasanthi; D. Reuben Jonathan; K.S. Ezhilarasi; M. Krishna Priya
Abstract
A novel chalcone derivative, (2E)-3-(3, 4 dimethoxy phenyl)-1-(1-hydroxy-2 naphthyl)prop-2-en-1-one (DHNP), C21H18O4, has been synthesized from the mixture of 4-hydroxy acetophenone (0.05mol) and 4-hydroxy-3-ethoxybenzaldehyde (0.05mol) by Claisen-Schmidt reaction mechanism. The structural ...
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A novel chalcone derivative, (2E)-3-(3, 4 dimethoxy phenyl)-1-(1-hydroxy-2 naphthyl)prop-2-en-1-one (DHNP), C21H18O4, has been synthesized from the mixture of 4-hydroxy acetophenone (0.05mol) and 4-hydroxy-3-ethoxybenzaldehyde (0.05mol) by Claisen-Schmidt reaction mechanism. The structural features of the grown crystal were elucidated by single X-ray diffraction (XRD) studies which confirm the title compound, belongs to the monoclinic system with the P21/n space group. Functional groups, the number of unique proton and carbon environments were identified using FT-IR, 1H, and 13C NMR spectral investigation. The optical behavior of the crystal was analyzed by UV-Vis absorption studies, and the value of the optical band gap energy (𝐸𝑔) of the crystal is found to be 3.386eV. The Photoluminescence (PL) spectrum of the compound indicates the green to yellow light emission in the visible region. By employing thermogravimetric analysis (TGA), the thermal stability of crystal and the dehydration and decomposition nature were found. The Coats and Redfern relation was applied to evaluate the kinetic and thermodynamic parameters. Mechanical properties such as the Hardness (HV), Meyer's index (n), Newtonian resistance pressure (W), load independent constant (b), and elastic stiffness constant (Cij) were calculated by performing a Vickers hardness test on the compound and found to exhibits an excellent mechanical power.
K.R. Basavalingaiah; Udayabhanu; S. Harishkumar; G. Nagaraju
Abstract
Cu2O and Ag-Cu2O nanoparticles were prepared via reflux method using EDTA. From the PXRD, FTIR, UV-DRS studies the synthesized NPs were characterized. The morphologies of the prepared NPs were studied by SEM and TEM analysis. The synthesized NPs were tested for photocatalytic and photoluminescence studies. ...
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Cu2O and Ag-Cu2O nanoparticles were prepared via reflux method using EDTA. From the PXRD, FTIR, UV-DRS studies the synthesized NPs were characterized. The morphologies of the prepared NPs were studied by SEM and TEM analysis. The synthesized NPs were tested for photocatalytic and photoluminescence studies. The PXRD data indicated that the synthesized nanoparticles belong to cubic phase structure and space group Pn-3m. The SEM data revealed that cube like structure were obtained. Cu2O and Ag-Cu2O Nps were taken for determine the photocatalytic activity study on methylene blue dye, the results indicated that Ag-Cu2O NPs exhibited promising photocatalytic activity. This is due to occurrence of Ag particles on the Cu2O material, which makes the catalyst more sensitive. Furthermore, a photoluminescence study reveals that Cu2O and Ag-Cu2O nano particles shown yellow light emission. Copyright © VBRI Press.
Martin Moebius; Joerg Martin; Melinda Hartwig; Ricardo Decker; Lothar Kroll; Reinhard R. Baumann; Thomas Otto
Abstract
Fibre-reinforced plastics offer excellent mechanical properties at low weight. Hence, such materials are ideally suited to reduce energy consumption and CO2 emission, e.g. in aircraft and automotive engineering, shipbuilding or in the field of renewable energies. However, in contrast to e.g. metals, ...
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Fibre-reinforced plastics offer excellent mechanical properties at low weight. Hence, such materials are ideally suited to reduce energy consumption and CO2 emission, e.g. in aircraft and automotive engineering, shipbuilding or in the field of renewable energies. However, in contrast to e.g. metals, lightweight structures are sensitive to mechanical loads exceeding a certain approved range. In order to detect mechanical overloads at an early stage and to avoid consequential failures in lightweight structures, we recently proposed a novel concept of a thin-film sensor for visualization of mechanical loads by using photoluminescence quenching of quantum dots. Here, we present results according to the optimization of the ionization efficiency of the cadmium selenide quantum dots by using poly(N-vinylkarbazol)(PVK) as charge transport material with favorable energy levels. Measurements of the photoluminescence intensity and electrical power confirm an increase of efficiency with almost the same photoluminescence drop compared to N,N,N′,N′-Tetrakis(3-methylphenyl)-3,3′-dimethyl-benzidine (HMTPD), most likely by the higher valence band offset between quantum dots and PVK. Furthermore, an integration of a layer stack with connected ceramic piezoelectric transducer demonstrates the successful use of the sensor system for mechanical load detection in lightweight structures.
V. Ponnusamy; A. Azhagiri; R. Satheesh Kumar; M.T. Jose
Abstract
Pure and Eu 2+ doped BaAl2O4 phosphors have been synthesized by simple solid state reaction technique. Synthesized BaAl2O4 samples were studied using powder X-ray diffraction analysis (XRD), Photoluminescence spectroscopy (PL), Fourier Transform - Infra Red Spectroscopy (FT-IR) and Scanning Electron ...
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Pure and Eu 2+ doped BaAl2O4 phosphors have been synthesized by simple solid state reaction technique. Synthesized BaAl2O4 samples were studied using powder X-ray diffraction analysis (XRD), Photoluminescence spectroscopy (PL), Fourier Transform - Infra Red Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). Alkaline earth divalent (Sr, Ca, Zn, Mg) and halides (F, Cl, Br, I) were used as co-dopants to enhance the PL properties of BaAl2O4:Eu 2+ phosphor. Significant impact of ionic radii of co-dopants on PL properties of the phosphor is reported.
Yidi Wang; Pui Fai NG; Bin Fei
Abstract
Hybrid organic–inorganic perovskite materials have attracted a lot of attention with their facile synthesis process and high efficiency of light absorption. However, poor stability is always a big barrier to commercial development. In this study, a new kind of organic perovskites MA0.6(AA)0.4PbBr3 ...
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Hybrid organic–inorganic perovskite materials have attracted a lot of attention with their facile synthesis process and high efficiency of light absorption. However, poor stability is always a big barrier to commercial development. In this study, a new kind of organic perovskites MA0.6(AA)0.4PbBr3 (AM-PE), which harnesses aniline as a replacement of conventionally used methylamine, was synthesized to increase the stability of MAPbBr3 (M-PE). The decomposition process of MAPbBr3 in acetone was investigated. Smaller PbBr2 particles were formed in the decomposition process, causing the change of photoluminescence emission wavelength from 540 nm to 610 nm. The photocatalysis and photoluminescence properties of M-PE and AM-PE were also compared. As a result, the introduction of aniline reduced the decomposition rate of AM-PE significantly and showed twice the catalysis efficiency of M-PE in the degradation of organic dye - malachite green.
Shrabani Mondal; Rashmi Madhuri; Prashant K. Sharma
Abstract
This letter assesses the origin of linear and planer micro-structural defects in SnO2 nanoparticles through high resolution transmission electron microscopy (HRTEM). For the purpose, SnO2 nanoparticles of size 5-15 nm are synthesized by chemical co-precipitation followed by calcinations. In the low temperature ...
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This letter assesses the origin of linear and planer micro-structural defects in SnO2 nanoparticles through high resolution transmission electron microscopy (HRTEM). For the purpose, SnO2 nanoparticles of size 5-15 nm are synthesized by chemical co-precipitation followed by calcinations. In the low temperature (200°C and 400°C) calcinations range no significant evidence of micro-structural defect are observed. Whereas, SnO2 nanoparticles calcined at 600°C shows better crystallinity with multiple 1-D linear defects along with 2-D planer defects. Contribution of size and strain effect causing such circumstances is illustrated in detail. Influence of these micro-structural defects on the luminescence properties of SnO2 nanoparticles is also elaborated in detail.
Selepe Joel Motloung; Kamohelo George Tshabalala; Odireleng Martin Ntwaeaborwa
Abstract
Samarium (Sm 3+ ) and thulium (Tm 3+ ) co-activated yttrium orthovanadatephosphate YV0.5P < sub>0.5O4: Sm 3+ , Tm 3+ powder phosphors were synthesized by solution combustion method and were annealed at 900 o C for 2 hours. The x-ray diffraction patterns confirmed that the tetragonal structure of ...
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Samarium (Sm 3+ ) and thulium (Tm 3+ ) co-activated yttrium orthovanadatephosphate YV0.5P < sub>0.5O4: Sm 3+ , Tm 3+ powder phosphors were synthesized by solution combustion method and were annealed at 900 o C for 2 hours. The x-ray diffraction patterns confirmed that the tetragonal structure of YV0.5P < sub>0.5O4 was crystallized. The patterns consisted of peaks from YVO4 and YPO4 suggesting that our product was an admixture of both compounds. The scanning and transmission electron microscopy image showed an agglomeration of particles with different sizes and shapes. The UV-vis reflectance spectra showed a broad absorption band extending from 200 — 550 nm associated with the O→V charge transfer transitions of [VO4] 3− . The photoluminescence (PL) data of singly doped phosphors showed one blue emission peak at 477 nm ( 1 G4— 3 H6) and three emission peaks at 567 nm ( 6 G5/2 — 6 H5/2), 603 nm ( 6 G5/2 — 6 H7/2) and 650 nm ( 6 G5/2 — 6 H9/2) corresponding to transitions of Tm 3+ and Sm 3+ ions respectively. The PL data from the Sm 3+ - Tm 3+ co-doped systems demonstrated an enhancement of visible emission of Tm 3+ by down-conversion process that involves energy capture by the host last and Sm 3+ that was subsequently transferred to Tm 3+ . These materials are evaluated as possible candidates to improve the power conversion efficiency of dye-sensitized solar cells.
Pratik Deshmukh; S. Satapathy; Anju Ahlawat; Khemchand Sahoo; P. K. Gupta
Abstract
The photoluminescence properties of Yb doped Y2O3 nanoparticles were investigated in visible region to resolve the origin of dissimilar fluorescence peaks at different excited wavelengths and to explore possible use of Yb: Y2O3 for white light emission, excited by available near UV LED. The peak observed ...
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The photoluminescence properties of Yb doped Y2O3 nanoparticles were investigated in visible region to resolve the origin of dissimilar fluorescence peaks at different excited wavelengths and to explore possible use of Yb: Y2O3 for white light emission, excited by available near UV LED. The peak observed at 370 nm in photoluminescence excitation spectrum is due to expected transition of electrons from 2 F7/2 to charge transfer band (CTB) associated with non-centrosymmetric C2 centers however, the excitation peak at 335 nm is due to transition of electrons from 2 F7/2 to the CTB associated with distorted centrosymmetric C3i centers. The Yb doping in nano Y2O3 not only modify the CTB but also helps in transition of electron from these CTBs to ground 2 F5/2 and 2 F7/2 levels of Yb. Strong broad emission peak is observed at 503 nm which is assigned to transition from distorted CTB (C3i) to 2 F5/2 energy levels. The findings are important because broad emission (from ~400 to ~650 nm) at 335 nm excitation (available AlGaN LED wavelength) due to C2 and C3i centers in Yb: Y2O3 may be used for white light emission applications.
Thoudam Nando Singhi; Thongam Gomti Devi; Shougaijam Dorendrajit Singh
Abstract
Eu 3+ doped TiO2 (0.2-1at. %) is synthesized successfully by non-aqueous sol-gel technique at low temperature. They are characterized structurally and optically with the used of X-ray diffraction (XRD), UV-visible spectrophotometer, Photoluminescence (PL), microscopy (SEM) and Transmission electron microscopy ...
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Eu 3+ doped TiO2 (0.2-1at. %) is synthesized successfully by non-aqueous sol-gel technique at low temperature. They are characterized structurally and optically with the used of X-ray diffraction (XRD), UV-visible spectrophotometer, Photoluminescence (PL), microscopy (SEM) and Transmission electron microscopy (TEM). The anatine toretile phase transition is observed at 750 o C and lattice distortion ratios are reduced whereas crystallites sizes are found to increase with increases of temperature. The emission spectrum under excitation at the 7 F0→ 5 L6 (393nm) transition of the Eu 3+ ion shows broad emission bands arising from the 5 DJ (J=0, 1) levels and with the emission decays lifetime varying between 0.243 and 0.375ms for samples prepared at different temperatures. The Judd-Ofelt intensity parameters W2 are found in the range 6.57 - 17.14 x10 -20 cm 2 at different concentrations and temperatures. Quantum yield of all the samples are more than 80% at different temperature. The average decay lifetime decreases with the increase of Eu 3+ concentration.
Umesh Rizal; Bhabani S. Swain; Bibhu P. Swain
Abstract
We have synthesized carbon nanoparticles (CNPs) via the sol-gel method using dextrose as carbon source with different concentration of ethanol. The effects of ethanol concentration (0.2 to 2.0 M) on the chemical network, electrochemical and photoluminescence properties of CNPs were examined using Fourier ...
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We have synthesized carbon nanoparticles (CNPs) via the sol-gel method using dextrose as carbon source with different concentration of ethanol. The effects of ethanol concentration (0.2 to 2.0 M) on the chemical network, electrochemical and photoluminescence properties of CNPs were examined using Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, cyclic voltammetry and photoluminescence (PL) spectroscopy. Field emission scanning electron microscopy (FESEM) image of CNPs shows CNPs of 40-80 nm were synthesized by sol-gel method. Chemical network study reveals the presence of various bonds such as C-H, C-H2, C-H3 and aromatic carbon present on the surface of the CNPs. Raman spectra shows that increasing of ethanol concentration decreases the crystalline size of CNPs. Cyclic voltammetry analysis shows prominent oxidation peaks at 0.1-0.2 V whereas the reduction peak observed at 0.2 V. The observed room temperature PL peak at 2.9 eV confirms a blue emission from CNPs.
P. Rehana; O. Ravi; B. Ramesh; G.R. Dillip; C. Madhukar Reddy; S. W. Joo; B. Deva Prasad Raju
Abstract
A facile melt quenching technique was employed to prepare Eu 3+ -ions doped TRZNB glasses using commercial powders through mixing the specific weights of batches. The compositions prepared were 10TeO2 + 15RO + 5ZnO + 10Nb2O5 + 59B2O3 + Eu2O3 (where R= Mg, Ca and Sr). Under 395 nm excitation wavelength, ...
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A facile melt quenching technique was employed to prepare Eu 3+ -ions doped TRZNB glasses using commercial powders through mixing the specific weights of batches. The compositions prepared were 10TeO2 + 15RO + 5ZnO + 10Nb2O5 + 59B2O3 + Eu2O3 (where R= Mg, Ca and Sr). Under 395 nm excitation wavelength, p < /span>hotoluminescence (PL) and lifetime measurements of Eu 3+ -doped TRZNB glasses were recorded and reported. The PL spectra composed of five emission bands that are originating from the 5 D0 metastable state to 7 FJ (J = 0 - 4) lower lying states. Using the emission intensities of 5 D0→ 7 F2 and 5 D0→ 7 F4 transitions, respectively, the Judd–Ofelt (J–O) intensity parameters such as Ω2 and Ω4 were calculated by considering the magnetic dipole (MD) 5 D0→ 7 F1 transition as reference. The radiative parameters such as spontaneous emission probabilities (AR), lifetimes (τm), branching ratios (βm) for different excited states were estimated theoretically. For all the glasses, the decay profiles were fitted to the single exponential equation. The obtained intense red emission at about 616 nm assigned to the 5 D0 → 7 F2 transition suggested the potentiality of present Eu 3+ -doped TRZNB glasses as a laser host.
Atul N. Yerpude; Sanjay Janrao Dhoble; B. Ramesh; Borelli Deva Prasad Raju
Abstract
In this study, Sm 3+ - and Dy 3 -doped SrAl4O7 phosphors were synthesized by combustion method. X-ray diffraction (XRD) measurement confirmed the monoclinic crystal structure of SrAl4O7. Sr-O and Al-O bonds were identified by Fourier transform infrared (FTIR) spectroscopy. Under 352 nm excitation, the ...
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In this study, Sm 3+ - and Dy 3 -doped SrAl4O7 phosphors were synthesized by combustion method. X-ray diffraction (XRD) measurement confirmed the monoclinic crystal structure of SrAl4O7. Sr-O and Al-O bonds were identified by Fourier transform infrared (FTIR) spectroscopy. Under 352 nm excitation, the SrAl4O7: Dy 3+ phosphor shown emission bands at 475 nm (blue) and 574 nm (yellow) that are due to 4 F9/2→ 6 H15/2, 6 H13/2 transitions, respectively. Photoluminescence spectra (PL) of SrAl4O7: Sm 3+ phosphor has shown bright orange red emission at 598 nm with an excitation wavelength of 405 nm. The decay curve of Sm 3+ and Dy 3+ single doped SrAl4O7 phosphors were well fitted to a bi-exponential function. The obtained results show that the prepared phosphors may be applicable in the field of eco-friendly solid state lighting technology.
M. Chowdhury; S.K. Sharma; R.J. Chaudhary
Abstract
SnO2/Fe2O3 composite thin films were deposited on quartz substrates at various oxygen partial pressures with a substrate temperature of 750 °C by pulsed laser deposition. The structural and optical properties of the deposited films were studied by X-ray diffraction (XRD), Atomic force microscopy ...
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SnO2/Fe2O3 composite thin films were deposited on quartz substrates at various oxygen partial pressures with a substrate temperature of 750 °C by pulsed laser deposition. The structural and optical properties of the deposited films were studied by X-ray diffraction (XRD), Atomic force microscopy (AFM), UV–visible spectroscopy and Photoluminescence. X-ray diffraction analysis revealed the formation of mixed phases (tetragonal SnO2 and hexagonal α-Fe2O3) at lower oxygen partial pressure (0.1 mTorr) and only tetragonal phase at higher oxygen partial pressures (50-250 mTorr). Atomic force microscopy studies show the dense and uniform distribution of composite films. The average RMS roughness of the films increases with increasing oxygen partial pressure. The bandgap was found varying between 3.55 and 3.85 eV for different oxygen pressures. A strong broad blue emission band was observed for all the oxygen partial pressures. The origin of the blue emission in the composite film is discussed with the help of vacancy creation. A correlation between oxygen partial pressure and the properties of SnO2/Fe2O3 .
R. Bargougui; K. Omri; A. Mhemdi; S. Ammar
Abstract
Nanocrystalline SnO2 oxides particles have been successfully synthesized via polyol process using diethylene glycol (DEG) as a solvent, followed by powder thermal treatment. The general applicability of the process is shown and the advantages in terms of properties and processability are described. The ...
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Nanocrystalline SnO2 oxides particles have been successfully synthesized via polyol process using diethylene glycol (DEG) as a solvent, followed by powder thermal treatment. The general applicability of the process is shown and the advantages in terms of properties and processability are described. The powders thus prepared were investigated using X-ray diffractometry. (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectra (PL). The X-ray diffraction patterns of the samples were indexed to the rutile phase for SnO2.The TEM images show uniform isotropic morphologies with average sizes close to10 nm. This decrease in particle size is accompanied with a decrease in the band-gap value from 3.55 eV for SnO2 down to 3.27 eV as shown by UV-visible spectra. It is demonstrated that the crystallite size less than 10 nm can be controlled by changing the quantity of added water (rate hydrolysis h=n H2O/n Metal).
Pragati Kumar; Nupur Saxena; Avinash Agarwal; Vinay Gupta
Abstract
Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures ...
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Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures (Ts): room temperature (RT) and 200 ºC. The role of Ts and its implications on the effect of dense electronic excitation provoked by swift heavy ion irradiation (SHII) on various optical and structural properties of CdS films is investigated under the influence of 70 MeV 58 Ni +6 ion beam. It reveals from the present studies that Ts may crucially affect the crystalline structure, vibrational and electronic states of the film and thereafter the functionality induced by ion beam. It is found that ion beam is capable to transform structural phase from mixed phase of cubic and hexagonal structure to either pure cubic or pure hexagonal phase of CdS depending upon the pre-existing preferred orientation in pristine film. The modification in crystallite size and band gap due to impact of ion beam is found to be strongly dependent on pre-existing structural phase, as determined by Ts. The studies presented here confirm that initial growth conditions play a key role even after post deposition SHII treatment in selecting precisely the functional behavior of the films.
N. S. Kokode; V. R. Panse; S. J. Dhoble
Abstract
In present work we studied the luminescence properties of Tb 3+ and Mn 2+ doped Ca2PO4Cl phosphor synthesized by wet chemical method were studied with extra heat treatment, to understand the mechanism of excitation and the corresponding emission of prepared phosphor. For the green emission, Tb 3+ ion ...
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In present work we studied the luminescence properties of Tb 3+ and Mn 2+ doped Ca2PO4Cl phosphor synthesized by wet chemical method were studied with extra heat treatment, to understand the mechanism of excitation and the corresponding emission of prepared phosphor. For the green emission, Tb 3+ ion is used as an activator, the excitation and emission spectra indicate that this phosphor can be effectively excited by 380 nm, to exhibit bright green emission centered at 545 nm corresponding to the f→f transition of Tb 3+ ions. The emission spectrum of Mn 2+ ion at 405 nm excitation 4 T1(4G) - 6 A1(6S) gives an emission band at 591 nm (orange-red). The observed photoluminescence (PL) measurements of Tb 3+ and Mn 2+ activated prepared phosphor indicates that these are the outstanding green and orange-red emitting potential phosphor , suitable application for the solid state lighting. The synthesized phosphors were analyzed by X-ray diffraction (XRD) for confirmation of phase and purity. The morphology and structure were characterized by scanning electron microscopy. Thus the phosphors in this system may be chosen as the green component for the tri-color lamp and certainly applied in w-UV LEDs. In the view of the excitation band and excellent luminescent properties, Ca2PO4Cl:Tb 3+ and Mn 2+ phosphor is expected to be a potential candidate for application in n-UV white LEDs and solid-state lighting because of its cost-efficient manufacturing, mercury-free excitation and eco-friendly characteristics.
Satinder Kumar; S. P. Lochab;Ravi Kumar; Arvind K. Gathania; Ankush Vij; A. K. Sharma; R. Dogra
Abstract
We synthesized single phase pure and Eu doped LiF having micro-cubical morphology by modified co-precipitation method. The complete solid solubility of Eu in LiF has been observed up to 0.04 mol% and afterwards phase segregation started. The absorption spectra of pure and Eu doped LiF revealed the formation ...
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We synthesized single phase pure and Eu doped LiF having micro-cubical morphology by modified co-precipitation method. The complete solid solubility of Eu in LiF has been observed up to 0.04 mol% and afterwards phase segregation started. The absorption spectra of pure and Eu doped LiF revealed the formation of γ-irradiation induced and dose dependent F, M and F3 color centers at room temperature. The concentrations of both F and M color centers calculated by using Smakula’s formula, increased almost ten times for γ- irradiated Eu doped LiF in comparison to γ-irradiated pure LiF. Non irradiated LiF doesn’t show any photoluminescence (PL) signal. However, γ-irradiated LiF showed broad emission peak around 681 nm, which is due to the excitation of F2 color centers. The Eu doped LiF samples exhibit PL emission peaks at 577, 591, 612, 648 and 690-698 nm correspond to Eu 3+ ion transitions from 5D0 to 7 FJ (J=0,1,2,3,4). The γ-irradiated Eu doped LiF show simultaneous PL emission spectrum of Eu 3+ ions and radiation induced F2 color centers. Thermoluminescence (TL) glow curves of γ- irradiated LiF and LiF: Eu (0.03 mol %) samples were also investigated and various trapping parameters for were evaluated by using Chen’s peak shape method
Annu Sharma; Jyoti Rozra; Isha Saini
Abstract
In the present work, effects of annealing temperature on structural and optical properties of silver-glass nanocomposites synthesized by the combined use of ion-exchange and subsequent thermal annealing in air have been investigated using Transmission electron microscopy (TEM), UV–Visible absorption ...
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In the present work, effects of annealing temperature on structural and optical properties of silver-glass nanocomposites synthesized by the combined use of ion-exchange and subsequent thermal annealing in air have been investigated using Transmission electron microscopy (TEM), UV–Visible absorption spectroscopy and Photoluminescence spectroscopy. The appearance of SPR peak characteristic of silver nanoparticle formation around 429 nm in absorption spectra of silver-glass nanocomposite samples indicates towards the formation of silver nanoparticles in glass. The size of silver nanoparticles has been found to increase with increase in annealing temperature. At an annealing temperature of 200°C the size of silver nanoparticles comes out to be 2.31 nm which increases to a value of 7.60 nm at an annealing temperature of 550°C. TEM investigation indicates that silver nanoparticles of size 6.57+1.14 nm are formed in glass matrix. UV-visible absorption and reflection data has been analyzed to ascertain optical properties such as absorption coefficient (α), refractive index (n) and dielectric constant (ε). Emissions bands in the photoluminescence spectra were analyzed to investigate different oxidation states of silver present in the prepared nanocomposite samples. Formation of Ago atoms from Ag + ions are responsible for the quenching of photoluminescence intensity at higher temperature. Such nanocomposites are expected to be promising materials for ultrafast optical switches and for sensing applications.
V. V. Shinde; S. J. Dhoble
Abstract
The subject of this work is the characterization of the photoluminescence properties of RE 3+ doped bromoapatite inorganic optoelectronic phosphor material. This paper reports the luminescence properties of RE 3+ (Where RE= Ce, Dy, and Eu) doped Ca5(PO4)3Br, which has been prepared by solid state ...
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The subject of this work is the characterization of the photoluminescence properties of RE 3+ doped bromoapatite inorganic optoelectronic phosphor material. This paper reports the luminescence properties of RE 3+ (Where RE= Ce, Dy, and Eu) doped Ca5(PO4)3Br, which has been prepared by solid state reaction route. The prepared phosphor is well characterized by XRD, SEM, FT-IR and photoluminescence (PL) measurement. The apatite Ca5(PO4)3Br:Ce 3+ shows an efficient broad emission at 340 nm and weak 362 nm emission when excited at 293 nm. Ca5(PO4)3Br:Dy 3+ phosphor shows an efficient blue and yellow emissions at 485 nm and 577 nm respectively when excited at 390 nm . Ca5(PO4)3Br:Eu 3+ phosphor shows an orange and weak red emission at 592 nm and 615 nm respectively when excited at 396 nm. The effect of the RE 3+ concentration on the luminescence properties of Ca5 (PO4)3Br:RE 3+ phosphors are also studied. The investigated prepared bromoapatite phosphors may be suitable for a near UV excited LED.
Niyaz Parvin Shaik; N. V. Poornachandra Rao; K. V. R. Murthy
Abstract
Pure LaPO4 and LaPO4: Eu (0.5 mol %) Ce (0.5 mol %) phosphors were synthesized by the solid-state reaction method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the particle size analysis were used to characterize ...
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Pure LaPO4 and LaPO4: Eu (0.5 mol %) Ce (0.5 mol %) phosphors were synthesized by the solid-state reaction method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the particle size analysis were used to characterize these samples. The XRD results reveal that the synthesized LaPO4:Eu (0.5 mol%) Ce (0.5 mol%) phosphors are well crystalline and assigned to the monoclinic structure with a main (120) diffraction peak. The calculated crystallite size of pure LaPO4 and LaPO4:Eu, Ce phosphors were 67.6nm and 64nm respectively. Upon excitation at 254nm wavelength, the emission spectrum of pure LaPO4 phosphor emits a maximum intensity peak at 470 (blue) nm. In the emission spectrum of LaPO4:Eu 3+ Ce 3+ phosphor, the low contributions of the red (613nm) 5D0-7F2 emissions and the high intensity of the orange-red (589nm)5D0-7F1 emission results in high color purities.The most intense emissions appearing in the 580-620nm region is responsible for the strong orange-red luminescence observed in the Eu,Ce doped LaPO4 phosphor whose CIE colour coordinates are x = 0.57 and y = 0.43.Thus the prepared phosphors can be used as an orange-red emitting material in the field of illuminations and display devices.
H. K. Dahule; S. J. Dhoble
Abstract
We have synthesized series of new phosphorescent cyclometalated iridium (III) complexes Ir(Br-DPQ)2(acac), with 2-(4-bromo-phenyl)-4-phenyl-quinoline (Br-DPQ) ligand and Ir(Cl-BrDPQ)2 (acac) with 4-chloro-2-(4-bromophenyl)-4-phenyl quinoline (Cl-BrDPQ) ligand. Synthesized complexes and ligands were characterized ...
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We have synthesized series of new phosphorescent cyclometalated iridium (III) complexes Ir(Br-DPQ)2(acac), with 2-(4-bromo-phenyl)-4-phenyl-quinoline (Br-DPQ) ligand and Ir(Cl-BrDPQ)2 (acac) with 4-chloro-2-(4-bromophenyl)-4-phenyl quinoline (Cl-BrDPQ) ligand. Synthesized complexes and ligands were characterized by X-ray diffraction, elemental analysis, infrared spectroscopy (FTIR) and thermal analysis (TGA/DTA,DSC). UV-vis absorption and emission spectroscopy, photoluminescence (PL) emission peaks of Br-DPQ and Cl-BrDPQ in different solvents such as chloroform, dichloromethane, THF, acetic acid and formic acid is between 425 to 460 nm The metal complex display pure red luminescence in solution and in powder states in the range of λmax 615-651 nm. The iridium metal complex Ir(Br-DPQ)2(acac) where (Br-DPQ=2-(4-bromo phenyl)-4-phenyl quinoline shows strong 1MLCTand 3MLCT absorption peak at, 227, 265, 283, 346, and 432 nm in tetrahydrofuran (THF) solution and Ir(Cl-BrDPQ)2(acac) where (Cl-BrDPQ)=4chloro2-(4-Bromo phenyl)-4-phenyl quinoline shows strong 1MLCTand 3MLCT absorption peak at 262, 330, 438, 476, 505 and 535 nm in dichloromethane solution. It is suggested that the synthesized iridium complexes may be efficiently used as the emissive dopants in phosphorescent organic light-lmitting devices (PhOLEDs). Thus these complexes could be promising candidates for potential applications in Phosphorescent organic light-emitting diodes PhOLEDs, light-emitting electrochemical cells and solid-state organic lighting applications.
Pragati Malik; Jyoti Singh; Rita Kakkar
Abstract
The primary aim of this review is to survey the literature on the ion sensing ability of quantum dots. Sensing of both cations and anions is important, since both play significant roles in various ecological and biological processes, which makes it important to ensure their concentration at balanced ...
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The primary aim of this review is to survey the literature on the ion sensing ability of quantum dots. Sensing of both cations and anions is important, since both play significant roles in various ecological and biological processes, which makes it important to ensure their concentration at balanced level. Contamination by heavy metal ions and various anions poses a serious threat to humans, aquatic organisms, and to the environment; therefore detection of these ions (in presence of other cations and anions), which are the major cause of environmental pollution is of immense significance at the present time. Owing to their enhanced fluorescence properties and photostability, QDs offer tremendous scope to be used for ion sensing. They offer several advantages over traditional chemical fluorophores. This review throws light on the mechanism adopted by CdSe QDs to act as flourophores. Owing to their enhanced photoluminescence properties, QDs offer selective and sensitive determination of various ions, which is a function of the capping on the surface of the QD nanosensor, i.e. it is possible to tune their sensing ability by changing the capping layer, which influences the QD's interaction with various analytes. Hence, these quantum dots may prove promising candidates in future for sensing approximately all types of analytes.
P. W. Yawalkar;S. J. Dhoble
Abstract
Synthesis of volatile Eu(acac)3phen and Tb(acac)3phen complexes by solution technique were reported in this paper. The combination of Eu and Tb complexes, namely TbxEu(1-x)(acac)3phen (x=0.1,0.3,0.5,0.7,0.9) were also synthesized by maintaining stoichiometric ratio. Optical properties of these synthesized ...
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Synthesis of volatile Eu(acac)3phen and Tb(acac)3phen complexes by solution technique were reported in this paper. The combination of Eu and Tb complexes, namely TbxEu(1-x)(acac)3phen (x=0.1,0.3,0.5,0.7,0.9) were also synthesized by maintaining stoichiometric ratio. Optical properties of these synthesized complexes were studied using photoluminescence technique. Eu(acac)3phen exhibits red intense emission at 612 nm with a sharp spectral bandwidth 5 nm when excited at a wavelength of 323nm, while Tb(acac)3 phen shows green emission at 547 nm when excited at 347nm. The emission spectra of TbxEu(1-x)(acac)3phen reveals that Tb0.7Eu0.3(acac)3 phen complex exhibits maximum intensity among all the stichiometrically doped complexes. When Tb0.7Eu0.3(acac)3 phen was molecularly doped in poly methyl Metacrylate (PMMA) to check its compatibility in polymers, enhancement in intensity was observed in these blended films, proving that these complexes can be used as emissive materials for fabricating OLEDs and displays by vacuum deposition as well as solution techniques.
Vishal R. Panse; N.S. Kokode; S.J. Dhoble
Abstract
In this paper we present luminescence results on Tb 3+ doped Sr2(BO3)Cl green phosphor. The vibrational properties of Sr2(BO3)Cl phosphor was studied by Fourier transform infrared spectroscopy. Photoluminescence studies have been carried out to understand the mechanism of excitation and the corresponding ...
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In this paper we present luminescence results on Tb 3+ doped Sr2(BO3)Cl green phosphor. The vibrational properties of Sr2(BO3)Cl phosphor was studied by Fourier transform infrared spectroscopy. Photoluminescence studies have been carried out to understand the mechanism of excitation and the corresponding emission in the as prepared phosphor. As the Tb 3+ ion is commonly used as an activator for the green emission, the excitation and emission spectra indicate that this phosphor can be effectively excited by 380 nm, to exhibit bright green emission centered at 546 nm corresponding to the f→f transition of Tb3 +ions.
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