CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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100°C. On further increasing the reaction temperature (at 125°C) the hexagonal form gets partially converted to monoclinic phase and at 185°C it transforms completely into monoclinic BiPO 4 . The average crystallite sizes are calculated by using Debye-Scherrer formula and are found to be 25, 47 and 51 nm for hydrated hexagonal BiPO 4 , hexagonal BiPO 4 and monoclinic BiPO4, respectively. The increase in crystal size may be explained based on the Ostwald ripening phenomenon where in, with increase temperature, bigger particles starts growing at the expanse of smaller particles. 185°C Monoclinic BiPO 4 Intensity (arb.units) 125°C 100°C RT Hexagonal BiPO 4 + Monoclinic BiPO 4 Hexagonal BiPO 4 Hydrated BiPO 4 10 20 30 40 50 60 70 2θ/° Fig.76. XRD patterns of 2.5 at % Eu 3+ doped BiPO 4 samples prepared at room temperature, 100, 125 and 185°C. In order to evaluate the conversion of hydrated hexagonal BiPO 4 to hexagonal and then to monoclinic from combined thermo-gravimetric and differential thermal analysis (TG- DTA) patterns of hydrated BiPO 4 sample were recorded (Fig.77). In TG, the weight losses are obtained mainly in the ranges of 50-180°C and 200-750°C. The former corresponds to the loss of water molecules adsorbed on the surface and the latter to the decomposition of 134
ethylene glycol moiety (stabilizing ligand). In DTA pattern mainly a sharp exothermic peak centered at 600°C was observed which is attributed to the phase transformation from hexagonal BiPO to monoclinic BiPO . 4 4 Weigth loss (%) 0 TG DTA -2 -4 -6 0.4 0.2 0.0 -0.2 -0.4 -0.6 Heat Flow (µV) -8 -0.8 200 400 600 800 1000 Temperature (°C) Fig.77. TG-DTA pattern of BiPO sample prepared at room temperature. 4 In order to understand structural changes occurring during the synthesis of BiPO 4 nanomaterials at different temperature, FT-IR spectra were recorded for these samples (Fig.78). The BiPO 4 nanomaterials prepared at room temperature and 100°C show similar spectra with sharp peaks at 539 and 600 cm -1 together with broad bands centered around 1000 cm -1 and 3500 cm -1 (3500 cm -1 band is not shown). The strong band centered at 1000 cm -1 is due to υ 3 stretching vibration of the PO tetrahedra and the peaks at 600 and 539 cm -1 4 correspond to δ(0-P-O) and v (P0 4 4), respectively [227]. Samples prepared at 125 and 185°C show similar spectra except splitting of peaks corresponding PO 4 stretching vibrations. The fine structure of the bands corresponding to PO 4 vibrations has been assigned to the reduction of the crystal symmetry from pseudo T to C d 1. In order to check, whether the variation in reaction temperature and crystalline phase has any effect on the particle size and morphology of BiPO , detailed TEM studies were carried out. Figure 79 shows the TEM images of BiPO 4 4 135
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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
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 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: espectively. Value of this integral
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
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
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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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CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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