180 From emission studies both steady state and time resolved revelaed charge separation in presence of graphene. Charge separation behavior as studied by monitoring lowest exciton bleach revealed an enhanced recombination time as compared to pure CdTe QD by transient absorption spectroscopy. The exciton recombination in the case of CdTe was complete within 50ps while dynamics in G-CdTe was found to be very slow with the longest lifetime component >400ps clearly indicating much better charge separation the case of G-CdTe nanocomposites. Studies on carrier quenching using benzoquinone (electron quencher) revealed a quench in the bleach signal with negligible change in lifetimes and their contributions indicating this recombination contribution actually comes from electron transferred to Graphene. 6.5. References 6.1. Geim, A. K. and Novoselov, K. S., Nature Mater., 2007, 6, 183. 6.2. Novoselov, K. S., A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Gregorieva, and A. A. Firsov, Science, 2004, 306, 666. 6.3.Berger, C.; Song, Z.; Li, T.; Li, X.; Ogbazghi, A. Y.; Feng, R.; Dai, Z.; Marchenkov, A. N.; Conrad, E. H.; First, P. N.; and Heer, W. A. De., J. Phys. Chem. B, 2004, 108, 19912. 6.4. Novoselov, K. S., A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos, and A. A. Firsov, Nature, 2005, 438, 197. 6.5. Katsnelson, M. I.; Novoselov,K. S.; Geim, A. K., Nature Physics, 2006, 2, 620.
181 6.6. Reina, A.; Jia, X.; Ho, J.; Nezich, D.; Son, H.; Bulovic, V.; Dresselhaus, M.; Kong, J., Nano Lett. 2009, 9, 30. 6.7. Hass, J., Feng, R.; Millán-Otoya, J. E.; Li, X.; Sprinkle, M.; First, P. N.; de Heer, W. A.; and Conrad, E. H., Phys. Rev. B, 2007, 75, 214109. 6.8. Li, D.; Mueller, M. B.; Gilje, S.; Kaner, R. B.; and Wallace, G. G. Nature Nanotech., 2008, 3, 101. 6.9. Zhou, S. Y.; G.-H. Gweon, A. V.; Fedorov, P. N.; First, W. A.; de Heer, D.-H.; Lee, F.; Guinea, A.; Castro Neto, H.; and Lanzara, A., Nature Mater., 2007, 6, 770. 6.10. Xiaoyin Yang, Xi Dou, Ali Rouhanipour, Linjie Zhi, Hans Joachim Rader, and Klaus Mullen, J. Am. Chem. Soc., 2008, 130, 4216. 6.11. Hummers, W. S. Jr; and Offeman, R. E. J. Am. Chem. Soc., 1958, 80, 1339. 6.12. A. P. Alivisatos, Science, 1996, 271, 933. 6.13. W. U. Huynh, J. J. Dittmer and A. P. Alivisatos, Science, 2002, 295, 2425. 6.14. A. Kongkanand, R. M. Domínguez, and P. V. Kamat, Nano Lett., 2007, 7, 676. 6.15. Y. Wang, H. –B. Yao, X. –H. Wang and S. -Hong Yu, J. Mater. Chem., 2011, 21, 562. 6.16. A. Cao, Z. Liu, S. Chu, M. Wu, Z. Ye, Z. Cai, Y. Chang, S. Wang, Q. Gong, Y. Liu, Adv. Mater., 2010, 22, 103. 6.17. Y. Lin, K. Zhang, W. Chen, Y. Liu, Z. Geng, J. Zeng, N. Pan, L. Yan, X. Wang and J. G. Hou, ACS Nano, 2010, 4, 3033.
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Charge Transfer Dynamics in Quantum
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DECLARATION I, hereby declare that
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ACKNOWLEDGEMENTS It is my privilege
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1.3.5. Defect Mediated Relaxation 2
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2. 8. 4. White Light Generation- 45
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6.2. Experimental 6.2.1.Synthesis o
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devices based on QDs it has been sh
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Furthermore generation of pump (~40
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shell). This clearly indicated that
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12. V. I. Klimov, J. Phys. Chem. B,
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1.13 Reactant and Product Potential
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light. Inset: Kinetic traces monito
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6.5 Transient decay kinetics of gra
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at 670 nm after exciting at 400 nm
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ABBREVIATIONS BET BQ CB CCD CdS CdT
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1 Chapter 1
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3 size dependent optical properties
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5 1.2. Physics of Semiconductors 1.
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7 As seen from the schematic, poten
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9 Substituting this in Schrödinger
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11 ( r, r ) ( r ) ( r ) (1.13) e
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13 E E E 2 2 2 EX ne, le nh,
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15 spherical symmetry of field. The
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17 gE ( ) 2Em 2 3 3 (1.25) For a
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19 1.3.2. Electron-Hole energy tran
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21 Impact Ionization Figure 1.7. Sc
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23 understanding on mechanistic asp
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25 carriers are unable to sample th
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27 CB VB QD Metal Figure. 1. 10. Sc
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29 energy barrier. Therefore it is
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31 1 f q 2 A qB (1.30) 2 In equa
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33 Vibrational contribution can be
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35 1. 7. 1. Electron Injection ET i
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37 Under assumption of invariance o
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39 distribution. To achieve good si
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41 initially achieved monodispersit
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43 and rate of charge transfer acro
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45 1.32 P. V. Kamat, J. Phys. Chem.
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47 Chapter 2
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49 chemical species. Since a partic
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51 fluorescence forms an important
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53 eliminated by use of standard wh
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55 sample. Raman spectroscopy is ba
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57 will appear bright and region wi
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59 volatile solvent is drop casted
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61 spots arise from diffraction fro
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63 The electrical signal is then ch
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65 delayed and inverted. The two si
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67 Pump-probe technique is one of t
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69 Amplifier Jade Stretcher fs Osci
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71 Figure 2.6. Optical layout of Ti
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73 Grating Convex Mirror Concave Mi
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75 changes the polarization from ho
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77 Grating Output Input Mirror Grat
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79 μJ has a very high peak power.
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81 2.6. Dynamical Theory of X-Ray D
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83 Chapter 3
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85 Therefore the study of interfaci
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87 3. 2. Experimental Section 3.2.1
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89 and intensity show absence of ot
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91 which is also neutral; therefore
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93 electron transfer times. This re
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95 r B a * 0 3.1 me / me Now the
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97 nonadiabatic case the electron t
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99 drastically reduced leading to a
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101 While the study of injection dy
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103 study. Based on the injection d
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105 17. L. E. Brus, J. Phys. Chem.
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107 Chapter 4
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109 of the QDs. As a result surface
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111 4.2.2. Synthesis: The CdTe QDs
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113 lower hole state. In CdSe the l
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115 4.2 inset. The kinetic traces a
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117 growth of the bleach kinetics (
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119 previous section we have discus
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121 lived charge transfer complex w
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123 100 times concentration of the
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125 4.5. References 4.1. Efros, Al.
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127 Chapter 5
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129 been made in the synthesis of t
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- Page 180 and 181: 133 5.3. Result and discussion: 5.3
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- Page 186 and 187: 139 1000 c b PL Intensity 100 10 a
- Page 188 and 189: 141 samples due to a very weak exci
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- Page 192 and 193: 145 Earlier authors [5.4] reported
- Page 194 and 195: 147 Sample t r(ps) t 1(ps) t 2(ps)
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- Page 200 and 201: 153 5.20. Sreejith Kaniyankandy, Sa
- Page 203 and 204: 155 CHAPTER 6 Charge Separation in
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- Page 207 and 208: 159 graphene in a 1M NaOH solution.
- Page 209 and 210: 161 Intensity (a.u.) 5 4 3 2 1 CdTe
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- Page 221 and 222: 173 A (mO.D) 10.0 0.0 -10.0 -20.0 0
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