CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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CHAPTER 3: Binary oxides 3.1. Introduction: Oxides like Ga 2 O 3 and Sb 2 O 3 belong to class of materials known as transparent semiconducting oxides and find extensive applications in electro-luminescent devices, sensor materials for absorption of molecules like CO and CO 2 , catalysts, fire retardants, anode material for the Li-ion batteries, etc. [48-51, 128-137]. Ga 2 O 3 exists in a variety phases, namely α, β, γ and ε modifications [138, 139], whereas Sb 2 O 3 exists in two crystalline forms, cubic (senarmonite form) and orthorhombic (valentinite form). Depending on the nature of crystallographic modifications, they have different properties. For example, cubic Sb 2 O 3 is used as an additive to improve the flame retardency of polymer resins whereas valentinite form of Sb 2 O 3 is an essential component in Sb 2 O 3 -B 2 O 3 glasses showing enhanced non-linear optical properties [140]. Similarly β-Ga 2 O 3 is a preferred material in optoelectronics for field emission applications. Different phases of gallium oxides are generally prepared by decomposition of a suitable precursor, like GaOOH whereas Sb 2 O 3 is generally prepared either by the oxidation of antimony metal or by the hydrolysis of SbCl 3 . Several reports are available [141-149] on the synthesis of GaOOH in different shapes and sizes. These include methods like, hydrothermal treatment, sono-chemical reactions and precipitation in aqueous medium by addition of urea. It is also observed that the shape is retained when GaOOH is thermally decomposed to Ga 2 O 3 [56, 150]. A number of reports are also available on the preparation of Sb 2 O 3 in variety of forms such as nanoparticles [151- 158], hollow nanospheres [159], nanowires, nanobelts and nanorods [64, 65, 160-163]. Doping GaOOH/ Ga 2 O 3 and Sb 2 O 3 nanomaterials with lanthanide ions (Ln 3+ ) is an attractive option to prepare efficient luminescent materials. In the following section a brief description on the optical and luminescence properties of both lanthanides, doped and undoped GaOOH and Sb 2 O 3 have been discussed. 54
Lanthanide ions doped Ga 2 O 3 nanomaterials [164-171] have been investigated by several workers. However, the effect of lanthanide doping on structural aspects of GaOOH nanomaterials, which is a precursor for Ga 2 O 3 , is not known. As the ionic radii of Ln 3+ and Ga 3+ are significantly different, it is quite interesting to know where the lanthanide ions are incorporated and what structural modification it makes with the GaOOH lattice during doping. Luminescence from different lanthanide ions can be used as a probe to understand the structural changes taking place with GaOOH brought about by lanthanide ions incorporation. Such studies are essential for understanding the mechanism of lanthanide ion incorporation in different structural modifications of Ga 2 O 3 host which are obtained by the decomposition of lanthanide ions containing GaOOH phase. The main reason, behind lack of such studies on GaOOH:Ln 3+ (Ln 3+ for lanthanide ions) nanomaterials, is the significant quenching of the lanthanide ion excited state brought about by vibrations of OH groups present in GaOOH samples. For example Li, et al. [56] have carried out luminescence studies on GaOOH:Dy 3+ nanorods and observed that Dy 3+ emission from the sample is completely quenched. These authors also reported that thermal decomposition of GaOOH:Dy 3+ (3%) nanorods leads to the formation of Ga 2 O 3 :Dy nanorods along with small amounts of Dy 3 Ga 5 O 12 . The secondary phase might have formed from the Dy 3+ ions which are not incorporated in the GaOOH lattice. Also considering the ionic radii of Dy 3+ and Ga 3+ ions under a coordination number of six (0.91 and 0.62 Å) [172] it is difficult to visualise that all the Dy 3+ ions have replaced Ga 3+ in the GaOOH/ Ga 2 O 3 lattice. Very few reports are available [64, 65, 163] regarding the optical properties of Sb 2 O 3 either in the nanocrystalline form or in the bulk form. Zhang, et al. [163] have investigated optical properties of Sb 2 O 3 nanoparticles, obtained by the oxidation of antimony metal, over the visible and near infrared regions and observed that the reflectivity in this region depends on the metal contents in Sb 2 O 3 nanoparticles. Deng, et al. [64, 65] have carried out 55
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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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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
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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
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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: pulse frequency) as excitation sour
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Page 97 and 98: Figure 19 (a-d) shows SEM images of
Page 99 and 100: Based on these results, it can be i
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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
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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
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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
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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.
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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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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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CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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