CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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lanthanide ions. Doping of lanthanide ions into GaOOH lattice causes structural destruction due to incorporation of lanthanide ions in between the GaO 6 octahedral layers at the expanse of hydrogen bonds and the resulting product mainly contains finely mixed Ga(OH) 3 and Eu(OH) 3 . During heat treatment, Eu 3+ ions can diffuse into the lattice and forms Eu 3+ doped Ga 2 O 3 . (a) (b) (c) (d) Fig.36. TEM images of (a) 0, (b) 0.75, (c) 3 and (d) 5 at % Eu doped β - Ga 2 O 3. 3.5 Effect of heat treatment on luminescence of Ga 2 O 3 :Ln 3+ nanomaterials: Figure 37 (a) shows the emission spectra of Tb 3+ doped GaOOH, a-Ga 2 O 3 and b-Ga 2 O 3 nanomaterials. All samples displayed four peaks ~ 489, 543, 588 and 622 nm corresponding to 5 D 4 Æ 7 F 5 6, D 4 Æ 7 F 5 5, D 4 Æ 7 F 4 and 5 D 4 Æ 7 F 3 transitions of Tb 3+ ions. Tb 3+ doped a-Ga 2 O 3 sample shows 80
strong emission compared to corresponding GaOOH and b-Ga 2 O 3 samples. The low emission intensity of Tb 3+ in GaOOH can be attributed to the quenching of Tb 3+ excited state due to hydroxyl groups and that in b-Ga 2 O 3 can be attributed to the formation of Ga 3 Tb 5 O 12 /terbium oxide phase due to heat treatment at 900°C. The decay curves correspond to 5 D 4 level of Tb 3+ ions in the sample are shown in Fig.37 (b) and measured lifetime values are given in Table 4. The excited state of Tb 3+ decays single exponentially in GaOOH and a-Ga 2 O 3 and biexponentially in b-Ga 2 O 3 . These results indicate that Tb 3+ ions are having only one type of environment in GaOOH and a-Ga 2 O 3 lattices whereas it is more than one type of environments in b-Ga 2 O 3 . This is further supported by the formation of Ga 3 Tb 5 O 12 /terbium oxide phase in Tb 3+ doped samples as confirmed by XRD studies. Intensity (arb.units) 10000 8000 6000 4000 2000 5 D 4 7 F 6 5 D 4 7 F 5 5 D 4 As-prepared 500 o C 900 o C 7 F 4 5 D 4 7 F 3 Normalised intensity 1 0.1 0.01 As-prepared 500 o C 900 o C 0 450 500 550 600 650 (a) Wavelength (nm) 0 2 4 6 8 10 (b) Time (ms) Fig.37. (a) Emission spectra, (b) decay curve corresponding to 5 D 4 level of Tb 3+ in 0.5 at % Tb 3+ doped GaOOH, α-Ga 2 O 3 and β-Ga 2 O 3 nanomaterials. (λ exc = 255 nm and λ em = 544 nm) Table 4. Lifetime values corresponding to 5 D 4 level of Tb 3+ from GaOOH:Tb 3+ heated at different temperatures. Sample τ 1 (ms) τ 2 (ms) As prepared GaOOH:Tb 3+ 326 (14%) 1284 (86%) 500°C (α-Ga 2 O 3 : Tb 3+ ) 2389 (100%) 900°C (β-Ga 2 O 3 : Tb 3+ ) 258 (13%) 2872 (87%) 81
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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
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 and 94: Lanthanide ions doped Ga 2 O 3 nano
Page 95 and 96: atoms at three corners and the lone
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: The cell parameters increases with
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
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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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