CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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Unlike SnO 2 , Sb 2 O 3 is an indirect band gap semiconducting material with a band gap of ~ 3.3 eV. It exists mainly in two crystalline forms, namely, the cubic senarmonite form and the orthorhombic valentinite form. Deng, et al. [64, 65] have carried out luminescence studies on self-assembled structures of Sb 2 O 3 nanorods and nanowires. They observed broad emission peak over the region of 390 to 500 nm, in addition to the band edge emission centered around 374 nm. Broad emission over the region of 390 to 500 nm has been attributed to the emission from oxygen vacancies related defect centers present in the lattice of Sb 2 O 3 . ZnGa 2 O 4 is also a transparent semiconducting oxide having spinel structure. It is a potential candidate for Field emission and vacuum fluorescent display applications because of its high thermal stability. Bae, et al. [66] prepared vertically aligned ZnG 2 O 4 nanowires by chemical vapor deposition method and observed strong photoluminescence and cathodeluminescence in the blue wavelength region. Different types of soft chemical methods [67, 68] have been reported for the preparation of ultra fine particles of ZnGa 2 O 4 , which show photoluminescence in the blue region. Their particle size and luminescence properties can be tuned by modifying the experimental conditions during its synthesis. Lanthanide ions doped luminescent nanomaterials: Lanthanide ions doped in different inorganic hosts are extensively used in various display applications. Extensive literature is available regarding the luminescence properties of lanthanide doped inorganic nanoparticles. In the following section, brief description regarding the previous studies on representative lanthanide ions doped inorganic nanoparticles (for example Y 2 O 3 :Ln, Y 3 Al 5 O 12 :Ln, YPO 4 :Ln and CePO 4 :Ln) is given. Y 2 O 3 is widely used as a host for various lanthanide ions and such phosphor materials are used in various display devices [69]. Number of studies has been reported on the luminescent properties of Y 2 O 3 :Ln 3+ (Ln 3+ = lanthanide ions) nanoparticles. Luminescence 24
depends strongly on the nature of the synthesis method and conditions employed [70-73]. For example, Sharma, et al. [73] synthesised Y 2 O 3 :Eu nanoparticles having size in the range of micrometers to nanometers with the help of organic surface modifiers like Tween-80 and Emulsogen-OG. The authors observed a five fold enhancement in emission intensity from the nanoparticles when 10 wt. % of surface modifier was added during the synthesis of Y 2 O 3 :Eu nanoparticles. Taner and Wang [74] investigated the luminescence properties of Y 2 O 3 :Eu nanoparticles prepared by flame spray pyrolysis method and compared it with that of conventional pyrolysis method. The intensity of 5 D 1 emission of Eu 3+ ions from the C 3i site (S 6 ) in Y 2 O 3 is significantly less compared to the emission from Eu 3+ ions in the C 2 site for these samples. Igarashi, et al. [75] compared luminescence properties of bulk and nanoparticles of Y 2 O 3 :Eu prepared using yttrium hydroxy carbonate precursor method and established that the increase in ionicity of Eu-O bond due to decrease in particles size is responsible for observed blue shift of excitation peak with decrease in particle size. Song and co-workers [76, 77] have observed that the radiative and non-radiative transition rates of Eu 3+ ions in Y 2 O 3 :Eu nanoparticles increased with decrease in particle size and this is attributed to the crystal lattice degeneration and surface effects. Further, ultraviolet (UV) light irradiation on Y 2 O 3 :Eu nanoparticles has been found to reduce the intensity of Eu-O charge transfer peak [78,89]. Temperature and particle size effect on photoluminescence properties of Y 2 O 3 :Tb nanoparticles have also been investigated by the same authors. Based on the studies it has been established that relative intensity of 5 D 4 → 7 F J transitions and oxygen defect emission ~ 620 nm characteristic of Y 2 O 3 host are related to extent of thermal quenching process [80]. Tb 3+ concentration dependence on photoluminescence intensity of Y 2 O 3 :Tb nanoparticles is investigated by Park, et al. [81]. These authors have observed that for Y 2 O 3 :Tb nanoparticles, prepared by solution route followed by annealing at 400°C and containing 8 wt. % Tb 3+ , gave optimum intensity for green emission. Mukherjee, et al. [82] have observed a variation 25
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SYNTHESIS AND CHARACTERIZATION OF L
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STATEMENT BY AUTHOR This dissertati
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Dedicated to ……… My beloved b
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also thankful to all the members of
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2.3 Synthesis of binary oxide nanom
Page 11 and 12: CHAPTER 5: Zinc Gallate ...........
Page 13 and 14: imaging, scintillators, lasers, etc
Page 15 and 16: morphology by heating at 500 and 90
Page 17 and 18: nanoparticles having hexagonal stru
Page 19 and 20: 100°C and 185°C, respectively in
Page 21 and 22: into poly methyl methacryllate (PMM
Page 23 and 24: 3. N. M. Dimitrijevic, Z. V. Saponj
Page 25 and 26: Fig.13: Fig.14: (a) Simplified ray
Page 27 and 28: Eu 3+ ions after heat treatment at
Page 29 and 30: 615 nm Fig.50: FT-IR patterns (a) a
Page 31 and 32: area electron diffraction pattern a
Page 33 and 34: different amounts of Eu 3+ . Fig.86
Page 35 and 36: and 545 nm, respectively. Fig.106:
Page 37 and 38: List of Tables: Table 1: Variation
Page 39 and 40: CHAPTER 1: Introduction 1.1 Histori
Page 41 and 42: Rods, cylinders, wires and tubes ar
Page 43 and 44: must be supersaturated either by di
Page 45 and 46: - + - + charge stabilized nanoparti
Page 47 and 48: exothermic reaction between the met
Page 49 and 50: constant, ħ is h/2π, e is the ele
Page 51 and 52: these platinum complexes have been
Page 53 and 54: (IR), visible and ultra-violet (UV)
Page 55 and 56: in Ce 3+ , Pr 3+ , Tb 3+ and CT abs
Page 57 and 58: assisted by lattice phonons of appr
Page 59 and 60: decay-time reduction is much easier
Page 61: nanocrystals is shown in Fig.10 [58
Page 65 and 66: corresponding emission and excitati
Page 67 and 68: doped nanomaterials of the above me
Page 69 and 70: will be formed and subsequently it
Page 71 and 72: Eu 3+ ions were also subjected to s
Page 73 and 74: transferred into a two-necked RB fl
Page 75 and 76: Where λ is the wavelength of X-ray
Page 77 and 78: Micro-structural characterization b
Page 79 and 80: electrons (i.e. diffraction mode).
Page 81 and 82: diffraction spots. By tilting a cry
Page 83 and 84: surface. The contact mode can obtai
Page 85 and 86: three types lines in the scattered
Page 87 and 88: solids tend to be broadened because
Page 89 and 90: sample fluoresce. The fluorescent l
Page 91 and 92: pulse frequency) as excitation sour
Page 93 and 94: Lanthanide ions doped Ga 2 O 3 nano
Page 95 and 96: atoms at three corners and the lone
Page 97 and 98: Figure 19 (a-d) shows SEM images of
Page 99 and 100: Based on these results, it can be i
Page 101 and 102: almost normal to the equatorial pla
Page 103 and 104: Table 2. Summary of important modes
Page 105 and 106: systematic disappearance of these t
Page 107 and 108: comparison, Eu 3+ ions alone in wat
Page 109 and 110: the samples, suggesting that Eu 3+
Page 111 and 112: These inferences are further substa
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Similar DTA peaks have been reporte
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GaOOH samples doped with different
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The cell parameters increases with
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strong emission compared to corresp
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curves are shown in Fig.39. Lifetim
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Similar results are also observed f
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intensity of XRD peaks correspond t
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compared to the bulk material and a
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is almost 1½ times that of peak B1
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3.8 Interaction of Eu 3+ ions with
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The spectrum shows strong emission
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The decay curves are found to be bi
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As prepared undoped Sb 2 O 3 sample
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Intensity(arb.units) 1.0 0.8 0.6 0.
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3+ having surface lanthanide ions.
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diffraction patterns from the GaPO
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5 D 0 7 F 2 level to 7 F 7 7 1 , F
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The second possibility is the excha
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chemical shift anisotropy is much h
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not have strong interaction with th
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(001) (110) (011) (101) (020) (101)
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growth centre compared to higher vi
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observed after excitation at 250 an
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3+ 3+ concentration quenching. Tb l
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Compared to the selected area elect
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lattice. Lanthanide ions occupying
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obtained after 275 nm excitation is
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The luminescence dynamics associate
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that the broad peak can be resolved
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espectively. Value of this integral
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ethylene glycol moiety (stabilizing
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Room temperature and 100°C synthes
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heavier metal ion as compared to La
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Similar studies were also carried o
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3+ 3+ faster decay component is ass
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the other hand the Eu 3+ lifetime h
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3+ 4.4.8 Luminescence studies on Sm
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CHAPTER 5: Zinc gallate (ZnGa 2 O 4
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In pure EG an amorphous product is
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water content in the reaction mediu
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nucleation, thereby leading to incr
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particles. Thus the TEM studies als
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value. The lattice parameters calcu
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Quantum yield of the blue emission
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5.5.2. Eu 3+ doped ZnGa 1.5 In 0.5
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CHAPTER 6: Tungstates [MWO 4 (M = C
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ionic radius of the metal cation ca
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lattice. Asymmetric ratio is ~ 12 f
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700 Intensity (arb.units) 600 λ ex
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Intensity (arb.units) 25000 20000 1
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Strong green emission has been obse
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consists of strong band at 255 nm a
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peak can be attributed to the cryst
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nm) is observed from Er 3+ doped Ga
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and Dy 3+ doped CaWO 4 nanoparticle
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REFERENCES 1. D. J. Barber, I. C. F
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32. K. A. Gschneidner, Jr., L. Eyri
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65. Z. Deng, F. Tang, D. Chen, X. M
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100. A. Rouanel, J. J. Serra, K. Al
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130. F. Li, W. Jianhuai, L. Jiongti
Page 233 and 234:
166. L. Fu, Z. Liu, Y. Liu, B. Han,
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205. R. Sasikala, V. Sudarsan, C. S
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238. E. Oldfield, R. A. Kinsey, K.
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271. B. G. Hyde, S. Andersson, ”I
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B. S. Naidu, B. Vishwanadh, V. Suda
Page 243:
9. Room temperature synthesis of mu
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CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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