CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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3+ 4.3.3 Studies on Ce co-doped SbPO 4 :Tb 3+ nanomaterials and their dispersion in silica: 3+ Figure 68 shows TEM images of SbPO4:Ce (2.5%),Tb 3+ (5%) samples dispersed in SiO 2 . The ribbons are shown in Fig.68 (a). Their length and width are in the range of 700-800 and 20-50 nm, respectively. In addition to these nanorods, nanoparticles of size 2-5 nm are also present as revealed by the TEM image (Fig.68 (b)). Nanoribbons are aggregated and are surrounded by silica, as can be seen from the contrast difference observed in the TEM image arising due to the high refractive index of SbPO 4 compared to silica. Selected area diffraction from the sample is shown in the Fig.68 (c). (a) (b) (c) (d) 3+ Fig.68. TEM images of (a) SbPO 4 :Ce (2.5%),Tb 3+ (5%) nanoribbons in silica and (b) 3+ SbPO4:Ce (2.5%),Tb 3+ (5%) nanoparticles in silica. A representative selected area electron diffraction pattern and a high resolution TEM image from these nanoribbon are shown in Fig.68 (c and d), respectively. 122
Compared to the selected area electron diffraction pattern shown in Fig.63 (c), the dots corresponding to the diffraction patterns observed in Fig.68 (c) are not symmetrically placed, indicating that there exists lesser extent of preferential orientation in the sample after dispersion in silica. High-resolution image of a nanoparticle is shown in Fig.68 (d). Lattice fringes can be clearly seen in the image. The distance between the lattice planes, 3.32 ± 0.05 Å, match well with the (020) plane of SbPO 4 phase. XRD and TEM studies do not give any indication regarding the incorporation of the lanthanide ions in SbPO 4 lattice. In order to confirm this aspect, detailed structural studies have been carried out using infrared and Raman spectroscopic techniques. 4.3.4 Proof for the incorporation of lanthanide ions into SbPO 4 lattice: Figure 69 shows the Raman spectrum of un-doped SbPO4, SbPO 4 :Ce (2.5%),Tb 3+ (5%), 3+ SbPO4:Ce (2.5%),Tb 3+ (5%)-SiO 2 samples. The patterns appear identical for all the samples. All the patterns are characterised by sharp peaks at ~ 210, 350, 471, 578, 618, 971 and 1048 cm -1 . In addition to this, broad peaks at ~ 437, 664, 770 and 931 cm -1 are observed. The position of these peaks is in close agreement with those reported by Nalin, et al. [245]. The SbPO 4 crystallize in C 2h 2 space group and comprises of PO 4 tetrahedral units bound to the Sb(III) polyhedral units (trigonal bipyramidal configurations) through asymmetrical bridging oxygen atoms [246]. The isolated PO 4 groups with Td symmetry, when placed at C 2h sites, (corresponding to the monoclinic SbPO 4 unit cell) results in the decomposition of the vibrational species into the following modes. A 1: A g + B u, 2F 2: 4A g +4B u +2A u+2Bg , E: A g +B u +A u+Bg Among these, the six A g and three B g modes are Raman active while the 3A u and 6Bu modes are IR active. The peaks at ~ 355, 623, 976 and 1053 cm -1 are of the A g type, while peaks at ~ 476 and 583 cm -1 are of the B g type. Replacement of Sb 3+ 3+ 3+ by lanthanide ions (Ce or Tb ) is expected to have significant effect on the P-O stretching modes of PO units in SbPO . We 4 4 3+ 123
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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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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 and 158: observed after excitation at 250 an
Page 159: 3+ 3+ concentration quenching. Tb l
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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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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