CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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in the ZnGa 2 O 4 lattice. It is known that In 3+ is heavier than Ga 3+ , as a result the energy corresponding to GaO 6 unit in the ZnGa 2-x In x O 4 nanoparticles will be less than that in ZnGa 2 O 4 . Hence, the λ max corresponding to emission and excitation of GaO 6 level shifts to higher values with increase in the In 3+ content. The decay curve corresponding to the excited state of blue emission from ZnGa 1.5 In 0.5 O 4 nanoparticles is shown in Fig.100 (b). It is found to be bi-exponential in nature with lifetime values 0.49 μs (56 %) and 1.85 μs (44 %). The faster component is due to surface GaO 6 units and longer component is due to GaO 6 present in the bulk of the ZnGa 2 O 4 :In 3+ lattice. Since surface GaO 6 units are directly bound to EG moiety, they will decay faster than bulk GaO 6 structural units. (a) (b) Fig.99. (a) TEM image, (b) HRTEM image of ZnGa 1.5 In 0.5 O 4 nanoparticles. SAED pattern from these nanoparticles is shown in the inset of Fig.99 (a) Normalised intensity 1.0 0.8 0.6 0.4 0.2 x = 0 x = 0.05 x = 0.2 x = 0.5 Intensity (arb.units) 1000 100 λ exc = 270 nm & λ em = 455 nm 0.0 10 350 400 450 500 550 600 0 5 10 15 20 Wavelength (nm) Time (μs) (a) (b) Fig.100. (a) Emission spectra of ZnGa 2-x In x O 4 (x = 0, 0.05, 0.2, 0.5) nanoparticles after exciting samples in the UV region (260 to 280 nm). (b) Decay profile corresponding to blue emission from ZnGa 1.5 In 0.5 O 4 nanoparticles. 160
Quantum yield of the blue emission was measured using integrating sphere by dispersing the nanoparticles in methanol and the maximum quantum yield of around 10% was observed for ZnGa 1.5 In 0.5 O 4 nanoparticles. These nanoparticles were incorporated into poly methyl methacrylate (PMMA) matrix by in situ polymerization of methyl methacrylate (MMA) using AIBN as radical initiator at 72°C. The resultant polymer is soluble in organic solvents like CHCl 3 , toluene, CCl 4 , etc. The polymer was dissolved in CHCl 3 and spin coated on a quartz plate at 2500 rpm. The film was exposed to 270 nm light and the blue emission coming from the nanoparticles incorporated film is photographed and is shown in Fig.101. These results establish the potential of these nanoparticles for polymer based display applications. In addition to the host emission, the scope of ZnGa 2 O 4 as a luminescent material will further improve if lanthanide ions can be incorporated in the lattice of ZnGa 2 O 4 . Fig.101. Photograph of blue light emission from thin film of PMMA containing ZnGa 1.5 In 0.5 O 4 nanoparticles, on a quartz substrate. The excitation wavelength was 270 nm. 5.5. Photoluminescence from lanthanide doped ZnGa 2 O 4 nanoparicles: 5.5.1. Ce 3+ doped ZnGa 2 O 4 nanoparticles: Figure 102 shows XRD patterns of undoped ZnGa 2 O 4 and 5 atom % Ce 3+ doped ZnGa 2 O 4 nanoparticles. The XRD peaks of Ce 3+ doped ZnGa 2 O 4 nanoparticle are broader and can be explained based on the difference in the ionic sizes of Ga 3+ (0.61Å) and Ce 3+ (1.15Å) under six coordination. Replacement of Ga 3+ ion by 161
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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
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comparison, Eu 3+ ions alone in wat
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the samples, suggesting that Eu 3+
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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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Page 153 and 154: (001) (110) (011) (101) (020) (101)
Page 155 and 156: growth centre compared to higher vi
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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
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: value. The lattice parameters calcu
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
Page 209 and 210: 700 Intensity (arb.units) 600 λ ex
Page 211 and 212: Intensity (arb.units) 25000 20000 1
Page 213 and 214: Strong green emission has been obse
Page 215 and 216: consists of strong band at 255 nm a
Page 217 and 218: peak can be attributed to the cryst
Page 219 and 220: nm) is observed from Er 3+ doped Ga
Page 221 and 222: and Dy 3+ doped CaWO 4 nanoparticle
Page 223 and 224: REFERENCES 1. D. J. Barber, I. C. F
Page 225 and 226: 32. K. A. Gschneidner, Jr., L. Eyri
Page 227 and 228: 65. Z. Deng, F. Tang, D. Chen, X. M
Page 229 and 230: 100. A. Rouanel, J. J. Serra, K. Al
Page 231 and 232: 130. F. Li, W. Jianhuai, L. Jiongti
Page 233 and 234: 166. L. Fu, Z. Liu, Y. Liu, B. Han,
Page 235 and 236: 205. R. Sasikala, V. Sudarsan, C. S
Page 237 and 238: 238. E. Oldfield, R. A. Kinsey, K.
Page 239 and 240: 271. B. G. Hyde, S. Andersson, ”I
Page 241 and 242: B. S. Naidu, B. Vishwanadh, V. Suda
Page 243: 9. Room temperature synthesis of mu
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