CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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asymmetric ratios of luminescence for SbPO 4:Eu 3+ and EuPO4 samples confirm that no separate EuPO 4 / TbPO 4 phase is formed, instead lanthanide ions like Tb 3+ and Eu 3+ are incorporated in SbPO4 host. Had these ions formed separate phase, strong Tb and Eu 3+ emission would not have been observed from the lanthanide ions doped SbPO 4 samples. Final confirmation for the lanthanide ion incorporation in the SbPO 4 host comes from the lifetime values of 5 D 3+ 0 level of Eu in SbPO 4 :Eu 3+ and EuPO 4 . The 5 D0 lifetime of Eu 3+ is 2.0 ms (97%) and 0.004 ms (3%) for SbPO :Eu 3+ 4 and the corresponding values are 0.8 ms (73%) and 0.42 ms (27%) for EuPO 5 3+ . Significantly higher D lifetime value corresponding to Eu 4 0 ion in SbPO 4 :Eu 3+ compared to that of EuPO further substantiate the fact that Eu 3+ 4 ions are incorporated in the SbPO host and not existing as separate EuPO . 4 4 With a view to compare the photoluminescence intensities of SbPO :Ln 3+ 4 nanoparticles/ nanoribbons with that of bulk materials, SbPO 4 :Eu 3+ and SbPO :Tb 3+ 4 , bulk materials were prepared by solid-state reaction between Sb O 2 3 and ammonium dihydrogen phosphate at 500°C. XRD patterns of the reaction product confirmed formation of crystalline SbPO 4 . Figure 66 shows the emission and excitation spectra from these samples. For the same amount of sample, photoluminescence intensities of bulk materials are comparable with that of nanomaterials. (Host absorption around 220 nm is more clearly seen in the inset of Fig.66 (a)). Based on these results it is inferred that the luminescent SbPO 4 nanomaterials prepared at low temperature are equally good as bulk materials and has an added advantage of dispersability in methanol and water. Luminescence measurements were also carried out for SbPO 4 nanoparticles/ 3+ nanoribbons as a function of Tb 3+ doping concentration. Figure 67 shows the emission spectrum from SbPO nanoparticles/ nanoribbons containing different amounts of Tb 3+ 4 ions and excited at 250 nm. The emission intensity is maximum for 2 atom % Tb 3+ doped samples and it systematically decreased with further increasing Tb 3+ concentration due to 120
3+ 3+ concentration quenching. Tb luminescence improves by co-doping of Ce in SbPO 4 :Tb 3+ 3+ 3+ nanomaterials. This has been attributed to the energy transfer from Ce to Tb ions in the lattice. In the following section, structure, morphological and luminescence characteristic of Ce 3+ co-doped SbPO :Tb 3+ nanomaterials are discussed. 4 Intensity (arb. units) 20 15 10 5 300 200 100 0 550 600 650 700 300 (b) 400 200 100 (a) 5 D4 7 F6 5 D0 7 F1 5 D0 7 F2 200 (220 nm) (250 nm) 200 300 400 500 200 300 400 500 0 450 500 550 600 650 700 Wavelength (nm) Fig.66. Emission spectrum of (a) SbPO 4 : Eu 3+ and (b) SbPO : Tb 3+ 4 bulk materials prepared by solid state reaction (excitation wavelength was 220 nm). Insets show corresponding excitation spectrum monitored at 616 and 545 nm emission. 5 D4 7 F4 5 D4 7 F5 5 D4 7 F3 Intensity ( arb.units) 250 200 150 100 50 λ exc = 255 nm 7 F6 5 D4 7 F5 0 450 500 550 600 650 Wavelength (nm) 5 D4 7 F4 5 D4 1 % Tb 2 % Tb 2.5 % Tb 5 % Tb Fig.67. Emission spectra of SbPO 4 nanoparticles/ nanoribbons doped with 1, 2, 2.5, and 5 at % Tb 3+ ions. Samples were excited at 250 nm. 7 F3 5 D4 121
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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
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will be formed and subsequently it
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Eu 3+ ions were also subjected to s
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transferred into a two-necked RB fl
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Where λ is the wavelength of X-ray
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Micro-structural characterization b
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electrons (i.e. diffraction mode).
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diffraction spots. By tilting a cry
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surface. The contact mode can obtai
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three types lines in the scattered
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solids tend to be broadened because
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sample fluoresce. The fluorescent l
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pulse frequency) as excitation sour
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Lanthanide ions doped Ga 2 O 3 nano
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atoms at three corners and the lone
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Figure 19 (a-d) shows SEM images of
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Based on these results, it can be i
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almost normal to the equatorial pla
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Table 2. Summary of important modes
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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 and 120: strong emission compared to corresp
Page 121 and 122: curves are shown in Fig.39. Lifetim
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: observed after excitation at 250 an
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
Page 171 and 172: espectively. Value of this integral
Page 173 and 174: ethylene glycol moiety (stabilizing
Page 175 and 176: Room temperature and 100°C synthes
Page 177 and 178: heavier metal ion as compared to La
Page 179 and 180: Similar studies were also carried o
Page 181 and 182: 3+ 3+ faster decay component is ass
Page 183 and 184: the other hand the Eu 3+ lifetime h
Page 185 and 186: 3+ 4.4.8 Luminescence studies on Sm
Page 187 and 188: CHAPTER 5: Zinc gallate (ZnGa 2 O 4
Page 189 and 190: In pure EG an amorphous product is
Page 191 and 192: water content in the reaction mediu
Page 193 and 194: nucleation, thereby leading to incr
Page 195 and 196: particles. Thus the TEM studies als
Page 197 and 198: value. The lattice parameters calcu
Page 199 and 200: Quantum yield of the blue emission
Page 201 and 202: 5.5.2. Eu 3+ doped ZnGa 1.5 In 0.5
Page 203 and 204: CHAPTER 6: Tungstates [MWO 4 (M = C
Page 205 and 206: ionic radius of the metal cation ca
Page 207 and 208: 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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