CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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luminescence studies on self-assembled structures of Sb 2 O 3 nanorods and nanowires. They observed broad emission peak in the region of 390 to 500 nm, in addition to the band edge emission centered around 374 nm. Broad emission over the region of 390 to 500 nm has been attributed to the emission from oxygen vacancies related defect centers present in the lattice of Sb 2 O 3 . In a related study Deng, et al. [65] observed blue emission around 433 nm from Sb 2 O 3 nanobelts, which has also been attributed to the oxygen related defect emission. Chen, et al. [173] has also observed broad emission in the region ~ 400-700 nm from orthorhombic Sb 2 O 3 . However, no proper explanation was given for the observed broad emission. Sb 3+ is known to be a good luminescent species when doped into different inorganic host lattices [174-176]. Oomen, et al. [174] have observed two emission bands, one in the UV and the other in the visible region from Sb 3+ doped LnPO 4 samples (where Ln = Sc, Lu and Y). These emission bands arise from transitions between 3 P 1 and 3 P 0 (excited states) to 1 S 0 (ground state) of Sb 3+ ions and are strongly temperature dependent due to dynamic Jahn-Teller effect. Antimony doping improves green emission from PbWO 4 single crystals due to creation of O i sites in the lattice [175]. However, in all these studies, luminescence properties of the Sb 2 O 3 with different morphologies have been given only limited attention, particularly when luminescent species like lanthanide ions are associated with them. The difficulty in incorporation of lanthanide ions in the Sb 2 O 3 lattice may possibly a reason for limited investigation on such materials. The factors responsible for this difficulty are (i) significant difference in the ionic radius between Eu 3+ ions (0.95Å under 6 coordination) and Sb 3+ ions (0.76 Å under four coordination) [177] and (ii) difference in the stable coordination numbers of Eu 3+ and Sb 3+ ions. There is also a vast difference in their electro-negativity values. Generally Eu 3+ ions prefer higher coordination number like 6, 8 and 9, whereas in orthorhombic Sb 2 O 3 , antimony has a slightly distorted tetrahedral geometry with oxygen 56
atoms at three corners and the lone pair of electrons of antimony at the fourth corner with all the O - Sb - O bond angles different [178]. In spite of significant difference in terms of ionic radius, electro-negativity, coordination numbers between Sb 3+ and Eu 3+ ions, it is of interest to understand the chemical interaction taking place between them, particularly in aqueous/organic solvents under alkaline conditions. This is because many technologically important luminescent oxide nanoparticles doped with lanthanide ions and Sb 3+ are prepared under these conditions. For example Wen, et al. [179] have demonstrated that by suitably modifying Eu 3+ /Sb 3+ ratio in YBO 3 crystal, nearly white light emission can be obtained. Their interaction under high temperature heat treatment is also important as lanthanide ions are co-doped with Sb 3+ ions in several oxide-based glasses, which are prepared at high temperatures [180, 181]. It is reported that presence of Sb 2 O 3 in silicate glass doped with Er 3+ , has significant effect on spontaneous emission rates of 4 I 13/2 level of Er 3+ in the glass [180]. Hence, it is of interest to understand the optical properties of the Sb 2 O 3 synthesised in both the presence and absence of lanthanide ions in detail. In the first section of this chapter, effect of lanthanide ion (Eu 3+ , Tb 3+ and Dy 3+ ) incorporation on the structural and morphological aspects of GaOOH nanorods has been presented. As the luminescence properties of Eu 3+ ions with respect to its environment are well understood, it has been used as a probe to monitor the structural changes taking place with GaOOH lattice brought about by lanthanide ion incorporation. In the second section of this chapter, the photoluminescence and structural properties of Sb 2 O 3 nanorods oriented along a particular direction and their interaction with lanthanide ions are discussed. The shape selective modifications in the structure and luminescence properties of the nanorods as well as the interaction of nanorods with lanthanide ions have been investigated using X-ray 57
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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
Page 43 and 44: must be supersaturated either by di
Page 45 and 46: - + - + charge stabilized nanoparti
Page 47 and 48: exothermic reaction between the met
Page 49 and 50: constant, ħ is h/2π, e is the ele
Page 51 and 52: these platinum complexes have been
Page 53 and 54: (IR), visible and ultra-violet (UV)
Page 55 and 56: in Ce 3+ , Pr 3+ , Tb 3+ and CT abs
Page 57 and 58: assisted by lattice phonons of appr
Page 59 and 60: decay-time reduction is much easier
Page 61 and 62: nanocrystals is shown in Fig.10 [58
Page 63 and 64: depends strongly on the nature of t
Page 65 and 66: corresponding emission and excitati
Page 67 and 68: doped nanomaterials of the above me
Page 69 and 70: will be formed and subsequently it
Page 71 and 72: Eu 3+ ions were also subjected to s
Page 73 and 74: transferred into a two-necked RB fl
Page 75 and 76: Where λ is the wavelength of X-ray
Page 77 and 78: Micro-structural characterization b
Page 79 and 80: electrons (i.e. diffraction mode).
Page 81 and 82: diffraction spots. By tilting a cry
Page 83 and 84: surface. The contact mode can obtai
Page 85 and 86: three types lines in the scattered
Page 87 and 88: solids tend to be broadened because
Page 89 and 90: sample fluoresce. The fluorescent l
Page 91 and 92: pulse frequency) as excitation sour
Page 93: Lanthanide ions doped Ga 2 O 3 nano
Page 97 and 98: Figure 19 (a-d) shows SEM images of
Page 99 and 100: Based on these results, it can be i
Page 101 and 102: almost normal to the equatorial pla
Page 103 and 104: Table 2. Summary of important modes
Page 105 and 106: 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
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5 D 0 7 F 2 level to 7 F 7 7 1 , F
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The second possibility is the excha
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chemical shift anisotropy is much h
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not have strong interaction with th
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(001) (110) (011) (101) (020) (101)
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growth centre compared to higher vi
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observed after excitation at 250 an
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3+ 3+ concentration quenching. Tb l
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Compared to the selected area elect
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lattice. Lanthanide ions occupying
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obtained after 275 nm excitation is
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The luminescence dynamics associate
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that the broad peak can be resolved
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espectively. Value of this integral
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ethylene glycol moiety (stabilizing
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Room temperature and 100°C synthes
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heavier metal ion as compared to La
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Similar studies were also carried o
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3+ 3+ faster decay component is ass
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the other hand the Eu 3+ lifetime h
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3+ 4.4.8 Luminescence studies on Sm
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CHAPTER 5: Zinc gallate (ZnGa 2 O 4
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In pure EG an amorphous product is
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water content in the reaction mediu
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nucleation, thereby leading to incr
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particles. Thus the TEM studies als
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value. The lattice parameters calcu
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Quantum yield of the blue emission
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5.5.2. Eu 3+ doped ZnGa 1.5 In 0.5
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CHAPTER 6: Tungstates [MWO 4 (M = C
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ionic radius of the metal cation ca
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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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