CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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Figure 38 (a) shows the emission spectra of b-Ga 2 O 3 doped with 0, 0.5, 1 and 2 at % Tb 3+ obtained after excitation at 255 nm. Undoped (0 at % Tb) b-Ga 2 O 3 sample shows a broad band centered around 455 nm and is assigned to emission from oxygen defect levels present in the host matrix. The emission intensity reduces with increase in Tb 3+ percentage in the sample. This is explained based on the energy transfer from host to Tb 3+ ions. The excitation spectra corresponding to host and Tb 3+ emission are shown in Fig.38 (b). Intensity (arb.units) 600 400 200 0 400 200 0 200 100 0 200 100 0 2% Tb 1% Tb 0.5% Tb undoped 350 400 450 500 550 600 650 Wavelength (nm) Normalised intensity 1.0 0.8 λ = 544 nm em λ em = 460 nm 0.6 0.4 0.2 0.0 200 250 300 350 400 Wavelength (nm) (a) (b) Fig.38 (a) Emission spectra of β-Ga 2 O 3 nanomaterials doped with 0, 0.5, 1 and 2 at % Tb 3+ ions. The corresponding excitation spectra for 1 at % Tb 3+ doped sample, monitored at 460 and 544 nm emission, are shown in Fig. 38 (b) The excitation spectra corresponding to host emission exhibits only one band at 255 nm whereas excitation spectra corresponding to Tb 3+ emission is characterized by strong band at 275 nm having shoulder at 255 nm along with weak bands above 350 nm. The broadband ~ 275 nm is assigned to 4f to 5d transition of Tb 3+ , the shoulder peak to host absorption and peaks above 350 nm are due to f-f transitions of Tb 3+ ions. Based on the excitation spectra, it is confirmed that energy transfer takes place from host to Tb 3+ ions in these samples. This is further supported by the excited state lifetime values corresponding to host emission observed from samples with different Tb 3+ contents. The corresponding decay 82
curves are shown in Fig.39. Lifetime values corresponding to host emission decreased with increase in the terbium ion concentration (Table 5). The decrease in lifetime values with increase in Tb 3+ concentration confirms the energy transfer from host to lanthanide ion. Normalised Intensity 1 0.1 0.01 1 0.1 0.01 1 0.1 0.01 1 0.1 2 % Tb 1% Tb 0.5% Tb undoped 0.01 0 1 2 3 4 Time (ms) Fig.39 Decay curves corresponding to excited state of the host emission of β-Ga 2 O 3 nanomaterials doped with 0, 0.5, 1 and 2 at % Tb 3+ ions. Table 5 Excited state lifetime values of host emission from β-Ga 2 O 3 :Tb nanomaterials after doping with different amounts of Tb 3+ ions. Sample τ 1 (ms) τ 2 (ms) β-Ga 2 O 3 110 (24%) 885 (76%) β-Ga 2 O 3 : 0.5% Tb 100 (26%) 811 (74%) β-Ga 2 O 3 : 1% Tb 94 (29%) 827 (71%) β-Ga 2 O 3 : 2% Tb 65 (32%) 590 (68%) The emission and excitation spectra from a representative β-Ga 2 O 3 :Dy and β- Ga 2 O 3 :Eu samples are shown in Fig.40(a-d). Emission spectrum shown in Fig. 40 (a) corresponds to β-Ga 2 O 3 :Dy nanorods and is obtained by exciting the host at 260 nm. Sharp emission peaks due to intra 4f transitions of Dy 3+ ions characterize the spectrum. Corresponding excitation spectrum obtained by monitoring Dy 3+ emission at 575 nm is 83
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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
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CHAPTER 5: Zinc Gallate ...........
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imaging, scintillators, lasers, etc
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morphology by heating at 500 and 90
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nanoparticles having hexagonal stru
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100°C and 185°C, respectively in
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into poly methyl methacryllate (PMM
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3. N. M. Dimitrijevic, Z. V. Saponj
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Fig.13: Fig.14: (a) Simplified ray
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Eu 3+ ions after heat treatment at
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615 nm Fig.50: FT-IR patterns (a) a
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area electron diffraction pattern a
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different amounts of Eu 3+ . Fig.86
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and 545 nm, respectively. Fig.106:
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List of Tables: Table 1: Variation
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CHAPTER 1: Introduction 1.1 Histori
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Rods, cylinders, wires and tubes ar
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must be supersaturated either by di
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- + - + charge stabilized nanoparti
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exothermic reaction between the met
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constant, ħ is h/2π, e is the ele
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these platinum complexes have been
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(IR), visible and ultra-violet (UV)
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in Ce 3+ , Pr 3+ , Tb 3+ and CT abs
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assisted by lattice phonons of appr
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decay-time reduction is much easier
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nanocrystals is shown in Fig.10 [58
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depends strongly on the nature of t
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corresponding emission and excitati
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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
Page 113 and 114: Similar DTA peaks have been reporte
Page 115 and 116: GaOOH samples doped with different
Page 117 and 118: The cell parameters increases with
Page 119: strong emission compared to corresp
Page 123 and 124: Similar results are also observed f
Page 125 and 126: intensity of XRD peaks correspond t
Page 127 and 128: compared to the bulk material and a
Page 129 and 130: is almost 1½ times that of peak B1
Page 131 and 132: 3.8 Interaction of Eu 3+ ions with
Page 133 and 134: The spectrum shows strong emission
Page 135 and 136: The decay curves are found to be bi
Page 137 and 138: As prepared undoped Sb 2 O 3 sample
Page 139 and 140: Intensity(arb.units) 1.0 0.8 0.6 0.
Page 141 and 142: 3+ having surface lanthanide ions.
Page 143 and 144: diffraction patterns from the GaPO
Page 145 and 146: 5 D 0 7 F 2 level to 7 F 7 7 1 , F
Page 147 and 148: The second possibility is the excha
Page 149 and 150: chemical shift anisotropy is much h
Page 151 and 152: not have strong interaction with th
Page 153 and 154: (001) (110) (011) (101) (020) (101)
Page 155 and 156: growth centre compared to higher vi
Page 157 and 158: observed after excitation at 250 an
Page 159 and 160: 3+ 3+ concentration quenching. Tb l
Page 161 and 162: Compared to the selected area elect
Page 163 and 164: lattice. Lanthanide ions occupying
Page 165 and 166: obtained after 275 nm excitation is
Page 167 and 168: The luminescence dynamics associate
Page 169 and 170: 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
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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
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9. Room temperature synthesis of mu
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