CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

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Fig.43. (a and b) AFM images showing the nanorods of Sb 2 O 3 at two representative regions of the sample. TEM and SAED images for the nanorods along with that of bulk sample are shown in (c)–(f), respectively. 3.7 Effect of morphology on the luminescence of Sb 2 O 3 : Figure 44 (a and b) shows the emission spectra from Sb 2 O 3 nanorods and bulk material as a function of temperature (in the range ~ 77–300 K). Line shapes corresponding to the emission spectrum from both nanorods and bulk materials remained same at all the temperatures. A broad emission at ~ 390 nm has been observed for Sb 2 O 3 nanorods and bulk materials at all the temperatures. Considering the band gap energy values of Sb 2 O 3 (~ 3.3 eV) [64] and based on previous Sb 3+ luminescence studies [163, 64], the peak around 390 nm has been attributed to the near band edge emission arising form Sb 2 O 3 . However for nanorods in addition to the band edge emission around 390 nm, an additional broad peak which appears as a doublet with peak maxima around 545 and 592 nm is also observed. These two peaks have significant intensity in the case of nanorods 88
compared to the bulk material and are arising due to the defect levels present in the band gap of Sb 2 O 3 . These can be the oxygen vacancies, the surface dangling bonds or the surface defects. Similar defect emission with comparable line shape has also been observed in semiconductors like TiO 2 , ZnO, etc. [205, 206]. Lifetime corresponding to the excited state of these emission centers could not be accurately measured as the decay is faster than the experimental time resolution of the luminescence set up (~1 ns). Thus, it can be concluded that the excited state lifetime is of the order of sub-nanoseconds, similar to what has been observed in the case of ZnO nanorods [206]. At this stage, it is difficult to understand the exact origin of defects levels. It is worth while to mention here that Deng, et al. [64] have observed blue emission around 433 nm from Sb 2 O 3 nanobelts, and they have attributed this to the oxygen related defect emission from the nanorods. In the case of ZnO nanorods [206], it has been demonstrated that the orange, red and green defect related emission originate from them depending on the preparation method, annealing temperature and atmospheres. Normalised intensity 1.0 0.5 0.0 1.0 0.5 0.0 1.0 0.5 0.0 * nano-rods * 400 500 600 400 500 600 As prepared 100 °C heated 200 °C heated 400 °C heated * * * * Bulk 400 500 600 Wavelength (nm) 77 K 100 K 150 K 200 K 250 K 300K (a) 77K 100K 150K 200K 250K 300K (b) (c) Fig.44. Emission spectra of (a) Sb 2 O 3 nanorods and (b) bulk Sb 2 O 3 as a function of temperature. Room temperature emission spectra of as prepared Sb 2 O 3 nanorods annealed at different temperatures are shown in (c). Excitation wavelength was 220 nm. Peaks marked * are artifacts. 89
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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
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 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: intensity of XRD peaks correspond t
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 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
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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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