CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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corresponds to f-f transition of Sm 3+ 4 ion. The decay curve corresponding to G5/2 level of Sm 3+ has been shown in Fig.89 (c). Bi-exponential nature of the decay curve has been attributed to Sm 3+ ions present on the surface and in bulk of the nanorods. 148
CHAPTER 5: Zinc gallate (ZnGa 2 O 4 ) 5.1. Introduction: Zinc gallate (ZnGa 2 O 4 ) belongs to the class of inorganic compounds having spinel structure. It crystallises in cubic structure with a space group of Fd3m [247]. ZnGa 2 O 4 is an insulator with a band gap of 4.4 eV and has potential applications as materials for low voltage field emission displays (FEDs), electro-luminescent devices (ELDs) and vacuum fluorescent displays (VFDs) [247-254]. ZnGa 2 O 4 exhibits higher chemical stability under high electric field and strong electron bombardment when compared with conventional sulfide based phosphors [251, 254]. Blue emission has been observed from ZnGa 2 O 4 and is due to a transition via a self-activation centre under UV or low voltage electron excitations [255]. The intensity and wavelength maximum corresponding to blue emission vary with the nature of dopants. For example detailed studies are available regarding the luminescent properties of ZnGa 2 O 4 when partially substituted with metal ions like Cd 2+ (for Zn 2+ ) and In 3+ (for Ga 3+ ) [ 256-258]. If nanoparticles of such luminescent materials are prepared with sufficient dispersability in organic solvents, then polymer based luminescent materials can be made out of them. Polymer based materials can be converted into devices by using cheap fabrication techniques. Primary requirement for incorporating nanoparticles in polymer matrix is to make them highly dispersible in organic solvents by stabilizing the nanoparticles with bulky organic ligands. However, such ligand-stabilised nanoparticles can be obtained only when the synthesis temperature is less than 250°C, so that as to prevent decomposition coordinated ligand. Hirano, et al. prepared ZnGa 2 O 4 nanoparticles at a relatively low temperature of 90°C from aqueous solution of ZnSO 4 and Ga 2 (SO 4 ) 3 by using precipitating agents like urea, aqueous ammonia and hexamethyl tetramine [248]. However, in this method ligand stabilization is difficult, as H 2 O being a solvent with low viscosity and poor coordinating characteristics does not prevent aggregation of the nanoparticles. Many methods are reported for the synthesis of ZnGa 2 O 4 nanomaterials in the form of nanowires, helical 149
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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
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
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: 3+ 4.4.8 Luminescence studies on Sm
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
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
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238. E. Oldfield, R. A. Kinsey, K.
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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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CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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